Variable Geometry Diffuser of Turbocharger Compressor for Passenger Vehicles 2003-01-0051
For the worldwide environmental problems and fuel economy concerns, turbochargers have become essential technology for diesel engines. The number of variable geometry turbocharger turbines which are used for diesel engines instead of conventional fixed geometry or wastegated turbines has increased. The flow range of the variable geometry turbine expands by changing the nozzle exit angle around the turbine wheel. Compressors also require wide flow range and high efficiency to match variable geometry turbines. On the other hand, to improve both the performance at low engine speed and the max output, gasoline engines also require the wide range and high efficiency turbocharger compressors.
Almost turbochargers for passenger vehicles are still using conventional fixed geometry compressors.
The new variable geometry diffuser whose vanes can be put in and out at the diffuser passage was developed for the turbocharger compressor. By this mechanism the compressor gets both the large capacity of the vaneless diffuser and the high efficiency of the vaned diffuser at small flow range, and the engine torque or fuel economy is improved at low speed.
This paper describes the structure, performance, some test and simulation results of the variable geometry diffuser.