【作者】 孙建军；

【导师】 韩永强；

【作者基本信息】 吉林大学 ， 车辆工程（专业学位）， 2019， 硕士

【摘要】 进入21世纪以来,随着中国经济的迅速发展,汽车产业得到了飞速发展,汽车几乎成了家庭必不可少的交通工具,对汽车的需求量日益增加。近几年,我国汽车产销量都在2000万辆以上,已成为世界汽车大国。汽车在给人类生活带来便利之时,也同样引发了严重的环境污染和能源消耗。随着人们对环境和能源问题的日益关注,如何降低汽车的燃油消耗和有害排放物已成为目前国内外的热点问题。自上世纪60年代起,全球各国就开始陆续对汽车排放物进行了强制性限制。我国于2007年7月1日开始执行国Ⅲ排放标准,2010年7月1日开始实施国IV排放标准,2017年1月1日起开始实施国Ⅴ排放标准,国Ⅵ排放标准于2019年7月部分城市开始实施。北京、河南等城市发公告在2019年1月提前实施国Ⅵ排放标准。随着排放法规的逐渐升级,新型满足新排放法规要求的发动机开发已刻不容缓。面对市场需求,为满足日趋严格的国家排放要求,直喷增压汽油机已成为必然方案。我公司也进行了1.8升增压直喷发动机预研和开发。为改善发动机燃烧、提升发动机动力性、经济性、排放性等,在发动机设计之初对发动机各零部件进行了大量的性能开发工作。发动机的性能开发对发动机的最终表现起到了决定性的作用。所以发动机的性能开发在各主机厂也形成了比较完善的体系和流程。在性能开发之初,可通过CAE手段进行发动机相关参数的仿真,比如增压器的初匹配,凸轮型线的设计,喷油器油束分布与发动机进气的混合,进气歧管的流量系数计各缸进气的均匀性等。经过CAE分析后,会提供几组供参考的零部件参数,经过性能开发试验,可以真实的测试出发动机的性能水平。一般发动机的性能开发包含增压器的匹配、燃烧室的匹配,凸轮型线的匹配,气道的匹配,喷油器匹配、活塞的匹配等等。通过大量的试验数据,可有效的测试分析出哪个零部件参数更适用于此发动机。车用废气涡轮增压器是现代汽车发动机较广泛应用的技术之一,汽油发动机为提高升功率和升扭采用增压技术。通过涡轮增压,可使发动机的性能提高60%~80%,甚至更高。发动机通过使用涡轮增压器可以提高发动机进气压力,从而提高进入发动机缸内的新鲜空气,提升发动机的功率和扭矩。本文通过对不同压气机压轮直径的增压器进行的性能测试,通过外特性测试、高原能力预测、部分负荷油耗测试对比,选出了匹配此款发动机最佳的增压器方案。即保证了发动机外特性的扭矩、功率达到性能开发目标,又保证了发动机在低转速区域内有良好的动态响应性能。使得这款发动机在1500rpm-4500rpm转速范围内都能达到260Nm的扭矩输出,在5500rpm输出130kW的功率,并在2800米高原实现无性能损失,很好的满足了整车对动力性的需求。直喷式汽油发动机是将高压喷油器安装在汽缸盖内,喷油器喷嘴直接安装在燃烧室内,燃油通过高压喷油器直接喷射到燃烧室与新鲜空气混合。汽油机缸内直喷发动机喷油压力可以达到200bar,高的喷射压力使燃油雾化效果更佳,提供了更好的混合气,从而改善发动机燃烧。在大负荷区域,缸内直喷可以起到降低缸内混合气温度的作用,从而降低发动机爆震倾向,降低发动机油耗。通过在大负荷区域内开启二次喷射,可有效降低点火时缸内混合气温度,对爆震和早燃都有很好的抑制作用。本文对3种喷油不同方案的喷油油束方案及2种喷油器流量进行了外特性测试、万有特性测试、早燃及机油稀释专项测试,通过对比外特性能性能,确保发动机在外特性性能能满足开发指标。通过对不同油束方案的测试,综合发动机比油耗、早燃、机油稀释等指标,选定的喷油器在整个万有特性范围内的最低比油耗降到了242g/kWh,有效降低了整车油耗。发动机凸轮直接驱动进气门,凸轮型线直接影响发动机气门升程、气门包角、气门初始相位,这些参数直接影响发动机进气效率、发动机性能、油耗等参数。通过凸轮型线的变化,还可以实现发动机在奥拓循环、米勒循环、阿特金森循环之间的切换。凸轮型线直接决定气门升程曲线,气门升程曲线决定了发动机的充气效率,泵气损失,直接影响发动机的动力性,经济性。随着国家排放、油耗法规的不断加严,对发动机的要求也越来越趋高,更向低污染、低油耗的方向发展,发动机的充气直接受到气门升程曲线影响,气门又由凸轮轴直接驱动,因此凸轮的设计对整个配气机构的性能起着决定性的作用。本文通过对凸轮轴不同型线进行外特性测试,万有特性测试,对比了外特性油耗、万有特性油耗结果,确定凸轮型线方案。通过凸轮轴的匹配,使得发动机比油耗得到进一步改善,最低比油耗降低至236 g/kWh,满足了公司混动车型对低油耗发动机需求。废气再循环(exhaust gas recirculation,EGR)技术降低发动机油耗的一项重要技术。现在越来越多的主机厂开始研发或使用EGR技术。低压EGR是从催化器后引出废气,经过EGR过滤器、EGR冷却器、EGR控制阀至增压器进气口,使经过催化还原反应的废气再进入气缸燃烧。本文通过对几个固定工况点进行不同EGR率的测试,测试发动机性比油耗、点火角,通过燃烧分析仪测量发动机的放热曲线、燃烧速率、泵气损失,燃烧稳定性等参数,通过对比不EGR下各性能参数的变化,得到EGR对发动机性能的影响。EGR对发动机的油耗有着较大的改善,可以减缓燃烧速率从而使得爆震临界点得到提前,使点火角更靠近最优点火角。EGR的引入同时也能减少发动机的泵气损失。但EGR的引入会使得发动机的燃烧逐渐恶化,并在某个EGR率后迅速恶化。所以在EGR的匹配过程中,燃烧稳定性也是一个重要的考核指标。本次性能开发,发动机性能指标为250Nm/(1500rpm-4500rpm),120kW/5500rpm。发动机最低比油耗240g/(k·Wh)。通过本次性能开发试验,发动机顺利达到开发指标,最低比油耗做到了231 g/(k·Wh),为公司提供了高性能低油耗发动机。更多还原

【Abstract】 Since the beginning of the 21 st century,with the rapid development of China’s economy,the automobile industry has developed rapidly,and the automobile has almost become an essential means of transportation for families.In recent years,China’s automobile production and sales are more than 20 million,has become the world’s largest automobile.When cars bring convenience to human life,they also cause serious environmental pollution and energy consumption.As people pay more attention to the environment and energy problems,how to reduce the fuel consumption and harmful emissions has become a hot issue at home and abroad.Since the 1960 s,countries around the world have imposed mandatory limits on car emissions.On July 1,2007 in China began to implement China Ⅲ emission standards,implemented on July 1,2010 IV emission standards,implemented on January 1,2017 countries Ⅴ emission standards,the Ⅵ emission standard parts of the city began in July 2019.Cities such as Beijing,henan send announcement in early January 2019 implemented a Ⅵ emission standards.With the gradual upgrading of emission regulations,it is urgent to develop new engines