Using natural gas(NG)as the primary fuel helps alleviate the fossil fuel crisis while reducing engine soot and nitrogen oxide(NO_(X))emissions.In this paper,the influences of a novel split injection concept on an NG h...Using natural gas(NG)as the primary fuel helps alleviate the fossil fuel crisis while reducing engine soot and nitrogen oxide(NO_(X))emissions.In this paper,the influences of a novel split injection concept on an NG high pressure direct injection(HPDI)engine are examined.Four typical split injection strategies,namely split pre-injection of pilot diesel(PD)and NG,split post-injection of PD and NG,split pre-injection of NG,and split post-injection of PD,were developed to investigate the influences on combustion and emissions.Results revealed that split pre injection of NG enhanced the atomization of PD,whereas the split post-injection of NG lowered the temperature in the core region of the PD spray,resulting in the deterioration of combustion.The effect of the split injection strategy on indicated thermal efficiency exceeded 7.5%.Split pre-injection was favorable to enhancing thermal efficiency,whereas split post-injection was not.Ignition delay,combustion duration,and premixed combustion time proportion were affected by injection strategies by 3.8%,50%,and 19.7%,respectively.Split pre-injection increased CH_(4) emission in the exhaust.Split post-injection,especially split post-injection of PD and NG,reduced the unburned CH_(4) emission by approximately 30%.When the split post-injection ratio was less than 30%,the trade-off between NO_(X) and soot was interrupted.The distribution range of hydroxyl radicals was expanded by pre-injection,and NO_(X) was generated in the region where the NG jet hit the wall.This paper provides valuable insights into the optimization of HPDI injection parameters.展开更多
Fuel injection timing is an important control parameter for engine combustion optimization and emissions control. However, the actual fuel injection timing is different from the nominal one commanded by the electronic...Fuel injection timing is an important control parameter for engine combustion optimization and emissions control. However, the actual fuel injection timing is different from the nominal one commanded by the electronic control unit, due to the system hydraulic lag or the possible communication malfunction. In this study,a simple estimate approach based on the injector inlet pressure is proposed to capture four critical characteristic instants at the start and end of injection. The critical characteristic moments estimated using this pressure-based approach are validated against those determined by the actual injection rate profiles, in the context of different single or split injection processes. The comparison revealed that the characteristic injection moments estimated by the injector inlet pressures and those determined by the actual injection rate profiles have a satisfactory agreement, certifying the broad applicability and reliability of this pressure-based approach in the detection of the real fuel injection start and end time.展开更多
Experiments are conducted to develop an understanding of how split injections can affect the combustion and emission characteristics of a D.I. diesel engine with a common-rail injection system. The ratio of the amount...Experiments are conducted to develop an understanding of how split injections can affect the combustion and emission characteristics of a D.I. diesel engine with a common-rail injection system. The ratio of the amount of fuel injected between two injection pulses and the injection interval is varied keeping the injected fuel quantity constant. Results show that under the 70D90-10 injection pattern, the engine achieves the lower NOx-smoke emissions and BSFC compared with the single injection pattern. The heat release rate and the temperature show that the split injections increase the initial premixed burn and retards the diffusion burn. With the balance of these two effects, the maximum in-cylinder temperature decreases while the 50% heat release point is held at almost the same crank angle. Therefore, both NOx emission and BSFC are improved while keeping the smoke emission at the same level.展开更多
The effects of various split injection strategies on the opposed-piston opposed-cylinder(OPOC)diesel engine combustion and emission characteristics have been studied numerically using AVL-Fire CFD tools.The five rate-...The effects of various split injection strategies on the opposed-piston opposed-cylinder(OPOC)diesel engine combustion and emission characteristics have been studied numerically using AVL-Fire CFD tools.The five rate-shaped main injections were used in split injection strategies.The results show that ignition delay from a rectangular injection rate is the shortest.Maximum pressure of the trapezoid injection rate is the largest.And the NOx emission of the rectangular injection rate is the largest.Meanwhile,the soot emission of the trapezoid injection rate is the least among the five injection rates.展开更多
