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Aiming at the problem of low turbulent velocity and incomplete combustion in the combustion process of the Wankel rotary engine (WRE), and setting turbulence‐induced blade (TIB) in the combustion chamber recess is an effective means to enhance the turbulent motion and promote combustion. Carifying the optimal arrangement position of TIB can get better combustion performance. Therefore, a computational fluid dynamics (CFD) simulation model of a WRE with TIB was established in this paper. Based on the differential pressure perturbation mechanism, the influence of the arrangement position of the TIB on the flow field and combustion performance were analyzed. The results showed that when the ratio of blade arrangement distance is less than 0.66, the pressure difference between the leading and trailing of the blade is small. At this time, the in‐cylinder flow is mainly disturbed by the forced disturbance of the TIB, the increase of the turbulent velocity is not obvious, and the diffusion velocity of the flame to the rotor direction is small. When the ratio of blade arrangement distance is greater than 0.66, the pressure difference between the leading and trailing of the blade is large. At this time, the In‐cylinder flow is affected by the pressure difference flow in addition to the forced disturbance of the TIB. The turbulent velocity is effectively enhanced, and the flame velocity is fast to the rotor direction. When the ratio of blade arrangement distance is 0.66, it shows the best combustion performance, and the indicated work is the largest. Compared to the scheme without TIB, the indicated work is increased by 16%. [ABSTRACT FROM AUTHOR]

In this study, a method for the monitoring of internal combustion engine operation by vibration signals is proposed. The work falls within the context of the increasingly stringent standards relating to the environmental impact of engines and the development of monitoring and control techniques to ensure increased engine performance as well as fuel saving and reduction of pollutant emissions. Experimentation was performed on a turbocharged light-duty compression ignition direct-injection engine. Two monoaxial accelerometers were installed on the engine compressor case, the speed of which has been demonstrated to be closely related to the engine operation. Vibration measurements of the engine compressor case have been processed by combining the Empirical Mode Decomposition technique with Independent Component Analysis and Short Time Fourier Transform to indirectly estimate the turbocharger speed. The obtained traces have been compared to the direct turbocharger velocity measures during the stationary running of the engine (speed and load conditions varied in the complete engine's range of operation). The results point out the potentiality of the methodology in algorithms devoted to identifying modifications of the combustion development regarding regular operation via indirect turbocharger speed monitoring. [ABSTRACT FROM AUTHOR]

Increasing efficiency while reducing emissions leads to high mean effective pressures, high compression ratios and increasingly lean operation for spark ignited large gas engines. Despite these boundary conditions, gas engines must be operated between knocking and misfiring at low cycle-to-cycle fluctuations. The excess air ratio and the ignition process of the lean mixture greatly influence the stability of the combustion process. To enable sufficiently low cycle-to-cycle fluctuation of the combustion process despite the ever increasing excess air ratio levels, it is necessary to understand and investigate the sub-areas of the engine process, for example, ignition, flow condition and mixture formation. This paper focuses on one sub-area of conventional spark ignition, the influence of the electric arc root position on the origin and stretching of the electric arc, because electric arc behavior is considered important in the subsequent combustion process. The results show that electric arc roots on the downstream end of the electrodes tend to enable a longer electric arc length at the first electric arc short circuit (i.e. the first abrupt shortening of the electric arc during its spark duration) than electric arcs with electric arc roots on the upstream ends of the electrodes. [ABSTRACT FROM AUTHOR]

Methanol is a promising alternative fuel due to its wide availability of raw materials, mature production processes, and low production cost. However, because of the low cetane number, methanol must include a more reactive fuel to assist with combustion when used in compression ignition (CI) engines. In this study, based on the optical CI engine platform, methanol is injected into the intake port, and diesel is directly injected into the cylinder to achieve dual-fuel combustion. The effects of the methanol energy ratios and diesel split injection strategies on combustion are investigated. The results show that the premixed blue flame was mainly concentrated in the near wall region, whereas the yellow flame produced by diesel combustion tended to concentrate in the central region as the methanol energy ratio increased. When the methanol energy ratio exceeded 50%, the ignition delay was significantly prolonged, while the flame area was greatly reduced. Meanwhile, the peak values for the cylinder pressure and heat release rate decreased significantly, indicating a significant deterioration in combustion. At the earlier diesel pre-injection timing at −58°, the overall dual-fuel combustion at each main injection timing exhibited low-temperature premixed combustion characteristics, with a lower peak exothermic rate and flame brightness. At the later pre-injection timing at −33°, the spray flame at all main injection timings could be observed, with higher peak heat release rates and indications of thermal efficiency. Combustion at later main injection timings was characterized by diffusion combustion, and the main injection timing could effectively regulate the combustion process through phase adjustment. [ABSTRACT FROM AUTHOR]

The article carries out a detailed analysis and evaluation of indicators related to the combustion process (pressure and temperature in the engine combustion chamber, heat release rate, heat release fraction) in a JCB 444 TA4i compression-ignition engine fuelled with diesel and hydrogenated vegetable oil (HVO). During the empirical tests, the operation of the exhaust gas recirculation (EGR) system was stopped, and no other changes were made to the engine settings (factory settings were used). In the first stage, the empirical tests were carried out on the speed characteristics of an engine dynamometer. Then, an experiment was carried out at the engine crankshaft speed corresponding to the maximum torque - which consisted of determining the indicators related to the combustion process at a constant mass flow of fuel: diesel and HVO fuel. This provided information on the effect of hydrogenated vegetable oil on the combustion process in relation to the diesel engine feed. The conclusions drawn from the empirical study can be used to develop guidelines to change the operating map of a compression-ignition engine when it is fed with hydrogenated vegetable oil. [ABSTRACT FROM AUTHOR]

Here in we report the nanocrystalline Ni1-xCdxNdyFe2-yO4 (0 ≤ x ≤ 1.0 in steps of 0.2: y = 0.0; 0.1) ferrites were synthesized by novel solution combustion technique. The sintered powders have been characterized by X-ray diffraction (XRD), Fourier transmission infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), Energy dispersive analysis by x-rays (EDAX) methods. DC electrical conductivity carried out by two probe method. Magnetic parameters were measured using vibrating sample magnetometer with an applied magnetic field up to 15 kOe at 300K. The XRD results confirmed the formation of single phase cubic spinel structure formation. It was found that the lattice parameter increased with increase in Cd2+ ion. The crystallite sizes have been found in the range of 44.24 nm–15.467 nm. Moreover, the formation of two prominent absorption bands confirmed the spinel structure. The SEM micrographs evidenced almost spherical shaped, agglomerated and grainy structure of nanoferrites. Moreover, the Curie temperature (TC) was decreased with increasing temperature and exhibit the semiconducting behaviour. Further, saturation magnetization (MS), remanence magnetization (Mr); coercivity (HC) were decrease with increase in the magnetic field. The magnetic parameters; MS, Mr, nB increases attain maximum thereafter decreases with increase in Cd2+ ion and Nd3+ ion content.

