Abstract
For the worldwide environmental problems and fuel economy concerns, turbochargers have become essential technology for diesel engines. The centrifugal compressors used for turbochargers are required to achieve the high efficiency and wide flow range. In order to satisfy these requirements, the new variable geometry diffuser with the moving vanes was developed. An annular diaphragm was applied to move the diffuser vanes pneumatically. The variable geometry diffuser had two modes, the vaned and vaneless diffuser modes, by putting in and out the diffuser vanes at the diffuser passage. By this mechanism both the large capacity and the high efficiency at the small flow range were achieved, and the diesel engine performance at low speed was improved.
