Flow field investigation on a wing installed Counter Rotating Ultra-high-bypass Fan engine simulator in the low speed wind tunnel DNW-LST

Abstract

For a better understanding of jet interference from wing mounted turbofan engines and for improved CFD modelling more detailed flow field studies and reliable test data are required. With this objective, within the framework of the DLR-NLR co-operation, flow field investigations have been carried out in the Low Speed Wind Tunnel LST 3x2.25 m² of the DNW (German Dutch Wind tunnels) on a twin-jet transport aircraft half model (ALVAST). The half model was tested in cruise configuration (clean wing without flaps) without and with a wing mounted engine simulator . Two types of engine simulators were used: a Through Flow Nacelle (TFN) and a turbo-powered Counter Rotating Ultra-high-bypass Fan (CRUF). All tests have been carried out at wind tunnel speed V0=60 m/s (Mach number M0=0.18). The flow fields behind the wing and engine simulators (TFN and CRUF) were investigated using a rake equipped with total pressure probes and a rake equipped with directional probes. In this way time-averaged flow field planes perpendicular to the tunnel flow were obtained. Non-intrusive flow field measurements were carried out using the Particle Image Velocimetry (PIV) technique. This technique was used to investigate the stream-wise development of the turbo-powered CRUF inlet and fan exhaust flow and the velocity flow field near wing and pylon. Information about both the unsteady and the time-averaged flow field was obtained. The measurement techniques proved to be successful for engine/airframe interference studies. The two techniques are complementary and the results correspond well with each other. Furthermore a useful database has become available for further improvement of the CFD modelling. CFD computations have already been made for the cruise configuration without engine simulator, which correspond reasonably well with the five-hole rake measurements