Research On Transient Process Combustion Principle And Emission Control Of The GDI Engine Direct Injection Start

Research on Transient Process Combustion Principle and Emission Control ofthe GDI Engine Direct Injection StartWith the rapid development of China's economy,the total amount of motor vehicles is increasing rapidly,and the challenge of energy shortage and environmental pollution is becoming more and more serious.A series of national environmental laws and regulations have been released,especially the motor vehicle emission regulations and fuel consumption regulations have become more stringent.The vehicles now experience a long idle time while driving,due to road congestion,worsening traffic conditions,especially while waiting for traffic lights in urban areas,which lead to more emissions of harmful pollutants and fuel consumption.Therefore the direct start-up process for vehicle idle condition emerges as an effective energy-saving method to reduce emission by flexibly controlling the fuel injection and ignition control parameters with GDI in cylinder,which means the engine can be started without starting motor,so that the inherent defects of traditional starting method are effectively abandoned.This technology relieves the city congestion and shortens the idle time while waiting for traffic lights,reduce oil consumption and emissions.With the advantages of safety,quick response,low modification cost and lower vibration noise,this technology get lots of attention and is expected to be popularized.This essay build transient test and control platform based on GDI engine to test and simulate the engine control parameters during forward and reverse direct starting process(including the engine injection timing,ignition timing and excess air coefficient),engine parameters(including injection pressure,coolant temperature,initial position of a piston etc.)and shutdown strategy(shutdown of the throttle opening and shutdown speed)and the effect on rotating,combustion and emission performance before direct start.This essay also concludes the research on the difference in cylinder mixture formation,combustion process and emissions production and the cylinder motion course starting condition and the traditional chemical kinetics and kinematics analysis;different thermal chemical atmosphere,atmosphere and jet energy influences the combustion process in the cylinder and the combustion of harmful substances forming process of initial boundary conditions,rich spark ignition engine transient combustion theory;define cylinder movement characteristics of starting process is simple and reliable for the first cycle stability required for ignition and subsequent boundary conditions can be stable;determine the impact of the starting transient process of combustion and emissions of key factors and optimal control strategy.This essay provides a theoretical basis for the start-up process of in cylinder direct injection gasoline engine with frequent,fast,high efficiency and low emission based on the strategy of active control transient combustion boundary to improve engine starting performance and reduce pollutant emissions.The main conclusions of this project are as follows:1.In direct starting mode,the cylinder mixture formation,combustion of harmful emissions and engine rotation process,characteristics and control parameters and starting conditions are closely related.A proper two injection strategy can increase the rate of heat generation and the rotational speed of the engine combustion.2.The initial position of the piston is an important factor which affects the direct start up mode.For the successful start-up of forward direct and reverse direct start-up,the initial positions of piston in the cylinder have overlaps and also differences.The initial position of the piston range decreases while during highest and lowest temperature,which achieves biggest range when the coolant gets to 70?.Increasing the injection pressure is conducive to achieve the initial position of the piston,only in a limited extent.90°CA-125°CA could achieve direct start up in the range of wide coolant temperature and injection3.Increasing the throttle opening during the shutdown process is easier to reduce the amount of residual gas in the cylinder,and the direct circulation mode of the first cycle ignition and the starting rate is greatly improved.At the same time,increasing the solar term door opening can also increase the ratio of piston stopping in the middle.The first cycle of the starter starting mode of are much wider than direct start-up mode and its ignition is more complex,so there will be a "spontaneous" situation.This project enriches engine transient combustion theory and also provides a theoretical basis and data support for the application and data support of GDI engine direct start mode.