This article presents the possibility of improving combustion using the effect of releasing hydrogen from a solution with nucleation of gas bubbles. This concept consists in dissolving hydrogen in diesel fuel until the equilibrium state of the solution is reached. At a later stage, the phenomenon is reversed, and this gas is released from the solution during its injection into the combustion chamber with a strong swirl. A characteristic feature of the solution is that when lowering the pressure (opening the atomizers), there is a decrease in the equilibrium thermodynamic potential, which results in the excess, dissolved hydrogen being released spontaneously, and this process is of a volumetric nature. This article is a continuation of the work carried out at Poznan University of Technology on the development of this concept. This article presents the results of tests for the impact of hydrogen dissolved in diesel fuel on the combustion process within a turbulent-flow environment. The tests were conducted in the combustion chamber of an engine equipped with a toroidal combustion chamber and direct injection. During the tests, the following factors were measured: the main indicators of motor operation, emission of hydrocarbons, carbon monoxide, nitrogen oxides, and particulate matters. [ABSTRACT FROM AUTHOR]

In this study, this process has been modeled and optimized using the design of experiment technique and response surface methodology (RSM). The RSM was employed to optimize the combustion process in the cement kiln. Kiln feed (X1 = 160–190 t h−1), fan speed (X2 = 840–870 rpm), kiln rotational speed (X3 = 2.8–3.4 rpm), kiln fuel rate (X4 = 3800–4150 L h−1), calciner fuel rate (X5 = 5700–6200 L h−1), pressure of kiln inlet (X6 = 98–102 Pa), and limestone saturation factor (LSF) (X7 = 94–95.8 %) as independent variables were investigated. The carbon monoxide and the kiln body temperature in RSM were considered as response variables. The absolute average error in the model predictions for the combustion process in the cement kiln, for the kiln body's temperature, is about 1.6 % and for carbon monoxide is about 15.5 %. [ABSTRACT FROM AUTHOR]

Recently, hydrogen application has been a new and promising technology in gas turbines, paving the way towards a cleaner and more sustainable energy future. However, challenges and considerations accompany this technology due to hydrogen's combustion characteristics compared to traditional fossil fuels. This review presents a comprehensive analysis of recent advancements in hydrogen-fueled gas turbines, focusing on their impacts on gas turbines, economic evaluation, and the development of commercial hydrogen gas turbines. Our analysis demonstrated that the unique combustion characteristics of hydrogen will influence combustion stability, flame dynamics, and the overall combustion process in gas turbines. The challenges associated with commercial hydrogen gas turbines encompass the high cost of hydrogen production, effective and efficient hydrogen combustion, material compatibility, and the imperative need for supportive regulatory measures. • Hydrogen influences combustion stability and the overall performance in gas turbines. • Economic viability of a hydrogen gas turbine depends on various factors. • Test results demonstrate the feasibility of commercial hydrogen gas turbines. • Cost of hydrogen gas turbines is expected to decrease for economies of scale. [ABSTRACT FROM AUTHOR]

The rapid development of electric vehicles has drawn extensive attention to using rotary engines as small-scale power generation devices. However, their wide application has been limited by drawbacks such as low combustion efficiency and high emissions. Therefore, to obtain rotary engines with high combustion efficiency and low emissions, this study explored the strengthening effect of natural gas/hydrogen hybrid fuel (NHHF) and Triangular Rotor Piston (TRP) structure on the combustion in the turbulent jet ignition rotary engine (TJI-RE) at different ignition advance angles (IAAs). Additionally, an experimental platform and a three-dimensional computational model for TJI-RE fueled by natural gas/hydrogen hybrid fuel (NHHF) were established in this study. The research results indicated that the TRP structure altered the combustion process by affecting the ignition area in the ignition stage and the turbulence kinetic energy during the combustion stroke. Furthermore, the SC-shaped cylinder exhibited the highest peak pressure for any fixed IAA. When the IAA was fixed at 30°CA (BTDC), the TJI-RE with the SC-shaped cylinder experienced a 12.12% increase in peak pressure and a 4.1% increase in indicated work compared to the FP-shaped cylinder. Additionally, the CO emission was reduced by 13.79%, while the NO emission showed a significant increase. • NHHF was used to reduce the carbon emissions of the RE. • A three-dimensional computational model of the TJI-RE was established. • The effect of piston structure on combustion in TJI-RE was systematically studied. • The optimal combination of piston structure and IAA for the TJI-RE was given. [ABSTRACT FROM AUTHOR]

The Diesel engine is expected to be available for operation at high altitude. However, power loss and emission deterioration have been plaguing highland Diesel engines. Therefore, this study aimed to investigate the impact of altitude on the performance and combustion characteristics of Diesel engines that is limited discussed in existing studies. The research was conducted by varying the altitude from 0-4500 m using a research Diesel engine and analyzing the combustion characteristics at different combustion phases with the help of triple Wiebe function. The results indicated a noticeable drop in power output with increasing altitude, and the deterioration of performance and emissions became significant when the altitude exceeded 3000 m. Specifically, the indicated specific CO, unburned hydrocarbon, and soot emissions increased while nitrogen NOx showed a reverse trend. Additionally, it was found that the lower cylinder pressure at high altitude extended the ignition delay and caused a higher heat release rate in the premixed combustion stage. Moreover, the high altitude condition shortened the duration of combustion and reduced the energy release fraction in the diffusion phase. Furthermore, the late combustion phase occurred earlier and lasted longer at high altitude, which consequently reduced the combustion and thermal efficiency. The most important finding is that the engine performance, especially the combustion efficiency, shows an abrupt degradation with altitudes above 3000 m. As a result, engines operating at extremely high altitudes require multi-stage turbocharging to compensate for combustion deterioration. [ABSTRACT FROM AUTHOR]

Hydrogen, as a zero-emission fuel, makes it possible to build a piston combustion engine that can be qualified as a drive for a "Zero Emission Vehicles", in terms of CO2 emissions. Thus, a hydrogen-powered piston combustion engine may be a future transitional technology for powertrains, especially in trucks and off-road vehicles, competitive with both electric drives and fuel cells. The article presents a multi-directional analysis of the prospects for the development and dissemination of hydrogen-powered internal combustion piston engines in motor vehicles. The current interest of the automotive industry in hydrogen-powered internal combustion engines, the current state of their development and the challenges that need to be overcome were presented. Various conditions that will determine their future in Europe were also indicated. [ABSTRACT FROM AUTHOR]

In this paper, a thermodynamic and reactivity study of light alcohol fuels was performed, based on experimental and numerical results. We also tested the influence of water addition on fundamental properties of the combustion reactivity dynamics in closed vessels, like the maximum explosion pressure, maximum rate of pressure rise and the explosion delay time of alcohol–air mixtures. The substances that we investigated were as follows: methanol, ethanol, n-propanol and iso-propanol. All experiments were conducted at initial conditions of 323.15 K and 1 bar in a 20 dm3 closed testing vessel. We investigated the reactivity and thermodynamic properties during the combustion of liquid fuel–air mixtures with equivalence ratios between 0.3 and 0.7 as well as some admixtures with water, to observe water mitigation effects. All light alcohol samples were prepared at the same initial conditions on a volumetric basis by mixing the pure components. The volumetric water content of the admixtures varied from 10 to 60 vol%. The aim of water addition was to investigate the influence of thermodynamic properties of light alcohols and to discover to which extent a water addition may accomplish mitigation of combustion dynamics and thermodynamic reactivity. [ABSTRACT FROM AUTHOR]