In theory,high compression ratio has the potential to improve the thermal efficiency and promote the power output of the SI engine.However,the application of high compression ratio is substantially limited by the knoc...In theory,high compression ratio has the potential to improve the thermal efficiency and promote the power output of the SI engine.However,the application of high compression ratio is substantially limited by the knock in practical working process.The objective of this work is to comprehensively investigate the application of high compression ratio on a gasoline engine based on the Miller cycle with boost pressure and split injection.In this work,the specific optimum strategies for CR10 and CR12 were experimentally investigated respectively on a single cylinder DISI engine.It was found that a high level of Miller cycle with a higher boost pressure could be used in CR12 to achieve an effective compression ratio similar to CR10,which could eliminate the knock limits at a high compression ratio and high load.To verify the advantages of the high compression ratio,the fuel economy and power performance of CR10 and CR12 were compared at full and partial loads.The result revealed that,compared with CR10,a similar power performance and a reduced fuel consumption of CR12 at foil load could be achieved by using the strong Miller cycle and split injection.At partial load,the conditions of CR12 had very superior fuel economy and power performance compared to those of CR10.展开更多
针对海洋平台普遍存在的吊机能力受限、作业空间狭小、防腐防爆要求严苛等问题,在成熟的陆地橇装连续管作业机技术基础上开展研究,突破了6项满足DNV认证要求的关键技术,研制出国内首套获得DNV认证的海洋防爆型连续管作业机,并通过模拟...针对海洋平台普遍存在的吊机能力受限、作业空间狭小、防腐防爆要求严苛等问题,在成熟的陆地橇装连续管作业机技术基础上开展研究,突破了6项满足DNV认证要求的关键技术,研制出国内首套获得DNV认证的海洋防爆型连续管作业机,并通过模拟井试验与现场应用验证。研究及试验结果表明:该设备具备良好的作业稳定性与适应性,整机防爆等级达到Exdeic nAⅡA T3 Gc,取得国家二类防爆证书;滚筒可分离技术显著降低了对平台吊机能力的要求;轻量化注入头在保持性能的同时解决了吊装难题。所得结论可为我国深海油气田开发装备的自主研制与国际化认证提供重要技术参数与实践参考。展开更多
New methods have been studied in the past few decades to decrease exhaust emissions and fuel consumption of diesel engines.Using new combustion methods as low-temperature combustion(LTC)strategies and also utilizing n...New methods have been studied in the past few decades to decrease exhaust emissions and fuel consumption of diesel engines.Using new combustion methods as low-temperature combustion(LTC)strategies and also utilizing new fuels as bio-diesel are beneficial ways to overcome diesel engine issues.This numerical study focused on the effect of split injection strategies as well as swirl ratio(SR)on the biodiesel premixed charge compression ignition(PCCI)combustion process and the related emissions.In this regard,KIVA-3V code as a CFD tool has been utilized to analyze the combustion and emission characteristics of the diesel engine.Single and split injection strategies have been executed on biodiesel PCCI combustion and have been compared in order to probe and examine the injection strategies.The results show that in both strategies,advancing the injection timing can lower the combustion emission and improve the engine performance by optimizing the start of injection(SOI)as sweet spot value.Utilizing a high swirl ratio with the split injection strategy has a negative effect on overall combustion,emission,and performance in comparison with the single injection strategy.For multi-injection scheme,SOI=−35 ATDC,SR=1.1,and for single injection scheme,SOI=−40 ATDC,SR=1.1 are considered as optimum cases regarding minimum total exhaust emissions and highest performance.展开更多
基金Supported by the National Natural Science Foundation of China(No.51909154)Shanghai Engineering Research Center of Ship Intelligent Maintenance and Energy Efficiency(No.20DZ2252300).
文摘Using natural gas(NG)as the primary fuel helps alleviate the fossil fuel crisis while reducing engine soot and nitrogen oxide(NO_(X))emissions.In this paper,the influences of a novel split injection concept on an NG high pressure direct injection(HPDI)engine are examined.Four typical split injection strategies,namely split pre-injection of pilot diesel(PD)and NG,split post-injection of PD and NG,split pre-injection of NG,and split post-injection of PD,were developed to investigate the influences on combustion and emissions.Results revealed that split pre injection of NG enhanced the atomization of PD,whereas the split post-injection of NG lowered the temperature in the core region of the PD spray,resulting in the deterioration of combustion.The effect of the split injection strategy on indicated thermal efficiency exceeded 7.5%.Split pre-injection was favorable to enhancing thermal efficiency,whereas split post-injection was not.Ignition delay,combustion duration,and premixed combustion time proportion were affected by injection strategies by 3.8%,50%,and 19.7%,respectively.Split pre-injection increased CH_(4) emission in the exhaust.Split post-injection,especially split post-injection of PD and NG,reduced the unburned CH_(4) emission by approximately 30%.When the split post-injection ratio was less than 30%,the trade-off between NO_(X) and soot was interrupted.The distribution range of hydroxyl radicals was expanded by pre-injection,and NO_(X) was generated in the region where the NG jet hit the wall.This paper provides valuable insights into the optimization of HPDI injection parameters.
基金the National Natural Science Foundation of China(No.51306114)
文摘Fuel injection timing is an important control parameter for engine combustion optimization and emissions control. However, the actual fuel injection timing is different from the nominal one commanded by the electronic control unit, due to the system hydraulic lag or the possible communication malfunction. In this study,a simple estimate approach based on the injector inlet pressure is proposed to capture four critical characteristic instants at the start and end of injection. The critical characteristic moments estimated using this pressure-based approach are validated against those determined by the actual injection rate profiles, in the context of different single or split injection processes. The comparison revealed that the characteristic injection moments estimated by the injector inlet pressures and those determined by the actual injection rate profiles have a satisfactory agreement, certifying the broad applicability and reliability of this pressure-based approach in the detection of the real fuel injection start and end time.
