Study On The Design And Performance Optimization Of A Turbocharged Si Engine Based On Model

Since1960, due to its many special advantages of internal combustion engine (ICE),such as the wide power and speed range, and convenient to use and good flexibility, theICE becomes the main the power equipment for the human beings. In new century, theautomotive amount sharply increases, the petroleum crisis and environment pollutionproblem are more and more critical. Studies on the ICE technology that is highlyefficient, energy and environment friendly are very necessary.Recently, small displacement engines with low emission and less fuel consumptionare welcome by consumers due to their high fuel economy level. Small displacementturbocharged engine can obtain the same power and torque level as the biggerdisplacement of natural aspirated (NA) engine while achieving higher fuel economy levelat the same time. Therefore, small displacement turbocharged SI engine represents thefuture development direction of the ICE industry, and would be gradually popularized inthe automotive industry.The modern turbocharged SI engines are highly complex. Especially, when the dualindependent VVT system are established in the engines, the design and operativevariables increase and interconnect with each other, which increases the design andoptimization difficulty. If we adopt conventional method (trial and errors), thedevelopment cost is high, work amount is significant, and the time period is long.Therefore, this thesis would investigate on the development and performance analysis for the objective turbocharged SI engine basing GT-Power model that is an engineeringdesign and optimization method basing on model. The main study aspects for this thesisinclude:(1) At first, a simulation model for the prototype1.0L NA engine is established byusing the GT-Power software. The model parameters in the GT-Power model areaccurately calibrated using experimental data. After accurately calibrated, the maximalerrors between the predicted torque, BSFC by the GT-Power model and theirexperimental results are2.5%and4.2%, respectively, which show the high predictionaccuracy of the GT-Power model. Then, a1.0L turbocharged engine simulation model isestablished basing on the1.0L NA engine model, and would be used to implement thedesign and optimization for the objective turbocharged SI engine.(2) The GT-Power model for the1.0L turbocharged SI engine is adopted to addressthe matching and selection for a turbocharger, which is aimed at obtaining optimumengine performance while improving the fuel economy. After initially matching theturbocharger, performance for the prototype engine is greatly improved, and in themeanwhile the fuel economy is also improved a little. However, according to the initialmatching results for the target turbocharged engine, it is found that the selectedturbocharger basically match with the target engine. But there exists the followingproblems: the torque and power in the lower speed range are lower than their objectivevalues, and need to be further optimized; work points for the compressor do not gothrough the operating area with highest efficiency, and need to be optimized to make thecompressor works in the highest efficiency area.(3) The optimization model through the coupling of the GT-Power model andmodeFRONTIER software are established. Then the geometrical parameters such as theintake and exhaust runner length, cam lift curve, and the operating parameters such asintake and exhaust valve timings are optimized by multi-objective genetic algorithm(MOGA) aimed at making the target turbocharged engine obtain optimum performance and fuel economy level at the same time.(4) Those design parameters such as the intake runner length, and operatingparameters such as the intake valve timing optimized by genetic algorithm are input intothe GT-Power model for the target turbocharged engine again to examine the torqueperformance and fuel economy level for the target turbocharged engine. In themeanwhile, the work area and efficiency for the turbine and compressor are alsoinvestigated. The GT-Power simulation results show that, in most speed range, the torqueand power for the target turbocharged engine are obviously enhanced comparing to theprototype engine.