This paper investigates the reliability of internal marine combustion engines using an integrated approach that combines Fault Tree Analysis(FTA)and Bayesian Networks(BN).FTA provides a structured,top-down method for ...This paper investigates the reliability of internal marine combustion engines using an integrated approach that combines Fault Tree Analysis(FTA)and Bayesian Networks(BN).FTA provides a structured,top-down method for identifying critical failure modes and their root causes,while BN introduces flexibility in probabilistic reasoning,enabling dynamic updates based on new evidence.This dual methodology overcomes the limitations of static FTA models,offering a comprehensive framework for system reliability analysis.Critical failures,including External Leakage(ELU),Failure to Start(FTS),and Overheating(OHE),were identified as key risks.By incorporating redundancy into high-risk components such as pumps and batteries,the likelihood of these failures was significantly reduced.For instance,redundant pumps reduced the probability of ELU by 31.88%,while additional batteries decreased the occurrence of FTS by 36.45%.The results underscore the practical benefits of combining FTA and BN for enhancing system reliability,particularly in maritime applications where operational safety and efficiency are critical.This research provides valuable insights for maintenance planning and highlights the importance of redundancy in critical systems,especially as the industry transitions toward more autonomous vessels.展开更多
The current work includes a numerical investigation of the effect of biodiesel blends with different aluminum oxide nanoparticle concentrations on the combustion process in the cylinder of a diesel engine.IC Engine Fl...The current work includes a numerical investigation of the effect of biodiesel blends with different aluminum oxide nanoparticle concentrations on the combustion process in the cylinder of a diesel engine.IC Engine Fluent,a specialist computational tool in the ANSYS software,was used to simulate internal combustion engine dynamics and combustion processes.Numerical analysis was carried out using biodiesel blends with three Al_(2)O_(3) nanoparticles in 50,100,and 150 ppm concentrations.The tested samples are called D100,B20,B20A50,B20A100,and B20A150 accordingly.The modeling runs were carried out at various engine loads of 0,100,and 200 Nm at a rated speed of 1800 rpm.The combustion characteristics are improved due to the catalytic effect and higher surface area of nano additives.The results showed the improvements in the combustion process as the result of nanoparticle addition,which led to the higher peak cylinder pressure.The increases in the peak cylinder pressures for B20A50,B20A100,and B20A150 about B20 were 3%,5%,and 8%,respectively,at load 200 Nm.The simulation found that the maximum temperature for biodiesel blends diesel was higher than pure diesel;this was due to higher hydrocarbon values of B20.Also,nano-additives caused a decrease in temperatures in the combustion of biofuels.展开更多
Knowing the optimal operating parameters of Stirling engines is important for efficient combustion through adaptability to changed pressures and oxygen atmospheres. In this study, the optimum operating conditions for ...Knowing the optimal operating parameters of Stirling engines is important for efficient combustion through adaptability to changed pressures and oxygen atmospheres. In this study, the optimum operating conditions for efficient combustion in a singular Stirling engine combustor at different oxygen atmospheres were investigated and determined. Numerical simulations were performed to investigate the effects of ejection ratio and pressure on combustion performance. In an oxygen/carbon dioxide atmosphere, the results show that increasing the ejection ratio substantially alters the flame distribution in the Stirling engine combustor, increasing heat transfer and external combustion efficiency. In contrast, increasing the ejection ratio reduces the average and maximum temperatures of the Stirling engine combustor. Increased pressure affects the flame distribution in the Stirling engine combustor and impedes the flow and convective heat transfer in the combustor, reducing the overall external combustion efficiency at pressures above 6.5 MPa. In an air/carbon dioxide atmosphere, an increased ejection ratio reduces the average and maximum temperatures in the Stirling engine combustor. However, the overall flame distribution does not change substantially. The external combustion efficiency tends to increase and then decrease because of two opposing factors: the increase in the convective heat transfer coefficient and the decrease in the temperature difference. Increasing pressure inhibits forced convection heat transfer in the Stirling engine combustor, reducing external combustion efficiency, which drops from 78% to 65% when pressure increases from 0.2 MPa to 0.5 MPa.展开更多
Powder-Fueled Water Ramjet Engine(PFWRE)is of great attraction for high-speed and long-voyage underwater propulsion,as well as air–water trans-media navigation applications due to its high energy density and thrust a...Powder-Fueled Water Ramjet Engine(PFWRE)is of great attraction for high-speed and long-voyage underwater propulsion,as well as air–water trans-media navigation applications due to its high energy density and thrust adjustability.However,the complex multiphase combustion process in the combustor significantly affects engine performance.In this study,a detailed model for aluminum particle combustion in water vapor is developed and validated via literature data as well as the ground direct-connected test we conducted.Thereafter,the numerical study on the multiphase combustion process inside the aluminum-based PFWRE combustor is carried out within the Euler–Lagrange framework using the developed model.Results show that a reverse rotating vortex pair before the primary water injection causes particles to flow back towards the combustor head and leads to product deposition.Aluminum particles external to the powder jet have shorter preheating time than internal particles and burn out in advance.The analysis of the particle combustion process indicates that the flame structure inside the combustor consists of the particle preheating zone,the surface combustion heat release zone,the gas-phase combustion heat release zone,and the post-flame zone.In the present configuration,as the particle size increases from 10μm to 20μm,the preheating zone length increases from 35 mm to 85 mm.Meanwhile,heat release from gas-phase combustion decreases,and the average temperature of the combustor head first increases and then decreases.This study not only provides insight into the multiphase combustion characteristics of the aluminum-based PFWRE combustor but also offers guidance for the design of the combustion organization schemes and engine structure optimization.展开更多
