Optimization Research Of Diesel Engine Performance And Emission Characteristics Based On GT-Power And KIVA-3V

Valve timing directly affects the quality of engine gas exchange process, especially the volumetric efficiency, scavenging efficiency and gas exchange loss. Gas exchange process determines the quality of combustion in cylinder, thus affecting the engine power, economy, emission levels and reliability. When engine work in high speed conditions, the valve overlap and late intake valve closing angle should be set to large value so that residual gas can be reduced, increasing the amount of fresh charge into the cylinder and the output power. When engine work in low speed conditions or idling speed, the valve overlap and late intake valve closing angle should be set to small value in order to obtain better idle stability. So a compromise should be choosed between high and low speed to make the overall engine performance well.In this paper, 9.5L turbocharged intercooled diesel engine simulation model established by using GT-Power software to study the influence of valve timing on engine power and fuel economy. And KIVA-3V will be used to simulation the emission by GT-Power simulation results as boundary condition. The main contents and conclusions are as follows:Design orthogonal experimental according to the range of valve timing and use established diesel engine simulation model, orthogonal experimental results prove that EVT is the predominant factor. IVT 228.5°CA and EVT 127.2°CA is the best valve timing base on analysis results of Single factor 7 level experimental. After valve timing optimization, torque increase by 1.2% from 1157.52 Nm to 1171.22Nm; BSFC decreased by 1.18%, from 191.34g/kWh to 189.07g/kWh in requirements working conditions(1100 ~1700rpm,40%~100%load).Analysis the influence of exhaust valve timing on engine power, fuel economy and emission by GT-Power simulation. The result shows that the power and fuel economy greatly improved with exhaust valve timing delay. For example, in 1700 rpm and full load condition, torque increase by 9.0% from 1401.14 Nm to 1527.23Nm; BSFC decrease by 8.1% from 221.661 g/kW h to 203.36 g/kWh when EVT changes from 111°CA to 127.2°CA. NOx increase with exhaust valve timing delay, for soot, the opposite is true.In view of NOX emission increased when exhaust valve timing adjusted from 119.5°CA to 127.2°CA, then using the high-precision combustion and emission KIVA-3V program to study the engine combustion and emissions. Firstly, verified the combustion model and emission model compared to test data. Then carry out numerical simulation analysis of combustion and emission before and after optimization. The simulation results show that the engine emission levels were China stageⅣregulation before and after optimization. Which means that power and fuel economy has been improved but emission levels does not change at the same time.