| 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 ? emission standards,implemented on July 1,2010 IV emission standards,implemented on January 1,2017 countries ? emission standards,the ? emission standard parts of the city began in July 2019.Cities such as Beijing,henan send announcement in early January 2019 implemented a ? 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. |
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