Installation Effects on Highly Loaded Turboprop S-Duct Intake Proximity

Abstract

S-duct intake of a highly loaded turboprop installed on a channel wing was investigated for the interaction effects using computational fluid dynamics. Performance effects on the aerodynamic interface plane (AIP) were compared for varying the intake proximity to propeller mid-plane and nacelle hub. A wrap-around intake with a length aspect ratio of L/D = 3 was used for the analysis. Propeller slipstream was approximated with an actuator disc model. Steady-state RANS simulations was run for cruise condition. The performance was analysed in terms of total pressure recovery and distortion coefficients on AIP. Circumferential and radial distortion intensity descriptors were used along with standard coefficients for the distortion levels. Gain in total pressure recovery was achieved when the intake distance to nacelle hub was increased, whereas it was decreased with farther distance to actuator disc. The larger gap between the nacelle hub and the S-duct intake increased both the distortion coefficient and circumferential intensity on the AIP, as opposed to the decrease in radial distortion intensity. A different trend was observed for the intakes closest to the actuator disc, which showed higher recovery, experienced lower distortion except in radial direction. Analysis of the swirl distortion coefficient on the intake AIP revealed multiple peaks along the circumference. The comparison of maximum positive peaks confirmed a decrease with increasing distance to nacelle hub as the radial distortion intensity. The negative swirl peak comparison revealed an increase with increasing distance to nacelle hub, similar to distortion coefficient. The results will serve as guidelines for the S-duct intake design process and its integration into highly loaded turboprop nacelle of the high-lift aircraft.