A novel steady-state optimization （SSO） of internal combustion engine （ICE） strategy is proposed to maximize the efficiency of the overall powertrain for hybrid electric vehicles, in which the ICE efficiency, the ...A novel steady-state optimization （SSO） of internal combustion engine （ICE） strategy is proposed to maximize the efficiency of the overall powertrain for hybrid electric vehicles, in which the ICE efficiency, the efficiencies of the electric motor （EM） and the energy storage device are all explicitly taken into account. In addition, a novel idle optimization of ICE strategy is implemented to obtain the optimal idle operating point of the ICE and corresponding optimal parking generation power of the EM using the view of the novel SSO of ICE strategy. Simulations results show that potential fuel economy improvement is achieved relative to the conventional one which only optimized the ICE efficiency by the novel SSO of ICE strategy, and fuel consumption per voltage increment decreases a lot during the parking charge by the novel idle optimization of ICE strategy.展开更多
In this study, combustion of methane was simulated using four kinetic models of methane in CHEMKIN 4.1.1 for 0-D closed internal combustion （IC） engine reactor. Two detailed （GRIMECH3.0 ＆ UBC MECH2.0） and two red...In this study, combustion of methane was simulated using four kinetic models of methane in CHEMKIN 4.1.1 for 0-D closed internal combustion （IC） engine reactor. Two detailed （GRIMECH3.0 ＆ UBC MECH2.0） and two reduced （One step ＆ Four steps） models were examined for various IC engine designs. The detailed models （GRIMECH3.0, ＆ UBC MECH2.0） and 4-step models successfully predicted the combustion while global model was unable to predict any combustion reaction. This study illustrated that the detailed model showed good concordances in the prediction of chamber pressure, temperature and major combustion species profiles. The detailed models also exhibited the capabilities to predict the pollutants formation in an IC engine while the reduced schemes showed failure in the prediction of pollutants emissions. Although, there are discrepancies among the profiles of four considered model, the detailed models （GRIMECH3.0 ＆ UBC MECH2.0） produced the acceptable agreement in the species prediction and formation of pollutants.展开更多
In the global background of“Carbon Peak”and“Carbon Neutral”,natural gas engines show great advantages in energy-saving and pollution reduction.However,natural gas engines suffer from the issues of combustion insta...In the global background of“Carbon Peak”and“Carbon Neutral”,natural gas engines show great advantages in energy-saving and pollution reduction.However,natural gas engines suffer from the issues of combustion instabilities when operating under lean burning conditions.In this paper,the role of turbulence enhancement in improving the lean combustion of natural gas was investigated in an optical SI engine with high compression ratios.Variable swirl control valves(SCV)were designed and intake tumble and swirl were combined to regulate turbulent motion and turbulent intensity.Particle image velocimetry was employed to measure in-cylinder turbulence,and transient pressure acquisition and high-speed photography were synchronously performed to quantify combustion evolutions.The results show that incylinder turbulent intensity is enhanced significantly through reducing SCV closing angles.Such that flame propagation speed and thermal efficiency are significantly improved with an increment of turbulent intensity,which indicated that mean effective pressures are not sensitive to spark timing.The analysis of flame images shows that the combined turbulence increases in the radial orientation from the spark plug to the cylinder wall,leading to an earlier flame kernel formation and a faster burning rate.Therefore,the combined turbulence has the potential in reducing the cyclic variations of lean combustion in natural gas engines.展开更多
Crankshaft assembly failure is one of the main factors that affects the reliability and service life of engines.The linear lumped mass method,which has been universally applied to the dynamic modeling of engine cranks...Crankshaft assembly failure is one of the main factors that affects the reliability and service life of engines.The linear lumped mass method,which has been universally applied to the dynamic modeling of engine crankshaft assembly,reveals obvious simulation errors.The nonlinear dynamic characteristics of a crankshaft assembly are instructionally significant to the improvement of modeling correctness.In this paper,a general expression for the non-constant inertia of a crankshaft assembly is derived based on the instantaneous kinetic energy equivalence method.The nonlinear dynamic equations of a multi-cylinder crankshaft assembly are established using the Lagrange rule considering nonlinear factors such as the non-constant inertia of reciprocating components and the structural damping of shaft segments.The natural frequency and mode shapes of a crankshaft assembly are investigated employing the eigenvector method.The forced vibration response of a diesel engine crankshaft assembly taking into account the non-constant inertia is studied using the numerical integral method.The simulation results are compared with a lumped mass model and a detailed model using the system matrix method.Results of non-linear torsional vibration analysis indicate that the additional excitation torque created by non-constant inertia activates the 2nd order rolling vibration,and the additional damping torque resulting from the non-constant inertia is the main nonlinear factor.The increased torsional angular displacement evoked by the high order excitation torque relates to the non-constant inertia.This research project is aimed at improving nonlinear dynamics theory,and the confirmed nonlinear parameters can be used for the structure design of a crankshaft assembly.展开更多
This paper proposes an H-infinity combustion control method for diesel engines. The plant model is the discrete dynamics model developed by Yasuda et al., which is implementable on a real engine control unit. We intro...This paper proposes an H-infinity combustion control method for diesel engines. The plant model is the discrete dynamics model developed by Yasuda et al., which is implementable on a real engine control unit. We introduce a two-degree-of-freedom control scheme with a feedback controller and a feedforward controller. This scheme achieves both good feedback properties, such as disturbance suppression and robust stability, and a good transient response. The feedforward controller is designed by taking the inverse of the static plant model, and the feedback controller is designed by the H-infinity control method, which reduces the effect of the trubocharger lag. The effectiveness of the proposed method is evaluated in simulations using the nonlinear discrete dynamics model.展开更多
The free piston Stirling engine external combustion system was simulated to investigate the diesel-air combustion characteristics in order to demonstrate its feasibility by computational fluid dynamics(CFD). The diffe...The free piston Stirling engine external combustion system was simulated to investigate the diesel-air combustion characteristics in order to demonstrate its feasibility by computational fluid dynamics(CFD). The different effects on combustion were distinguished by analyzing the combustion burner, the injection position of diesel oil, the front tube arrangement of Stirling heater head and the back fin. The results show that the tilted front tube arrangement of the heater head with the back fin is the best practicable technology while the distance between the diesel nozzle position and the swirler top is 0. Its total heat flux is 15.6 kW, and the average heat transfer coefficients of the front and back tubes are 127 W/(m2· K) and 192 W/(m2· K), respectively. The heat transfer is mainly through convection, and the proportion of radiative heat transfer is only 16.9%. The best combustion efficiency of the free piston Stirling engine external combustion system is 86%.展开更多