In response to increasingly stringent emissions regulations and the depletion of conventional fuel sources, integrating carbon-free fuels into the transport sector has become imperative. While hydrogen (H2) presents significant technical challenges, ammonia (NH3) could present a better alternative offering ease of transport, storage, and distribution, with both ecological and economic advantages. However, ammonia substitution leads to high emissions of unburned NH3, particularly at high loads. Combustion chamber retrofitting has proven to be an effective approach to remedy this problem. In order to overcome the problems associated with the difficult combustion of ammonia in engines, this study aims to investigate the effect of the piston bowl shape of an ammonia/diesel dual fuel engine on the combustion process. The primary objective is to determine the optimal configuration that offers superior engine performance under high load conditions and with high ammonia rates. In this study, a multi-objective optimization approach is used to control the creation of geometries and the swirl rate under the CONVERGETM 3.1 code. To maximize indicated thermal efficiency and demonstrate the influence of hydrogen enrichment on ammonia combustion in ammonia/diesel dual fuel engines, a synergistic approach incorporating hydrogen enrichment of the primary fuel was implemented. Notably, the optimum configuration, featuring an 85% energy contribution from ammonia, outperforms others in terms of combustion efficiency and pollutant reduction. It achieves over 43% reduction in unburned NH3 emissions and a substantial 31% improvement in indicated thermal efficiency. [ABSTRACT FROM AUTHOR]

The article presents experimental research and calculations of spark ignition engine indicators, using hydrogen-containing H 2 /O 2 gas, when the engine is running at low power. The engine throttle was opened 8°, the amount of H 2 /O 2 gas was increased from 0 to 7.9 % of the mass of gasoline, the stoichiometric (λ = 1) air/fuel ratio was maintained. Research shows that the addition of the H 2 /O 2 gas leads a great influence on the energetic and ecologic indicators of the engine and this depends on the change in the combustion process and the change in the composition of the fuel. The calculation methodology of the combustion process when the engine is fuelled with pure gasoline and with additives of hydrogen-containing gas presented. Presented results how addition of H 2 /O 2 leads to a reduction in the duration of the combustion process and also has a significant effect on a faster rise of combustion pressure and temperature. Shorter combustion duration leads to a rise of the indicated efficiency of the engine, the heat utilisation factor and an increase in the indicated power. As a result of bench tests, an increase in the effective power and a decrease in the brake-specific fuel consumption of the engine were found. When assessing the influence of H 2 /O 2 on the concentration of CO 2 in the exhaust gas, no decreases was not observed, as hydrogen improves the combustion process. Only the concentration of incomplete combustion process products (e.g., HC) decreases, but the concentration of NO x increases at the same time. • Study of indicators of the engine operating at low power by changing the amount of H 2 /O 2 in a wide range. • Described method for calculating the indicated engine parameters, taking into account the addition of H 2 /O 2. • Determined indicators of the combustion process for the gasoline engine operating with the H2/O2 additive. • The addition of an H2/O2 (7.9% of mass) enhances heat usage efficiency and raises the indicated efficiency to 13.9%. • The H 2 /O 2 additive reduces BSFC but does not significantly affect the CO 2 emissions of the SI engine. [ABSTRACT FROM AUTHOR]

Dealing with municipal sludge in an effective way is crucial for urban development and environmental protection. Co-processing the sludge by burning it in a decomposition furnace in the cement production line has been found to be a viable solution. This work aims to analyze the effects of the co-disposal of municipal sludge on the decomposition reactions and NOx emissions in the decomposing furnaces. Specifically, a practical 6000 t/d decomposition furnace was taken as the research object. To achieve this, ANSYS FLUENT with a UDF (user-defined function) was applied to establish a numerical model coupling the limestone decomposition reaction, fuel combustion, and NOx generation and reduction reactions. The flow, temperature, and component field distributions within the furnace with no sludge were firstly simulated with this model. Compared with site test results, the model was validated. Then, with sludge involved, the structure and operation parameters of the decomposition furnace for the co-disposal of municipal sludge were investigated by simulating the flow field, temperature field, and component field distributions. Parametric studies were carried out in three perspectives, i.e., sludge mixing ratio, preheating furnace arrangement height, and sludge particle size. The results show that all three aspects have great importance in the discomposing process. A set of preferable values, including a sludge mixing ratio of 10%, preheating furnace height of 21.5 m, and sludge particle diameter of 1.0 mm, was obtained, which resulted in a raw material decomposition rate of 89.9% and a NO volume fraction of 251 ppm at the furnace outlet. [ABSTRACT FROM AUTHOR]

In this study, a method for the monitoring of internal combustion engine operation by vibration signals is proposed. The work falls within the context of the increasingly stringent standards relating to the environmental impact of engines and the development of monitoring and control techniques to ensure increased engine performance as well as fuel saving and reduction of pollutant emissions. Experimentation was performed on a turbocharged light-duty compression ignition direct-injection engine. Two monoaxial accelerometers were installed on the engine compressor case, the speed of which has been demonstrated to be closely related to the engine operation. Vibration measurements of the engine compressor case have been processed by combining the Empirical Mode Decomposition technique with Independent Component Analysis and Short Time Fourier Transform to indirectly estimate the turbocharger speed. The obtained traces have been compared to the direct turbocharger velocity measures during the stationary running of the engine (speed and load conditions varied in the complete engine’s range of operation). The results point out the potentiality of the methodology in algorithms devoted to identifying modifications of the combustion development regarding regular operation via indirect turbocharger speed monitoring.

Methanol is a promising alternative fuel due to its wide availability of raw materials, mature production processes, and low production cost. However, because of the low cetane number, methanol must include a more reactive fuel to assist with combustion when used in compression ignition (CI) engines. In this study, based on the optical CI engine platform, methanol is injected into the intake port, and diesel is directly injected into the cylinder to achieve dual-fuel combustion. The effects of the methanol energy ratios and diesel split injection strategies on combustion are investigated. The results show that the premixed blue flame was mainly concentrated in the near wall region, whereas the yellow flame produced by diesel combustion tended to concentrate in the central region as the methanol energy ratio increased. When the methanol energy ratio exceeded 50%, the ignition delay was significantly prolonged, while the flame area was greatly reduced. Meanwhile, the peak values for the cylinder pressure and heat release rate decreased significantly, indicating a significant deterioration in combustion. At the earlier diesel pre-injection timing at −58°, the overall dual-fuel combustion at each main injection timing exhibited low-temperature premixed combustion characteristics, with a lower peak exothermic rate and flame brightness. At the later pre-injection timing at −33°, the spray flame at all main injection timings could be observed, with higher peak heat release rates and indications of thermal efficiency. Combustion at later main injection timings was characterized by diffusion combustion, and the main injection timing could effectively regulate the combustion process through phase adjustment.

