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The quest for renewable energy sources has resulted in alternative fuels like ammonia, which offer promising carbon-free fuel for combustion engines. Ammonia has been demonstrated to be a potential fuel for decarbonizing power generator, marine, and heavy-duty transport sectors. Ammonia's infrastructure for transportation has been established due to its widespread primary use in the agriculture sector. Ammonia has the potential to serve as a zero-carbon alternative fuel for internal combustion engines and gas turbines, given successful carbon-free synthesis and necessary modifications to legacy heat engines. While its storage characteristics surpass those of hydrogen, the intrinsic properties of ammonia pose challenges in ignition, flame propagation, and the emissions of nitrogen oxides (NOx) and nitrous oxide (N2O) during combustion in heat engines. Recent noteworthy efforts in academia and industry have been dedicated to developing innovative combustion strategies and enabling technologies for heat engines, aiming to enhance efficiency, fuel economy, and emissions. This paper provides an overview of the latest advancements in the combustion of neat or high-percentage ammonia, offering perspectives on the most promising technical solutions for gas turbines, spark ignition, and compression ignition engines. [ABSTRACT FROM AUTHOR]

Automotive radiators are primarily utilized in vehicles to dissipate the heat generated by the engine block into the surrounding. Utilizing coolants with superior thermophysical properties reduces the engine power consumption and improves the cooling engine performance. Comprehending the correlation between coolant characteristics and its thermohydraulic behavior is essential for advancing this innovative cooling technology. This investigation introduces a detailed parametric study of an automotive radiator using diversified coolant mixtures. Ethylene glycol (EG)/water mixtures, namely, (40:60), (50:50), and (60:40) are utilized as a coolant. The influences of the operational mechanism parameters, that is, inlet coolant temperature, intake air temperature, airflow rate, coolant flowrate, and coolant mixture ratio on the effectiveness, heat transfer, and fluid flow characteristics of the radiator are investigated. A thermohydraulic coupled model, based on the effectiveness‐NTU and thermal resistance theories, are developed for simulation of the investigated radiator. The outcomes revealed that the heat transfer rate is more significantly influenced by the inlet temperatures of the coolant and air than by the flowrate. Findings reveal optimal conditions for radiator design to be a coolant mixture of (40 EG:60 Water), coolant mixture Reynolds number of 1087.5, air Reynolds number of 2175, 11°C air‐intake temperature, and 94.25°C coolant mixture temperature for engine cooling maximization. The findings also indicated optimum mixture yielded the maximum advantage ratio (AR) and heat transfer with lowest pumping power, which achieved 7.94% and 19.30% higher AR compared to (50:50) and (60:40) mixture solutions, respectively. From energy consumption reduction prospective, the optimal EG/water coolant mixture results in a reduction in pumping power by 25.11% and 49.77%, compared to the (50:50) and (60:40) mixtures, respectively, under the same optimal operating conditions. Conclusively, the optimized automotive radiator design explored in this study offers a promising approach to improving vehicle technology and increasing cooling efficiency in internal combustion engines. [ABSTRACT FROM AUTHOR]

The methods of increasing the efficiency of internal combustion engines through heat utilization are examined. A proposed classification of heat utilization systems for mobile energy vehicles is presented. External utilization harnesses the heat generated by a diesel engine to fulfill the needs of consumers not directly related to the engine, such as interior heating and air conditioning systems. Internal recycling focuses on enhancing the power, environmental performance, and economic performance of an engine and its related systems. Various heat utilization schemes are compared. For the economic conditions of the European Union (EU), a turbocompounding diesel engine is acceptable if its agricultural tractor rated power is more than 275 kW and its combine harvester rated power is more than 310 kW. Steam injection into the combustion chamber is utilized to improve the technical and economic performance of gas turbine engines. This technology is also produced in Ukraine and is proposed for use in internal combustion engines. It is suggested to inject water vapor into a turbocharger turbine. This approach reduces the number of components in the heat recovery system, thereby lowering its cost. A recycling chiller can be employed to cool the air after it passes through the air cleaner, enhance the efficiency of the air cooler, and improve the performance of the thermoelectric generators. This device is particularly effective at relatively high air temperatures and can be recommended for agricultural machinery that operates in such conditions, such as combines. With the application of this new technology, it is possible to increase the power of diesel engines by 15...20% and reduce fuel consumption by up to 14%. Further research will focus on substantiating the parameters of recycling systems for different classes of vehicles. Developing a methodology to justify the effective application of heat utilization systems in agricultural mobile energy vehicles is advisable. [ABSTRACT FROM AUTHOR]

Currently, a significant number of automobiles are equipped with internal combustion engines. In urban areas, a significant number of transportation methods have detrimental environmental effects through the release of pollutants resulting from the combustion of fossil fuels. In addition to the emission of toxic pollutants, internal combustion engines experience significant energy losses through exhaust emissions. Advanced technological applications have the potential to recover of a portion of the waste heat from exhaust ducts. Evaluations conducted by scholars across several disciplines highlight diverse perspectives on the recycling of thermal energy from exhaust gases as a means of mitigating pollution sources. However, this review focuses on the utilization of thermoelectric generators for harvesting a fraction of the aforementioned dissipated energy. The energy harvesting system is comprised of three components: the heat exchanger, which serves as the heat source; the cooler, which functions as the heat sink; and the thermoelectric generators, which act as the heat engine sandwiched between the heat exchanger and the cooler. This review examines the diverse exterior designs of heat exchangers and coolers and categorizes them accordingly. Additionally, it identifies the optimal installation locations for harvesting systems and explores the impact of design variations, choice of metals for manufacturing, and internal topography on the generation of electrical power. The primary findings of this review emphasize the significance of prioritizing the design of heat exchangers over coolers. This is because the uniformity of the temperature distribution within the heat exchanger plays a crucial role in governing the overall performance. Moreover, the installation of the system on petrol engines was seen as more cost-effective in comparison to its installation on diesel engines, primarily due to the higher magnitude of energy emitted from the exhaust gases of the former as opposed to the latter. To the best of the author's knowledge, this review classification has never been performed before. This can be considered a brief path map and a starting point for future work by researchers and investigators in designing heat exchangers and coolers and choosing the locations of TEG system installations. Then profitable investment from the data that has been prepared and summarized. [ABSTRACT FROM AUTHOR]

