The Design Of Scavenging Process Test Scheme For Two-stroke Marine Diesel Engine

Due to the high thermal efficiency and safe operation of two-stroke diesel engine,more and more two-stroke diesel engine had been used in marine diesel engine. Butcompared with the four-stroke engine, traditional two-stroke diesel engine the time ofscavenging is short, the inlet and exhaust process at the same time. This is a seriousproblem that fresh air and exhaust gas is mixed, so that the coefficient of residual gas isbig in cylinder, the effect of scavenging was poor. At the same time, the scavenging effectis one important index for the two-stroke diesel engine economy and dynamic property.Therefore, it is important to mastery the scavenging coefficient for the design of thetwo-stroke diesel engine.This paper is about the design of the scavenging process experiment platform for largemarine two-stroke diesel engine. The main scheme was static steady flow scavenge testbench, which was measurement the effect of scavenge under different position of thepiston. It is easier to measure the air velocity inside the cylinder by using PIV test method.The flow state in cylinder could be got through the calculation of computer software. Inthe designated position of scavenging, the piston was fixed. The different scavenging portopening was controlled by lifting mechanism of the piston. In order to make simplify theexperiment equipment and reduce the cost, it adopted the endoscopic PIV measurement.Relied on the powerful data processing ability of PIV equipment; it is easy get flow fieldin cylinder under different opening of scavenging port.In order to verify the feasibility of the designed test bench, this article also uses themethod of numerical simulation to study the scavenging process of the designed test bench.The calculation model includes the scavenging box, cylinder and exhaust. Throughcalculating the velocity and pressure value of the field in different opening of thescavenging port, these calculation verify that the feasibility of scavenging processmeasurement under this platform. It also provides theoretical basis for the arrangement ofscavenging measuring points in the bottom of cylinder.