The combustion process of traditional diesel engines is mainly determined by the injection timing of diesel. There is a trade-off relationship between the soot and NOx (nitrogen oxides) during this combustion process, making it difficult to reduce these two emissions simultaneously. The use of methanol can not only solve the above problem, but also replace some fossil fuels. However, the effects of methanol injection into the intake duct on the flame propagation in diesel/methanol dual-fuel engines is not yet clear, and there is relatively little research on it. The effects of methanol addition on the combustion process of diesel/methanol dual fuel (DMDF) were achieved based on a modified optical engine in this paper. One injector is installed on the intake inlet to inject methanol, and the other injector is installed in the cylinder to inject diesel in two stages before the top dead center of compression. There are three tests conducted separately in this paper. Firstly, the effects of the methanol ratio (40%, 50%, 60%, and 70%) on the combustion process are investigated, with the total heat remaining unchanged. Secondly, the effects of the pre-injection mass of diesel (20%, 30%, 40%, and 50%) on the combustion process are investigated, which keeps the total diesel mass unchanged. Finally, the effects of the total mass of diesel on the combustion process are investigated while maintaining the mass of methanol unchanged. The dual-fuel combustion process is recorded by a high-speed camera. A combustion analyzer and other equipment were used to analyze the combustion. The results showed that CA10 is delayed, the pressure and the heat release rate (HRR) are reduced, and the number of pixels of the KL factor (KL) decreases significantly with the increasing methanol ratio. CA10 and CA50 are advanced, the pressure and HRR decrease, and the KL increases when the mass of pre-injected diesel increases. CA10 and CA50 are advanced, respectively, and CA90 is postponed due to the increase in diesel mass. The pressure and HRR increase, and the KL increases when the total mass of diesel increases. [ABSTRACT FROM AUTHOR]

Ammonia and hydrogen are two carbon-free alternative fuels for engines. Considering that there are few studies on improving an ammonia-hydrogen engine's lean combustion performance, this investigation based on an engine with the Miller cycle employs hydrogen direct injection (HDI) and NH 3 port injection and then proposes an adjustment strategy to vary the start of injection (SOI) of HDI for affecting the engine combustion process. When ammonia volume share (AVS) is greater than 50%, the engine shows poor performance. Nevertheless, the stratification effect of hydrogen jets may be used to elevate the hydrogen concentration around spark plug by properly delaying SOI and then creating the locally rich mixture with a high hydrogen share, which prominently promotes the flame kernel formation, shortens CA0-90, reduces C o V P m a x , and enables the engine to reach approximately 36% BTE. It is notable that very late SOI can slightly deteriorate the heat release process and lower engine performance. • Ammonia-hydrogen engines have poor combustion process under lean conditions. • A strategy to improve the lean combustion performance of the engine is proposed. • Effects of NH 3 –H 2 premixing and H 2 stratification effect on the engine are balanced. • Properly delaying SOI enhances the ignition and combustion process of the engine. [ABSTRACT FROM AUTHOR]

In order to determine the best injection parameters of hydrogen, an experimental work was performed. The test engine was equipped with the installation for the hydrogen supply, and it was tested how the injection timing and number of injection influence on the combustion process. As the control parameters were taken the engine working stability, as well as the indicating efficiency. It was determined that the injection parameters, significantly influence on the engine working cycle, as well as on the combustion process. The adequate injection timing as well as the adequate number of injections, is crucial, for maintaining the stable work oof the IC engine, as well as for indicating efficiency. In order to provide the stable engine work, with the satisfying indicating efficiency, it is necessary provide multiple injections, more accurate two injections, where one serves to provide the adequate amount of fuel for the working cycle, while the second serves to slowdown the combustion process. [ABSTRACT FROM AUTHOR]

This article presents the results of an assessment of the combustion process of blends of n-hexane and canola oil. Tests were conducted for pure canola oil and its blends with n-hexane, with a max. n-hexane content of 20% by volume. The tests were carried out using the constant volume combustion chamber (CVCC) method as well as a diesel engine. For comparison purposes, the results for typical diesel fuel are also presented. Tests on the self-ignition properties of the n-hexane–canola oil blend, conducted in a CVCC according to the normative method for diesel fuel, showed little effect on the combustion process. However, previous tests conducted on a diesel engine of a passenger car showed a favorable effect of the n-hexane addition to canola oil on the combustion process in the engine, the performance and environmental parameters obtained. This shows that for some fuels, the evaluation of self-ignition and combustion properties in a constant volume combustion chamber, under conditions corresponding to diesel fuel tests, is not sufficient. The findings of this research may be beneficial in optimizing the diesel engine combustion systems fueled by renewable fuels. As the results of the tests have shown, the standardized method for determining the combustion process of the CVCC method does not always fully reflect the results obtained in engine tests. The results obtained by the CVCC method can be successfully used when comparing fuels, but when considering the selection of fuel for the engine, the results obtained in engine tests should be relied on first and foremost. [ABSTRACT FROM AUTHOR]

This article presents the possibility of improving combustion using the effect of releasing hydrogen from a solution with nucleation of gas bubbles. This concept consists in dissolving hydrogen in diesel fuel until the equilibrium state of the solution is reached. At a later stage, the phenomenon is reversed, and this gas is released from the solution during its injection into the combustion chamber with a strong swirl. A characteristic feature of the solution is that when lowering the pressure (opening the atomizers), there is a decrease in the equilibrium thermodynamic potential, which results in the excess, dissolved hydrogen being released spontaneously, and this process is of a volumetric nature. This article is a continuation of the work carried out at Poznan University of Technology on the development of this concept. This article presents the results of tests for the impact of hydrogen dissolved in diesel fuel on the combustion process within a turbulent-flow environment. The tests were conducted in the combustion chamber of an engine equipped with a toroidal combustion chamber and direct injection. During the tests, the following factors were measured: the main indicators of motor operation, emission of hydrocarbons, carbon monoxide, nitrogen oxides, and particulate matters.

