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Direct water injection provides feasible solution for combustion optimization and efficiency enhancement within internal combustion Rankine cycle engine, while the feedback signal of close-loop direct water injection control is still absent. Ion current detection monitors in-cylinder electron variation which shows potential in revealing direct water injection process. For better understanding of unprecedented augment of ion current signal under direct water injection within internal combustion Rankine cycle engine, a chemical kinetic model is established to calculate the effect of intake oxygen fraction, fuel quantity, initial temperature and residual water vapor on in-cylinder electron formation based on GRI Mech 3.0 and ion current skeleton mechanism. The simulation results indicate direct water injection process show significant impact on in-cylinder electron formation through chemical interactions between H2O and other intermedia species including HO2, O2, CH3 and H, these reactions provides additional OH radical for propane oxidation facilitation, which result in large portion of CH radical formation and therefore, lead to higher in-cylinder electron generation. The initial temperature plays a vital role in determining whether residual water vapor show positive or negative effect by in-cylinder temperature coordination of direct water injection. Results of this work can be used to explain phenomenon related to direct water injection and ion current signal variation under both internal combustion Rankine cycle or traditional petrol engine.

Актуальность. Из 26 промышленно-разрабатываемых месторождений ООО «ЛУКОЙЛ-Западная Сибирь» в Шаимском нефтегазоносном районе пласты средней юры продуктивны на 21 месторождении. В них сосредоточено 56 % извлекаемых запасов нефти. Залежи отложений средней юры имеют сложное геологическое строение и характеризуются неоднородностью по разрезу, не выдержаны по простиранию, имеют в целом низкие фильтрационно-емкостные свойства. Запасы нефти в отложениях пластов тюменской свиты отнесены к трудноизвлекаемым по стратиграфической принадлежности. Отбор нефти в них от начальных извлекаемых запасов по состоянию на 01.01.2021 г. составляет всего 8,6 %. Темп отбора от НИЗ 0,4 % в год. Исследование особенностей выработки коллекторов тюменской свиты является актуальной задачей. Цель: выявить ключевые геолого-физические особенности разработки коллекторов тюменской свиты для поиска методов и технологий повышения эффективности их разработки. Объекты: коллекторы тюменской свиты Шаимского района. Методы: контент-анализ, анализ и обобщение имеющегося опыта разработки коллекторов тюменской свиты на примере трех месторождений ООО «ЛУКОЙЛ-Западная Сибирь». Результаты. Обобщены особенности геологического строения, выработки запасов пластов тюменской свиты и основные направления совершенствования технологии разработки. По результатам проведенного анализа выработки коллекторов тюменской свиты выявлены существенные различия в эффективности выработки запасов нефти. По результатам интерпретации гидродинамических исследований, проведенных на рассматриваемых месторождениях, на двух выявлены коллекторы с двойной средой, что может оказывать существенное влияние на достижение различной эффективности разработки указанных месторождений. Во многом низкая эффективность разработки объектов тюменской свиты обусловлена применяемыми системами разработки, запроектированными на недостаточно геологически изученных залежах. Важной прикладной задачей эксплуатации порово-трещиноватого коллектора является определение величины дренируемых запасов и возможность прогнозирования их выработки с применением характеристик вытеснения, соответствующих типу продуктивного пласта. Research relevance. Middle Jurassic reservoirs are oil-bearing in 21 fields from total of 26 being produced by JSC LUKOIL-West Siberia in the Shaimsky oil-and-gas area, they contain 56 % of recoverable oil reserves. Middle Jurassic reservoirs have complex geological structure and are characterized by cross-sectional heterogeneity and lateral discontinuity, have low reservoir properties in general. Oil reserves in the reservoirs of Tyumen geological interval are classified as hard-to-recover based on the fields stratigraphy. Cumulative oil production from these reservoirs reached only 8,6 % from the total initial recoverable reserves as of 01.01.2021. Production rate is 0,4 % of the initial recoverable reserves per year. Research of the development of Tyumen geological interval reservoirs is a relevant exercise. The purpose of the research is to reveal key geological and geophysical features of the development of Tyumen geological interval reservoirs in order to identify the best methods and technologies to increase efficiency of their development. Subject: reservoirs of Tyumen geological interval in the Shaimsky area. Methods: literature research, analysis of the available experience of the development of Tyumen geological interval reservoirs based on the example of three fields of JSC LUKOIL-West Siberia. Executive summary. The paper analyzes and summarizes the specificities of geological structure, experience of the development of Tyumen geological interval reservoirs and the main methods of production enhancement and improvement of field development. Significant distinctions in the efficiency of field development are revealed based on the results of the carried-out analysis of geological and geophysical characteristics of the development of Tyumen geological interval reservoirs. According to the results of interpretation of the hydrodynamic researches conducted on considered fields, in two of them reservoirs with dual flow conditions (through both matrix and fractures) have been identified, which could have essential impact on the efficiency of development of these specified fields. Low performance of the development of Tyumen geological interval reservoirs is often caused by the use of uniform grid of the production wells, chosen due to insufficient knowledge of fields geological structure. The key issue is the evaluation of the recoverable reserves and the possibility to forecast production parameters using corresponding characteristics of oil drainage in accordance with the type of produced reservoir.

The development of engine technologies and research on combustion processes are focused on finding new generation CI engines with simple control of the combustion process while efficiently maintaining desirable engine performance and meeting emission regulations. This comprehensive study on the relatively low hydrogen energy fraction (0.65–1.80%), supplied by onboard water electrolysers and on water injection, was performed on the performance and emission parameters of the CI engine. The article presents results of both experiment and simulation about the effect of hydroxygen and water injection on the combustion process, auto-ignition delay, combustion intensity, the temperature of the mixture and engine performance at BMEP of 0.2 MPa, 0.4 MPa, 0.6 MPa, and 0.8 MPa at a speed of 1900 rpm. For the first part, the test engine operated with diesel fuel with 3.5 L/min of hydroxygen gas supplied with an external mixture formation. The HHO has an effect on the combustion process at all range of BMEP. A decrease in BTE and increase in BSFC were noticed during tests. The peak pressure and the rate of heat release decreased, but the NOx decreased as well. The second part of experiment was performed with the injection of a substantial amount of water, 8.4–17.4 kg/h (140–290 cm3/min), and the same amount of hydroxygen. The injection of water further decreased the NOx, therefore, HHO and WI can be used to meet emission regulations. A simulation of the combustion process was carried out with the AVL BOOST sub-program BURN. The AVL BOOST simulation provided a detailed view of the in-cylinder pressure, pressure-rise, combustion intensity shape parameter and SOC.

