Experimental Investigation of Fan Aerodynamic Performance for Fan-In-Wing Applications

The aerodynamic performance of a series of generic isolated fan configurations are experimentally investigated in the Naval Surface Warfare Center Carderock Division (NSWCCD) 8-by-10 foot Subsonic Wind Tunnel. The goal of this work is to develop a benchmark dataset that can enhance the fundamental understanding of the fluid dynamic interactions between a generic fan and wing for Fan-In-Wing (FIW) and embedded fan configurations These configurations have significant applications for aircraft as well as underwater systems. The research is performed in three phases; isolated fans in hover flow conditions, FIW configurations in hover flow conditions, and FIW configurations in transition from hover to forward flight. The present work (Phase 1) describes the model, facility, instrumentation, standalone test stand development, and results of the isolated fan wind tunnel tests. Five different fan configurations specifically tailored for understanding the various aerodynamic phenomena associated with FIW performance are tested to examine the effects of fan rotational frequency, blade pitch, blade twist, number of blades, and fan solidity. The results quantify how each of the fan design and operational variables significantly affect aerodynamic performance. For example, higher solidity fans are able to carry more thrust but are less efficient than lower solidity fans. Positively twisted blades achieve similar thrust levels to negatively twisted blades but are less efficient. In general, the results indicate that all of the design variables independently affect the inflow distribution on the blades and, therefore, the overall aerodynamic performance as well as the stall characteristics. The effects of these design variables on the full FIW performance, however, are expected to be different because of the mutual aerodynamic interaction between the fan and the surrounding wing. Therefore, the isolated fan test results will be used as a baseline for comparison with the full FIW configuration performance that will be investigated in Phases 2 and 3.