For capturing and recycling of CO_(2)in the internal combustion engine,Rankle cycle engine can reduce the exhaust pollutants effectively under the condition of ensuring the engine thermal efficiency by using the techn...For capturing and recycling of CO_(2)in the internal combustion engine,Rankle cycle engine can reduce the exhaust pollutants effectively under the condition of ensuring the engine thermal efficiency by using the techniques of spraying water in the cylinder and optimizing the ignition advance angle.However,due to the water spray nozzle need to be installed on the cylinder,which increases the cylinder head design difficulty and makes the combustion conditions become more complicated.In this paper,a new method is presented to carry out the closing inlet and exhaust system for internal combustion engines.The proposed new method uses liquid oxygen to solidify part of cooled CO_(2)from exhaust system into dry ice and the liquid oxygen turns into gas oxygen which is sent to inlet system.The other part of CO_(2)is sent to inlet system and mixed with oxygen,which can reduce the oxygen-enriched combustion detonation tendency and make combustion stable.Computing grid of the IP52FMI single-cylinder four-stroke gasoline-engine is established according to the actual shape of the combustion chamber using KIVA-3V program.The effects of exhaust gas recirculation(EGR)rate are analyzed on the temperatures,the pressures and the instantaneous heat release rates when the EGR rate is more than 8%.The possibility of enclosing intake and exhaust system for engine is verified.The carbon dioxide trapping device is designed and the IP52FMI engine is transformed and the CO_(2)capture experiment is carried out.The experimental results show that when the EGR rate is 36%for the optimum EGR rate.When the liquid oxygen of 35.80-437.40 g is imported into the device and last 1-20 min,respectively,21.50-701.30 g dry ice is obtained.This research proposes a new design method which can capture CO_(2)for vehicular internal combustion engine.展开更多
Increasing energy consumption in the transportation sector results in challenging greenhouse gas(GHG)emissions and environmental problems.This paper involved integrated assessments on GHG emissions and emergy of the l...Increasing energy consumption in the transportation sector results in challenging greenhouse gas(GHG)emissions and environmental problems.This paper involved integrated assessments on GHG emissions and emergy of the life cycle for the internal combustion engine(ICE)and electric automobiles in the USA over the entire assumed fifteen-year lifetime.The hotspots of GHG emissions as well as emergy indices for the major processes of automobile life cycle within the defined system boundaries have been investigated.The potential strategies for reducing GHG emissions and emergy in the life cycle of both ICE and electric automobiles were further proposed.Based on the current results,the total GHG emissions from the life cycle of ICE automobiles are 4.48 E+07 kg CO2-e which is320 times higher than that of the electric automobiles.The hotspot area of the GHG emissions from ICE and electric automobiles are operation phase and manufacturing process,respectively.Interesting results were observed that comparable total emergy of the ICE automobiles and electric automobiles have been calculated which were 1.54 E+17 and 2.20 E+17 sej,respectively.Analysis on emergy index evidenced a better environmental sustainability of electric automobiles than ICE automobiles over the life cycle due to its higher ESI.To the authors’knowledge,it is the first time to integrate the analysis of GHG emissions together with emergy in industrial area of automobile engineering.It is expected that the integration of emergy and GHG emissions analysis may provide a comprehensive perspective on eco-industrial sustainability of automobile engineering.展开更多
In order to enhance catalytic combustion efficiency, a premixed hydrogen /air combustion model of the micro turbine engine is established under different excess air ratio, inlet velocity and heat transfer coefficient....In order to enhance catalytic combustion efficiency, a premixed hydrogen /air combustion model of the micro turbine engine is established under different excess air ratio, inlet velocity and heat transfer coefficient. And effects of inlet velocity, excess air coefficient and heat transfer coefficient on the catalytic combustion efficiency of the hydrogen have been analyzed by the FLUENT with CHEMKIN reaction mechanisms and the fuzzy grey relation theory. It is showed that inlet velocity has a more intuitive influence on the catalytic combustion efficiency of the hydrogen. A higher efficiency can be obtained with a lower inlet velocity. The optimum excess air coefficient is in the range of 0.94 to 1.0, the catalytic combustion efficiency of the hydrogen will be declined if the excess air coefficient exceeded 1.0. The effect of heat transfer coefficient on the catalytic combustion efficiency of the hydrogen mainly embodies in the case of the excess air coefficient exceeded 1.0, however, the effect will be declined if the heat transfer coefficient exceeded 4.0. The fuzzy grey relation degrees of the inlet velocity, heat transfer coefficient and excess air coefficient on the catalytic combustion efficiency of the hydrogen are 0.640945, 0.633214 and 0.547892 respectively.展开更多
To improve the combustion chamber shape that can decrease the directed injection （DI） diesel emission, the theories of DI diesel spray, combustion and pollutant formation model are analysed and implemented based on ...To improve the combustion chamber shape that can decrease the directed injection （DI） diesel emission, the theories of DI diesel spray, combustion and pollutant formation model are analysed and implemented based on the CFD code FIRE. Results show that the chamber with contracting orifice can get stronger squish swirl intensity. The results of the verification studies show a good accordance with the measurements and reveal that the individual processes of spray, evolution, combustion and pollutant formation are well captured in FIRE. Finally, based on the analyzing and comparing of the calculation results of different chambers, a combustion chamber of contracting orifice geometry with lower emission is proposed.展开更多