Although the world is shifting toward using more renewable energy resources, combustion systems will still play an important role in the immediate future of global energy. To follow a sustainable path to the future and reduce global warming impacts, it is important to improve the efficiency and performance of combustion processes and minimize their emissions. Machine learning techniques are a cost-effective solution for improving the sustainability of combustion systems through modeling, prediction, forecasting, optimization, fault detection, and control of processes. The objective of this study is to provide a review and discussion regarding the current state of research on the applications of machine learning techniques in different combustion processes related to power generation. Depending on the type of combustion process, the applications of machine learning techniques are categorized into three main groups: (1) coal and natural gas power plants, (2) biomass combustion, and (3) carbon capture systems. This study discusses the potential benefits and challenges of machine learning in the combustion area and provides some research directions for future studies. Overall, the conducted review demonstrates that machine learning techniques can play a substantial role to shift combustion systems towards lower emission processes with improved operational flexibility and reduced operating cost. [ABSTRACT FROM AUTHOR]

This article contains the results of mathematical modeling of the self-ignition delay (τc sum) of a single droplet for various fuels, and the results of measurement verification (τc) of this modeling in diesel engines. The result of modeling the τc sum (as a function of the diameter and ambient temperature of the fuel droplet) revealed two physical and two chemical stages that had different values of the weighting factor (WFi) in relation to the total delay of self-ignition. It was also found that the WFi values of individual phases of the self-ignition delay differed for different fuels (conventional and alternative), and in the total value of τc sum. The measured value of the self-ignition delay (τc) was determined in tests using two diesel engines (older—up to EURO II and newer generation—from EURO IV). The percentage difference in the Δτc sum value obtained from modeling two fuels with different cetane number values was compared with the percentage difference in the Δτc value for the same fuels obtained during the engine measurements. Based on this analysis, it was found that the applied calculation model of the self-ignition delay for a single fuel droplet can be used for a comparative analysis of the suitability of different fuels in the real conditions of the cylinder of a diesel engine. This publication relates to the field of mechanical engineering. [ABSTRACT FROM AUTHOR]

Due to unique properties, production and operation features, water-fuel emulsion (WFE) could be considered as one of the most promising type of alternative fuels for diesel engines. Experimental research showed that compared to traditional diesel fuel, application of water-fuel emulsion allows to reduce nitrogen oxides and soot emissions, which is due primarily to a decrease in the level of maximum temperatures in the engine cylinder, as well as a more uniform distribution of fuel over the combustion chamber volume thanks to its secondary dispersion (micro-explosion phenomena). To control the stability of water-fuel emulsion properties during engine operation it is recommended to install water content sensor in the fuel supply system. [ABSTRACT FROM AUTHOR]

In earlier designs, the compression-ignition engine units were controlled by means of mechanical elements. They were levers, rods, springs, pawls, cams and others. The quality of such control did not ensure the required repeatability of control parameters in the fuel injection and combustion process. After the introduction of the standards limiting engine emissions of the limited exhaust components, the aforementioned engine control systems were not able to meet the requirements. The mechanical regulation of mechanical systems has been replaced by electronic control systems. It was the development of computer techniques and software that enabled design solutions of control systems for injection and combustion process parameters in engines with sufficient accuracy and repeatability of test results. The modern EDC (Electronic Diesel Control) control system, due to the computing power of microprocessors increased in recent years, enables meeting high requirements of modern Common Rail injection systems. The article presents issues in the area of four thematic levels: the design and modernization of the engine, its operation, diagnostic problems in order to determine reasons of unit failures and bench-top methods for assessing the effectiveness of unit repairs as well as issues concerning alternative fuels.

Azadirachta indica (Neem) gum was effectively used in the combustion process as the sustainable fuel for the synthesis of ZnO nanoparticles using zinc nitrate as the metal precursor. Thermal degradation of gum intermediate, which contains uniformly distributed Zn ions in gum matrix, by means of exothermic combustion reaction results in the formation of ZnO nanoparticles at a relatively lower temperature of 220∘C. Further, the phase stabilization of ZnO nanoparticles was performed at 700∘C for 3 h in ambient condition, which also led to the complete removal of organic residues. FTIR, XRD, SEM-EDX and TEM characterization of the ZnO nanoparticles reveals its phase purity and organic-free nature with a size ranging between 40 and 60 nm. Its optical activities were studied by UV–Visible and photoluminescence studies and the UV–Visible analysis reveals its band gap energy as 3.17 eV. Further, the synthesized ZnO nanoparticles showed splendid germicidal activity against Staphylococcus aureus (gram-positive bacteria), Escherichia coli (gram-negative bacteria) and Candida albicans (fungal pathogen). In addition, the bio-synthesized ZnO nanoparticles showed excellent antioxidant behavior with the 81% of free radical quenching while employing 100 μ g/mL nanoparticle concentration. [ABSTRACT FROM AUTHOR]

• Leather shavings do not allow for autothermal combustion when combusted directly. • Adding wood biomass to tannery waste results in a complete combustion of such mixture. • Lower quality pellets combustion results in a prominent afterburn. • Large percentage of additive leads to ash sintering, smaller additions result in fine ash. • The ash from wet blue tannery waste combustion traps large amounts of Cr 2 O 3. Leather processing companies are struggling with the problem of increasing costs of post-production waste disposal. Therefore, the issue of thermal waste disposal at the plant and the use of generated heat in the production process is becoming more and more popular. Leather waste on its own does not allow for autothermal combustion despite the sufficient higher heating value (HHV). Therefore the Authors proposed to improve the flammability of the fuel by adding a small amount of wood sawdust to leather waste and produce premixed pellets. Six such samples were incinerated in a laboratory-scale reactor, which enables the simultaneous measurement of characteristic temperatures, exhaust gas analysis and sample mass loss rate. Research has shown that even a small addition of sawdust enables a stable combustion process and does not cause the formation of sinters. In addition, studies of the ash showed that in the case of chromium-containing waste, a large part of it remained in the ash in the form of Cr 2 O 3. Nevertheless, very fine ash causes the small fraction chromium to be carried with the flue gas stream, therefore controlled agglomeration of the ash structure would be advisable in the final installation. Emission analysis showed high and moderately high NO x and SO 2 emissions, decreasing with the increase in the amount of sawdust addition in the sample. Research has shown that leather waste is not a burden, but can be an attractive and safe source of energy for the company, while improving waste management in a circular economy. [ABSTRACT FROM AUTHOR]

Future high-power-density engines require high level of intake boost. However, the effects of boosting on mixing, combustion and emissions in existing studies are inconsistent. In this paper, the mixing, combustion and emission characteristics with intake pressures of 100–400 kPa at low, medium and high loads are studied. The results show that the increase of intake pressures is conducive to the enhancement of air entrainment, while the air utilization ratios are reduced, thus requiring injection pressure to be optimized to effectively improve the mixing. For the intake pressures of 100 kPa, the average chemical reaction path is low-temperature reaction route, while the path of higher intake pressures is dominated by high-temperature pyrolysis. For soot emissions, when the equivalence ratio is lower than 0.175, the oxygen in the cylinder is sufficient, so the effect of temperature decrease is more significant, which leads to the increase of soot emissions with the increase of intake pressures. Otherwise, the effect of increasing oxygen concentration is more significant, so soot decreases accordingly. When the peak of global temperature is lower than 1800 K, the effect of the increase of oxygen concentration is more dominant, so the NOx emission increases with the increase of intake pressures. Otherwise, the rule of NOx emissions is consistent with temperature changes. [ABSTRACT FROM AUTHOR]