The objective of this study is to design a heat-recovery boiler for a 1 MW-class gas engine-based cogeneration system intended to recover heat from engine exhaust gas. To accommodate high-pressure applications, a water tube-type boiler is selected. For ensuring effective water circulation within the boiler, an innovative modular-type boiler based on the mini-boiler concept is developed. This boiler comprises finned tube-type risers, and their heat-transfer characteristics are measured and compared with the conventional correlation used in the design process. Additionally, an inlet guide vane is developed to address the temperature nonuniformity resulting from the shape mismatch between the gas engine outlet and heat-recovery boiler inlet. The performance of the proposed boiler was evaluated by integrating it into an experimental rig. The diamond-shaped inlet guide vane, which was designed by computational fluid dynamics, facilitated a uniform temperature distribution. However, the temperature became nonuniform downstream owing to the influence of a downcomer. Although the modular heat-recovery boiler effectively produced steam from gas engine exhaust gasses, its heat-transfer performance in the downstream section was lower than expected, necessitating additional heat-transfer area. [ABSTRACT FROM AUTHOR]

The study aims to improve the waste thermal energy retrieval from flue gas of an internal combustion engine (ICE). The recovered waste heat energy was used for distillation by using a thermal distillation system. The performance of the thermal distillation unit was investigated by varying the evaporator (boiler) type and engine load (25, 50, 75 %). Four different types of boilers were used including one smooth copper tube and other three were two, three and four axial finned copper tube evaporators. The impact of boiler type and engine load on the net retrieved energy and exergy, net energy and exergy efficiency, and distillate yield rate of thermal distillation unit was also examined. The results showed that the net extracted heat energy and exergy for axial finned tube evaporator was approximately 26.823 - 45.513 % and 7.614 - 25.203 W higher than that of smooth tubes evaporator at 25 and 75 % engine load, respectively. The distillation yield was found to be ~ 2.35 liter/hour in the case of four axial finned tube boiler at 75 % engine load. [ABSTRACT FROM AUTHOR]

The homogeneous charge compression ignition (HCCI) and combustion chamber geometry play significant roles in improving the potential of compression ignition engines and their environmental sustainability. However, a major hindrance to the progress of HCCI technology has been the notable decline in brake thermal efficiency and emit high levels of hydrocarbon (HC) and carbon monoxide (CO) which is mainly due to the low temperatures during combustion and low post oxidation of these components. Combustion chambers like hemispherical combustion chamber (TCC) and toroidal combustion chamber (TCC) are known to provide better combustion characteristics due to their increased surface‐to‐volume ratio. Moreover, injection timing and spray position have shown a significant effect on the controlling onset of combustion and emission in HCCI engine. Therefore, the primary objective of this numerical study is to enhance the engine characteristics in HCCI mode using an HCC and TCC piston bowl geometry coupled with multistage injection and compare the results with flat piston bowl geometry. The results show that the toroidal shape piston geometry provides 3%–5% higher brake thermal efficiency compared to the conventional piston geometry. Additionally, the energy balance analysis revealed that the combination of modified piston geometry and multi stage injection improved the combustion process by reducing the energy losses due to incomplete combustion and heat transfer to the engine walls. These findings suggest that the proposed injection strategy combined with modified piston geometry has the potential to enhance the performance of HCCI engines and reduce their environmental impact. [ABSTRACT FROM AUTHOR]

It is possible to increase the heat conduction in the engine by mixing nano-sized metal particles into the liquid coolant. In this study, the temperature changes in the cooling system of the engine operated at 1000, 2000, 3000, and 4000 rpm were investigated by adding 0.1% and 0.2% SiO2, TiO2, Al2O3 nanofluids to the base coolant in the engine cooling system of a vehicle. In addition, the changes in CO2, HC, CO, NOx, and O2 exhaust emissions at these speeds were also investigated. It was observed that the heat conduction increased as the ratio of nanofluids added to the base fluid increased, but the heat conduction decreased at 3000 and 4000 rpm. The positive heat conduction effect seen in all nanofluid mixtures studied for lowtemperature values was not observed when the coolant temperature values increased with the increase in engine speed. Therefore, it was determined that nanofluid mixtures did not improve heat conduction under all conditions. With the increase in the particle ratio, it has observed that the engine coolant remained at lower temperature values, resulting in an improvement in heat conduction. For CO2, HC, CO, and O2 emissions, there were no significant differences in the exhaust emission values compared to the base fluid. It has been determined that there are decreases of approximately 28%, 27%, 25%, and 21%, respectively, in NOx emission values for different engine speeds. In general, the best results in temperature and emission measurements were obtained with 0.2% SiO2 nanofluid. [ABSTRACT FROM AUTHOR]

Energy efficiency and thermal management continue to be critical areas in the vehicle development process. Independent of whether it is a vehicle with an internal combustion engine, hybrid, or fully electrical, engineers require proper and accurate tools to comprehend heat transfer in engine bays. However, developing such tools using a fully detailed production geometry can be challenging. This work presents a simplified and flexible test rig design of the vehicle underhood environment in two different variants: a passenger car and a commercial truck. The rig design in CAD and experimental data for the two rig configurations are made available upon request. These data will allow for the validation of different simulation approaches against the experimental dataset. An example of such a validation is presented in this paper. The load case scenario represented includes constant speed driving under heavy loads continued by a complete halt, which is followed by soaking for 100 min. The differences in experimental results for different rig variants are shown and analyzed. A good correlation between the experiments and CFD is obtained. [ABSTRACT FROM AUTHOR]