To study the economic advantages of hydrogen internal combustion engine, an experimen- tal study was carried out using a 2.0 L port fuel-injected （PFI） hydrogen internal combustion engine. Influences of fuel-air equ...To study the economic advantages of hydrogen internal combustion engine, an experimen- tal study was carried out using a 2.0 L port fuel-injected （PFI） hydrogen internal combustion engine. Influences of fuel-air equivalence ratio φ, speed, and ignition advance angle on heat efficiency were determined. Test results showed that indicated thermal efficiency （ ITE ） firstly increased with fuel- air equivalence ratio, achieved the maximum value of 40. 4% （ φ = 0.3 ）, and then decreased when was more than 0. 3. ITE increased as speed rises. Mechanical efficiency increased as fuel-air equiva- lence ratio increased, whereas mechanical efficiency decreased as speed increased, with maximum mechanical efficiency reaching 90%. Brake thermal efficiency （BTE） was influenced by ITE and me- chanical efficiency, at the maximum value of 35% （φ =0.5, 2 000 r/min）. The optimal ignition ad- vance angle of each condition resulting in the maximum BTE was also studied. With increasing fuel- air equivalence ratio, the optimal ignition angle became closer to the top dead center （ TDC ）. The test results and the conclusions exhibited a guiding role on hydrogen internal combustion engine opti- mization.展开更多
A 500 N model engine filled with LO2/GCH4 was designed and manufactured.A series of ignition attempts were performed in it by both head spark plug and body spark plug.Results show that the engine can be ignited but th...A 500 N model engine filled with LO2/GCH4 was designed and manufactured.A series of ignition attempts were performed in it by both head spark plug and body spark plug.Results show that the engine can be ignited but the combustion cannot be sustained when head spark plug applied as the plug tip was set in the gaseous low-velocity zone with thin spray.This is mainly because flame from this zone cannot supply enough ignition energy for the whole chamber.However,reliable ignition and stable combustion can be achieved by body spark plug.As the O/F ratio increases from 2.61 to 3.49,chamber pressure increases from 0.474 to 0.925 MPa and combustion efficiency increases from 57.8%to 95.1%.This is determined by the injector configuration,which cannot produce the sufficiently breakup of the liquid oxygen on the low flow rate case.展开更多
The basic difference non-equal interval model GM(1,1) in grey theory was used to fit and forecast data series with non-equal lengths and different inertias, acquired from oil monitoring of internal combustion engines....The basic difference non-equal interval model GM(1,1) in grey theory was used to fit and forecast data series with non-equal lengths and different inertias, acquired from oil monitoring of internal combustion engines. The fitted and forecasted results show that the length or inertia of a sequence affects its precision very much, i.e. the bigger the inertia of a sequence is, or the shorter the length of a series is, the less the errors of fitted and forecasted results are. Based on the research results, it is suggested that short series should be applied to be fitted and forecasted; for longer series, the newer datum should be applied instead of the older datum to be analyzed by non- equalinterval GM(1,1) to improve the forecasted and fitted precision, and that data sequence should be verified to satisfy the conditions of grey forecasting.展开更多
With the purpose of efficiently predicting structural radiated noise of internal combustion engine（I.C.E.）,a new simulation technique is introduced,which is an approach based on boundary element method （BEM）,acous...With the purpose of efficiently predicting structural radiated noise of internal combustion engine（I.C.E.）,a new simulation technique is introduced,which is an approach based on boundary element method （BEM）,acoustic transfer vector（ATV） technique and coupled boundary element model and finite element model （BEM-FEM） approach.Analyses of vibration exciting loads,computing structural dynamic characteristics and dynamic responses have led to theoretical results,which are tested on an L6 diesel engine to validate this proposed technique in engineering practice.展开更多
In order to address typical problems due to the huge demand of oil for consumption in traditional internal combustion engines,a new more efficient combustion mode is proposed and studied in the framework of Computatio...In order to address typical problems due to the huge demand of oil for consumption in traditional internal combustion engines,a new more efficient combustion mode is proposed and studied in the framework of Computational Fluid Dynamics(CFD).Moreover,a Non-dominated Sorting Genetic Algorithm(NSGA-Ⅱ)is applied to optimize the related parameters,namely,the engine methanol ratio,the fuel injection time,the initial temperature,the Exhaust Gas Re-Circulation(EGR)rate,and the initial pressure.The so-called Conventional Diesel Combustion(CDC),Homogeneous Charge Compression Ignition(HCCI)and the Reactivity Controlled Compression Ignition(RCCI)combustion modes are compared.The results show that RCCI has a higher methanol ratio and an earlier injection timing with moderate EGR rate and higher initial pressure.The initial temperature increases as the methanol ratio increases.In comparison,CDC has the lowest hydrocarbon and CO emissions and the highest combustion efficiency.At different crankshaft rotation angles corresponding to 50%of the combustion amount(CA50),the combustion temperature and boundary layer temperature of HCCI change significantly,while those of RCCI undergo limited variations.At the same CA50,the exergy losses of HCCI and RCCI are lower than that of the CDC.On the basis of these findings,it can be concluded that the methanol/diesel RCCI engine can be used to obtain a clean and efficient combustion process,which should be regarded as a promising combustion mode.展开更多
Research on dual-fuel(DF)engines has become increasingly important as engine manufacturers seek to reduce carbon dioxide emissions.There are significant advantages of using diesel pilot-ignited natural gas engines as ...Research on dual-fuel(DF)engines has become increasingly important as engine manufacturers seek to reduce carbon dioxide emissions.There are significant advantages of using diesel pilot-ignited natural gas engines as DF engines.However,different combustion modes exist due to variations in the formation of the mixture.This research used a simulation model and numerical simulations to explore the combustion characteristics of high-pressure direct injection(HPDI),partially premixed compression ignition(PPCI),and double pilot injection premixed compression ignition(DPPCI)combustion modes under a low-medium load.The results revealed that the DPPCI combustion mode provides higher gross indicated thermal efficiency and more acceptable total hydrocarbon(THC)emission levels than the other modes.Due to its relatively good performance,an experimental study was conducted on the DPPCI mode engine to evaluate the impact of the diesel dual-injection strategy on the combustion process.In the DPPCI mode,a delay in the second pilot ignition injection time increased THC emissions(a maximum value of 4.27g/(kW·h)),decreased the emission of nitrogen oxides(a maximum value of 7.64 g/(kW·h)),increased and then subsequently decreased the gross indicated thermal efficiency values,which reached 50.4%under low-medium loads.展开更多
基金supported by Istanbul Technical University(Project No.45698)supported through the“Young Researchers’Career Development Project-training of doctoral students”of the Croatian Science Foundation.
