Robust model of a transient wind tunnel for off-design aerothermal testing of turbomachinery

•First attempt to use transient wind tunnel for fluid machinery at off-design.•Accurate wind tunnel numerical model to be coupled with measurements.•Experimental characterization of turbomachines under transient conditions.•Transient turbine map model assessed against experimental data.•Turbine stage operating at extreme off-design regimes: stirring and reverse flow.

Short duration wind tunnels offer an economical approach to study the aero-thermal operation of propulsion components, while reproducing temperature ratios, Reynolds and Mach numbers of the actual engine conditions. The present paper aims at modeling with high fidelity the von Karman Institute compression tube facility. This wind tunnel was simulated using the EcosimPro suite to characterize the behavior of each subcomponent during the whole test envelope, including the turbine map at off-design. The numerical predictions were then assessed through the comparison with experimental data. The model was proven to be an effective tool to accurately evaluate all the operating regimes that a research turbine experienced during the experimental sequence. Consequently, the present model allows exploiting the complete test run duration to obtain unique experimental data from the turbomachinery operating at far off-design conditions. The capability to experimentally test components at off-design is fundamental to understand the flow physics of any gas turbine engine operating at extreme conditions and to characterize the transient performances of fluid-machinery in high-speed propulsion concepts. However, technical dissemination on these aspects is scarce.