Elliptical pressure swirl jet issuing into stagnant air

Abstract

In this study, the effect of aspect ratio of elliptical cross section for a pressure swirl nozzle injecting into stagnant air was investigated experimentally. Three elliptical nozzles with aspect ratios of 1, 1.5, and 2 were manufactured. Shadowgraphy technique was utilized to visualize flow characteristics of the pressure swirl injectors. An in-house image processing code was used to obtain cone angle, breakup length, lateral spread, drop size distribution, and Sauter mean diameter (SMD). It was found that discharge coefficient increased by increasing the elliptical cross section's aspect ratio. By increasing the aspect ratio from 1, the issuing jet's cone angle became different from different viewing angles and was out of symmetry. The cone angle from front view was always larger than from side view. The asymmetry on the elliptical surface caused the thickness of the liquid film at the edges to be higher than in the middle. This asymmetry was amplified as the aspect ratio was increased resulting in the edges having a longer breakup length than in the middle. It was found that the lateral spread decreased and the interaction of the air core with the liquid was reduced with increasing aspect ratio, resulting in an increase in breakup length and drop sizes. Benjamin's model for discharge coefficient was modified, and the influence of aspect ratio was added to the model. Models were developed based on Rizk and Lefebvre and Sivakumar's relations for spray cone angle and breakup length, respectively. Also, a correlation based on Wang and Lefebvre's model was presented for SMD. These developed models were compared with our measurements and other published data with good agreements.