Features of calculation and modeling of flow of rotors and pucher propellers for aerial vehicle in the condition of very rarefied atmosphere

Abstract

This article presents the structure of designing and modeling the flow of rotors and pusher propellers in a highly rarefied atmosphere. The aerodynamic characteristics of an airfoil are key factors in determining design accuracy and performance prediction. The blade elements operate at different Reynolds numbers and angles of attack. The blade profile was selected based on an estimate of the lift-to-drag ratio for expected Reynolds numbers under the design conditions. This paper considers the features of the operation of propellers in a highly rarefied atmosphere. When modeling propellers operate in rarefied atmosphere, it is necessary to pay special attention to the choice of a model for the turbulent viscosity of the medium. The greatest difficulties in the design of stratospheric propellers arise when solving the problems of excessive diameter, weight and shape of the blades. To solve this problem, in this paper, it is proposed to use joined double row blades. This approach made it possible to eliminate the aerodynamic shading of the blades and increase their aerodynamic load. The use of double-row blades will provide the necessary rigidity and strength of the blades and will lead to weight reduction. Additionally, due to the double-row design, it becomes possible to reduce the diametrical dimensions of the propeller. An analytical technique for profiling double-row blades has been developed. The proposed approach is based on the joint application of the one-dimensional propeller theory and numerical gas dynamics methods. The one-dimensional theory is used to obtain the original geometric shape of the propeller for given characteristics, and the methods of numerical gas dynamics, which are based on solving the Reynold averages of the Navier-Stokes equations, are used to solve the problems of spatial modeling of the flow and obtain refined propeller characteristics. Considering the design requirements and operational limitations, it is proposed to use propellers with joined double-row blades in conditions of rarefied atmosphere.