Over the past few years, fuel prices have increased dramatically, and emissions regulations have become stricter in maritime applications. In order to take these factors into consideration, improvements in fuel consumption have become a mandatory factor and a main task of research and development departments in this area. Internal combustion engines (ICEs) can exploit only about 15–40% of chemical energy to produce work effectively, while most of the fuel energy is wasted through exhaust gases and coolant. Although there is a significant amount of wasted energy in thermal processes, the quality of that energy is low owing to its low temperature and provides limited potential for power generation consequently. Waste heat recovery (WHR) systems take advantage of the available waste heat for producing power by utilizing heat energy lost to the surroundings at no additional fuel costs. Among all available waste heat sources in the engine, exhaust gas is the most potent candidate for WHR due to its high level of exergy. Regarding WHR technologies, the well-known Rankine cycles are considered the most promising candidate for improving ICE thermal efficiency. This study is carried out for a six-cylinder marine diesel engine model operating with a WHR organic Rankine cycle (ORC) model that utilizes engine exhaust energy as input. Using expander inlet conditions in the ORC model, preliminary turbine design characteristics are calculated. For this mean-line model, a MATLAB code has been developed. In off-design expander analysis, performance maps are created for different speed and pressure ratios. Results are produced by integrating the polynomial correlations between all of these parameters into the ORC model. ORC efficiency varies in design and off-design conditions which are due to changes in expander input conditions and, consequently, net power output. In this study, ORC efficiency varies from a minimum of 6% to a maximum of 12.7%. ORC efficiency performance is also affected by certain variables such as the coolant flow rate, heat exchanger's performance etc. It is calculated that with the increase of coolant flow rate, ORC efficiency increases due to the higher turbine work output that is made possible, and the condensing pressure decreases. It is calculated that ORC can improve engine Brake Specific Fuel Consumption (BSFC) from a minimum of 2.9% to a maximum of 5.1%, corresponding to different engine operating points. Thus, decreasing overall fuel consumption shows a positive effect on engine performance. It can also increase engine power output by up to 5.42% if so required for applications where this may be deemed necessary and where an appropriate mechanical connection is made between the engine shaft and the expander shaft. The ORC analysis uses a bespoke expander design methodology and couples it to an ORC design architecture method to provide an important methodology for high-efficiency marine diesel engine systems that can extend well beyond the marine sector and into the broader ORC WHR field and are applicable to many industries (as detailed in the Introduction section of this paper). [ABSTRACT FROM AUTHOR]

The focus of internal combustion engine development for urban vehicles is shifting towards reducing materials by making them lighter. In order to maintain thermal and flow levels, a model was developed to study the thermal behavior of valve seats during periodic contact, which can also help improve engine performance and fuel efficiency. The model, composed of two cylindrical bars in periodic contact, takes into account the evolution and topography of the contact surface. The model's performance was evaluated through various experimental studies and showed a maximum difference of 5.05% with experimental values, in good agreement with previous literature. The results showed that heat flux increases with increasing contact frequency and thermal diffusivity affects conductive transfer. This model can be used by manufacturers to evaluate cylinder head temperature and by the automotive industry to improve heat transfer in engines. [ABSTRACT FROM AUTHOR]

The proper estimation of thermal behavior of the block and coolant after engine shutdown is essential, because when the engine is shut down and coolant flow stops, cylinder head temperature may increase enough to vaporize a fraction of the coolant within the jackets, eventually causing the pressure to rise and a quantity of the coolant leaks out. Also, the cylinder head will be hotter than the block as a result; their non-homogeneous expansion causes strain–stresses on the head gasket. A simplest and most convenient method to study transient heating and cooling problems is using analytical solution. It has been considered that heat is transferred under one-dimensional, unsteady-state conditions with no internal generation of thermal energy. Results show that the total heat transfer from block to the coolant can be obtained by multiplying engine coolant heat rate ( q ˙ cooling ) just before shutdown by L2/α ratio. So the cast iron block transfers much more heat (about 4 times) to the coolant than aluminum block. Hence, the time needed for the aluminum block to reach steady-state conditions is about 4 times faster than cast iron block. Accordingly, in order to reduce fuel consumption and emissions in the warm-up period, the thickness of the block should be minimized as much as possible. For example, the thickness of iron block should be about half the thickness of the aluminum block. Also in order to reduce the heat transfer to the coolant ( q ˙ cooling ), the engine should be brought to idle for a short period and finally shut down. In order to determine the control strategy of intelligent cooling system (ICS), the present study suggests that the water pump should be started a few seconds (more than 5 s) after engine shutdown and operated at a lower speed. The main results and innovations of the present work are that the L2/α ratio plays a fundamental role in the design of the engine head and block geometry and the determination of the ICS control strategy after engine shutdown. [ABSTRACT FROM AUTHOR]

Green hydrogen, produced using renewable energy, is nowadays one of the most promising alternatives to fossil fuels for reducing pollutant emissions and in turn global warming. In particular, the use of hydrogen as fuel for internal combustion engines has been widely analyzed over the past few years. In this paper, the authors show the results of some experimental tests performed on a hydrogen-fueled CFR (Cooperative Fuel Research) engine, with particular reference to the combustion. Both the air/fuel (A/F) ratio and the engine compression ratio (CR) were varied in order to evaluate the influence of the two parameters on the combustion process. The combustion duration was divided in two parts: the flame front development (characterized by laminar flame speed) and the rapid combustion phase (characterized by turbulent flame speed). The results of the hydrogen-fueled engine have been compared with results obtained with gasoline in a reference operating condition. The increase in engine CR reduces the combustion duration whereas the opposite effect is observed with an increase in the A/F ratio. It is interesting to observe how the two parameters, CR and A/F ratio, have a different influence on the laminar and turbulent combustion phases. The influence of both A/F ratio and engine CR on heat transfer to the combustion chamber wall was also evaluated and compared with the gasoline operation. The heat transfer resulting from hydrogen combustion was found to be higher than the heat transfer resulting from gasoline combustion, and this is probably due to the different quenching distance of the two fuels. [ABSTRACT FROM AUTHOR]

