Abstract

Modeling of the engine behavior in windmilling conditions is an important engineering objective. The relight capability of the engine is mainly associated with the air mass flow rate that passes through the engine high pressure core in those conditions. This is one of the parameters that drive the combustion chamber volume. Predicting the engine behavior is challenging, especially early in the development process. The pressure losses along the core are distributed between the different stages of the compressors and turbines, which are operated extremely far from their design point. Engine manufacturers must anticipate with sufficient margins to ensure that the specifications are met when the engine is finally qualified in flight. This article focuses on the behavior of compressor cascades in such conditions, corresponding to high negative incidences. A recently designed high pressure compressor is studied in windmilling conditions using three complementary approaches. First, engine tests are used to obtain validated 0D data for two flight conditions. Then, state of the art Lattice-Boltzmann Method (LBM) simulations are carried out to have insight in the flow characteristics inside the compressor. They are compared to the available experimental data. Finally, a 1D model using stage by stage Euler equation for turbomachinery is used. This kind of modeling is of particular interest because it can be used early in the design process. The correlations for losses and deviation angle from the literature are modified to account for the particularity of the flow in those conditions. One shows that the three approaches give consistent results.

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