CFD analysis of counter-rotating open rotors using a rotating actuator disk model

In the world of transportation today, efficiency is essential and energy efficient systems are in high demand. Due to its high propulsive efficiency, an Open Rotor gas turbine engine has the potential to significantly minimize the specific fuel consumption and reduce CO2 emissions in a new generation of transport aircraft. In mid-1980’s GE invested significant effort in advanced turbo-prop technology (ATP) and unducted fan technology (UDF). However, in spite of its potential for 30% savings in fuel consumption over existing turbofan engines with comparable performance, for a variety of technical and business reasons, the advanced turboprop concept never quite got-off the ground. However, with current emphasis on “Green Aviation” NASA and aircraft engine industry (GE, Pratt-Whiney and Rolls-Royce) are investing significant resources in Open Rotor engine research and development. The goal of this study is to develop a numerical model to study the performance of counter rotating open rotors (CROR). Advanced CFD studies using the unsteady Reynolds – Averaged Navier-Stokes (URANS) equations are quite complex and computationally intensive. Therefore as a first step, a simplified model based on the rotating actuator disk method is developed to replace the two spinning rotors with two rotating actuator disks on an axisymmetric model. The URANS computations for this model are performed using the CFD solver ANSYS- FLUENT. The results of computations are compared using the wind tunnel data on F31/A31 CROR from NASA Glenn’s Research Facility for both the subsonic and transonic upstream flow. It is shown that this simplified model has strong agreement between the computed hub pressure distribution and the test data, while maintaining the computational simplicity.