Researchers are focusing on the optimization of alternative fuel blends for ICEs and the recovery of waste heat energy through the use of TEGs to meet rising demand and reducing global warming. This study addresses the issue of selecting the optimal biodiesel blend and engine operating parameters through the application of MCDM methods, while evaluating engine performance, combustion, and emissions when waste heat is recovered. In particular, vegetable-based biodiesel was blended at five distinct volumetric ratios and assessed in a diesel engine under a series of conditions. The experiment was conducted with three injection timings, three engine speeds, and four engine loads. A holistic scientific decision-making model was developed to determine the optimal fuel and operating conditions, employing the CRITIC and MAIRCA methods. Of the 180 experimental scenarios, the optimal condition was identified as the use of B20 biodiesel at 1500 rpm, 25% engine load, and standard injection timing, which yielded an EE of 25.5. Compared to the diesel fuel, 20% and 18.75% reduction in CO and HC emissions, respectively, was observed, while a 3.34% and 4.07% increase in CO2 and NOx emissions, respectively, was noted. The SEC was recorded at 14,119 kJ/kWh and the SER at 63.7 kJ/kWh. Moreover, the use of B10 biodiesel at 1500 rpm, 75% engine load, and − 2 °C retarded injection timing was identified as the second-best alternative. This decision algorithm indicates that B20 biodiesel by using in a engine with TEG at lower engine loads has the potential to achieve high efficiency and low emissions. [ABSTRACT FROM AUTHOR]

Heat produced inside internal combustion engines can become the cause of engine damage and failure. The engine cooling system in vehicles plays a crucial role to avoid damage as a result of internal heating. Thus, the role of radiators in removing excessive heat from the engine is important. Nanofluids are used in this regard to improve the heat transfer performance of radiators. Among different nanofluids, Al2O3/water and ZnO/water nanofluids have been proven better heat transfer coolants for automobile cooling systems. Therefore, in this study, we developed the automotive radiator test rig to compare the performance of ZnO/water and Al2O3/water nanofluids. The radiator test rig was modified to find accurate results. The overall comparison between both nanofluids showed that Al2O3 nanoparticles are more effective as compared to ZnO nanoparticles in the coolant. [ABSTRACT FROM AUTHOR]

The Euro 7 legislation and the Zero-Impact Emissions concept aim at significantly improving air quality. Technologies that reduce pollutant emissions beyond current gasoline passenger cars have already been intensively investigated, but a holistic system layout considering extended boundary conditions is missing so far. This paper therefore develops technical solutions to achieve a Euro 7 scenario and Zero-Impact Emissions for a 2030+ vehicle. First, challenging test scenarios are identified to develop compliant vehicles. The scenarios cover extreme conditions in real-world driving, such as hot and cold ambient conditions, stop-and-go in rural areas or high speed and steep gradients on highways. Different technology options are discussed and selected for the investigations. An empirical–physical simulation model for the exhaust gas aftertreatment system is extended with new technologies, such as an electrical heater disc in front of the catalyst or a burner in the exhaust system. In addition to stoichiometric engine operation and increased catalyst volume, the results show that the expected Euro 7 regulations can be achieved in all extreme scenarios by combining additional exhaust gas heating with engine power limitation or pre-heating. Moreover, even Zero-Impact Emissions are achieved in most cases with the same technology options. [ABSTRACT FROM AUTHOR]

The thermal wall function method offers an effective pathway for modeling heat transfer in engines. This paper reexamined the traditional construction method of the thermal wall function and improved it by correcting the integration scheme in the boundary layer; then, an enhanced heat transfer model was introduced. Since the heat release from the chemical reactions is of great significance to the near-wall flow, it is necessary to construct a law of the wall including the heat release effect. A new law of the wall including the impacts of the pressure work and the heat release from chemical reactions was obtained based on the analogy between the momentum transfer and the heat transfer predicted using the improved thermal wall function. In the analogy process, the formula of the eddy-viscosity ratio was reconstructed for the whole boundary layer, and then, the Prandtl number for turbulent flow was improved. The current research is beneficial for predicting the near-wall flow and heat transfer characteristics under conditions with strong interactions between the wall and the flame. [ABSTRACT FROM AUTHOR]

Stationary heating devices can be used to warm up the coolant of an internal combustion engine or the cabin air of a vehicle. This kind of heat engine transforms the chemical energy content of liquid fuels into heat energy. The combustion process and the emission of such a device is in focus in this study, which would be the first part in a greater project in the field. Therefore, some relevant parameters have been established. Relevant cycles have been chosen for the kinds of heat engines. It means a normal mode cycle for the stationary device and a WLTC cycle in the case of the direct injection gasoline engine. Fuel used was the same for both. This heat transfer process is such, that the combustion seems to be quite simple and rough in the stationary device compared to that of in internal combustion engine. This means an inhomogenous combustion with non-premixed flame at a low combustion temperature. This situation affects the emission characteristic accordingly, so causes low NOx and relatively high particle relevant emission comes out from the device. As far as the device's particle relevant emission is concerned it would be suitable for further investigation described at the end of the article. [ABSTRACT FROM AUTHOR]

