Research on Design Domain of Propeller-Driven Hybrid-Mode Aerial Vehicle

Abstract

Propeller-driven hybrid-mode aerial vehicle (PHAV) is the object of this study. Because of its vertical take-off and landing capacity and high horizontal-cruise performance, PHAV is an ideal candidate to undertake intermediate-range emergent missions, such as disaster rescue, goods delivery, emergent battle and so on. However, many designs have failed to realize the indexes due to the failure in handling the contradiction between the two flight modes: vertical flight mode and horizontal flight mode. A feasible approach to the solution of this problem is to consider the requirements of the two modes in formulation of the design domain. In this paper, the design domain of PHAV has been studied. With aerodynamic performance, propulsion efficiency and weight properties considered, a design domain of wing loading W/S and propeller-wing area ratio A/S has been built up. And a nonlinear programming aimed at maximum margin of weight fraction has been conducted. As a distinct feature, a high area ratio would probably be obtained in a design of PHAV. After the programming, the maximum attainable area ratios of different configuration techniques, such distributed powerplants, stop rotor and ducted fan, have been discussed in a more general way, and the problems brought by high area ratio have been also discussed. As a conclusion, the margin of weight fraction of a PHAV is sufficient for endurance, payload, additional weight of propulsion system, strengthened structure, equipment, maneuverability and novel configuration. NomenclatureA = gross disc area propellers AR = aspect ratio a = acceleration B = number of propeller blades  = inflow angle at blade element CL = lift coefficient Cl = roll moment coefficient yielded by torque of propeller CD = drag coefficient CT = thrust coefficient D = drag DL = disk loading d = propeller diameter E = lift-drag ratio e = correction factor f = power ratio g = gravity acceleration 2  = efficiency J = advance ratio of propeller  = margin of weight fraction L = lift Ma = Mach number N = number of propellers n = rotation speed of propeller or load factor P = power q = thrust factor of duct R = propeller radius  = density or atmospheric density S = wing area T = thrust t = time  = thrust-weight ratio V = velocity VS = sonic velocity W = weight W/S = wing loading  = general factor Subscript BE = balde element DF = ducted fan d = propeller disc Eq = equipment F = fuel system H = horizontal flight mode I = ideal N = nonideal P = propulsion system Pl = payload S = structure system V = vertical flight mode