A Blade Element Theory Based Actuator Disk Methodology for Modeling of Fan Engines in RANS Simulations

Abstract

A modified actuator disk method based on blade element momentum theory is applied to an UHBR turbofan engine with the DLR TAU Code. The method is compared against RANS simulations with a common thermodynamic engine boundary condition and high-fidelity 360° uRANS simulations as well as RANS mixing-plane data from the design process of the engine conducted with the DLR flow solver TRACE. The input data of the actuator disk model comprise sectional lift and drag coefficients of the rotor and stator blades which are obtained by 2D RANS computations of the blade sections performed with the TAU Code. The boundary conditions for these 2D computations are derived from the aforementioned RANS mixing-plane results obtained during the design process of the investigated engine. Good agreement between the RANS actuator disk method and the uRANS results as well as the RANS mixing-plane data is observed. The actuator disk model is able to predict global engine performance data for different engine operating points. Detailed analysis shows that the actuator disk model is able to reproduce characteristic non-uniform inflow phenomena that could in the past only be modeled with uRANS computations. Additionally the model is capable to accurately predict the thrust distribution between rotor and stator. Therefore it is able to fill the gap between the currently used thermodynamic engine boundary condition and high-fidelity uRANS computations with only a minor increase in required computational resources.