Numerical Simulation On Off-Design Performance In A Ship-Turbocharger Turbine And Redesign Of The Turbine

Internal combustion engine is the most widely used in modern human society, it is the most important power engine in all walks of life playing as an irreplaceable important role. Turbochargers can effectively improve the working conditions for internal combustion engine. And turbocharging technology has become one of the most effective measures for increasing engine power and economy, reducing exhaust and noise. Requirements of energy saving and environmental protection need more application and development of turbochargers. Because of the inherent characteristics of turbocharger, the internal combustion engine matches the turbochargers well under design condition, while under off-design condition, they can not make the best performance. So it is of importance to increase the performances of turbocharger under off-design condition for high efficiency.In this thesis, the 3D flow characteristic in a ship-turbocharger turbine was numerically simulated under several off-design conditions, by using FINE/Turbo CFD software package of NUMECA, specially developed for turbomachinery. Flow performances were analyzed and compared under three conditions with different inlet velocity and parameters. Numerical results showed good agreement with experimental data. Based on the discovered problems, redesign of the rotor blade was conducted, and then the flow performance was increased under lower-load conditions. Through the numerical analysis of the flow within the volute, the structure of the inlet volute was redesigned too, the flow loss of the inlet gas was reduced, and the turbine inlet conditions were improved.The study results can provide valuable experience and reference for future design and research of the ship-turbocharger turbine to some extent. The improvements on the turbine's off-design performances in this thesis are proved to be succesful in matching design between the engine and the turbocharger.