Thermodynamic Cycle Simulation Of High Efficiency Engine With Electrically Assisted Turbocharger

Electric-assisted turbocharger has attracted much attention because of its flexible control and quick response.It is found that the electric-assisted supercharging technology can improve the engine dynamic performance and effectively solve the problem of "turbine hysteresis".This paper studies the electric assisted booster technology to improve the thermal efficiency of the gasoline engine innovation path,energy flow characteristics of the numerical method is applied to analysis of gasoline engine,not only can solve the problem of low thermal efficiency of part load of the gasoline engine,can also make up for the electric turbocharged gasoline engine problem of thermal efficiency at big load,and it has important significance for gasoline engine thermal efficiency improving.Based on chongqing key industry generic key technology innovation special project "supercharger design and control key technology research and application"(project number: cstc2015zdcy-ztzx60014),the main research content is as follows:First of all,according to the actual geometry size of a direct injection turbocharged gasoline engine and bench test,thermodynamic numerical model is established,and using the experimental data of thermodynamics numerical model for the parameter calibration,the calibration results show that the construction of thermodynamics numerical model can well represent actual operation condition of the engine.Furthermore,based on the established thermodynamic model,the CAM profile was redesigned,the combination of the compression ratio and profile was determined according to the running characteristics of gasoline engine,the motor module was added,and the compressor was re-matched.Finally,a new thermodynamic numerical model of the electrically assisted turbocharged gasoline engine was constructed.Then,the first law of thermodynamics is used to analyze the energy balance of the original engine.The results show that the main flow direction of the fuel energy of the original engine is exhaust,effective work and heat transfer,and exhaust has higher temperature,pressure and flow rate,which has great potential for recovery and utilization in engineering practice.Further,the energy conservation analysis of the turbocharged system shows that the energy recovered by the turbine only accounts for a small part of the exhaust energy,and the maximum energy recovered by the turbine under full load is 13.39 kw.The cooling and heat transfer process of the inlet air in the intercooler is an approximate isothermal process.Because the gas energy is mainly in the form of thermodynamic energy related to temperature,the intercooler takes about 80% of the inlet air energy out of the thermodynamic system of the gasoline engine.From the perspective of energy recovery and utilization,the energy effectively utilized by the turbocharging system only accounts for about 2% of the exhaust energy,and the utilization rate of the exhaust energy is very low.Finally,the first law of thermodynamics is analyzed,and the results show that: 1)the expansion process of the electrically assisted supercharged gasoline engine is more sufficient,so that more gas energy in the cylinder is converted into effective work.The maximum reduction percentage of exhaust loss is 4.9%.2)Electric-assisted turbocharged gasoline engine valve opened greater than the original machine at partial load and valve fully open at large load,pump gas process work is positive,thus improving the pump gas loss.The maximum decrease percentage of pump air loss caused by the increase of throttle opening is 4.2%,and the maximum decrease percentage of pump air loss caused by the positive work of the pump air process is 1.6%.3)The difference of heat transfer loss between the electrically assisted supercharged gasoline engine and the original engine mainly depends on the combustion work stroke.Due to the increase of the compression ratio of the electric-assisted turbocharged gasoline engine,the working fluids extrusion and turbulent flow velocity in the cylinder near the compression top dead center increases,so the heat transfer rate of the initial work is greater.The maximum heat transfer loss of the electric-assisted turbocharged gasoline engine increases by 2.4%.4)The difference in friction loss is mainly due to the piston reciprocating friction loss caused by the different surface pressure of the piston.Since the cylinder pressure of the electrically assisted turbocharged gasoline engine is greater than that of the original engine,the friction loss of the electrically assisted supercharged gasoline engine is slightly greater than that of the original engine,and the maximum increase of friction loss is 1.3%.5)The energy distribution characteristics of engine show that the effective thermal efficiency of the electric-assisted supercharged gasoline engine is increased by 10.46%,which indicates that the electric-assisted supercharger technology has a significant effect on the thermal efficiency.