Domestic condensing boilers are equipped with perforated burners ensuring short-length premixed flames issues from a series of circular holes and slits. Despite some efforts that have been devoted to understanding the effect of hole diameter, pattern, and hole-to-hole distance on the resulting flames, very little is known about the flames from a series of slits. In this work 3-dimensional numerical simulations with skeletal kinetic mechanisms are performed to determine the structure of premixed methane-air flames issuing from two-slits patterns, often recurring in practical burner designs, i.e. several equally-spaced slits and a group of four slits. The arrangement of the slits greatly influences the resulting flames. A significant change in the flame behaviour occurs depending on the inlet velocity; at low speeds, the flames issuing from the slits present a flat region, while increasing the speed they assume a conical shape along the slit length. Neighbour flames are distinct from each other at low speeds, while they interact strongly with increasing the velocity. Interestingly, a series of several slits produce a single long wedge-shaped flame, while the group of four slits generates a single conical flame. [ABSTRACT FROM AUTHOR]

In this paper, a thermodynamic and reactivity study of light alcohol fuels was performed, based on experimental and numerical results. We also tested the influence of water addition on fundamental properties of the combustion reactivity dynamics in closed vessels, like the maximum explosion pressure, maximum rate of pressure rise and the explosion delay time of alcohol–air mixtures. The substances that we investigated were as follows: methanol, ethanol, n-propanol and iso-propanol. All experiments were conducted at initial conditions of 323.15 K and 1 bar in a 20 dm3 closed testing vessel. We investigated the reactivity and thermodynamic properties during the combustion of liquid fuel–air mixtures with equivalence ratios between 0.3 and 0.7 as well as some admixtures with water, to observe water mitigation effects. All light alcohol samples were prepared at the same initial conditions on a volumetric basis by mixing the pure components. The volumetric water content of the admixtures varied from 10 to 60 vol%. The aim of water addition was to investigate the influence of thermodynamic properties of light alcohols and to discover to which extent a water addition may accomplish mitigation of combustion dynamics and thermodynamic reactivity.

In response to increasingly stringent emissions regulations and the depletion of conventional fuel sources, integrating carbon-free fuels into the transport sector has become imperative. While hydrogen (H2) presents significant technical challenges, ammonia (NH3) could present a better alternative offering ease of transport, storage, and distribution, with both ecological and economic advantages. However, ammonia substitution leads to high emissions of unburned NH3, particularly at high loads. Combustion chamber retrofitting has proven to be an effective approach to remedy this problem. In order to overcome the problems associated with the difficult combustion of ammonia in engines, this study aims to investigate the effect of the piston bowl shape of an ammonia/diesel dual fuel engine on the combustion process. The primary objective is to determine the optimal configuration that offers superior engine performance under high load conditions and with high ammonia rates. In this study, a multi-objective optimization approach is used to control the creation of geometries and the swirl rate under the CONVERGETM 3.1 code. To maximize indicated thermal efficiency and demonstrate the influence of hydrogen enrichment on ammonia combustion in ammonia/diesel dual fuel engines, a synergistic approach incorporating hydrogen enrichment of the primary fuel was implemented. Notably, the optimum configuration, featuring an 85% energy contribution from ammonia, outperforms others in terms of combustion efficiency and pollutant reduction. It achieves over 43% reduction in unburned NH3 emissions and a substantial 31% improvement in indicated thermal efficiency.

Dealing with municipal sludge in an effective way is crucial for urban development and environmental protection. Co-processing the sludge by burning it in a decomposition furnace in the cement production line has been found to be a viable solution. This work aims to analyze the effects of the co-disposal of municipal sludge on the decomposition reactions and NOx emissions in the decomposing furnaces. Specifically, a practical 6000 t/d decomposition furnace was taken as the research object. To achieve this, ANSYS FLUENT with a UDF (user-defined function) was applied to establish a numerical model coupling the limestone decomposition reaction, fuel combustion, and NOx generation and reduction reactions. The flow, temperature, and component field distributions within the furnace with no sludge were firstly simulated with this model. Compared with site test results, the model was validated. Then, with sludge involved, the structure and operation parameters of the decomposition furnace for the co-disposal of municipal sludge were investigated by simulating the flow field, temperature field, and component field distributions. Parametric studies were carried out in three perspectives, i.e., sludge mixing ratio, preheating furnace arrangement height, and sludge particle size. The results show that all three aspects have great importance in the discomposing process. A set of preferable values, including a sludge mixing ratio of 10%, preheating furnace height of 21.5 m, and sludge particle diameter of 1.0 mm, was obtained, which resulted in a raw material decomposition rate of 89.9% and a NO volume fraction of 251 ppm at the furnace outlet.

The growth in demand for the production of heat and electricity requires an increase in fuel consumption by power equipment. At the moment, the most demanded thermal equipment for construction and modernization is gas turbine units. Gas turbines can burn a variety of fuels (natural gas, synthesis gas, methane), but the main fuel is natural gas of various compositions. The use of alternative fuels makes it possible to reduce CO 2 and NO x emissions during the operation of a gas turbine. Under conditions of operation of thermal power plants at the wholesale power market, it becomes probable that combined cycle power units, designed to carry base load, will start to operate in variable modes. Variable operation modes lead to a decrease in the efficiency of power equipment. One way to minimize or eliminate equipment unloading is to install an electrolysis unit to produce hydrogen. In this article the technology of "Power to gas" production with the necessary pressure at the outlet of 30 kgf/cm2 (this pressure is necessary for stable operation of the fuel preparation system of the gas turbine) is considered. High cost of hydrogen fuel during production affects the final cost of heat and electric energy, therefore it is necessary to burn hydrogen in mixture with natural gas. Burning a mixture of 5% hydrogen fuel and 95% natural gas requires minimal changes in the design of the gas turbine, it is necessary to supplement the fuel preparation system (install a cleaning system, compression for hydrogen fuel). In addition, the produced hydrogen can be stored, transported to the consumer. For the possibility of combustion of a mixture of natural gas and hydrogen fuel in a gas turbine the methodology of calculation of thermodynamic properties of working bodies developed by a team of authors under the guidance of Academician RAS (the Russian Academy of Sciences) V.E. Alemasov has been adapted, resulting in a program that allows to obtain an adequate mathematical model of the gas turbine. The permissible range of the working body temperature is limited to 3000 K. This paper presents the developed all-mode mathematical model of a gas turbine. On the basis of mathematical modeling of a gas turbine, a change in the main energy and environmental characteristics is shown depending on the composition of the fuel gas. Adding 5% hydrogen to natural gas has little effect on the gas turbine air treatment system, the flow rate remains virtually unchanged. CO 2 emissions decrease, but there is an increase in the amount of H 2 O in the turbine exhaust gases. [ABSTRACT FROM AUTHOR]

