Study On Characteristics Of Scavenging Based On Four Stroke Turbocharged Diesel Engine

The modern engine technology improves over time, variable valve, variable manifold, turbocharged, they are all widely used to improve the gas exchange process, which means that the gas exchange process occupies an important position in the research of internal combustion engines. Scavenging as an important part of engine exchange process, which directly affects the amount of residual gases in the cylinder and the heat load of parts, affects engine power, economy, emission levels and the reliability eventually. For a long time, the scavenging process of two stroke engine is a very popular research object, but not four.This paper is devote to the scavenging characteristics study of four stroke turbocharged diesel engine by combination of experiment, working process numerical simulation and CFD. The main contents and conclusions are as follows:Firstly, carry out the transient flow test of intake and exhaust based on turbocharged diesel engine. The analysis of test data show that the scavenging performance of this engine is poor in high and low speed condition, especially in high speed and low load conditions.Next, analysis the influence of engine parameters by the working process numerical simulation based on GT-Power software. Parameters including intake, exhaust valve timing and exhaust manifold diameter, length. The simulation results indicates that the exhaust valve timing effect on scavenging performance is biggest among these four parameters.Then, optimize the engine design according to the impact analysis, optimization need put off intake and exhaust valve timing by 10°CA, meanwhile, does not change the structure of exhaust manifold. And the results of comparison before and after optimization show that the optimization is very successful. For high speed and low load conditions, optimization can reduce coefficient of residual gas about 1%, and the exhaust temperature decreases about 12 K. But power down slightly and BSFC increased about 1% at the same time.Finally, found the disadvantage of scavenging details about this engine by analysis 3D transient numerical simulation results, and comparing the simulation results of before and after optimization to verify the optimization results.