Understanding the Performance of Thrust-Augmenting Ejectors

Abstract

Computational solutions of the Reynolds-averaged Navier–Stokes equations have been used to understand the performance of thrust-augmenting ejectors for vertical and short takeoff and landing aircraft. These solutions show how ejector performance depends on the principle ejector design parameters, including the ejector inlet area, the diffuser exit area, and the length of the ejector duct, as well as the type and configuration of the primary jet nozzles. It is concluded that there is a relatively sharp peak in ejector performance that occurs over a relatively narrow range of inlet area ratios where the character of the flow changes from duct flow to free jet flow. Both the peak performance and the optimum inlet area ratio are seen to increase with the length of the ejector duct. Both increasing the jet entrainment rate and the addition of wall jets are shown to enhance the performance of short aircraft ejectors.