The application of rapeseed oil (RO) blends with diesel fuel and/or alcohols and/or ethers is known to significantly affect the combustion process. Aiming to further investigate the effects of rapeseed oil in a blend with diethyl ether (DEE) on this process, the coefficient of variation of the mean indicated pressure (COVMIP) of a 2.5l direct injection diesel engine was calculated. The analysis of the experimental results revealed the repeatability of the combustion process variability of diesel fuel (DF), rapeseed oil (RO), and DEE/RO blends containing up to 20% DEE. In these cases, the COVMIP does not exceed 4%. Additionally, it became obvious that for a higher content of DEE in blend with RO, the cyclic repeatability of the mean indicated pressure (MIP) was reduced. Thus, the values of COVMIP for fuels containing 30 and 40% of DEE by vol. in blend with RO were even three times higher than the values obtained for the reference fuel i.e., DF. The results indicate that the increased content of DEE in the mixture with RO is disadvantageous as it leads to excessive unevenness of the engine operation compared to its fueling with DF. The observed deterioration of the combustion process is caused by the vapor locks, which are formed due to the evaporation of volatile DEE in the fuel line, leading to the interrupted operation of the fuel injector. [ABSTRACT FROM AUTHOR]

To investigate the feasibility of diesel engines with high butanol substitution rate (BSR), the performance and emissions of diesel–butanol dual fuel engines are studied numerically. It i based on a four-cylinder diesel engine, which is modified into a diesel–butanol dual fuel engine with port-injected butanol fuel and direct-injected diesel fuel. The simulation is performed using GT-Power software, and simulation results are validated with the experimental data. The engine speeds are set at 1600, 2300, and 3600 rpm, respectively. The engine load is set at 25%, 50%, and 75% engine load, respectively. The BSR varies from 0% to 80% with an interval of 10%. The results show that, with the increase of BSR, the peak cylinder pressure (PCP), and the maximum pressure rise rate (MPRR) decrease, while the brake mean effective pressure (BMEP) and the indicated thermal efficiency (ITE) increase under various working conditions. Among them, the MPRR increases by 9%–12%, while the ITE increases by 6%–7%. In terms of emissions, the nitrogen oxide (NOX) decreases obviously (decrease by 32%–54%), while the carbon monoxide (CO) and the hydrocarbons (HC) decrease slightly (CO: decrease by 4%–10%, HC decrease by 3%–4%). [ABSTRACT FROM AUTHOR]

The combustion process of traditional diesel engines is mainly determined by the injection timing of diesel. There is a trade-off relationship between the soot and NOx (nitrogen oxides) during this combustion process, making it difficult to reduce these two emissions simultaneously. The use of methanol can not only solve the above problem, but also replace some fossil fuels. However, the effects of methanol injection into the intake duct on the flame propagation in diesel/methanol dual-fuel engines is not yet clear, and there is relatively little research on it. The effects of methanol addition on the combustion process of diesel/methanol dual fuel (DMDF) were achieved based on a modified optical engine in this paper. One injector is installed on the intake inlet to inject methanol, and the other injector is installed in the cylinder to inject diesel in two stages before the top dead center of compression. There are three tests conducted separately in this paper. Firstly, the effects of the methanol ratio (40%, 50%, 60%, and 70%) on the combustion process are investigated, with the total heat remaining unchanged. Secondly, the effects of the pre-injection mass of diesel (20%, 30%, 40%, and 50%) on the combustion process are investigated, which keeps the total diesel mass unchanged. Finally, the effects of the total mass of diesel on the combustion process are investigated while maintaining the mass of methanol unchanged. The dual-fuel combustion process is recorded by a high-speed camera. A combustion analyzer and other equipment were used to analyze the combustion. The results showed that CA10 is delayed, the pressure and the heat release rate (HRR) are reduced, and the number of pixels of the KL factor (KL) decreases significantly with the increasing methanol ratio. CA10 and CA50 are advanced, the pressure and HRR decrease, and the KL increases when the mass of pre-injected diesel increases. CA10 and CA50 are advanced, respectively, and CA90 is postponed due to the increase in diesel mass. The pressure and HRR increase, and the KL increases when the total mass of diesel increases.

This study characterises materials that belong to the group of refuse-derived fuels (RDF). This group of materials regarded as an alternative fuel is derived from industrial, municipal solid and commercial wastes. The aim of this study is to evaluate the quality of waste composition, demonstrate statistically different values and the energy efficiency of the fuel derived from waste. Data on incinerated waste were collected from two different sources. The basic physical and chemical parameters of waste include density and water content. The lower heating value (LHV) of waste, chlorine concentration and ash content of two groups of incinerated waste were also evaluated and compared for a given period of time (one year, with monthly breakdown). Statistical analysis indicated the differences in the combustion of waste groups, visualized by box plots and other diagrams to show the distribution of the results. An analysis of exhaust gas parameters was carried out, both in terms of chemical composition and energy parameters. The RDF combustion process was presented through simulations for the adopted conditions of heat recovery. It was found that for each kilogram of RDF, about 3.85 kWh (13860 kJ) of heat can be obtained. The combustion process was simulated using Aspen Plus software. [ABSTRACT FROM AUTHOR]

Aiming at the problems of secondary pollution and resource waste caused by inaccurate input of coal and ammonia in coal‐fired power plant, an optimal controlling method of combustion and denitration coordinated operation based on Deep Deterministic Policy Gradient (DDPG) is proposed in this paper. First, the environmental model is constructed by the Stacking algorithm to predict the NOx emission concentration of the combustion and denitration system, which provides environmental state feedback for the optimal controlling model. Second, the optimization controlling model is constructed based on the DDPG algorithm within the standard limitation of denitration efficiency and NOx emission concentration. This model takes the minimization of comprehensive cost as its optimization objective to realize the optimal control of controllable variables in the cooperative operation process of combustion and denitration. The experimental results of real operational data from 1000 MW boiler unit in a power plant locating in south China show that the optimization results of coordinated operation for the combustion and denitration system are better than single‐stage optimization results. In addition, the total cost is reduced by 1%–3% on average compared with before optimization. [ABSTRACT FROM AUTHOR]

Research in the field of building mathematical models for combustion processes has been ongoing ever since the chemical reactions of combustion were first discovered. The authors of this review have systematized mathematical models of coal–water suspension (CWS) combustion processes, the sequence of analytical and experimental studies, and have also shown the global genesis of the CWS use. In addition, this review touches upon a topic that is inextricably linked with the combustion of CWS, namely their transportation from the place of coal mining to their place of thermal utilization. For developing countries, their own energy independence is in the foreground, as it is the basis for their economic independence and also a means for other sectors of their economy to be protected from the impact of market changes in fuel prices in the future spot world market. The authors of this review explored the possibility of using Kyrgyz brown coal and transporting it through a coal pipeline from a mountainous area to an industrial site for thermal utilization in specialized steam boiler units. As the economic analysis showed, for the conditions of the Republic of Kyrgyzstan, the use of CWS and coal pipelines with rising prices for natural gas is economically justified. The recommendations of the authors are used in scientific reports and methodological recommendations for the energy and mining sectors of the Republic of Kyrgyzstan, how the recommendations can also be applied to similar conditions in the highlands of Russia, China, and India. [ABSTRACT FROM AUTHOR]