that meet the requirements of the new emission regulations.Faced with the market demand,in order to meet the increasingly stringent national emission requirements,direct injection turbocharged gasoline engine has become an inevitable solution.Our company has also carried out pre-research and development of a 1.8-liter turbocharged direct injection engine.In order to improve engine combustion,power performance,economy and emission performance,a lot of performance development work has been done on various parts of the engine at the beginning of engine design.Engine performance development plays a decisive role in the final performance of the engine.So the engine performance development in the main engine plant has also formed a more complete system and process.At the beginning of performance development,engine related parameters can be simulated by means of CAE,such as initial matching of supercharger,design of CAM profile,mixing of fuel injector oil bundle distribution with engine inlet,and flow coefficient of intake manifold,etc.After the CAE analysis,several sets of component parameters for reference will be provided.After the performance development test,the performance level of the motivation can be truly tested.General engine performance development includes supercharger matching,combustor matching,CAM profile matching,airway matching,injector matching,piston matching and so on.Through a large number of test data,it can effectively test and analyze which part parameters are more suitable for this engine.Exhaust gas turbocharger is one of the most widely used technologies in modern automobile engines.Turbocharged engines can improve performance by 60 to 80 percent or more.By using turbochargers,the engine can increase the intake pressure of the engine,thus improving the fresh air entering the engine cylinder and improving the power and torque of the engine.In this paper,through the performance test of the supercharger with different compressor wheel diameters,through the external characteristic test,plateau capacity prediction,partial load fuel consumption test comparison,the best supercharger matching this engine was selected.It not only ensures that the torque and power of the external characteristics of the engine can reach the performance development goal,but also ensures that the engine has a good dynamic response performance in the low-speed region.Direct injection gasoline engine is the high-pressure injector installed in the cylinder cover,injector nozzle is directly installed in the combustion chamber,fuel through the high-pressure injector directly injected into the combustion chamber and mixed with fresh air.The injection pressure of the direct injection engine in the cylinder of gasoline engine can reach 200 bar.The high injection pressure makes the fuel atomization effect better and provides a better mixture,thus improving the engine combustion.In the heavy load area,direct injection in the cylinder can play a role in reducing the temperature of the mixture in the cylinder,thus reducing the engine knock tendency and reducing the engine fuel consumption.By starting the secondary injection in the heavy load area,the temperature of the mixture in the cylinder can be effectively reduced during ignition,which has a good inhibitory effect on detonation and preignition.In this paper,the external characteristic test,universal characteristic test,early combustion test and engine oil dilution special test were carried out on the injection beam scheme of three different injection schemes and the flow rate of two injectors.By comparing the performance