The Optimal Design Of The Variable Geometry Exhaust System And Turbocharger

Turbo technology has been an indispensable key technology of internal combustion engine in improving the internal combustion engine performance and energy saving and emission reduction. VGT (Variable geometry turbocharger), as a generally recognized effective solution to the problem that caused by narrow effective operation interval and non-adjustable boost pressure which is common in the usual fixed geometry turbocharger, is widely used in vehicle engine, but less in marine engine. This paper studies the optimization of VGT in marine diesel engine.This paper adopts a double-deck VGT which has4runners with a part circumferential intake structure. When engine works at a low speed, turbine inlet regulating valve is closed to make sure only the inner port is open in volute to reduce the circulation of volute area and improve the turbine inlet pressure and useful work while supercharging pressure increased. When engine works at a high speed, the valve regulates on the basis of different performance requirements to change the flow area and match well with the engine in all conditions. Then this paper uses ANSYS CFX software for the numerical simulation of the VGT, and analyzes different structure schemes.First, the paper studies the location of the valve which is the major part of this VGT on the basis of comparison between two structure models. The analysis shows that the turbine efficiency and output power of the project which valve is arranged above are higher than the project which valve is arranged below. Second, analysis between different volute flow areas are taken and reason of air loss is find to get the optimal design case. The analysis shows that the turbine efficiency and output power of the project which has the smallest volute throat section area is higher than the other projects. Third, contrastive analysis among different circumferential inlet angle is taken to make optimal case. The analysis shows that the turbine efficiency and output power of the project whose inlet angle is210°is higher than the other projects. Finally, analysis between different pipes is taken. The analysis shows that the turbine efficiency and output power of the project whose internal flow passage has a small passage and a big passage is higher than the other projects. Then we can get a best design through above projects.