In earlier designs, the compression-ignition engine units were controlled by means of mechanical elements. They were levers, rods, springs, pawls, cams and others. The quality of such control did not ensure the required repeatability of control parameters in the fuel injection and combustion process. After the introduction of the standards limiting engine emissions of the limited exhaust components, the aforementioned engine control systems were not able to meet the requirements. The mechanical regulation of mechanical systems has been replaced by electronic control systems. It was the development of computer techniques and software that enabled design solutions of control systems for injection and combustion process parameters in engines with sufficient accuracy and repeatability of test results. The modern EDC (Electronic Diesel Control) control system, due to the computing power of microprocessors increased in recent years, enables meeting high requirements of modern Common Rail injection systems. The article presents issues in the area of four thematic levels: the design and modernization of the engine, its operation, diagnostic problems in order to determine reasons of unit failures and bench-top methods for assessing the effectiveness of unit repairs as well as issues concerning alternative fuels. [ABSTRACT FROM AUTHOR]

The article proposes a method for designing combustion chambers for gas turbine engines based on a combination of the use of calculations in a one-dimensional and three-dimensional formulation of the problem. This technique allows you to quickly design at the initial stage of creating and development of the existing combustion chambers using simplified calculation algorithms. At the final stage, detailed calculations are carried out using three-dimensional numerical calculations. The method includes hydraulic calculations, on the basis of which the distribution of the air flow passing through the main elements of the combustion chamber is determined. Then, the mixing of the gas flow downstream of the flame tube head and the air passing through the holes in the flame tube is determined. The mixing quality determines the distribution of local mixture compositions along the length of the flame tube. The calculation of the combustion process is carried out with the determination of the combustion efficiency, temperature, concentrations of harmful substances and other parameters. The proposed method is tested drawing on the example of a combustion chamber of the cannular type. The results of numerical calculations, experimental data and values obtained using the proposed method for various operating modes of the engine are compared.

Diagnostics of pulverized coal combustion can be carried out in the field of process monitoring and analysis of measurement data. The information about changes in the flame is presented in the form of time series, which can be analyzed in the time and frequency domain. The paper presents an analysis of signals of changes in the intensity of the flame glow during pulverized coal combustion using power spectral density. On the basis of the periodograms determined using the Welch method, it was possible to determine the frequency components present in the signal.

This article presents the results of an assessment of the combustion process of blends of n-hexane and canola oil. Tests were conducted for pure canola oil and its blends with n-hexane, with a max. n-hexane content of 20% by volume. The tests were carried out using the constant volume combustion chamber (CVCC) method as well as a diesel engine. For comparison purposes, the results for typical diesel fuel are also presented. Tests on the self-ignition properties of the n-hexane–canola oil blend, conducted in a CVCC according to the normative method for diesel fuel, showed little effect on the combustion process. However, previous tests conducted on a diesel engine of a passenger car showed a favorable effect of the n-hexane addition to canola oil on the combustion process in the engine, the performance and environmental parameters obtained. This shows that for some fuels, the evaluation of self-ignition and combustion properties in a constant volume combustion chamber, under conditions corresponding to diesel fuel tests, is not sufficient. The findings of this research may be beneficial in optimizing the diesel engine combustion systems fueled by renewable fuels. As the results of the tests have shown, the standardized method for determining the combustion process of the CVCC method does not always fully reflect the results obtained in engine tests. The results obtained by the CVCC method can be successfully used when comparing fuels, but when considering the selection of fuel for the engine, the results obtained in engine tests should be relied on first and foremost.

This article contains the results of mathematical modeling of the self-ignition delay (τc sum) of a single droplet for various fuels, and the results of measurement verification (τc) of this modeling in diesel engines. The result of modeling the τc sum (as a function of the diameter and ambient temperature of the fuel droplet) revealed two physical and two chemical stages that had different values of the weighting factor (WFi) in relation to the total delay of self-ignition. It was also found that the WFi values of individual phases of the self-ignition delay differed for different fuels (conventional and alternative), and in the total value of τc sum. The measured value of the self-ignition delay (τc) was determined in tests using two diesel engines (older—up to EURO II and newer generation—from EURO IV). The percentage difference in the Δτc sum value obtained from modeling two fuels with different cetane number values was compared with the percentage difference in the Δτc value for the same fuels obtained during the engine measurements. Based on this analysis, it was found that the applied calculation model of the self-ignition delay for a single fuel droplet can be used for a comparative analysis of the suitability of different fuels in the real conditions of the cylinder of a diesel engine. This publication relates to the field of mechanical engineering.

The use of biofuels to power compression–ignition engines makes it possible to reduce emissions of certain harmful components of exhaust gases. The purpose of this study was to determine the influence of second-generation biofuels on the course of indicator graphs and heat release characteristics of the Perkins 1104D-44TA compression–ignition engine. For comparative purposes, the same tests were carried out by feeding the engine with first-generation biofuel and diesel fuel. Babassu butyl esters (BBuE) were used as the second-generation biofuel. The second fuel was a first-generation biofuel—rapeseed oil methyl esters (RME). Analysis of the results made it possible to draw conclusions about the effect of using 2nd and 1st generation biofuels on the parameters of the combustion process. When the DF engine was powered, the lowest fuel dose per work cycle was obtained. In the case of RME and BBuE fuels, it depends on the engine load. For low loads, higher consumption is for RME, and for higher loads, fuel consumption for BBuE in-creases most often. This is due to the lower calorific value of the esters. The results of these tests indicate that feeding the engine with BBuE and RME fuel in most loads resulted in higher maximum combustion pressures compared to feeding the engine with DF which may be directly related to the higher cetane number of these fuels compared to DF and the oxygen content of these fuels. Feeding the engine with BBuE and RME esters compared to DF did not result in large differences in the maximum heat release rates HRmax. However, the values of the first and second maximum heat release rates x1max and x2max, in addition to the type of fuel, are strongly influenced by the operating conditions, especially the engine load. Analyzing the combustion angles of 5, 10, 50, and 90% of the fuel dose, it can be seen that feeding the engine with BBuE and RME esters for most measurement points results in faster combustion of the fuel dose compared to DF. [ABSTRACT FROM AUTHOR]

In order to optimize the combustion chamber of a highly intensified single-cylinder diesel engine, including improvement of the air utilization rate in the combustion chamber, optimization of the fuel/air mixture process, reduction of the soot emission in the cylinder, and obtainment of the optimal combustion performance parameters, a re-entrant combustion chamber with step-typed lip (RCSL) and a re-entrant combustion chamber with tilted lip (RCTL) were innovatively designed and the effects of the throat diameter on the combustion process was obtained through experiments. When the RCSL with a diameter of 72 mm worked, target for the Brake Mean Effective Pressure (BMEP) of 2.6 MPa could be achieved under the condition of excess air coefficient of 1.5~1.7. At the same time, this had the advantages of lower fuel consumption, lower exhaust temperature, lower smoke level, and shorter combustion duration. Under the same BMEP, the RCTL had lower fuel consumption, exhaust gas temperature and maximum combustion pressure, as well as faster heat release rate (HRR) and shorter combustion duration than the RCSL. [ABSTRACT FROM AUTHOR]