Investigation of Spanwise tip Blowing in Rotating Wings

Abstract

The loss of efficiency of a wing due to the wingtip vortex is a very well-known phenomenon. In the case of aircraft, it manifests itself as the induced drag, whereas in the case of rotary-wing, the vortices that form a corkscrew wash. Along with effects on performance parameters, this so-called phenomenon of blade vortex interaction (BVI) can occur due to the interaction of the trailing vortex of the blade with the other preceding blade. This can cause large variation in the velocity field, which results in an unsteady structural load and noise. Helicopters operating near the ground can cause entrainment of dust particles on the ground, which effects the pilot’s field of view. To mitigate this, several means have been introduced in past years, one of which is the use of passive spanwise blowing as presented here. A centrifugal driven (or pumping) spanwise blowing blade is the focus of our study. Previous studies were performed to study the effect of tip jets. The effect of wingtip injection has been shown to reduce or diffuse the tip vortices. However, the performance parameter data on different pitch angles and different rpm is previously not been analyzed. The current study is conducted to investigate the effects of tip jet in non-twisted propellers or rotary wings, on performance parameters at different pitch angles and RPM. An experiment is devised to measure the thrust and torque of the rotor at specific RPMs. The experimental campaign consisted of two different types of geometries, tested over a wide range of RPM and pitch angles. the thrust and torque measurements were analyzed and compared to the baseline studies as well as previous literature. Coefficients of thrust and power were measured and compared with baseline cases. The analysis indicates a marked improvement in performance at certain RPM and pitch angles due to the tip-jet effect. Another objective is to devise a Numerical scheme based on a literature review to analyze other properties such as sectional pressure on the blade surface. This numerical approach is first validated. Then that approach is used to analyze further the cases from experiment. The results vi obtained from the Numerical simulation compare well with the result we got from the experiments.