Effect of Throttling on Dual-Bell Sneak-Transition Side Loads

Abstract

An experimental investigation has been conducted on a subscale dual-bell nozzle to study the effect of throttle settings on sneak-transition side loads. The results are from a cold-gas test campaign conducted in a high-altitude simulation chamber for three throttle settings of 1, 2, and . An analysis is carried out by correlating the simultaneously acquired side-load measurements and real-time wall pressure data from transducers mounted in the vicinity of the wall inflection. The study reveals that the longer is the time duration of separation front in the region of wall inflection, the higher is the amplitude of overall sneak-transition side loads. Increasing the throttle settings from 1 to significantly reduces not only the overall sneak-transition duration but also the amplitude of flow unsteadiness in the region of wall inflection during the intermittent flow condition of the sneak transition and, hence, the associated side loads. It is further observed that even though the total transition time decreases with an increase in throttle settings, the actual transition side-load peak amplitude remains more or less similar irrespective of throttle setting.