Integrated energy systems (IES) for combined power, heat and refrigeration supply achieved a wide application due to high flexibility in matching current loading. So as electricity is easily convertible into any other form of energy, gas engines are widely applied as driving engines characterized by high electrical and overall efficiency of about 45% and 90%, respectively. However, the highest thermal efficiency is achieved at full matching heat generated by the engine and heat transformed. This is often impossible in actual practice, especially if the heat is transformed into refrigeration by the most efficient and widespread absorption lithium-bromide chillers (ACh) and the heat not consumed by the ACh is removed from the atmosphere through an emergency radiator. The unused heat might be transformed by an ejector chiller (ECh) as the simplest and cheapest. So as the thermodynamic efficiency of any combustion engine is influenced essentially by the sucked air temperature, the excessive refrigeration produced by the ECh, is used for IES cooling to generate additional electricity and increase the electrical and overall efficiency of the engine. Such a redistribution of heat enables the enhancement of the efficiency of IES with an absorption-ejector chiller (AECh). The modified criteria for the comparative estimation of thermodynamic efficiency of innovative IESs with AEChs without overgenerated heat lost against a typical IES with an ACh and heat lost are proposed. In contrast to well-known electrical and heat efficiency, it considers the magnitude of heat loss and enables us to compare the heat efficiency of any version of transforming heat to refrigeration with an ideal basic version of IES based on a highly efficient ACh, transforming all the heat removed from the engine without heat loss. Some alternative scheme decisions for heat recovery systems have been developed based on monitoring data. They might be easily implemented into a typical IES with ACh. [ABSTRACT FROM AUTHOR]

(1) Background: the shipping industry forced ships to adopt new energy-saving technologies to improve energy efficiency. With the timing modulation for the marine low-speed diesel engine S-CO2 Brayton cycle, the waste heat recovery system is optimized to improve fuel economy. (2) Methods: with the 6EX340EF marine low-speed diesel engine established in AVL Cruise M and verified by the bench test data, the model of the S-CO2 Recompression Brayton Cycle (SCRBC) system for the low-speed engine flue gas waste heat recovery was developed in EBSILON, and verified by SANDIA experimental data. On this basis, the effects of injection timing and valve timing parameters on the comprehensive performance of the main engine and the waste heat recovery system were investigated. By optimizing the timing modulation parameters through multi-objective genetic algorithm (MOGA) and evaluating the flue gas waste heat recovery from the perspective of thermodynamic performance and emission reduction, the research on the performance modulation method of the S-CO2 Brayton Cycle for flue gas waste heat in marine low-speed engines has been completed. (3) Results: the SCRBC with waste heat modulation will further increase the total power and efficiency, which in turn brings about a reduction in the fuel consumption rate. The efficiency of the SCRBC system with the addition of waste heat modulation increases by 2.28%, 1.04% and 2.07% at 50%, 75% and 100%, respectively. After adding the residual heat modulation, the maximum annual CO2 emission reduction of 748.51 × 103 kg·a−1 occurred at 50% load; with the exergy analysis, the cooler has the largest system exergy loss of 165 kW, with the exergy loss efficiency of 2.06% under 100% load. (4) Conclusions: the research on the performance modulation method of S-CO2 Brayton cycle for flue gas waste heat in the marine low-speed engine has been completed, which further improves the efficiency of the system and can be extended to other engines. [ABSTRACT FROM AUTHOR]

• A splitting organic Rankine cycle prototype is established. • Experiment proof that there is a splitting ratio that maximizes the performance. • Compared to single-loop ORC, splitting ORC's performance increases by 8.3%. • Splitting configuration has been proven feasible in improving system performance. The organic Rankine cycle (ORC) is an effective method for internal combustion engines' waste heat recovery. The waste heat from internal combustion engines primarily includes exhaust gas and engine cooling water. However, single-loop preheating and dual-loop ORC configurations are difficult to balance the recovery efficiency of the dual heat sources and the complexity of the equipment. The splitting ORC, as an effective method for enhancing the utilization of waste heat sources, has been proposed. This study developed for the first time a test bench for a splitting ORC with a recuperator (SR-ORC) for internal combustion engines' waste heat recovery, aiming to verify the enhancement effect of the system's performance by splitting the working fluid into two branches to recover the engine cooling water and exhaust gas waste heat respectively. The research results indicate that there exists an optimal working fluid pump speed and splitting ratio to maximize the net output power and efficiency of the system. Moreover, under the engine condition of rotating speed of 1100 rpm and torque of 600 N·m, the system achieves a maximum net power output of 2.81 kW, a maximum internal combustion engine efficiency improvement of 1.6 %, and a maximum thermal efficiency of 10.1 % at the maximum heat source safety operating range. Compared to the non-splitting mode of this test bench with the same engine and heat source condition, these values represent a relative improvement of 8.3 %, 9.6 %, and 27.9 %, respectively. [ABSTRACT FROM AUTHOR]

Due to the scarcity of fossil fuels and the potential for energy shortages, the use of energy-efficient devices is of utmost importance. There is an increasing trend in the utilization of heat pumps in air conditioning systems (heating/cooling) for both residential and commercial buildings. This article focuses on the analysis of the technical and economic aspects of gas engine heat pumps (GEHP) in various climates throughout Iran. The evaluation of this article revolves around two perspectives: that of the consumers and the government. The implementation of GEHP has been carefully considered from the consumers' perspective to ensure it does not have any negative effects on them. Additionally, from the government's point of view, the available resources are considered, and the supply of electricity and gas, along with their cost and energy consumption, are thoroughly investigated by the Ministries of Energy and Petroleum. The findings indicate that, from the consumers' perspective, the economic efficiency of GEHP can be up to 11 times higher than that of electric heat pumps (EHP). Moreover, from the government's viewpoint, GEHP leads to a reduction of over 92 % in electricity consumption, 5 % in gas consumption, and 92 % in annual expenses for the Ministry of Energy. Furthermore, the implementation of GEHP increases the income of the Ministry of Petroleum by 9.8 times. • Gas engine heat pumps (GEHPs) proposed to address electricity grid imbalance in Iran. • Consumer and government benefits of GEHPs across diverse Iranian regions analyzed. • Results show GEHPs reduce electricity consumption & costs for the Ministry of Energy. • GEHPs decrease gas consumption & boost revenue for the Ministry of Petroleum. [ABSTRACT FROM AUTHOR]

