Abstract
It is a well known fact that turbocharger works
with pulsating exhaust flow in its entire operating
life, hence the need to predict unsteady performance.
This paper presents the unsteady performance
prediction resultof a single entry nozzleless
mixed flow turbine under steady flow and 60
Hz pulsating flow at 43.0 rps/
√
K operating speed.
The modeling method coupled one-dimensional gas
dynamic modelwith a mean-line model to predict
the turbine efficiency by appropriate losses consideration.
The coupled method assumes that the turbine
volute has a large volume and length, so that
unsteadiness effect of the pulsating flow is significant
while the rotor is assumed to behave quasisteadily.
A pressure drop boundary is used to simulate
pressure drop across the turbine volute. The
coupled method was validated with the experimentally
measured steady state results of the same turbine.
Experimentally measured total conditions of
the flow were used as inlet conditions for the model
during unsteady analysis. The predicted isentropic
power averaged results show convincing match with
the experimental data. This will set forward a systematic
approach for engine designers to evaluate
turbine performance beyond what will be normally
provided by turbocharger manufacturers, which is
the steady state map.
