Design of Swirl Recovery Vanes for Wing-Mounted Tractor Propeller Propulsion System

Abstract

Increasing pressure of reducing fuel consumption has led to renewed interests in propeller propulsion devices for their high propulsive efficiency. In a propeller propulsion system, the torque applied to the propeller results in angular momentum in propeller slipstream. This angular momentum is not only a form of energy loss that does not contribute to the propulsive performance, but also disturb the wing lift and drag distributions leading to deviated wing performance compared to a clean wing case. A series of design solutions have been introduced for dealing with this term, and current thesis mainly focus on the concept of Swirl Recovery Vane (SRV). SRVs are a set of stationary vanes mounted at downstream of the propeller, aiming at recovering the swirl in the propeller slipstream, which may produce extra thrust without extra power consuming. Previous research mainly focus on design of SRVs for an isolated propeller case. Considering a wing-mounted tractor propeller configuration, with benefit already gained in terms of wing induced drag reduction by wing swirl recovery, the swirl residual in propeller slipstream gives opportunities of introducing SRVs for extra thrust production, such that the system performance can be further improved. Due to the lack of such research, current project is about design of Swirl Recovery Vanes for a maximized system propulsive performance for Wing-Mounted Tractor Propeller Propulsion System at cruise condition. A wing design case is also performed for the same propeller slipstream without installed SRV, by comparison of performance gain of these two cases, the conclusion can be drawn that whether it’s beneficial to introduce SRVs in a typical wing-mounted tractor propeller configuration. A Surrogate-BasedMulti-Fidelity optimization framework is developed for the design purpose. The strategy is to replace the direct optimization of expensive high-fidelity analysis by an iterative re-optimization of a corrected low-fidelitymodel. The low-fidelity method includes a slipstream model in which the velocities are obtained from RANS simulation of an isolated propeller, a lifting line based SRV designmodule and a surface singularity method based wing analysis and design module. The high-fidelity method is the Euler equationbased simulation. Furthermore, an alignment procedure between low- and high-fidelity results is established based on the shape-preserving response prediction(SPRP) algorithm, which assumes the variation of highfidelity results can be predicted by the low-fidelity results. Two main optimization tasks are performed to reach the final objective. The wing twist optimization for minimum induced drag under propeller slipstream indicates that the CDi can reduced up to 5.93%. A series of one-blade SRV design cases are performed at different streamwise and azimuthal positions relative to wing. Results indicate that an upstream installed vane causes an un-expected induced drag increase of a downstream wing through its wake and tip vorticies development. This can be avoided when the vane is moved to downstream of wing. The optimum system performance is obtained when the vane is located at down-going blade side(DBS). By extra thrust produced by vane, a system induced drag reduction of 6.08% drag counts is achieved, which is almost equal to that obtained by wing twist design. Further conclusion is drawn that SRV should be installed as close to wing trailing edge as possible to obtain an maximized system performance in terms of system induced drag reduction.