文摘This paper investigates the reliability of internal marine combustion engines using an integrated approach that combines Fault Tree Analysis(FTA)and Bayesian Networks(BN).FTA provides a structured,top-down method for identifying critical failure modes and their root causes,while BN introduces flexibility in probabilistic reasoning,enabling dynamic updates based on new evidence.This dual methodology overcomes the limitations of static FTA models,offering a comprehensive framework for system reliability analysis.Critical failures,including External Leakage(ELU),Failure to Start(FTS),and Overheating(OHE),were identified as key risks.By incorporating redundancy into high-risk components such as pumps and batteries,the likelihood of these failures was significantly reduced.For instance,redundant pumps reduced the probability of ELU by 31.88%,while additional batteries decreased the occurrence of FTS by 36.45%.The results underscore the practical benefits of combining FTA and BN for enhancing system reliability,particularly in maritime applications where operational safety and efficiency are critical.This research provides valuable insights for maintenance planning and highlights the importance of redundancy in critical systems,especially as the industry transitions toward more autonomous vessels.
文摘The current work includes a numerical investigation of the effect of biodiesel blends with different aluminum oxide nanoparticle concentrations on the combustion process in the cylinder of a diesel engine.IC Engine Fluent,a specialist computational tool in the ANSYS software,was used to simulate internal combustion engine dynamics and combustion processes.Numerical analysis was carried out using biodiesel blends with three Al_(2)O_(3) nanoparticles in 50,100,and 150 ppm concentrations.The tested samples are called D100,B20,B20A50,B20A100,and B20A150 accordingly.The modeling runs were carried out at various engine loads of 0,100,and 200 Nm at a rated speed of 1800 rpm.The combustion characteristics are improved due to the catalytic effect and higher surface area of nano additives.The results showed the improvements in the combustion process as the result of nanoparticle addition,which led to the higher peak cylinder pressure.The increases in the peak cylinder pressures for B20A50,B20A100,and B20A150 about B20 were 3%,5%,and 8%,respectively,at load 200 Nm.The simulation found that the maximum temperature for biodiesel blends diesel was higher than pure diesel;this was due to higher hydrocarbon values of B20.Also,nano-additives caused a decrease in temperatures in the combustion of biofuels.
基金Supported by the Shanghai Rising Star Program (Grant No. 21QB1403900)the Shanghai Municipal Commission of Science and Technology (Grant No. 22170712600)。
文摘Knowing the optimal operating parameters of Stirling engines is important for efficient combustion through adaptability to changed pressures and oxygen atmospheres. In this study, the optimum operating conditions for efficient combustion in a singular Stirling engine combustor at different oxygen atmospheres were investigated and determined. Numerical simulations were performed to investigate the effects of ejection ratio and pressure on combustion performance. In an oxygen/carbon dioxide atmosphere, the results show that increasing the ejection ratio substantially alters the flame distribution in the Stirling engine combustor, increasing heat transfer and external combustion efficiency. In contrast, increasing the ejection ratio reduces the average and maximum temperatures of the Stirling engine combustor. Increased pressure affects the flame distribution in the Stirling engine combustor and impedes the flow and convective heat transfer in the combustor, reducing the overall external combustion efficiency at pressures above 6.5 MPa. In an air/carbon dioxide atmosphere, an increased ejection ratio reduces the average and maximum temperatures in the Stirling engine combustor. However, the overall flame distribution does not change substantially. The external combustion efficiency tends to increase and then decrease because of two opposing factors: the increase in the convective heat transfer coefficient and the decrease in the temperature difference. Increasing pressure inhibits forced convection heat transfer in the Stirling engine combustor, reducing external combustion efficiency, which drops from 78% to 65% when pressure increases from 0.2 MPa to 0.5 MPa.
基金supported by the National Natural Science Foundation of China(No.22305053).
文摘Powder-Fueled Water Ramjet Engine(PFWRE)is of great attraction for high-speed and long-voyage underwater propulsion,as well as air–water trans-media navigation applications due to its high energy density and thrust adjustability.However,the complex multiphase combustion process in the combustor significantly affects engine performance.In this study,a detailed model for aluminum particle combustion in water vapor is developed and validated via literature data as well as the ground direct-connected test we conducted.Thereafter,the numerical study on the multiphase combustion process inside the aluminum-based PFWRE combustor is carried out within the Euler–Lagrange framework using the developed model.Results show that a reverse rotating vortex pair before the primary water injection causes particles to flow back towards the combustor head and leads to product deposition.Aluminum particles external to the powder jet have shorter preheating time than internal particles and burn out in advance.The analysis of the particle combustion process indicates that the flame structure inside the combustor consists of the particle preheating zone,the surface combustion heat release zone,the gas-phase combustion heat release zone,and the post-flame zone.In the present configuration,as the particle size increases from 10μm to 20μm,the preheating zone length increases from 35 mm to 85 mm.Meanwhile,heat release from gas-phase combustion decreases,and the average temperature of the combustor head first increases and then decreases.This study not only provides insight into the multiphase combustion characteristics of the aluminum-based PFWRE combustor but also offers guidance for the design of the combustion organization schemes and engine structure optimization.