A third paper [[3]] modelled the performance of a cogeneration system in a greenhouse and evaluates its economic efficiency versus the European country and the kind of cultivation. The first [[1]] analysed the long-term economic performance of some projects in the Mediterranean climate of Athens, Greece, while the second [[2]] focused on the short-term, detailed economic performance of a cogeneration system in a hospital. The most favourable conditions for cogeneration use were found in Italy and the United Kingdom, with average spark ratios of more than 4, resulting in an annual total cost of heating energy close to -7 EUR/m SP 2 sp per year. [Extracted from the article]

In this paper the most promising developments of technology for gas engine-driven heat pumps for the last 15 years are presented. The purpose is to present the latest research studies and changes in this type of device, as well as to help readers to search for publications containing relevant aspects of gas engine heat pumps. Gas engine-driven heat pumps are devices for parallel heating and cooling production based on compressor heat pump technology. However, unlike heat pumps with compressors powered by electric motors, gas engine-driven heat pumps are driven by gas internal combustion engines. The reviewed solutions are an interesting alternative to traditional heating systems, characterized by the higher than 1.0 Performance Energy Ratio which expresses the degree of conversion of the energy contained in the fuel supplied to the device into energy transported to the utility needs. Presented in this review, papers show different solutions for conversion of the energy contained in the fuel into mechanical and thermal energy, and mechanical energy through the shaft system is used to drive the compressor of the heat pump. The presented study shows that, due to the complexity of the system and the wide range of applications, the technology has been subjected to detailed analyses and optimizations during the last 30 years in order to increase the efficiency of devices. [ABSTRACT FROM AUTHOR]

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The organic Rankine cycle (ORC) has been widely studied to recover waste heat from internal combustion engines in commercial on-road vehicles. To achieve a cost-effective ORC, a trade-off between factors such as costs, power outputs, back pressure, and weight needs to be carefully worked out. However, the trade-off is still a huge challenge in engine waste heat recovery. In this study, a thermoeconomic optimization study of a vehicle-mounted ORC unit is proposed to recover waste heat from various exhaust gas conditions of a light-duty vehicle. The optimization is carried out for four organic working fluids with different critical temperatures, respectively. Under the investigated working fluids, the lower specific investment cost (SIC) and higher mean net output power (MEOP) of ORC can be achieved using the organic working fluid with higher critical temperature. The maximum mean net output power is obtained by taking RC490 as working fluid and the payback period (PB) is 3.01 years when the petrol is EUR 1.5 per liter. The proposed strategy is compared with a thermodynamic optimization method with MEOP as an optimized objective. It shows that the proposed strategy reached SIC results more economically. The importance of taking the ORC weight and the back pressure caused by ORC installation into consideration during the preliminary design phase is highlighted. [ABSTRACT FROM AUTHOR]

Combined heat and power systems based on internal combustion engines have been widely used in last decades. Optimization of internal combustion engines from the standpoint of availability is a significant issue in cogeneration systems. Despite the noticeable advantages of homogeneous charge compression ignition engines such as high fuel efficiency and low particulate matters and nitrogen oxides emissions, controlling of ignition timing is a major concern in these engines. Utilizing exhaust gas recirculation technology is a method to control ignition timing in homogeneous charge compression ignition engines. The main objective of the present study work is to investigate the effect of exhaust gas recirculation technology on waste heat recovery from homogeneous charge compression ignition engines. A validated multi-zone combustion model is used for simulation of homogeneous charge compression ignition engine and availability analysis. Model is coupled with a semi-detailed chemical kinetics mechanism to predict the combustion species and reactions. Methane is used as engine fuel and study is conducted with different proportions of exhaust gases between 0 and 40 percent. The results show that lower contents of exhaust gas (10% or 20%) lead to higher recoverable energy form exhaust gases of engine. Engine output works increase by exhaust gas addition and cyclic irreversibility decrease. Exhaust gas addition results in higher efficiencies of first and second law and improves the utilization factor of the fuel chemical energy. Statistical analysis show that exhaust gas effects on recoverable waste heat from engine exhaust gases and utilization factor is significantly meaningful. [ABSTRACT FROM AUTHOR]

• A coupling control method of superheat and nitrogen oxides is proposed to control GEHP system. • The superheat regulation time is less than 400 s and the stability is good under the coupling control. • The fluctuation of the unit outlet temperature is less than 0.5 °C under variable load conditions. • The primary energy ratio of GEHP can reach 1.59 under coupling control and the NO x emission is less than 100 ppm. • The coupling control strategy achieve excellent performance and emission characteristic. Gas engine heat pump (GEHP) is gradually developing due to the high energy efficiency. However, the gas engine is easily disturbed by load fluctuation, which affects the stability of GEHP operation and causes higher nitrogen oxides (NO x) emission concentrations. Therefore, an efficient control method is necessary to ensure system stability, improve energy efficiency and reduce NO x emissions. In this paper, a coupling control strategy of superheat and NO x is proposed. The results show that the superheat can maintain stability with the small overshoot and adjustment time of less than 400 s when the engine speed changes. When the superheat setting value changed continuously, the superheat overshoot and error are less than 0.5 °C and the adjustment time is about 100 s. Meanwhile, the system outlet temperature is stable, the overshoot is less than 1 °C. The amplitude variation of the refrigerating capacity is similar to the amplitude variation of the superheat. The variation range of total heat capacity is greater than that of refrigerating capacity. In addition, the performance and emission of the GEHP are respectively studied when the superheat is 4 °C and 7 °C, at the optimum excess air coefficient. The NO x emissions are always below 100 ppm, but the primary energy ratio (PER) is higher under the superheat of 4 °C. Therefore, the proposed coupling control strategy can achieve good stability, excellent performance and emission characteristics. [ABSTRACT FROM AUTHOR]