Актуальность работы обусловлена тем, что при разработке сложнопостроенных карбонатных залежей зачастую возникают сложности, связанные с системой поддержания пластового давления и выбором оптимальных технологий, направленных на эффективную выработку запасов нефти. В данных условиях для поддержания уровня добычи на рентабельном уровне необходимо оптимизировать забойные давления скважин. Нефтяным компаниям, разрабатывающим карбонатные залежи, стоит обращать внимание на величину оптимального забойного давления, которая обеспечивает наиболее рациональную выработку запасов. Несмотря на то, что данный вопрос рассматривается достаточно долгое время многими отечественными и зарубежными учеными, он на сегодняшний момент времени остается нерешенным и в то же время имеет значительную научную и практическую значимость. Целью работы является обоснование значения оптимального забойного давления добывающих скважин и его влияния на выработку запасов из сложнопостроенного карбонатного коллектора Гагаринского нефтяного месторождения. Объект: карбонатная залежь Гагаринского нефтяного месторождения. Методы: фильтрационные установки с моделированием пластовых условий УИК-5ВГ и AFS-300; использование гидродинамического симулятора Tempest версии 8.3.1 компании Roxar. Результаты. Смыкание естественных трещин приводит не только к снижению производительности скважин и к неполной выработке запасов нефти в зоне дренирования, но и к низкой эффективности применяемых мероприятий, а также к ухудшению гидродинамической связи между скважинами. Следовательно, в данных условиях важным и необходимым является обоснование оптимальных забойных давлений добывающих скважины на начальных этапах разработки карбонатных залежей. Проведенные лабораторные исследования и расчеты с помощью геолого-гидродинамической модели карбонатной залежи, которая учитывает особенности строения пустотного пространства, показали практическое значение (выражается в увеличение добычи нефти) оптимизации забойного давления добывающих скважин, эксплуатирующих карбонатные трещиноватые коллектора. Проведенный расчет экономической составляющей оптимизации (регулирование величины забойного давления) работы трех добывающих скважин Гагаринского месторождения позволит дополнительно получить 19,5 млн р. The relevance of the research is caused by the fact that when developing the complex carbonate deposits, the difficulties often arise. They are associated with the operation of the reservoir pressure maintenance system and the choice of optimal technologies for development of oil reserves. Under these conditions, to maintain the production at a profitable level, it is necessary to optimize the bottomhole pressure of the wells. For oil companies developing carbonate deposits, it is worth paying attention to the value of the optimal bottomhole pressure, which ensures the most rational development of reserves, and not critical. Even though this issue has been considered for quite a long time by many domestic and foreign scientists, it remains unresolved now and at the same time it has significant scientific and practical importance. The main aim of the study is to substantiate the optimal bottomhole pressure of producing wells and its influence on the development of reserves from the complex carbonate reservoir of the Gagarinskoe oil field. Object: carbonate reservoir of the Gagarinskoe oil field. Methods: filtration units with reservoir conditions modeling UIK-5VG and AFS-300; using Roxar's Tempest Fluid Dynamic Simulator version 8.3.1. Results. Closing of natural fractures leads not only to a decrease in well productivity and to incomplete production of oil reserves in the drainage zone, but also to a low efficiency of the measures used, as well as to a deterioration in the hydrodynamic connection between wells. Therefore, under these conditions, it is important and necessary to substantiate the optimal bottomhole pressures of producing wells at the initial stages of the development of carbonate deposits. Laboratory studies and calculations using a geological and hydrodynamic model of a carbonate reservoir, which takes into account the peculiarities of the geological structure, have shown the practical value (expressed in an increase in oil production) of optimizing the bottomhole pressure of producing wells operating fractured carbonate reservoirs. The calculation of the economic component of optimization (regulation of the bottomhole pressure value) of the operation of three production wells of the Gagarinskoe field will additionally receive 19,5 million rubles.

This paper presents a streamlined design procedure for water-based noise suppression systems that are applicable to multiple classes of rocket engines. A newly adapted steady quasi-one-dimensional two-phase model is employed to predict the evolution of the exhaust gases interacting with water droplets. Such a model is embedded into a two-step optimization procedure with the objective of finding the most efficient combination of the suppressor operative parameters. This information is then used to design the hardware of the system, which consists in a set of injectors, with the task of producing atomized water jets directed towards the exhaust gases, and a toroidal manifold, with the task of delivering water to the injectors at uniform conditions of pressure and velocity. Finally, the proposed design procedure is applied to a 15 kN thrust class oxygen/methane liquid rocket engine. Technical specifications of the resulting water-based noise suppression system are provided along with a detailed three-dimensional CAD model.

The effect of water injection at the air side and water addition at fuel side on engine?s performance of a Diesel engine was studied under oxygen enriched intake air using neat mahua oil as fuel. Initially experiments were carried out using neat mahua oil as fuel with different oxygen concentrations such as 21% (ambient), 22.4%, 23.8%, and 24.7% by volume at the air side. The optimal oxygen concentration was found based on the engine?s brake thermal efficiency. At the optimal oxygen concentration water injection was done on air side at 4% by mass and the experiments were repeated with neat mahua oil as fuel under oxygen enrichment mode. Finally, mahua oil emulsion was prepared using the same amount of water (i. e. 4%) and tested in the engine. A comparative study was made for the same amount of water (i. e. 4% as optimal) for water injection and neat mahua oil emulsion on engines behavior. Oxygen enrichment increased the brake thermal efficiency with all concentrations and reached the maximum value from 25.2% with ambient oxygen to a maximum of 30.6% at 23.8% of oxygen enrichment at the maximum brake mean effective pressure of 5.4 bar whereas it was 30.8% with neat diesel. The smoke, HC, and CO emissions were significantly reduced with oxygen enrichment. However, oxygen enrichment increased the NO emissions at all concentrations. Injection of water and emulsification techniques reduced the NO emissions considerably. Emulsification showed more reduction in NO emission than water injection for the same amount of water. It was concluded from the study that neat mahua oil could be effective used as fuel in compression ignition engines by combusting it under oxygen enriched condition. The optimal oxygen concentration of 23.8% could be recommended for the highest brake thermal efficiency. Injection of water at the intake manifold and emulsification techniques could solve the problem of higher NO emissions. The optimal amount of water that could be injected without affecting the engines power and brake thermal efficiency could be recommended as 4% by volume. Emulsification has the added advantage of further improvement in engine?s brake thermal efficiency.

Capillary and interfacial forces are of great influences of trapping hydrocarbon in porous media after primary and secondary recovery processes. The trapped crude oil in the reservoir can be mobilized and produced by reducing these forces. Thus, surfactant flooding, as a main enhanced oil recovery (EOR) method, is usually applied to reduce the interfacial tension (IFT) of crude oil–water system in porous medium and improves the oil recovery. This study focused on the effect of [C8Py][Cl] and [C18Py][Cl] ionic liquids (ILs), as a new family of surfactant, in combination with various salts including sodium chloride, potassium chloride, magnesium sulfate and potassium sulfate on IFT reduction. EOR injection solutions were prepared from mixing the ILs at different concentrations of 100, 250, 500 and 1000 ppm with the salts ranging from 500 to 80,000 ppm. Obtained results showed that the minimum IFT value from both ILs was achieved when the concentration of the ILs was about 1000 g/mL, and the concentrations of KCl, K2SO4, MgSO4 and NaCl were 1000, 2000, 500 and 80,000 ppm, respectively. The minimum IFTs were achieved when NaCl and ILs concentrations were the maximum and MgSO4 concentration was the minimum.

One of the promising ways to increase fuel and modern gas turbine energy efficiency is using cyclic air intercooling between the stages of high- and low-pressure compressors. For intercooling, it is possible to use cooling in the surface heat exchanger and the contact method when water is injected into the compressor air path. In the presented research on the cooling contact method, it is proposed to use a thermopressor that implements the thermo-gas-dynamic compression process, i.e., increasing the airflow pressure by evaporation of the injected liquid in the flow, which moves at near-sonic speed. The thermopressor is a multifunctional contact heat exchanger when using this air-cooling method. This provides efficient high-dispersion liquid spraying after isotherming in the high-pressure compressor, increasing the pressure and decreasing the air temperature in front of the high-pressure compressor, reducing the work on compression. Drops of water injected into the air stream in the thermopressor can significantly affect its characteristics. An increase in the amount of water increases the aerodynamic resistance of the droplets in the stream. Hence, the pressure in the flow parts of the thermopressor can significantly decrease. Therefore, the study aims to experimentally determine the optimal amount of water for water injection in the thermopressor while ensuring a positive increase in the total pressure in the thermopressor under conditions of incomplete evaporation. The experimental results of the low-consumption thermopressor (air consumption up to 0.52 kg/s) characteristics with incomplete liquid evaporation in the flowing part are presented. The research found that the relative water amount to ensure incomplete evaporation in the thermopressor flow part is from 4 to 10% (0.0175–0.0487 kg/s), without significant pressure loss due to the resistance of the dispersed flow. The relative increase in airflow pressure is from 1.01 to 1.03 (5–10 kPa). Based on experimental data, empirical equations were obtained for calculating the relative pressure increase in the thermopressor with evaporation chamber diameters of up to 50 mm (relative flow path length is from 3 to 10 and Mach number is from 0.3 to 0.8).