基金National Hi-tech Research end Development Program of China (863 Program,No.2002AA501700,No.2003AA501012)
文摘A novel steady-state optimization （SSO） of internal combustion engine （ICE） strategy is proposed to maximize the efficiency of the overall powertrain for hybrid electric vehicles, in which the ICE efficiency, the efficiencies of the electric motor （EM） and the energy storage device are all explicitly taken into account. In addition, a novel idle optimization of ICE strategy is implemented to obtain the optimal idle operating point of the ICE and corresponding optimal parking generation power of the EM using the view of the novel SSO of ICE strategy. Simulations results show that potential fuel economy improvement is achieved relative to the conventional one which only optimized the ICE efficiency by the novel SSO of ICE strategy, and fuel consumption per voltage increment decreases a lot during the parking charge by the novel idle optimization of ICE strategy.
文摘In this study, combustion of methane was simulated using four kinetic models of methane in CHEMKIN 4.1.1 for 0-D closed internal combustion （IC） engine reactor. Two detailed （GRIMECH3.0 ＆ UBC MECH2.0） and two reduced （One step ＆ Four steps） models were examined for various IC engine designs. The detailed models （GRIMECH3.0, ＆ UBC MECH2.0） and 4-step models successfully predicted the combustion while global model was unable to predict any combustion reaction. This study illustrated that the detailed model showed good concordances in the prediction of chamber pressure, temperature and major combustion species profiles. The detailed models also exhibited the capabilities to predict the pollutants formation in an IC engine while the reduced schemes showed failure in the prediction of pollutants emissions. Although, there are discrepancies among the profiles of four considered model, the detailed models （GRIMECH3.0 ＆ UBC MECH2.0） produced the acceptable agreement in the species prediction and formation of pollutants.
基金Projects(52076149,51825603)supported by the National Natural Science Foundation of China。
文摘In the global background of“Carbon Peak”and“Carbon Neutral”,natural gas engines show great advantages in energy-saving and pollution reduction.However,natural gas engines suffer from the issues of combustion instabilities when operating under lean burning conditions.In this paper,the role of turbulence enhancement in improving the lean combustion of natural gas was investigated in an optical SI engine with high compression ratios.Variable swirl control valves(SCV)were designed and intake tumble and swirl were combined to regulate turbulent motion and turbulent intensity.Particle image velocimetry was employed to measure in-cylinder turbulence,and transient pressure acquisition and high-speed photography were synchronously performed to quantify combustion evolutions.The results show that incylinder turbulent intensity is enhanced significantly through reducing SCV closing angles.Such that flame propagation speed and thermal efficiency are significantly improved with an increment of turbulent intensity,which indicated that mean effective pressures are not sensitive to spark timing.The analysis of flame images shows that the combined turbulence increases in the radial orientation from the spark plug to the cylinder wall,leading to an earlier flame kernel formation and a faster burning rate.Therefore,the combined turbulence has the potential in reducing the cyclic variations of lean combustion in natural gas engines.
基金supported by National Natural Science Foundation of China (Grant No. 50975026)Ministerial Eleventh Five-Year Plan Basic Product Pre-research Project of China (Grant No. D2220062905)
文摘Crankshaft assembly failure is one of the main factors that affects the reliability and service life of engines.The linear lumped mass method,which has been universally applied to the dynamic modeling of engine crankshaft assembly,reveals obvious simulation errors.The nonlinear dynamic characteristics of a crankshaft assembly are instructionally significant to the improvement of modeling correctness.In this paper,a general expression for the non-constant inertia of a crankshaft assembly is derived based on the instantaneous kinetic energy equivalence method.The nonlinear dynamic equations of a multi-cylinder crankshaft assembly are established using the Lagrange rule considering nonlinear factors such as the non-constant inertia of reciprocating components and the structural damping of shaft segments.The natural frequency and mode shapes of a crankshaft assembly are investigated employing the eigenvector method.The forced vibration response of a diesel engine crankshaft assembly taking into account the non-constant inertia is studied using the numerical integral method.The simulation results are compared with a lumped mass model and a detailed model using the system matrix method.Results of non-linear torsional vibration analysis indicate that the additional excitation torque created by non-constant inertia activates the 2nd order rolling vibration,and the additional damping torque resulting from the non-constant inertia is the main nonlinear factor.The increased torsional angular displacement evoked by the high order excitation torque relates to the non-constant inertia.This research project is aimed at improving nonlinear dynamics theory,and the confirmed nonlinear parameters can be used for the structure design of a crankshaft assembly.
文摘This paper proposes an H-infinity combustion control method for diesel engines. The plant model is the discrete dynamics model developed by Yasuda et al., which is implementable on a real engine control unit. We introduce a two-degree-of-freedom control scheme with a feedback controller and a feedforward controller. This scheme achieves both good feedback properties, such as disturbance suppression and robust stability, and a good transient response. The feedforward controller is designed by taking the inverse of the static plant model, and the feedback controller is designed by the H-infinity control method, which reduces the effect of the trubocharger lag. The effectiveness of the proposed method is evaluated in simulations using the nonlinear discrete dynamics model.