Soot trapping on GPF, TWC Membrane fabrication on GPF, and soot trapping on TWC membrane have been studied using computer numerical simulation. The results of pressure drop, filtration efficiency, and morphology visualization satisfied the experimental results. The simulation could clarify the trapping phenomena up to 3D-nanoscale resolution, which overcame an experimental limitation. Visualization revealed the particles first trapped on the substrate generating a dendrite structure at the constricted area. Then, it expanded by accumulating flying particles until the bridge structure was completed, which is the same point of 100% filtration efficiency that proved the hypothesis from the experiment. [ABSTRACT FROM AUTHOR]

We develop a general method for calculating the thermal efficiency of arbitrary thermodynamic cycles defined in the pressure-volume (p–V) diagram. To demonstrate how effective our approach is, we calculate the thermal efficiency of ideal gas engines for a few non-trivial cycles in the p–V diagram, including a circular shape, a heart shape, a cycloid of Ceva, and a star-shaped curve. We determine the segments along the cycle where heat is absorbed or released from the heat engine. Our method can be applied to any gas model, and, as an example, we present the results for the van der Waals gas. [ABSTRACT FROM AUTHOR]

The fuel efficiency of gas engines is effected by the temperature of intake air at the suction of turbocharger. The data on dependence of fuel consumption and engine electric power on the intake air temperature were monitored for Jenbacher gas engine JMS 420 GS-N.LC to evaluate its influence. A waste heat of engine is rejected for heating water to the temperature of about 90 °C. The heat received is used in absorption lithium-bromide chiller to produce a cold in the form of chilled water. A cooling capacity of absorption chillerfirstly is spent for technological needs and then for feeding the central air conditioner for cooling the ambient air incoming the engine room, from where the air is sucked by the engine turbocharger. The monitoring data revealed the reserves to enhance the efficiency of traditional cooling system of intake air by absorption chiller through deeper cooling. This concept can be realized in two ways: by addition cooling a chilled water from absorption chiller to about 5-7 °C for feeding engine intake air cooler or by two-stage cooling with precooling ambient air by chilled water from adsorption chiller, in the first stage and subsequent deep cooling air to the temperatures 7-10 °C in the second stage of intake air cooler by using a refrigerant as a coolant. In both cases the ejector chiller could be applied as the most simple in design. [ABSTRACT FROM AUTHOR]

Software applications can be valuable tools to assist in the study of thermal engines and thermodynamics. This study presents a spreadsheet that allows students to model and analyze a commercial turbocharger coupled to an internal combustion engine. The air‐fuel cycle of both naturally aspirated and turbocharged engines is computed. The computation method is based on iterative procedures that, in a straightforward way, lead to the performance analysis of the compressor, turbine, and the coupled system. The spreadsheet requires the engine geometry, its rated and peak torque conditions, and the compressor‐turbine maps. The analysis of the engine‐turbocharger coupling provides its operating range, and it gives experience to students about this type of device in an easy and reliable way. [ABSTRACT FROM AUTHOR]

With the daily rise in environmental issues due to the use of conventional fuels, researchers are motivated to use renewable energy sources. One of such waste heat and low-temperature differential driven energy sources is the Stirling engine. The performance of the Stirling engine can be improved by finding out the optimum operating and geometrical parameters with suitable working gas and thermal model. Based on this motivation, the current work focuses on the multiobjective optimization of the Stirling engine using the finite speed thermodynamic model and methane gas as the working fluid. Considering output power and pressure drop as two objective functions, the system is optimized using 11 geometrical and thermal design parameters. The optimization results are obtained in the form of the Pareto frontier. A sensitivity assessment is carried out to observe the decision variables, which are having a more sensitive effect on the optimization objectives. Optimization results reveal that 99.83% change in power output and 78% change in total pressure drop can take place in the two-dimensional optimization space. The optimal solution closest to the ideal solution has output power and pressure drop values as 12.31 kW and 22.76 kPa, respectively. [ABSTRACT FROM AUTHOR]

Internal combustion engines are used in most vehicles around the world to power the transport sector. Efficiency improvement, emission reduction, and utilization of alternative fuels are the main aspects of current IC engine research. Hydrogen-enhanced combustion proved to be one of the efficient ways to achieve such goals. But the problem lies in the storage of hydrogen for the transportation sector, and on-board fuel reforming is a promising option for solving this issue. It deals with transforming a suitable liquid fuel (methanol) into an H 2 -rich gas using a catalytic conversion process. For sustaining the reforming reaction, the required heat energy is taken from engine exhaust waste heat, this process is known as thermochemical recuperation. Number of studies on the reformers utilized for on-board hydrogen generation using engine exhaust heat are limited in the literature. The present study investigates the performance of a reactor that uses the exhaust gas heat energy for sustaining the reforming reaction. A numerical analysis was performed over a selected reactor where exhaust gases were flowing at one side, while on the other, the reforming reaction was taking place with the help of heat provided by high-temperature exhaust gases. A packed bed-type reactor was chosen for the current study and a parametric study was conducted where the effects of various operating parameters on both reacting and heating sides on the reactor's performance were investigated. It was found that temperature was the most influential inlet parameter among others. Steam/Carbon ratio and flow configuration had a negligible effect on the hydrogen yield as well as methanol conversion. Reactant inlet velocity increment revealed a significant drop in methanol conversion as it reduces the residence time for reforming reaction in the catalyst zone. • Hydrogen-enhanced combustion for improving engine performance and emission reduction. • Solving problem of hydrogen storage through on-board generation using methanol reforming. • Utilizing engine exhaust heat for driving reforming reaction: Thermochemical recuperation. • Reformer design and conducting numerical study. • Focusing on methanol conversion and H 2 - yield dependency by carrying parametric study. [ABSTRACT FROM AUTHOR]

