Influence of a variable guide vane nozzle on the design parameters of a radial turbine stage

Abstract

In the field of turbocharging, radial machines are commonly used. However the changing flow conditions provided by the engine at the inlet of the turbine stage imply usual off-design functioning, and require a good response of the stage to these conditions. An improvement to widen the operating range of the device has been achieved by using variable-geometry stators. Such a variation around the design geometry is likely to disturb the characteristics of the nozzle; the initial design parameters are not preserved. An experiment was set up to identify the behavior of a small dimension radial inflow turbine stage depending on nozzle opening configuration. The influence of the variable geometry system is identified. Then the consequences on the relevant design parameters, criteria and correlations traditionally proposed in the literature are presented.