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Computational Fluid Dynamics (CFD) is frequently used to predict complex flow phenomena and assist in engine design and optimization. The scavenge process within a 2-stroke engine is key to engine performance especially in high performance racing applications. In this paper, FLUENT CFD code is used to simulate the scavenging process within a 125cc single cylinder racing engine. A variety of different port designs are simulated and scavenge characteristics compared and contrasted. The predicted CFD results are compared with measured scavenge data obtained from the QUB single-cycle scavenge rig. These results show good agreement and provide valuable insight into the effect of port design features on the scavenging process.

The improvement of computer simulation packages with experimentally validated sub-models has benefited the engine designer in reducing development time and costs. Such packages offer invaluable information regarding the internal gas dynamics and gas exchange characteristics. Presented are measured dynamometer results of a RS Honda 125 cm3 two-stroke single-cylinder motorcycle grand prix road-racing engine operating at full throttle from 9000 rev/min to 13000 rev/min. The engine is instrumented to provide in-cylinder and exhaust pipe pressure crank-angle histories. All relevant engine geometry, discharge coefficients, scavenging characteristics and combustion data are used to simulate the engine using a one-dimensional (1-D) engine simulation package. In-cycle crankshaft angular velocity fluctuations are also considered. Performance parameters such as power, BMEP and delivery ratio, together with pressure diagrams are compared to the measured data.