Computational evaluation of turbo and electric powered simulators for wind tunnel tests of ultra-high bypass engines

Experimental testing of aircraft configurations requires the use of representative engine units to simulate powered-on conditions. For ultra-high bypass ratio engines featuring a tighter aircraft integration, the installation effects need to be carefully assessed. This paper presents a computational evaluation of two powered simulator models for wind tunnel tests of an ultra-high bypass turbofan, based on a traditional air-driven Turbo Powered Simulator (TPS) and an Electric Powered Simulator (EPS). Starting from two-dimensional axisymmetric analyses, the design of the baseline turbofan engine and the choice of the duplication parameters of the simulators are described. Several aspects related to the non-reproducibility of the core flow at wind tunnel level are discussed, in terms of mass flow matching, TPS core nozzle pressure ratio and plug shape of the EPS. The selected solutions are evaluated for an underwing installed configuration at cruise condition, with a flight Mach number of 0.80 and a constant lift coefficient of 0.50. The comparison of the flow field and the resulting installation drag of the simulators with the baseline engine shows an important influence of the core flow. The TPS installation drag is estimated to be 18% larger than the baseline, compared to a value 10% lower for the EPS. A post-check assessment at a higher cruise Mach number of 0.85 with an improved geometry reveals that the new TPS insertion offset remains almost the same at this new condition. The study highlights a potential lower bias in reproducing the installation drag in wind tunnel tests using an electric-driven simulator concept, but also confirms that the established TPS technology can provide an acceptable drag agreement with the baseline case, for an ultra-high bypass engine.