Effects of Trumpet on the Flow Characteristics of Pressure Swirl Injectors

Abstract

The instantaneous spray images of a pressure swirl injector with a trumpet have been captured by a Photron Fastcam SA-Z camera. A characteristic wave structure tracing method based on mutual information has been proposed to measure the wave velocity, and the relation between wave velocity and film velocity has been investigated theoretically. A semi-empirical flow characteristics prediction model has been proposed, and the flow characteristics in the trumpet have been calculated. The results show that the film velocity equals the varicose wave velocity and is slightly larger than the sinuous wave velocity. Therefore, the wave velocity obtained from experiment can be used as film velocity in the range of allowable error. The proposed characteristic wave structure tracing method overcomes the defect of the direct measurement method. The measured axial wave velocity increases linearly with the increase of the liquid mass flow rate. The predicted spray cone angle agrees well with the experiments when the trumpet is considered, and it increases with the increase of liquid mass flow rate. In the trumpet section, the film thickness and tangential velocity significantly decrease, whereas the axial velocity increases. That is why the film thickness at the injector exit and spray cone angle decrease with the increase of the trumpet angle.