文摘The free piston Stirling engine external combustion system was simulated to investigate the diesel-air combustion characteristics in order to demonstrate its feasibility by computational fluid dynamics(CFD). The different effects on combustion were distinguished by analyzing the combustion burner, the injection position of diesel oil, the front tube arrangement of Stirling heater head and the back fin. The results show that the tilted front tube arrangement of the heater head with the back fin is the best practicable technology while the distance between the diesel nozzle position and the swirler top is 0. Its total heat flux is 15.6 kW, and the average heat transfer coefficients of the front and back tubes are 127 W/(m2· K) and 192 W/(m2· K), respectively. The heat transfer is mainly through convection, and the proportion of radiative heat transfer is only 16.9%. The best combustion efficiency of the free piston Stirling engine external combustion system is 86%.
基金Supported by National Natural Science Foundation of China(Grant No.51176082)Importation and Development of High-Caliber Talents Project of Beijing Municipal Institutions of China(Grant No.CIT&TCD20140311)Beijing Municipal Natural Science Foundation of China(Grant No.SQKZ201510016004)
文摘For capturing and recycling of CO_(2)in the internal combustion engine,Rankle cycle engine can reduce the exhaust pollutants effectively under the condition of ensuring the engine thermal efficiency by using the techniques of spraying water in the cylinder and optimizing the ignition advance angle.However,due to the water spray nozzle need to be installed on the cylinder,which increases the cylinder head design difficulty and makes the combustion conditions become more complicated.In this paper,a new method is presented to carry out the closing inlet and exhaust system for internal combustion engines.The proposed new method uses liquid oxygen to solidify part of cooled CO_(2)from exhaust system into dry ice and the liquid oxygen turns into gas oxygen which is sent to inlet system.The other part of CO_(2)is sent to inlet system and mixed with oxygen,which can reduce the oxygen-enriched combustion detonation tendency and make combustion stable.Computing grid of the IP52FMI single-cylinder four-stroke gasoline-engine is established according to the actual shape of the combustion chamber using KIVA-3V program.The effects of exhaust gas recirculation(EGR)rate are analyzed on the temperatures,the pressures and the instantaneous heat release rates when the EGR rate is more than 8%.The possibility of enclosing intake and exhaust system for engine is verified.The carbon dioxide trapping device is designed and the IP52FMI engine is transformed and the CO_(2)capture experiment is carried out.The experimental results show that when the EGR rate is 36%for the optimum EGR rate.When the liquid oxygen of 35.80-437.40 g is imported into the device and last 1-20 min,respectively,21.50-701.30 g dry ice is obtained.This research proposes a new design method which can capture CO_(2)for vehicular internal combustion engine.
基金financially supported by National Natural Science Foundation for Young Scientists of China(Grant No.51608531)
文摘Increasing energy consumption in the transportation sector results in challenging greenhouse gas(GHG)emissions and environmental problems.This paper involved integrated assessments on GHG emissions and emergy of the life cycle for the internal combustion engine(ICE)and electric automobiles in the USA over the entire assumed fifteen-year lifetime.The hotspots of GHG emissions as well as emergy indices for the major processes of automobile life cycle within the defined system boundaries have been investigated.The potential strategies for reducing GHG emissions and emergy in the life cycle of both ICE and electric automobiles were further proposed.Based on the current results,the total GHG emissions from the life cycle of ICE automobiles are 4.48 E+07 kg CO2-e which is320 times higher than that of the electric automobiles.The hotspot area of the GHG emissions from ICE and electric automobiles are operation phase and manufacturing process,respectively.Interesting results were observed that comparable total emergy of the ICE automobiles and electric automobiles have been calculated which were 1.54 E+17 and 2.20 E+17 sej,respectively.Analysis on emergy index evidenced a better environmental sustainability of electric automobiles than ICE automobiles over the life cycle due to its higher ESI.To the authors’knowledge,it is the first time to integrate the analysis of GHG emissions together with emergy in industrial area of automobile engineering.It is expected that the integration of emergy and GHG emissions analysis may provide a comprehensive perspective on eco-industrial sustainability of automobile engineering.
基金Project(51776062) supported by the National Natural Science Foundation of ChinaProject(201208430262) supported by the National Studying Abroad Foundation Project of the China Scholarship Council
文摘In order to enhance catalytic combustion efficiency, a premixed hydrogen /air combustion model of the micro turbine engine is established under different excess air ratio, inlet velocity and heat transfer coefficient. And effects of inlet velocity, excess air coefficient and heat transfer coefficient on the catalytic combustion efficiency of the hydrogen have been analyzed by the FLUENT with CHEMKIN reaction mechanisms and the fuzzy grey relation theory. It is showed that inlet velocity has a more intuitive influence on the catalytic combustion efficiency of the hydrogen. A higher efficiency can be obtained with a lower inlet velocity. The optimum excess air coefficient is in the range of 0.94 to 1.0, the catalytic combustion efficiency of the hydrogen will be declined if the excess air coefficient exceeded 1.0. The effect of heat transfer coefficient on the catalytic combustion efficiency of the hydrogen mainly embodies in the case of the excess air coefficient exceeded 1.0, however, the effect will be declined if the heat transfer coefficient exceeded 4.0. The fuzzy grey relation degrees of the inlet velocity, heat transfer coefficient and excess air coefficient on the catalytic combustion efficiency of the hydrogen are 0.640945, 0.633214 and 0.547892 respectively.
文摘To improve the combustion chamber shape that can decrease the directed injection （DI） diesel emission, the theories of DI diesel spray, combustion and pollutant formation model are analysed and implemented based on the CFD code FIRE. Results show that the chamber with contracting orifice can get stronger squish swirl intensity. The results of the verification studies show a good accordance with the measurements and reveal that the individual processes of spray, evolution, combustion and pollutant formation are well captured in FIRE. Finally, based on the analyzing and comparing of the calculation results of different chambers, a combustion chamber of contracting orifice geometry with lower emission is proposed.
