A Radial Inflow Turbine Impeller for Improved Off-Design Performance

Abstract

Given the instantaneous operating conditions of the radial inflow turbine on a diesel engine and the possible requirement of a variable geometry turbine casing, an alternate approach was used to design an impeller which could accommodate the large variations in inlet states. Several impeller designs were generated and tested. Each was found to give a performance advantage in some portion of the turbine map. A blunt inlet shape design was found to give the best performance at all suspected inlet conditions. A final design turbine wheel was generated to cover the operating range of a variable geometry turbine casing. It was found that this impeller gave improved efficiencies at all operating conditions.

A Contribution to the Study of Exit Flow Angle in Radial Turbines

“…Inviscid numerical simulation has been presented by several authors (e.g. Mulloy and Weber (1982), Choo and Civinskas (1985)). A typical result is shown in Fig 1, adapted from the work of Molloy and Weber by addition of lines of circles which show average velocities between hub and shroud.…”

“…Note that the appropriate radius is neither the hydraulic or rms radius rh (= (R2 + r2 )/2) nor the average radius r (_ (R + r)/2). In fact : r<r,<rh (6) The work of Choo and Civinskas applies to the turbine tested by McLallin and Haas (1980). This turbine produced approximately 16 kW at 35000 rpm, and relative air velocities were of the order of 200 m/sec.…”