[Display omitted] • A variable universe fuzzy PID control algorithm is proposed for the superheat. • The combined model of electronic expansion valve and evaporator is established. • Simulation and experimental verification are implemented. • The proposed control method has strong robustness and fast regulation. Gas engine heat pump (GEHP) is more and more widely used in various commercial buildings and residential buildings because of its advantages of high efficiency, energy saving and environmental protection. However, unstable superheat is easy to cause unstable operation of GEHP system, resulting in lower energy efficiency and unnecessary energy waste. Therefore, to achieve the reliable control of superheat, a variable universe fuzzy Proportional-Integral-Differential (PID) control method is proposed in this study. First, the combined control model of electronic expansion valve (EEV) and evaporator is established. A step response curve of superheat to the opening of EEV and the parameters of the control model are obtained by experiment. In addition, simulation of the proposed control method has been performed and compared with other two methods to evaluate the control performance. Meanwhile, the proposed control method is applied to the test bench for superheat control. The results showed that the fluctuation of superheat after reaching the steady state under the control method was kept within 0.3 °C, and the superheat could return to the steady state in a short time after being disturbed. Both simulation and experiment results indicate that the proposed control method has strong robustness and fast regulation. [ABSTRACT FROM AUTHOR]

The cooling system is an important subsystem of an internal combustion engine, which plays a vital role in the engine's dynamical characteristic, the fuel economy, and emission output performance at each speed and load. This paper proposes an economical and precise model for an electric cooling system, including the modeling of engine heat rejection, water jacket temperature, and other parts of the cooling system. This model ensures that the engine operates precisely at the designated temperature and the total power consumption of the cooling system takes the minimum value at some power proportion of fan and pump. Speed maps for the cooling fan and pump at different speeds and loads of engine are predicted, which can be stored in the electronic control unit (ECU). This model was validated on a single-cylinder diesel engine, called the DK32. Furthermore, it was used to tune the temperature of the water jacket precisely. The results show that in the common use case, the electric cooling system can save the power of 255 W in contrast with the mechanical cooling system, which is about 1.9% of the engine's power output. In addition, the validation results of the DK32 engine meet the non-road mobile machinery China-IV emission standards. [ABSTRACT FROM AUTHOR]

A novel heat recovery strategy for internal combustion engines is proposed. The aim is to recover thermal energy from the engine exhaust gases and through cylinder walls to heat pressurized water to supercritical conditions and to directly inject such supercritical water into the combustion chamber. Herein, this strategy is applied to a spark ignition, four‐stroke, port fuel injection engine. An in‐house solver, which includes a heat exchanger model, has been developed to conduct numerical simulations of the apparatus. At first, the engine model has been validated by comparing the results with experimental measurements. Then, a parametric analysis has been conducted to maximize the engine efficiency by varying the injection start timing, the injector diameter, and the water/fuel ratio. A single‐objective genetic algorithm has been used to select the optimal set of such parameters. Finally, a multiobjective genetic algorithm has been used to maximize the engine efficiency and minimize the exhaust gas–water heat exchanger size. The results show that the proposed approach may lead to a significant increase in the engine efficiency, up to about 12%. [ABSTRACT FROM AUTHOR]

Theoretical and experimental investigations indicate that at high loads such as 3/4 throttling or more and high speeds such as 3000 rpm or more, the exhaust gas temperatures of the Internal Combustion engines are about 900-1000 K. The amount of heat wasted with exhaust gas of the Internal Combustion engines is equivalent to the power of them. By considering this feature of the Internal Combustion engines, a Hybrid engine consisting of an Internal Combustion (IC) engine and a gamma type Stirling engine was proposed and analyzed from the thermodynamic point of view. Hybrid engine is formed by combining the Stirling and IC engines via a common crankshaft and a common cylinder. The Internal Combustion engine may be a four stroke Diesel engine having an unconventional piston consisting of a crown and a rod. Via using this kind of pistons, two chambers are created in the same cylinder where one of them take part at above of the piston crown, while the other is taking part at below of the piston crown. In the combined engine presented here, the chamber at below of the piston crown is used as the expansion volume of the Stirling engine while the other chamber is being used as operational volume of the Diesel engine. In this study the thermodynamic performance of the Hybrid engine was investigated via using statistical values of common Diesel engines. For Stirling engine; 800 K heater surface temperature, 392 K cooler surface temperature, 800 W/m2K heat transfer coefficient in regenerator, 300 W/m2K heat transfer coefficient in cooler and heater, 250 rad/s engine speed and 12.5 bar air charging pressure were used as principal inputs. The output power of the Diesel engine was assumed to be 120 kW which provides 120 kW heat to Stirling engine. The heat transfer areas of cooler, heater and regenerator were optimized as 0.33 m2, 0.6 m2 and 4.6 m2 respectively. The optimum thermal efficiency and power of the Stirling engine were determined as 47 % and 24 kW. The total thermal efficiency of the combined engine is expected to increase 6 % compared to the stand-alone Internal Combustion engine. For 12.5 bar average gas pressure in the cylinder of Diesel engine, the working fluid mass in the Stirling engine was determined as 17g. [ABSTRACT FROM AUTHOR]