Design And Experiment Of Turbo-cooling System For Spark Ignition Engine

In recent years,high compression ratio and high pressure ratio engine has become a trend because of energy shortage and stricter emission regulation.The main factor limiting increase of compression ratio and pressure ratio of gasoline engine is knocking.Limited by the heat transfer medium,the volume and efficiency factors,temperature of boost gasoline engine intake air after intercooler is still high,and knocking tendency is high.In this paper,the turbo-cooling system for a supercharged gasoline engine is researched,which could lower temperature of boost gasoline engine intake air through turbo-expander,and the knocking tendency of the gasoline engine is decreased.As a result,the pressure ratio of the turbocharger can be improved,which would improve the performance of gasoline engines.In this paper,the original engine simulation model of a 1.5L supercharged gasoline engine is established in simulation software,and the model is corrected by matching several points on the full-load characteristics of the gasoline engine.Based on the simulation model,the turbine-cooling system was set up.Different intake air temperature was obtained by changing the expansion ratio of the Air-turbo.The influence of different intake air temperature and intake pressure on the power and economy of the gasoline engine is compared and analyzed.The inlet temperature is lower than the original engine by 20 degrees centigrade in the simulation calculation,and the boost ratio of the turbo-cooling system is improved under the premise of no detonation.Finally,torque and power of engine increased by about 12%,and fuel consumption slightly lower than the original engine.The basic design parameters of turbo-cooling system are obtained by thermodynamic calculation and simulation results.Based on the 0-0 cross section design method,the design of compressor and turbine volute is completed through simulation software.The preliminary design of compressor and turbine impeller was fulfilled by numerical calculation.Finally,the compressor and turbine impeller are optimized by simulation software based on Uniform Design Experimentation.The drawings of Turbo-cooling turbocharger is finished by CAD,and the prototype of turbocharger is accomplished with assistance of factory.Turbocharger characteristic curve can be obtained through turbocharger experiment,which show that expansion of air-turbo is about 1.4 and the effective efficiency is about 50% on design point,and pressure ratio of compressor range from 1.05 to 1.30 and the efficiency range from 50% to 60%.Based on the experiment results,simulation model was reestablished,and the turbo-cooling system was completed based on experimental results.The simulation results show that extra job should be done to optimize the design of turbo-cooling system.