An Open Virtual Test Case for Open Fans

Abstract This article presents an open virtual test case of an Open Fan geometry. The Open Fan is the newest and most promising unducted aero-engine concept. It is expected to be quieter and mechanically less complex than a counter-rotating open rotor (CROR), while delivering a similar level of fuel burn. The fuel burn and emission improvements with respect to an ultra-high bypass ratio (UHBR) ducted fan are expected to be very significant. A challenge will be to minimize the acoustic impact. Currently, there is no publicly available state-of-the-art Open Fan design, or even a state-of-the-art CROR geometry, that researchers can use to conduct independent simulations. A realistic industrially driven Open Fan virtual test case has been released by the PANDORA project consortium. The key outcome of the PANDORA project is an estimate of the improvements delivered by the Open Fan configuration with respect to a CROR in terms of noise, performance, and emissions. The added value of having a realistic design is that it naturally drives the research in the correct direction and provides the range of parameters in which the physics must be properly solved and understood. In this work, a new Open Fan geometry will be presented along with the pitch settings at various operating conditions. The aerodynamics of an Open Fan is more demanding than that of a CROR. In fact, the Open Fan presents a higher aerodynamic loading and Mach number for the same thrust. The aerodynamic performance of the Open Fan configuration is obtained using RANS simulations. This type of simulation is also helpful in assessing the influence of design changes on the Open Fan performance. RANS simulations have been successfully used to compute the aerodynamic loading, thrust, and efficiency at different operating conditions.