基金Supported by the National Natural Science Foundation of China(51276019)
文摘To study the economic advantages of hydrogen internal combustion engine, an experimen- tal study was carried out using a 2.0 L port fuel-injected （PFI） hydrogen internal combustion engine. Influences of fuel-air equivalence ratio φ, speed, and ignition advance angle on heat efficiency were determined. Test results showed that indicated thermal efficiency （ ITE ） firstly increased with fuel- air equivalence ratio, achieved the maximum value of 40. 4% （ φ = 0.3 ）, and then decreased when was more than 0. 3. ITE increased as speed rises. Mechanical efficiency increased as fuel-air equiva- lence ratio increased, whereas mechanical efficiency decreased as speed increased, with maximum mechanical efficiency reaching 90%. Brake thermal efficiency （BTE） was influenced by ITE and me- chanical efficiency, at the maximum value of 35% （φ =0.5, 2 000 r/min）. The optimal ignition ad- vance angle of each condition resulting in the maximum BTE was also studied. With increasing fuel- air equivalence ratio, the optimal ignition angle became closer to the top dead center （ TDC ）. The test results and the conclusions exhibited a guiding role on hydrogen internal combustion engine opti- mization.
基金Project(613239)supported by the National Basic Research Program of China
文摘A 500 N model engine filled with LO2/GCH4 was designed and manufactured.A series of ignition attempts were performed in it by both head spark plug and body spark plug.Results show that the engine can be ignited but the combustion cannot be sustained when head spark plug applied as the plug tip was set in the gaseous low-velocity zone with thin spray.This is mainly because flame from this zone cannot supply enough ignition energy for the whole chamber.However,reliable ignition and stable combustion can be achieved by body spark plug.As the O/F ratio increases from 2.61 to 3.49,chamber pressure increases from 0.474 to 0.925 MPa and combustion efficiency increases from 57.8%to 95.1%.This is determined by the injector configuration,which cannot produce the sufficiently breakup of the liquid oxygen on the low flow rate case.
文摘The basic difference non-equal interval model GM(1,1) in grey theory was used to fit and forecast data series with non-equal lengths and different inertias, acquired from oil monitoring of internal combustion engines. The fitted and forecasted results show that the length or inertia of a sequence affects its precision very much, i.e. the bigger the inertia of a sequence is, or the shorter the length of a series is, the less the errors of fitted and forecasted results are. Based on the research results, it is suggested that short series should be applied to be fitted and forecasted; for longer series, the newer datum should be applied instead of the older datum to be analyzed by non- equalinterval GM(1,1) to improve the forecasted and fitted precision, and that data sequence should be verified to satisfy the conditions of grey forecasting.
基金Sponsored by the National Natural Science Foundation of China (50505047)Program for the Top Young Academic Leaders of Higher Learning Institutions of Shanxi
文摘With the purpose of efficiently predicting structural radiated noise of internal combustion engine（I.C.E.）,a new simulation technique is introduced,which is an approach based on boundary element method （BEM）,acoustic transfer vector（ATV） technique and coupled boundary element model and finite element model （BEM-FEM） approach.Analyses of vibration exciting loads,computing structural dynamic characteristics and dynamic responses have led to theoretical results,which are tested on an L6 diesel engine to validate this proposed technique in engineering practice.
文摘In order to address typical problems due to the huge demand of oil for consumption in traditional internal combustion engines,a new more efficient combustion mode is proposed and studied in the framework of Computational Fluid Dynamics(CFD).Moreover,a Non-dominated Sorting Genetic Algorithm(NSGA-Ⅱ)is applied to optimize the related parameters,namely,the engine methanol ratio,the fuel injection time,the initial temperature,the Exhaust Gas Re-Circulation(EGR)rate,and the initial pressure.The so-called Conventional Diesel Combustion(CDC),Homogeneous Charge Compression Ignition(HCCI)and the Reactivity Controlled Compression Ignition(RCCI)combustion modes are compared.The results show that RCCI has a higher methanol ratio and an earlier injection timing with moderate EGR rate and higher initial pressure.The initial temperature increases as the methanol ratio increases.In comparison,CDC has the lowest hydrocarbon and CO emissions and the highest combustion efficiency.At different crankshaft rotation angles corresponding to 50%of the combustion amount(CA50),the combustion temperature and boundary layer temperature of HCCI change significantly,while those of RCCI undergo limited variations.At the same CA50,the exergy losses of HCCI and RCCI are lower than that of the CDC.On the basis of these findings,it can be concluded that the methanol/diesel RCCI engine can be used to obtain a clean and efficient combustion process,which should be regarded as a promising combustion mode.
基金Project(2017YFE0102800)supported by the National Key R&D Program of ChinaProject(19JCYBJC21200)supported by the Tianjin Natural Science Foundation,China。
文摘Research on dual-fuel(DF)engines has become increasingly important as engine manufacturers seek to reduce carbon dioxide emissions.There are significant advantages of using diesel pilot-ignited natural gas engines as DF engines.However,different combustion modes exist due to variations in the formation of the mixture.This research used a simulation model and numerical simulations to explore the combustion characteristics of high-pressure direct injection(HPDI),partially premixed compression ignition(PPCI),and double pilot injection premixed compression ignition(DPPCI)combustion modes under a low-medium load.The results revealed that the DPPCI combustion mode provides higher gross indicated thermal efficiency and more acceptable total hydrocarbon(THC)emission levels than the other modes.Due to its relatively good performance,an experimental study was conducted on the DPPCI mode engine to evaluate the impact of the diesel dual-injection strategy on the combustion process.In the DPPCI mode,a delay in the second pilot ignition injection time increased THC emissions(a maximum value of 4.27g/(kW·h)),decreased the emission of nitrogen oxides(a maximum value of 7.64 g/(kW·h)),increased and then subsequently decreased the gross indicated thermal efficiency values,which reached 50.4%under low-medium loads.
