Advanced Numerical and Experimental Techniques for the Extension of a Turbine Mapping 2013-24-0119
1D codes are nowadays commonly used to investigate a turbocharged ICE performance, turbo-matching and transient response. The turbocharger is usually described in terms of experimentally derived characteristic maps. The latter are commonly measured using the compressor as a brake for the turbine, under steady “hot gas” tests. This approach causes some drawbacks:
each iso-speed is commonly limited to a narrow pressure ratio and mass flow rate range, while a wider operating domain is experienced on the engine;
the turbine thermal conditions realized on the test rig may strongly differ from the coupled-to-engine operation;
a “conventional” net turbine efficiency is really measured, since it includes the effects of the heat exchange on the compressor side, together with bearing friction and windage losses.
In the present work, advanced experimental techniques aiming to extend the pressure ratio and mass flow rate ranges are summarized and results are compared to conventional test-rig findings.
A recently developed 1D turbine model is described basing on the solution of the flow equations inside the stationary and rotating ducts composing the device. The model is tuned with reference to experimental data collected on the conventional test-rig for a variable geometry turbine (VNT) and a mixed-flow waste-gated turbine (WGT). Then, for the WGT, the model is applied to extend the base map. The results very well agree to the experimental map obtained on the advanced test-rig.
The turbine model is finally used to provide the actual turbine aerodynamic efficiency, which does not account for compressor heat exchange, bearing friction and windage losses. The results are moreover validated against literature derived 3D CFD simulation findings.
The model hence shows the potential to overcame the limitations of a conventional test-rig for a turbine mapping.