Research On High Compression Ratio Influence And Optimization Of High Thermal Efficiency Turbocharged Direct Injection Dhe Combustion System

This thesis focuses on the influence and optimization of high compression ratio application of turbocharged direct injection DHE(Dedicated Hybrid Engine)combustion system.The research background is that China today is faced with the shortage of oil resources and the increasing proportion of oil energy imports,the situation of national energy security is becoming more and more serious,at the same time,the national regulations for vehicle fuel consumption requirements are becoming more and more strict,the latest national fifth phase vehicle fuel consumption regulations have been issued and implemented.The requirement of reducing fuel consumption has become the primary technical problem in the development of automobile industry.The adoption of hybrid technology can significantly reduce vehicle fuel consumption,develop hybrid vehicles with low fuel consumption,and then gradually change to electric vehicles in the future is an important direction of national automobile development strategy.Turbocharged direct injection gasoline engine is widely used in China’s domestic market,so compared with Japan and South Korea,NA / PFI(Natural Aspiration / Port Fuel Injection)is widely used as DHE,the development of high thermal efficiency turbocharged direct injection DHE is of great significance.The development and application of high compression ratio of turbocharged direct injection DHE combustion system is the core technology to improve the thermal efficiency and reduce fuel consumption of ICE(Internal Combustion Engine).It is of great economic value and strategic significance to master the application technology of high compression ratio of turbocharged direct injection DHE combustion system,which is also the research purpose of this thesis.Based on the reseach background,this research summarized and combed the current research status of DHE combustion system at home and abroad,especially the research progress of Japanese and Korean enterprises,domestic enterprises and research institutions on DHE combustion system,and summarized the key points and level of combustion system research of these enterprises.Two key technical difficulties and challenges currently faced in the study of turbocharged direct injection DHE combustion system are summarized.They are knock and abnormal combustion control in high compression ratio applications,and how to adapt the design of intake port combustion chamber to high compression ratio applications.The basic object of this research is a traditional turbocharged direct injection gasoline engine,with a compression ratio of 10.5.which the design focused on power output,and so the thermal efficiency is lower.In this paper,three high compression ratio schemes of 12.5,13 and 13.5 are designed.In order to adapt to the application of high compression ratio,two optimization schemes are designed for the intake port,and three transverse schemes,two longitudinal schemes are designed for the combustion chamber according to the layout of spark plugs of overhead fuel injectors.Based on the design schemes,the different core parameters,compression ratio and intake port combustion chamber of turbocharged direct injection DHE combustion system are simulated and analyzed.The effects of different combustion system design parameters on in-cylinder mixed flow,combustion parameters,power and economy under high compression ratio are studied.Among them,the comparative study of transverse combustion chamber and longitudinal combustion chamber is emphasized.The simulation results show that the spark plug layout scheme of transverse injector can greatly improve the in-cylinder tumble ratio of combustion system,and the maximum transient increase is 80%.Based on the simulation results,two compression ratio schemes were trial produced and verified by combustion development thermodynamics test.The high compression ratio type selection test,full load test and partial load test of the combustion system development are completed.The final test results are highly consistent with the simulation results.The combustion system type selection test selected the optimal combustion system scheme of transverse combustion chamber CC-6,intake port tumble ratio of 3.06,compression ratio of 13 finally,the universal test verified that the gasoline engine has reached the maximum 42.5% effective thermal efficiency index.Finally,the application optimization law of high compression ratio and the sensitivity between the key parameters and the performance of high compression ratio combustion system are summarized.The important discovery is that under the condition of high compression ratio,the transverse high tumble ratio intake port combustion chamber can greatly improve the mixing quality in the cylinder,which is an important premise for the application of high compression ratio.The design schemes of this turbocharged direct injection DHE combustion system with effective thermal efficiency of more than 42% is also summarized.At the end,the future research on combustion system with higher thermal efficiency is prospected,and it is pointed out that the further improvement of thermal efficiency of internal combustion engine in the future lies in improving specific heat ratio and reducing related losses.