The extraction of hydrocarbons is associated with obtaining certain amounts of water, which is heavily contaminated with a wide range of chemical compounds that negatively affect the environment. At present, practically the only method of managing extracted reservoir waters is their injection into absorbing horizons. Large changes in parameters (pH, Eh, temperature, etc.) occurring during the extraction and storage of water, as well as the contact of the injected water with reservoir water and rock, may result in the precipitation of secondary sediments. The complexity of the injected water/native water/deposit rock system and the wide range of possible interactions do not always allow for correct interpretation of the processes and their impact on near-well zone permeability. One of the factors which has a decisive influence on dissolution/precipitation is temperature change. Applying analytical data of water with low (W-1) and high (W-2) mineralization, calculations were carried out with the use of PRHEEQC software. Changes in solubility index values were determined at ambient temperature (20 °C) and reservoir temperature (94 °C). The obtained results indicate that with increasing temperature, SI changes for a given chemical compound may run in different directions and take different values, depending on the composition of the injected water. The calculations indicate the possibility of a change in the direction of the reaction from dissolution to precipitation, which may lead to clogging of the near-well zone. Simulations of the injected water’s contact with minerals present in the reservoir rock were also carried out. The obtained data indicate that these minerals, in the entire studied temperature range, dissolve in the injected water, but the solubility of anhydrite and dolomite decreases with increasing temperature. If the water is saturated with minerals at low temperature, after heating in the bed, sedimentation and blockage of rock pores may occur, which means there is a reduction in the efficiency of water injection.

This study presents the development of water injection system for turbocharged spark ignition engine. The water injection control system is built for turbocharged spark ignition (SI) engine where water was injected at the intake port just before the throttle body. The data was collected from the simulation through the GT-Power software to determine the optimized injection output for the engine. Single-stage statistical engine responses and boundary models were established by using Model-Based Calibration Toolbox. Control system was built using Simulink and simulation tests were conducted based on the speed and throttle position as the variables. The highest value of brake torque achieved in the GT-Power simulation was taken as the base value to determine the injection amount. The mean value of the predicted injection was recorded at 12.29 g/s while the variance of the predicted injection to the optimized injection was below 1%. The control system was simulated with the set predicted injection and the standard deviation of the predicted injection was 1.18. The control system simulation recorded a low percentage of 0.04% variance to the optimized injection with the pulse width modulation signal. The control system is ideal to be constructed and tested on actual engine test bed.

The study presents the use of CORQUENCH simulator to simultaneously model the molten corium, composition of concrete, molten corium heat transfer models and solve the related chemical reactions. Using this modeling technique, the chemical reaction capabilities of CORQUENCH were successfully utilized which enabled the modeling of interaction between molten corium and concrete. The developed model was validated against experimental data and the results showed that the temperature of corium, composition of concrete and water injection time have a pronounced effect on mitigating depth of ablation and reactor integrity in case of a nuclear accident. In addition, the composition of concrete is the main controlling factor to mitigate ablation in the investigated case study. An alternative to concrete, could be a certain igneous rock (tested in this study), can lead to comparatively low rates of ablation due to its high thermal resistant properties. Furthermore, the injection of water (as a cooling agent) into the reactor cavity should also be optimized to enhance corium quenching to avoid ablation via basement melt-through. As a consequence of concrete ablation by molten corium, the depth of ablation is expected to decrease to zero ablation with the suggested material in the selected case study. The concrete ablation mechanisms during MCCI are very case-dependent on the concrete solidus, liquidus and ablation temperature, respectively.

Article number 117250 Despite their high thermal efficiency (>50%), large two-stroke (2 T) diesel engines burning very cheap heavy fuel oil (HFO) produce a high level of carbon dioxide (CO2). To achieve the low emission levels of greenhouse gases (GHG) that will be imposed by future legislation, the use of hydrogen (H2) as fuel in 2 T diesel engines is a viable option for reducing or almost eliminate CO2 emissions. In this work, from experimental data and system modelling, an analysis of dual combustion is carried out considering different strategies to supply H2 to the engine and for different H2 fractions in energy basis. Previously, a complete thermodynamic model of a 2 T diesel engine with an innovative scavenging model is developed and validated. The most important drawbacks of this type of engines are controlled in this work using dual combustion and water injection, reducing nitrogen oxides emissions (NOx), self-ignition and combustion knocking. The results show that the developed model matches engine performance data in diesel mode, achieving a higher efficiency and mean effective pressure (MEP) in hydrogen mode of 53% and 14.62 bar respectively. Consejería de Economía, Conocimiento, Empresas y Universidad(Junta de Andalucía) AT17_5934_US

The application of compressor water injection in aeroengines is of renewed interest in the civil aviation industry. Water due to its unprecedented heat capacity has the potential to cool the engine air through evaporation and thus reduce the NOx emissions formed in a combustion process. It is well known that the evaporative cooling increases thermodynamic cycle efficiency and thus improves the fuel economy. A relatively unexplored area, however, is the entropy generation due to water phase change as well as the balance between the corresponding entropy yield and the savings from the cooling of the core compressor flow. Hence, little consensus in the literature exists on the ultimate effect of water injection on compressor efficiency. In this study, a numerical analysis of water injection on an axial transonic rotor was carried out. The compressor model was tested at near-peak efficiency conditions with and without water injection. The flow was analysed using the Eulerian-Lagrangian approach with two-way coupling and the k-ω Shear Stress Transport turbulence model with Reattachment Modification. A universal, second thermodynamic law approach to quantify the entropy generation is proposed and used to evaluate the compressor flow. Results show that evaporation can facilitate the compression process and does not impair the compressor efficiency if applied at favourable conditions. The entropy generation in droplet-laden flow scales according to the gains from cooling effect and losses due to the evaporation and increased friction in the fluid. Some of the discrepancies in the public domain could be addressed, showing that the observed improvement in compressor efficiency is highly sensitive to the entropy flux measurement location. Most benefits from water injection were observed at the rotor tip proving the case for part-span injection from an entropy balance perspective.

The present study is aimed at developing a numerical model to reproduce coupled hydro-mechanical processes associated with fault reactivation by fluid injection in low permeability rock, as part of the DECOVALEX-2019 project Task B. We proposed a modeling approach for simulating the processes using the TOUGH-FLAC simulator, and modeled a fault reactivation experiment conducted at Mont Terri Rock Laboratory in Switzerland. The first step of the study involved benchmark calculations considering a simplified fault plane and geometry. Fluid flow along a fault was modeled using elements of aperture-sized thickness on the basis of Darcy's law and the cubic law in TOUGH2, whereas the mechanical behavior of a single fault was represented by zero-thickness interface elements in FLAC3D upon which a slip and/or separation is allowed. A methodology to connect a TOUGH2 volume element to a FLAC3D interface element was developed for handling the hydro-mechanical interactions on the fault during fluid injection. Two different fault models for describing the evolutions of hydraulic aperture by elastic fracture opening and failure-induced aperture increase were considered in the benchmark calculations. In the coupling process, the changes in geometrical features and hydrological properties induced by mechanical deformation were continuously updated. The transient responses of the fault and host rock to stepwise pressurization were examined during the simulation. The hydro-mechanical behavior, including the injection flow rate, pressure distribution around the borehole, stress conditions, and displacements in normal and shear directions were monitored in the surrounding rock and along the fault. The results of benchmark calculations suggest that the developed model reasonably represents the hydro-mechanical behavior of a fault and the surrounding rock. This modeling approach was applied to the fault reactivation experiment of the Mont Terri Rock Laboratory. In this interpretive modeling, a parametric study was conducted to examine the effects of input parameters regarding in situ stress and fault properties on the hydro-mechanical responses of the fault to water injection. Then, an optimal parameter set to reproduce the field experiment results was chosen by trial-and-error. The injection flow rate and pressure response during fault reactivation closely matched those obtained at the site, which indicates the capability of the model to appropriately capture the progressive pathway evolution during fault reactivation tests at the site. The anchor displacements were overestimated by the model, but a fair agreement was obtained in terms of the order of magnitude and the variation tendency.

