The Effect of Compressor and Turbine Specific Speed on Turbocharger Efficiency and Engine Performance

As a result of dimensional and cost limitations, the specific speed of today's turbochargers for vehicular diesel engine applications are higher than optimum. Performance of turbochargers therefore falls below the state-of-the-art. According to the analysis presented in this paper, one avenue for improvement of turbocharger overall efficiency is reduction of compressor and turbine specific speed. A technique for optimizing turbocharger overall performance is presented, based on variation of component specific speed. It is concluded that the concept of lower specific speed turbochargers deserves further study. It is essential that the balance between the advantages and disadvantages of this concept be carefully evaluated by turbocharger and diesel engine manufacturers.