of external characteristic,the performance of engine external characteristic can meet the development index.By testing different fuel bundle schemes and integrating the specific fuel consumption,early combustion,engine oil dilution and other indicators,the minimum specific fuel consumption of the selected injector in the entire characteristic range was reduced to 242g/kWh,effectively reducing the fuel consumption of the whole vehicle.The engine CAM directly drives the inlet valve.The CAM profile directly affects the engine valve lift,valve envelope Angle and valve initial phase.These parameters directly affect the engine inlet efficiency,engine performance,fuel consumption and other parameters.Through the change of CAM profile,the engine can be switched between otto cycle,miller cycle and atkinson cycle.CAM profile directly determines the valve lift curve,valve lift curve determines the engine inflation efficiency,pump air loss,directly affect the engine power,economy.Thanks to the ongoing national emissions and fuel consumption regulations and strict,is becoming more and more hasten is high to the requirement of the engine,more to the direction of low pollution,low fuel consumption,engine air directly affected by the valve lift curve,valve is directly driven by the camshaft,so of valve-train CAM design for the whole performance plays a decisive role.In this paper,through the camshaft different profile of the external characteristics of the test,universal characteristics test,comparison of the external characteristics of the fuel consumption,universal characteristics of the fuel consumption results,to determine the CAM profile program.Through the matching of camshaft,the specific fuel consumption of the engine is further improved,and the minimum specific fuel consumption is reduced to 236 g/kWh,meeting the requirements of the company’s hybrid models for low-fuel engines.Exhaust gas recirculation(EGR)is one of the most important techniques to reduce engine oil consumption.Now more and more oems begin to develop or use EGR technology.The low-pressure EGR is the exhaust gas from the catalytic converter,which passes through the EGR filter,EGR cooler,EGR control valve to the inlet of the supercharger,and then enters the cylinder for combustion after the catalytic reduction reaction.This article through to several fixed point for different EGR rate test,test the engine fuel consumption,ignition Angle,through the combustion analyzer to measure the heat release curve of engine,combustion rate and pumping loss,combustion parameters such as stability,by comparing the change of performance parameters under the EGR not,get an EGR influence on engine performance.EGR can greatly improve the fuel consumption of the engine and slow down the combustion rate so that the critical point of detonation can be advanced and the ignition Angle can be closer to the optimal fire Angle.The introduction of EGR can also reduce the pump loss of the engine.However,the introduction of EGR will gradually deteriorate the combustion of the engine and rapidly deteriorate after a certain EGR rate.Therefore,combustion stability is also an important assessment index in the matching process of EGR.In this performance development,engine performance indexes are 250Nm/(1500rpm-4500rpm)and 120kW/5500 rpm.The engine has a minimum fuel consumption of 240g/(k·Wh).Through this performance development test,the engine successfully reached the development target,and the lowest specific fuel consumption reached 231 g/(k·Wh),providing the company with high performance and low fuel consumption engine.更多还原