As a promising technique to reduce the in-cylinder temperature and exhaust temperature, mitigate combustion knock, improve combustion phasing and decrease NOx emissions, water injection applied on different types of engines has attracted extensive attention in recent years to further improve fuel economy and fulfill stricter emission regulations. Since mechanisms of water injection with different aims are distinct, benefits on engine performances and emissions are also varied. This paper intends to give a comprehensive review of water injection applied on the internal combustion engine. First, different implementations of water injection are introduced, followed by a detailed description of water evaporation processes. Second, mechanisms of the in-cylinder combustion process with water addition are discussed with respect to the heat release rate, knock tendency and emission formations. Next, recent works of water injection applied on different kinds of engines are reviewed with special attentions given to the comparisons of different implementations and injection parameters. Furthermore, comparisons and combinations of water injection with other advanced engine techniques are summarized. Finally, critical issues of current research on the water injection technique are discussed.

This paper discusses experimental and theoretical investigations about a re-designed co-rotation scroll machine, operating in compressor and expander mode. The machine has been tested under various operational conditions, with the aim to determine the influence of the input variables on the machine performance. A maximum internal isothermal efficiency in compressor mode of 53% was obtained, while an improvement of the internal isothermal efficiency in expander mode from 34% to 84% was achieved. In expander mode, a maximum internal shaft power of 4600 W was measured at a rotor speed of 41.6 Hz with a supply pressure of 6 bar. However, the mechanical losses reduce the net shaft power to 2.400 W. A deterministic model of the co-rotating machine in compressor and expander mode has been developed in order to understand the internal phenomena governing the machine performance. Using this model as an expander, the mechanical power, mass flow rates and exhaust temperatures were predicted within a range of ±9%, ±7%, and ±10 K respectively, compared to experimental data. Further, the evolution of the deterministic and semi-empirical leakage areas are compared concluding that they are in the same order of magnitude, independently of the operation mode and operational conditions.

The performance benefit of compressor water injection for a stand-alone jet engine has been investigated in previous work conducted by the authors, as well as other studies. For the same required thrust, the benefits include reduced specific fuel consumption, turbine inlet temperature and NOx emissions. The additional weight implication for aircraft (narrow and wide-body type) with their typical engine type (two and three-spool) for the varied range is investigated here. The emphasis of this study is to establish whether the performance benefit restricted to take-off and parts of the climb, offsets the additional weight penalty of the water injection system, onboard the aircraft. An in-house aircraft performance tool has been used and the changes in performance due to water injection are determined by an evaporation model previously developed. This study shows that the shortest range of 4 missions offers small overall fuel savings of 0.42% per flight cycle. The longest mission, in which the injection equipment is carried for longer (though mostly empty water tank), brings about an overall increase in fuel consumed, by about 0.05%. For the same range, the aircraft powered by a three-spool engine shows better performance. However, both aircraft equally benefit from landing and take-off NOx emission reductions of around 43%. Water Injection is shown to result in similar performance benefits as 25% take-off derate but without the penalties in fuel burn or increased take-off and climb times. Reductions in turbine inlet temperature obtained are worth considerable attention as a means of decreasing the direct operating costs of an airline.

The need for more fuel-efficient turbofan engines has led to a rise in compressor pressure ratio and turbine inlet temperature respectively. The latter has been possible with advancements in turbine blade technology. Nevertheless, this higher temperature during combustion increases the production of thermal Nitrogen Oxides. Contrary to this high-pressure, high-temperature aero-engine design trend, regulations are pushing towards capping or reducing emissions. Injecting atomised water into a jet engine is an alternative to mitigate Nitrogen Oxides that is applied extensively to stationary gas turbines. The application for jet engines is very limited and dates back to the early Boeing 707 and 747 for thrust augmentation. The focus of this study is to investigate the performance benefits of water injection when applied to 2 and 3-spool compressors, under a wide range of different environmental conditions, and for different injection properties. In this first paper, a thermo-analytical compressor model with water droplet investigations in the Lagrangian frame of reference is explored. The methodology is applied to two different engine architectures, representative of modern turbofan engines. This water injection study focuses on cooling the core and shows that the percent reduction in compressor discharge temperature is promising over a wider range of ambient conditions than expected. The effect of droplet sizes or quantity utilised were seen to be more influential. The 3-spool compressor also appears to benefit more from water injection, mainly due to the higher operating pressures and temperatures found on the Intermediate Pressure Compressor which enables more efficient evaporation, as compared to a booster compressor. Given the design of this compressor, two locations of injections were considered. Reductions in Compressor Discharge Temperature of 60 and 80 K were seen for the 2 and 3-spool engines, for a 2% injection ratio, accompanied by reductions in specific compressor work of 16 and 17%. Part 2 of this study has considered boundary conditions obtained here, to investigate the performance and emissions of complete jet engines.

Take-off and climb up to 3000 ft are the flight segments in which the aero-engine experiences the highest operating temperatures, which are known to be accompanied by a high production rate of Nitrogen Oxides (NOx). This contaminant has negative health implications on the human population, vegetation and wildlife that is in frequent proximity or exposure. Water injection into the compressor offers the possibility of reducing NOx. Nevertheless, limited studies have focused on the emissions reduction potentials and the wider questions of the influence of engine type and of wide-ranging ambient conditions. This study continues from Part 1 and explores the implications of the studied ambient conditions on the overall respective engine systems and their consequent emission reduction. An in-house gas turbine performance simulation software has been implemented to model and simulate the engine performance. For the emissions estimation, correlations were made from the information provided by the Engine Emissions Data Bank to quantify the reductions in Nitrogen Oxides. The 2 and 3-spool engine models investigated demonstrated significant reductions in compressor discharge and turbine inlet temperatures due to water injection. In this condition, the rotational speeds of the compressors are seen to be reduced to counter the mass flow augmenting effect of water injection and to satisfy the fixed thrust constraint. This along with lower compressor specific work brings about an improvement in the specific fuel consumption (5.3% and 7.8%, respectively) and general performance at low and high ambient temperatures. A higher advantage was seen for the 3-spool engine over the 2-spool as shown. Significant reductions in Nitrogen Oxide emissions of over to 50% are also demonstrated.

In most reservoirs with oil rims, as the production begins, the gas–oil and oil–water fluid interfaces start deforming because of the imbalance between viscous and gravitational forces, leading to coning or cusping. This can be overcome using proper withdrawal rate, offset from water–oil contact and horizontal length. Further smart horizontal wells require optimization of nozzle size and compartment length also. To see the effect of these parameters on recovery, a three-dimensional geological model of a clastic reservoir from Upper Assam Basin has been used. This model was history matched for a period of 16 years on 46 wells. After successful validation of model on field scale and well level, performance prediction was carried out to see the effect of withdrawal rate, offset from water–oil contact, horizontal length, compartment length and nozzle size using vertical/horizontal and ICD completion. From the analysis, it is evident that application of advanced well completion, ICD, is suitable for such reservoir. Depending on the scenario, maximum cumulative oil production was obtained from ICD wells with 1.08 MMm3 compared to vertical well with cum oil production of 0.63 MMm3. Economic analysis has been carried out for the examined scenarios.

