Research On High Efficiency Clean Combustion Of Hybrid Commercial Vehicle Engine And Vehicle Matching Technology

With the increasingly prominent of energy and environmental issues,fuel consumption and emission regulations for the automotive industry are becoming more and more stringent.Hybrid technology can improve vehicle economy and reduce emissions through braking recovery,idle elimination and powertrain efficiency optimization.The high efficiency clean combustion technology such as reactivity controlled compression ignition(RCCI),premixed charge compression ignition(PCCI)and homogeneous charge compression ignition(HCCI)can improve engine economy and reduce emissions by optimizing the combustion process.Hybrid technology and high efficiency clean combustion technology of engine have become important fields of current research.This paper resolved the matching and application key issues of RCCI new combustion mode engine on parallel hybrid commercial vehicle.Firstly,a dynamic programming energy management strategy aiming at minimizing global fuel consumption and a vehicle model are established.Secondly,the distribution characteristics of engine operating points and high efficiency range characteristics under typical driving cycle conditions are studied.Then,based on the research and analysis of combustion characteristics of RCCI engine,performance research and optimization of RCCI hybrid engine have been done.Finally,the performance analysis and evaluation of the hybrid vehicle are carried out.The main research contents and conclusions of this paper are as follows:1.Vehicle modeling and optimizing of engine high efficiency range based on dynamic programming energy management strategies: Dynamic system configuration analysis and dynamic modeling are carried out.In order to shield the influence of control strategy on vehicle performance evaluation,so this paper chose the cumulative fuel consumption of the vehicle under the given typical driving cycle conditions(CCBC and C-WTVC driving cycle)as global optimization objective.The design of dynamic programming process and algorithm of energy management strategy are completed.The energy distribution trajectory that minimizes the cumulative fuel consumption of driving cycle is solved.The M-K-Means clustering analysis method is proposed and applied to study the distribution characteristics of engine operating point under typical driving cycle conditions.Three operating point distribution concentrated areas are obtained and the influence of the efficiency optimization of different concentrated areas for the vehicle economy is analyzed.These works provide direction and basis for the optimization of the whole vehicle performance.2.Research on combustion characteristics and emission characteristics of engine with RCCI combustion process: The original engine is a high-pressure common rail turbocharged diesel engine.A single cylinder RCCI thermodynamic engine test platform is built by adding the inlet injection gasoline supply system,the two-stage inlet pressurization system,and the performance test system on the original engine.The effects of gasoline-diesel fuel ratio,EGR rate,diesel injection timing and other control parameters on the combustion process and emission of the engine are studied,which provided a theoretical basis for the subsequent optimization of engine high efficiency region and performance research.The results show that with the increase of gasoline ratio,the combustion duration is gradually shortened,and the heat release form is gradually transformed from single peak heat release to double peak heat release,the obvious two-stage combustion phenomenon emerges,and indicated thermal efficiency is improved.The increase of gasoline ratio will significantly reduce the emission of engine particulates,but will increase the emission of CO and HC.The increase of EGR rate increases the specific heat capacity of the in-cylinder mixture,reduces the incylinder temperature,thus slowing down the combustion rate,and prolongs the ignition delay period of gasoline spontaneous combustion.The center of gravity of combustion heat release moves backward,and the two stage combustion phenomenon is more obvious.At the same time,increasing EGR rate can reduce the pressure rise rate and reduce the maximum cylinder pressure,so as to broaden the application limit of gasoline ratio.Early diesel injection helps to improve the thermal efficiency,but with the advance of diesel injection timing,the improvement of indicated thermal efficiency is gradually not obvious.On the other hand,the advance of diesel injection timing will also make the cylinder temperature and pressure increased significantly,which will have a great impact on pollutant emissions.3.Performance research and optimization on hybrid engine of RCCI combustion mode: On the basis of constructing the combustion mechanism of RCCI combustion mode,one-dimensional performance model and three-dimensional combustion model of the engine are built.Based on the previous conclusions of thermodynamic engine experimental research,this paper sets efficiency optimization of operating condition distribution concentration areas as objective,the GT-power and Converge cosimulation method are used to study the influence of different gasoline ratios and other control parameters on engine performance.The simulation analysis and performance optimization of the engine are completed.Based on the simulation research,the engine performance test bench is built.Experimental study on performance optimization of the whole vehicle is carried out.The optimization results of external characteristics and universal characteristics of RCCI hybrid engine are obtained.Compared with the original engine,the efficiency in the operating condition concentration area is significantly improved,and the optimization of the engine high efficiency range is realized.4.The vehicle model building and vehicle performance analysis based on Cruise:Backward vehicle longitudinal dynamic model is built based on AVL-Cruise software.Matlab Simulink is used to complete the design of real-time power following control strategy.The power and economy performance of the vehicle are analyzed when the original engine and the RCCI engine are carried separately,and the comparative analysis is carried out.The results show that the power performance of RCCI hybrid engine meets the requirements of vehicle design and development.Under different driving cycle conditions,the vehicle economy is improved,the comprehensive fuel consumption is reduced,and the efficiency of the vehicle power system is improved.