基金This project is supported by National Natural Science Foundation of China(No. 50676107)State Key Laboratory of Automotive Safety and Energyof China (No. KF2006-07).
文摘Experiments are conducted to develop an understanding of how split injections can affect the combustion and emission characteristics of a D.I. diesel engine with a common-rail injection system. The ratio of the amount of fuel injected between two injection pulses and the injection interval is varied keeping the injected fuel quantity constant. Results show that under the 70D90-10 injection pattern, the engine achieves the lower NOx-smoke emissions and BSFC compared with the single injection pattern. The heat release rate and the temperature show that the split injections increase the initial premixed burn and retards the diffusion burn. With the balance of these two effects, the maximum in-cylinder temperature decreases while the 50% heat release point is held at almost the same crank angle. Therefore, both NOx emission and BSFC are improved while keeping the smoke emission at the same level.
基金Supported by the National Natural Science Foundation of China(51605447)
文摘The effects of various split injection strategies on the opposed-piston opposed-cylinder(OPOC)diesel engine combustion and emission characteristics have been studied numerically using AVL-Fire CFD tools.The five rate-shaped main injections were used in split injection strategies.The results show that ignition delay from a rectangular injection rate is the shortest.Maximum pressure of the trapezoid injection rate is the largest.And the NOx emission of the rectangular injection rate is the largest.Meanwhile,the soot emission of the trapezoid injection rate is the least among the five injection rates.
基金the National Natural Science Foundation of China (Grant Nos.91641203,51476114,and 91741119)the National Key Research and Development Program of China(2017YFB0103400)。
文摘In theory,high compression ratio has the potential to improve the thermal efficiency and promote the power output of the SI engine.However,the application of high compression ratio is substantially limited by the knock in practical working process.The objective of this work is to comprehensively investigate the application of high compression ratio on a gasoline engine based on the Miller cycle with boost pressure and split injection.In this work,the specific optimum strategies for CR10 and CR12 were experimentally investigated respectively on a single cylinder DISI engine.It was found that a high level of Miller cycle with a higher boost pressure could be used in CR12 to achieve an effective compression ratio similar to CR10,which could eliminate the knock limits at a high compression ratio and high load.To verify the advantages of the high compression ratio,the fuel economy and power performance of CR10 and CR12 were compared at full and partial loads.The result revealed that,compared with CR10,a similar power performance and a reduced fuel consumption of CR12 at foil load could be achieved by using the strong Miller cycle and split injection.At partial load,the conditions of CR12 had very superior fuel economy and power performance compared to those of CR10.
文摘针对海洋平台普遍存在的吊机能力受限、作业空间狭小、防腐防爆要求严苛等问题,在成熟的陆地橇装连续管作业机技术基础上开展研究,突破了6项满足DNV认证要求的关键技术,研制出国内首套获得DNV认证的海洋防爆型连续管作业机,并通过模拟井试验与现场应用验证。研究及试验结果表明:该设备具备良好的作业稳定性与适应性,整机防爆等级达到Exdeic nAⅡA T3 Gc,取得国家二类防爆证书;滚筒可分离技术显著降低了对平台吊机能力的要求;轻量化注入头在保持性能的同时解决了吊装难题。所得结论可为我国深海油气田开发装备的自主研制与国际化认证提供重要技术参数与实践参考。
文摘New methods have been studied in the past few decades to decrease exhaust emissions and fuel consumption of diesel engines.Using new combustion methods as low-temperature combustion(LTC)strategies and also utilizing new fuels as bio-diesel are beneficial ways to overcome diesel engine issues.This numerical study focused on the effect of split injection strategies as well as swirl ratio(SR)on the biodiesel premixed charge compression ignition(PCCI)combustion process and the related emissions.In this regard,KIVA-3V code as a CFD tool has been utilized to analyze the combustion and emission characteristics of the diesel engine.Single and split injection strategies have been executed on biodiesel PCCI combustion and have been compared in order to probe and examine the injection strategies.The results show that in both strategies,advancing the injection timing can lower the combustion emission and improve the engine performance by optimizing the start of injection(SOI)as sweet spot value.Utilizing a high swirl ratio with the split injection strategy has a negative effect on overall combustion,emission,and performance in comparison with the single injection strategy.For multi-injection scheme,SOI=−35 ATDC,SR=1.1,and for single injection scheme,SOI=−40 ATDC,SR=1.1 are considered as optimum cases regarding minimum total exhaust emissions and highest performance.