Water injection wells often develop casing leaks that result in crossflow between two formations. The crossflow can be upward or downward depending on the respective location of each formation and the gravitation hydrostatic column between the formations. Traditionally, crossflow rates are measured by running production logs (flowmeter); a process that require well intervention. Such intervention in a well with compromised downhole integrity is not preferred as it incur additional cost and exposes the oilfield operator to possible mechanical risks such as stuck tools. In this work, we present a numerical method to predict crossflow rates without such intervention. The method requires readily available input from the water injection that includes injection flow rates and pressures, in addition, to shut-in well data. The workflow developed in this study includes nodal analysis and well performance modeling. A water injection well (Well-XYZ) was selected to validate the developed workflow as a case study in this paper. Well-XYZ has an upward crossflow that resulted from a downhole leak. The numerical method starts with building a well performance model before the leak develops. The injection data (pressure and flow rates) before leak development are used for this model. Second, a well with the same physical dimensions of Well-XYZ is imagined and modeled as a producing well from the downhole formation to the leak point. The shut-in well data of Well-XYZ are used to build the production well model. Third, we choose the leak point as the system node and obtain its pressure either by direct measurement or through calculation. Once the system node pressure is obtained, it is inputted as the wellhead producing pressure of the imagined well and its production rate will be the crossflow rate. The results of this method were tested by running a production log on Well-XYZ. The results of the production log showed that the method was able to accurately predict the crossflow rate with a less than 2% error.

15 pages, 5 figures, 2 tables.-- This is an open access article distributed under the Creative Commons Attribution License, The performances of three non-destructive sensors, based on different principles, bioelectrical impedance analysis (BIA), near-infrared spectroscopy (NIR) and time domain reflectometry (TDR), were studied to discriminate between unfrozen and frozen-thawed fish. Bigeye tuna (Thunnus obesus) was selected as a model to evaluate these technologies. The addition of water and additives is usual in the fish industry, thus, in order to have a wide range of possible commercial conditions, some samples were injected with different water solutions (based on different concentrations of salt, polyphosphates and a protein hydrolysate solution). Three different models, based on partial least squares discriminant analysis (PLS-DA), were developed for each technology. This is a linear classification method that combines the properties of partial least squares (PLS) regression with the classification power of a discriminant technique. The results obtained in the evaluation of the test set were satisfactory for all the sensors, giving NIR the best performance (accuracy = 0.91, error rate = 0.10). Nevertheless, the classification accomplished with BIA and TDR data resulted also satisfactory and almost equally as good, with accuracies of 0.88 and 0.86 and error rates of 0.14 and 0.15, respectively. This work opens new possibilities to discriminate between unfrozen and frozen-thawed fish samples with different non-destructive alternatives, regardless of whether or not they have added water., This research was funded by the SEATRACES Project (www.seatraces.eu, accessed on 24 November 2021) funded by the EU Interreg Atlantic Area Program (project number EAPA_87/2016)

This work analyzes NOx reduction in a marine diesel engine using ammonia injection directly into the cylinder and compares this procedure with water injection. A numerical model based on the so-called inert species method was applied. It was verified that ammonia injection can provide almost 80% NOx reduction for the conditions analyzed. Furthermore, it was found that the effectiveness of the chemical effect using ammonia is extremely dependent on the injection timing. The optimum NOx reduction was obtained when ammonia is injected during the expansion stroke, while the optimum injection timing using water is near top dead center. Chemical, thermal, and dilution effects of both ammonia and water injection were compared. The chemical effect was dominant in the case of ammonia injection. On the other hand, water injection reduces NOx through dilution and, more significantly, through a thermal effect.

Re-entrant jet causes cloud cavitation shedding, and cavitating vortical flow results in flow field instability. In the present work, a method of water injection is proposed to hinder re-entrant jet and suppress vortex in cloud cavitating flow of a NACA66 (MOD) hydrofoil (Re = 5.1 × 105, σ = 0.83). A combination of filter-based density corrected turbulence model (FBDCM) with the Zwart–Gerber–Belamri cavitation model (ZGB) is adopted to obtain the transient flow characteristics while vortex structures are identified by Q criterion & λ2 criterion. Results demonstrate that the injected water flow reduces the range of the low-pressure zone below 1940 Pa on the suction surface by 54.76%. Vortex structures are observed both inside the attached and shedding cavitation, and the water injection shrinks the vortex region. The water injection successfully blocks the re-entrant jet by generating a favorable pressure gradient (FPG) and effectively weakens the re-entrant jet intensity by 46.98%. The water injection shrinks the vortex distribution area near the hydrofoil suction surface, which makes the flow in the boundary layer more stable. From an energy transfer perspective, the water injection supplies energy to the near-wall flow, and hence keeps the steadiness of the flow field.

Reducing fuel consumption and thus CO2 emissions is one of the most urgent tasks of current research in the field of internal combustion engines. Water Injection has proven its benefits to increase power or optimize fuel consumption of passenger cars. This technology enables knock mitigation to either increase the engine power output or raise the compression ratio and efficiency while enabling λ = 1 operation in the complete engine map to meet future emission targets. Current systems have limited container capacity. It is necessary to refill the water tank regularly. This also means that we cannot get the benefits of an engine with a higher compression ratio. For this reason, the self-contained system was investigated. This article is a methodology for finding the right design of a self-contained water injection system, but also a vehicle test that proves the function.

The potential benefits of water injection on performance and emissions were investigated on a downsized PFI twin-cylinder turbocharged spark ignition engine. Experiments were carried out at high load condition (~15.5 bar IMEP) within the engine speed range from 3500 to 4500rpm with a step of 500 rpm. For each test case the effect of the injected water quantity on combustion and exhaust emissions was investigated by sweeping from 10%w to 30%w the water to gasoline ratio. The water was injected at the same timing as the gasoline by a low pressure injection system external controlled. Tests were performed at WOT conditions exploring, for each operating condition, a spark sweep from knock-free up to knock-limited operation. Compared to the full gasoline reference case, the water injection allowed to advance extensively the spark timing without knock occurrence. The 20% water to gasoline mass fraction gave the best improvements in terms of IMEP. The reduction of combustion temperature, due to the water injection, coupled to the spark timing advance without knock, led to a stable reduction of the temperature at the turbine inlet.

Efficient compressed air energy storage requires reversible isothermal compression and expansion devices. The isothermal compression and expansion processes can either be approached by several stages with intercooling or by the more convenient injection of a liquid, often water. While volumetric machines are readily available for dry processes the compression and expansion of a gas with the presence of liquid is still problematic. The concept of a co-rotating scroll has been identified as a promising technology to cope with the presence of liquid. The current paper discusses the first experimental results of an oil-free co-rotating scroll prototype tested in expansion mode on a wide range of rotational speeds, varying water injection flow rates and with different nominal flank clearances. A maximal overall isothermal efficiency of 34% and a maximum output power of 1.74 kWel were measured with this first prototype, providing the proof of the technical feasibility of the oil-free co-rotating scroll expander concept. The experimental data indicate a positive effect of water injection suggesting good heat transfer behaviour between the water and the air in the individual chambers, which is a result of the relatively long residence time compared to other volumetric concepts. The experimental sensitivity analysis yields a strong dependency of the machine performance on both the nominal flank clearance and on the injected water rate. The analysis through a semi-empirical model suggests the inversion of a classical trend, i.e. the increase in total leakage area with rotor speed. This is resulting from the centrifugal loads acting on the flanks and deforming them to produce increased radial and flank clearances. The injection of water is suggested to significantly decrease the leakage. A deterministic reduced order model of the co-rotating scroll expander was developed in order to better understand the governing phenomena within the machine and to provide design guidelines for further prototypes. A novel leakage model takes into account for the structural deformation of the flanks and the scroll involutes as a result from the rotor speed. By means of this comprehensive thermodynamic model, mechanical power, mass flow rate and exhaust temperature were predicted within a range of ±12% and ±4 K respectively compared to experimental data. The calibrated model suggests an achievable isothermal efficiency of 87% for an improved co-rotating scroll concept, thus offering promising perspectives not only for compressed air storage, but also for wet expansion in Absorption Power Cycles, trilateral flash cycle and Organic Rankine Cycles.

