Abstract:
Fan-in-Wing (FIW) and other embedded fan configurations have the potential to enhance the performance of future vertical take-off and landing aircraft by achieving efficient hover and high-speed forward flight. However, there is a continuing need for research to characterize the fundamental aerodynamics associated with these types of embedded fan systems. To this end, the present work experimentally investigates the aerodynamic performance of a series of generic FIW configurations in the Naval Surface Warfare Center Carderock Division (NSWCCD) 8- by 10-ft Subsonic Wind Tunnel. The goals are to understand how the aerodynamic performance of a FIW in hover is affected by different fan design parameters and also to create a benchmark dataset for model validation. The research is conducted in three phases; isolated fans in hover, FIW configurations in hover, and FIW configurations in transition from hover to forward flight. This paper describes the experimental approach and results obtained from the second phase of testing, which examines a number of different generic FIW configurations. Particular focus is placed on examining the effects of fan rotational frequency, blade pitch angle, number of blades, fan solidity, blade twist, and fan axial position within the wing duct. Furthermore, to better quantify the aerodynamic performance of the fan and the wing as well as the interactions within FIW systems, the model is designed such that the fan performance can be measured independently of the total FIW system performance. The results show that the fan and the wing form a complex and coupled aerodynamic environment that can, at times, be counter-intuitive when compared to results expected from an isolated fan. In general, the results suggest that all of the design variables affect the inflow distribution on the blades and, therefore, the overall aerodynamic performance as well as the stall characteristics of the fan and total FIW system. It is also clear that the future FIW systems must consider an integrated design philosophy that treats the fan and the wing as a coupled aerodynamic system. These results, along with those obtained in Phase I, will ultimately be used as a baseline for comparison with results in Phase III of the study which will examine the generic FIW configuration in transition and forward flight.