In this study, an experimental investigation was conducted to assess the combustion and emissions of a single cylinder diesel engine using water injection in the exhaust manifold. Water is injected into the exhaust manifold and by opening the exhaust valve during the intake stroke, the injected water, and exhaust gases are reentered the engine cylinder then mixed during the intake and compression stroke and participated in the combustion process. The purpose of this injection strategy is to utilize the exhaust gases enthalpy to evaporate water before combustion to reduce soot and NO x emissions without decrease combustion temperature. The results show that water injection leads to increase in the cylinder pressure, apparent heat release rate (AHRR) in premixed combustion phase and, the ignition delay comparing with EGR without water injection. The indicated mean effective pressure (IMEP) for EGR without water injection is lower than conventional diesel combustion with 14%. However, with water injection, the IMEP increased with 11% comparing to EGR without water injection. NO x emissions reduced up to 85% comparing to conventional diesel combustion due to the EGR effect. Soot concentration increased dramatically with EGR. However, with water injection, soot emissions reduced by up to 40% but still higher than conventional diesel combustion.

It is well known that the downsizing philosophy allows the improvement of the brake specific fuel consumption (BSFC) at part load operation for spark ignition (SI) engines. On the other hand, the BSFC is penalized at high load because of the knock occurrence and of further limitations on the turbine inlet temperature (TIT). Knock control forces the adoption of a late combustion phasing, causing a deterioration of the thermodynamic efficiency, while the TIT control requires the enrichment of the air-to-fuel ratio (A/F), with additional BSFC drawbacks. In this work, two promising techniques are investigated by a 1D approach with the aim of improving the fuel economy of a turbocharged SI engine at full load knock-limited operation. The first technique is the recirculation of low-pressure cooled exhaust gas (EGR), while the second is the injection of liquid water at the intake ports. Proper “in-house developed” sub-models are used to describe the turbulence, combustion and knock phenomena. The effects of the above techniques are studied in six operating points at full load and different speeds for various A/F levels and inert content, by varying the EGR rate and water-to-fuel ratio. The presented results highlight that both the solutions involve significant BSFC improvements, especially in the operating conditions at medium engine speeds. In fact, the introduction of inert gas in the cylinder contributes to reduce the knock tendency, resulting in the possibility to advance the combustion phasing and reduce, or even avoid, the mixture over-fuelling. The heat subtracted by the water evaporation enhances the above effects, resulting in an improved fuel economy. However, the BSFC advantages are limited by the maximum allowable in-cylinder pressure, TIT, turbocharger speed, and boost level. The developed numerical procedure is able to take into account the complex interactions among different driving parameters affecting the engine behaviour. It can be hence very useful to define a numerical engine pre-calibration and to realistically predict the EGR- and water injection-related BSFC advantages.

This work models the impact of direct water injection on the combustion process in a spark ignition engine. It uses a two-zone kinetic model coupled with detailed combustion chemistry to highlight the thermodynamic and chemical-kinetic interactions between gasoline combustion and water injection. The modelling results agree closely with measurements from a highly boosted, direct injection gasoline engine. This study first proposes an approach to model the mass fraction burned (MFB) profile using a representative in-cylinder pressure trace. The derived MFB profile is then used as the input for a two-zone kinetic model. Within this model, predictive kinetic modelling is used to estimate the knock limited spark advance (KLSA) for a baseline engine operating condition without water injection and subsequently, for several conditions with water injection. Predicted KLSA values obtained using this method agree closely with measured results. Utilising the approach developed in this study, the modelled MFB profile at the baseline operating condition was found to be similar to that obtained at the condition with a water/fuel ratio (WFR) of 60%. This result is likely due to the competing and contrasting effects of reduced in-cylinder temperature versus more advanced combustion phasing at conditions with water injection. Further thermodynamic analysis shows that the charge cooling effect afforded by direct water injection is much greater than the dilution effect in terms of advancing the knock limited combustion phasing. Water injection also affects the kinetic processes that take place in the unburned gas zone, but mainly by altering the in-cylinder thermodynamic conditions – the injected water is not directly involved in the low temperature chemistry in the unburned gas zone, it simply acts as a collision partner.

We present results from an international model comparison study involving a series of controlled fault activation experiments in Opalinus Clay at the Mont Terri Laboratory, Switzerland. The fault activation experiments were conducted in situ by water injection at variable pressure from boreholes targeting different parts of the Main Fault crossing several tunnels and galleries of the Mont Terri Laboratory. The model simulations focused on (1) an experiment activating a discontinuity (fracture or minor fault) within the damage zone of the main fault, and (2) an experiment activating discontinuities close to the core of the Main Fault. The experimental data consist of coupled hydraulic and mechanical responses monitored at an injection borehole and a monitoring borehole located a few meters away. After overcoming several modeling issues along with necessary model developments, a reasonably good agreement was achieved between the modeling results and the field observations. The fault activation experiments displayed an abrupt flow rate increase associated with a sudden fracture opening and rupture propagation after the injection pressure reached above the estimated normal stress on the fracture. This was followed by an abrupt flow rate decrease, indicating hydraulic closing, once the injection pressure decreases to an estimated 1–2 MPa below the stress normal to the opened fracture. The models were able to capture this abrupt hydromechanical behavior, including an observed dominant opening behavior along with the rupture propagation, while the spatial extent of the shear rupture and the quantity of peak injection flow were the most challenging to predict.

Within the context of increasing boost pressure and application of alternative methods for controlling knock, the present study scrutinized the effects of water injection on combustion characteristics and emissions. Conditions of wide open throttle and fixed spark timing were investigated in an optically accessible unit, that featured a UV-enhanced window-mirror combination fitted in an elongated piston configuration. Commercial gasoline was used in the direct injection fuel system, while water was delivered to the intake manifold. Engine performance was found to feature a slightly decreasing trend when increasing the injected water quantity in three steps, at 10, 20 and 30% of the mass flow of gasoline. Nonetheless, the maximum drop in indicated mean effective pressure was below 2%, even though the spark timing was kept constant. Changes in combustion stability were negligible. Thermodynamic analysis was coupled with cycle-resolved flame visualization and spectroscopy. The latter technique allowed the radiative emission related to sodium to be directly associated with the injected water quantity, thus allowing further detailed evaluations correlated with evaporation effects. Flame front characteristics confirmed minor effects on combustion evolution, with a slight increase of wrinkling when water flow was augmented. Finally, quasi-dimensional modelling allowed evaporated water quantities to be estimated at the time of ignition and during combustion.

The high temperature and high pressure supersonic jet is one of the key problems in the design of solid rocket motors. To reduce the jet temperature and noise, cooling water is typically injected into the exhaust plume. Numerical simulations for the gas-liquid multiphase flow field with mixture multiphase model were developed and a series of experiments were carried out. By introducing the energy source terms caused by the vaporization of liquid water into the energy equation, a coupling solution was developed to calculate the multiphase flow field. The temperature data predictions agreed well with the experimental results. When water was injected into the plume, the high temperature core region area was reduced, and the temperature on the head face was much lower than that without water. The relationship between the reduction of temperature on the bottom plate and the momentum ratio is developed, which can be used to predict the cooling effect of water injection in many cases.

International journal of engine research 17(1), 86-96 (2016). doi:10.1177/1468087415599867, Published by Sage Publications, London

วารสารวิชาการและวิจัย มทร.พระนคร สาขาวิทยาศาสตร์และเทคโนโลยี, 12, 1, 125-136

Water injection is a well-known efficient way to improve the performance of internal combustion engines. Amazingly, most of previous studies have yet only assess this process in an experimental manner, depriving us of an understanding of its specific influence on different operating phases of the engine (density of the aspirated fresh mixture, work required by the compression stroke, and so on) but also of the possibility to predict its effects if set up on an existing engine. Thanks to a theoretical framework specifically developed, and similar to the one commonly used for the analysis of air conditioning systems, we start in this paper to untangle in a theoretical manner the different consequences of water injection on internal combustion engines.This first study is specifically focused on the fresh mixture density increase, due to the vaporisation of liquid water in the intake manifold. Results show that, in the best scenarios, we cannot expect to increase the amount of fuel finally aspirated into the cylinders by more than 10%. The methodology presented here, as well as the python software specifically developed, can be of a precious help for the optimisation of such process if applied to existing or future engines.

Water injection in highly boosted gasoline direct injection (GDI) engines has become an attractive area over the last few years as a way of increasing efficiency, enhancing performance and reducing emissions. The technology and its effects are not new, but current gasoline engine trends for passenger vehicles have several motivations for adopting this technology today. Water injection enables higher compression ratios, optimal spark timing and elimination of fuel enrichment at high load, and possibly replacement of EGR. Physically, water reduces charge temperature by evaporation, dilutes combustion, and varies the specific heat ratio of the working fluid, with complex effects. Several of these mutually intertwined aspects are investigated in this paper through computational fluid dynamics (CFD) simulations, focusing on a turbo-charged GDI engine with port water injection (PWI). Different strategies for water injection timing, pressure and spray targeting are investigated. Two combustion modeling approaches are used and compared, the perfectly stirred reactor model with reduced chemical kinetics for a TPRF surrogate, and the G-equation turbulent combustion model. Combustion rate results are validated against available experimental engine data, in regular and knocking conditions. Multi-cycle simulations are required because of the wall film dynamics, and therefore have been performed to assess the effect of water injection strategies. The results of the study are an assessment of the optimal injection parameters, in terms of injector location, injection timing and primary atomization quality, for achieving the maximum effectiveness of water injection. Knock occurrences are in very good agreement with the experimental data and its suppression is demonstrated through the injection of water at a ratio of 30% to the fuel mass.

The objective of this study was to compare the injection and spray characteristics of water with n-heptane using a port fuel injection (PFI) system. In this study, the injection pressure was changed to 0.3–0.9 Mpa and the energizing duration was changed to 0.5–4 ms. To investigate spray characteristics, the injection quantities of n-heptane and water were measured. Macroscopic spray characteristics were determined through spray visualization. The Sauter mean diameter (SMD) and velocity of spray droplets were measured with a phase Doppler anemometry (PDA) experiment. Spray tip penetration, spray angle, SMD of droplets, and spray droplet velocity were compared. As the injection pressure increased, the injection quantity and the droplets velocity increased. However, the spray tip penetration, SMD of the droplet, and the spray angle decreased. The increase in energizing duration led to an increase in the injection quantity without affecting other spray characteristics. The higher density of water also increased injection quantity, resulting in a decrease in spray tip penetration and increases of SMD and velocity of spray droplets due to high viscosity and surface tension of water.

The effect of erythorbic acid (EA) on the aqueous formation of CdS quantum dots (QDs) at room temperature was explored in this work. Without N2 protection, CdS QDs were synthesized in water by a one-pot non-hot-injection approach at room temperature. The Cd and S sources were CdCl2 and Na2S, respectively, together with 3-mercapto-propionic acid (MPA) as the passivating ligand. The experimental results indicate that the use of the oxygen scavenger, i.e., EA, was critical for the formation of the CdS QDs with reasonably good optical properties, and it is also important to tune experimental parameters such as MPA-to-Cd molar ratios, pH, and reactant concentrations. The mechanism about the EA promoted formation of CdS QDs was discussed in terms of NMR, IR, in situ absorption, and photoemission studies. The very reason for the EA promoted formation of CdS QDs is due to its reducibility and passivation on the QD surface (particularly in alkaline environment). The present study suggests that the use of EA could be a practical means to enable the room-temperature formation of QDs in water. © 2014 Elsevier B.V.

Heat extraction by cold water circulation disturbs the thermo-chemical equilibrium of a geothermal reservoir, activating the dissolution/precipitation of minerals in the fractures. Calcite being a more reactive mineral than other rock minerals composing the earth curst, we investigate the permeability alteration during geothermal heat production from carbonate reservoirs. In this study the simulations are performed using the code FEHM with coupled thermo-hydro-chemical (THC) capabilities for a three dimensional domain. The computational domain consists of a single fracture connecting the injection and production wells. For reactive alteration of aperture, the model considers that the kinetics of dissolution/precipitation is coupled to the equilibrium interactions among the aqueous species/ions. The reaction rate predominantly depends on the temperature dependent solubility and advective-dispersive solute transport in the fracture. Due to the nonuniform flow fields resulting from injection and production, the coupled thermo-hydro-chemical processes initiate significant variation of the aperture alteration rate over the fracture. We have considered different operating conditions such as different mass injection rate, injection temperature and concentration of minerals. Our simulations show that dissolution and precipitation can occur simultaneously at different locations in fracture. Furthermore the reaction rate varies with time and the reaction rate can also switch between dissolution and precipitation. To illustrate this interesting behavior, the variations of shape and size of zero reaction rate contours with time are shown. An interesting outcome is a non-monotonic evolution of the overall transmissivity between the wells. The alteration of overall transmissivity largely depends on the concentration of mineral in the injected water with respect to the solubility at the initial fracture temperature. For both dissolution and precipitation controlled cases, the rapid changes in transmissivity provide challenges for maintaining circulation of water at constant mass flow rate. � 2013 Elsevier Ltd.

We reviewed published results from six projects where hydraulic stimulation was performed in granitic rock. At each project, fractures in the formation were well-oriented to slip at the injection pressures used during stimulation. In all but one case, thousands of cubic meters of water were injected, and in every case, flow rates on the order of tens of liters per second were used. Despite these similarities, there was a large variation in the severity of induced seismicity that occurred in response to injection. At the three projects where induced seismicity was significant, observations at the wellbore showed evidence of well-developed brittle fault zones. At the three projects where induced seismicity was less significant, observations at the wellbore indicated only crack-like features and did not suggest significant fault development. These results suggest that assessments of the degree of fault development at the wellbore may be useful for predicting induced seismicity hazard. We cannot rule out that the differences were caused by variations in frictional properties that were unrelated to the degree of fault development (and it is possible that there is a relationship between these two parameters). The projects with more significant seismicity tended to be deeper, and if this is a meaningful correlation, it is unclear whether depth influenced seismic hazard through the degree of fault development, frictional properties, or some other variable. The results of this paper are not conclusive, but they suggest that there may be significant opportunity for future research on identifying geological conditions that increase induced seismicity hazard.

Over the past few years several geochemical evaluations of CO2 storage in Dutch potential reservoirs are carried out, including predictions of the short- and long-term impact of CO2 on the reservoir using geochemical modelling. The initial mineralogy of the reservoir is frequently obtained from core analysis and is then used to compute the formation water composition. In this paper geochemical modelling with TOUGHREACT is used to predict and compare the short- and long-term geochemical impact of CO 2 injection into three reservoirs. The mineralogical composition of these reservoirs is an assemblage based on commonly observed minerals from the Buntsandstein and Rotliegend formations. These formations contain potential onshore and offshore CO2 storage locations in the Netherlands. The results predict drying out and salt precipitation in the near-well area, due to water evaporation by the injected dry CO2. Several mineral transformations are predicted, dominated by the transformation of albite into dawsonite, thereby fixing CO2. Due to the relatively low density of dawsonite, the porosity significantly decreases, which can lead to a pore pressure increase. Disabling of dawsonite precipitation in the simulations, thereby taking into account the ongoing debate on dawsonite stability, only shows a small increase of the porosity. Future (experimental) work should be focused on dawsonite occurrence for accurate predictions of the long-term reservoir integrity. © 2011 Published by Elsevier Ltd.

One of the most important characteristic signatures of the exhaust plume from rocket motor is the afterburning phenomenon, and the injected water into the plume could inhibit the afterburning. The calculation model for the gas-liquid multiphase flow field with chemical reaction in the plume is built. By inducing the energy source terms caused by the vaporization of liquid water, condensation of the vapor and chemical reaction in the energy equation, the gas-liquid multiphase flow field and the afterburning phenomenon are calculated in a coupling way. Mixture multiphase flow model is used to calculate the gas-liquid flow field, and the vaporization mechanism is used to investigate the water vaporization process. The temperature contours are obtained and accord well with the experimental photos. The mass fraction contours of primary species are obtained, which can indicate the extent of inhibition effect of water injection on the afterburning phenomenon in the plume. When water is injected into the plume, the region of afterburning reduces a lot, and temperature on the ground wall declines rapidly, which can decrease the ablation of the combustion gas to the launch ground.

Reservoir depletion and subsequent CO2 injection into the depleted geological reservoir induce stress changes that may mechanically damage top seal and wells, or trigger existing faults, creating the leakage pathways for CO2 escape from the reservoir. The role of geomechanics is to assess the mechanical impact of stress changes on seals, wells and faults. Since many hydrocarbon fields are geometrically complex and irregular, and the rock properties are spatially variable, such an assessment can be conveniently done with a numerical modeling of the field. Based on numerical analyses, recommendations can be given regarding the overall suitability of the depleted geological reservoir for CO2 disposal and safe CO2 injection. © 2009 Korean Society of Civil Engineers and Springer-Verlag Berlin Heidelberg GmbH.

This paper describes an experimental investigation of the effect of transverse liquid injection (distilled water) on the acoustic field generated by confined supersonic flow past a cavity. The effect of cavity depth in the absence/ presence of liquid injection on the acoustic field is studied. In the presence of liquid injection, the effects of injection pressure and injection location on the acoustic field are investigated. The dependence of suppression/amplification of the acoustic amplitudes (compared with the absence of injection) on the injection condition and cavity depths is ascertained. In general, liquid injection in the presence of cavity resulted in higher amplitudes. Even square cavities that did not exhibit oscillations in the absence of injection generated significant acoustic amplitudes in the presence of liquid injection at high injection pressures. Phase-locked schlieren imaging was performed to sequence the fluiddynamic events. Schlieren images indicate the interaction of the shock wave generated by the flow past the liquid jet and the oblique shock generated at the cavity-leading edge. The schlieren images show that the amplitude increase observed for higher injection pressures for a range of cavity depths is accompanied by an unsteady normal shock ahead of the cavity-leading edge (which does not span the entire width of the test model, but is located locally in front of the liquid jet). Copyright � 2008 by T. K. Ganesh Anavaradham, R. I. Sujith, O. J. Shreenivasan, S. R. Chakravarthy, and S. Panneerselvam. Published by the American Institute of Aeronautics and Astronautics, Inc.

Twin-shaft screw-type expanders offer a high potential for energy conversion in the lower and medium power range, for instance as expansion engines in Rankine cycles for exhaust heat recovery. With regard to minimizing internal leakages and lubricating moving machine parts, an auxiliary liquid or liquid working fluid can be fed to the screw expander. In this paper, indicator diagrams of a twin-shaft screw-type expander prototype designed at the Chair of Fluidics at TU Dortmund University are presented and analyzed in detail. The experimental investigations are carried out at a hot-air test rig with expander inlet manifold water injection. The time-dependant working chamber pressure is recorded by means of high-resolution absolute pressure transmittters. Hereby, specific aspects of working chamber pressure measurements are mentioned. Based on the indicator diagrams, relevant influence mechanisms on the expander's operational behavior resulting from water injection are determined. Additionally, the impact of the injected water on the volumetric and isentropic efficiency is presented.

In the production well of a low-enthalpy geothermal doublet hot water is pumped from reservoirs at about 50-1007deg;C. After passing through a heat exchanger, the cold water is re-injected at about 20-357deg;C in the injection well into the reservoir, which initially has the same temperature as the produced water. Under some circumstances, this may lead to the initiation of thermal fractures around the injection well, an effect known from water injection in oil wells. This will increase the productivity index (PI), thereby also increasing the efficiency and profitability of the doublet. Using a simple analytical approach, we studied whether thermal fractures are theoretically expected under typical reservoir and injection conditions. From data at high temporal resolution of two geothermal doublets were studied over a longer period of injection to check if the development of a thermal fracture is observed The conclusion that can be drawn from the calculations is that cold fractures hardly develop under the assumed conditions. However, the uncertainty on the pressure estimation necessary for the fracture calculation is relatively large. Possible fracture development is very sensitive to value of the minimum horizontal stress and lowering by 10% allows the initiation of fractures in both doublets.

The flow of particulate suspensions and brines in porous media is encountered in a wide range of industrial situations such as oil production, soil erosion, and ground water pollution and in the operation of filter beds. Three major classes of such problems are addressed in this paper, namely particle movement, deposition and filtration. Particle movement and deposition are known to be serious problems in oil reservoirs where incompatible brine is brought into contact with the formation. Dramatic reductions in permeability are observed in such cases due to the release of fine particles that subsequently plug flow channels downstream. An experimental investigation was undertaken to look into the possible causes of the injectivity loss in a typical Iranian oilfield. Glass bead and sand beds were used to study the general behavior of fine particle movement and deposition in porous media. The experiments were conducted with injection rates from 12.5 to 200 cm3/min. Aluminium oxide particles were suspended in the injected water to simulate fine particle migration in porous media. The particles were injected at concentrations ranging from 15 to 2000 ppm. It was observed that the build-up of flow resistance was mostly due to frontal face plugging. In subsequent experiments, aluminium oxide particles were added to the glass beads to study the effect of particles initially present in the glass bead pack. A mathematical model is presented that simulates the porosity impairment by particle movement and deposition. This model is based on the mass balance of particles flowing through the porous medium, and predicts the initial porosity and subsequently its reduction with time. The equations are relatively general and can be used to model the permeability reduction for any given pore or particle size distribution.

In this numerical study, the cooling of exhaust gas issued from a rocket engine in a ground test facility has been investigated by solving the three-dimensional governing equations. Simulations have been performed by employing discrete phase model with plain-orifice atomizer to cool the exhaust flow effectively by injecting the coolant (water) in the form of a fine spray. The effects of coolant flow rate, inlet gas temperature, injection pressure, injector diameter, gas cooler length, and distribution of water droplets on the cooling characteristics, such as the temperature at the gas cooler exit, droplet diameter, and percentage of unevaporated water have been discussed in detail. Simulations highlight that optimum particle diameter needs to be identified for effective cooling, and also uniform cooling of the exhaust gas is attained by employing staggered injector distribution (more injectors at the periphery compared to the core region). Predicted values of static temperature and pressure agree well with the experimental data obtained from a scaled-down model high-altitude test facility. � 2014 American Society of Civil Engineers.

In this study experiments are conducted on the flow within a horizontal pipe with two closed side branches of equal length. This configuration is referred to as "quasi-cross configuration" as the distance between the two closed side branches is much smaller than the acoustic wavelength of the first acoustic mode. Focus is placed upon investigating of the effect of high amounts of injected water on Flow-Induced Pulsations (FIPs). A first test with only dry air is performed and pressure fluctuations are measured at the closed end of each side branch to investigate FIPs. Several tests are conducted with increasing amounts of water, in droplet form, which is injected with a nozzle positioned upstream the branches. To understand the effect of the multiphase flow pattern, tests are performed with the injector located far from and close to the side branches. With far injector and at low injection rates, no decrease of pulsations is observed while the amount of injected water increases. At high injection rates, a shift of the pulsation peak to lower velocities and an increase of the Strouhal number calculated by using the diameter of the side branch and the superficial gas velocity are reported. With close injector, pulsations are eliminated as the injection rate increases. At low injection rates, an increase of the Strouhal number is also observed.