Characterizing shock waves induced by phase change of superheated liquid jets
2022-01-0594
03/29/2022
- Event
- Content
- The under-expanded nature of flash-boiling spray was considered an important cause of spray collapse via some numerical investigation. However, due to the high optical thickness, the under-expanded nature in flash-boiling jet was difficult to observed by optical diagnosis. The main objective of this study is to prove the existence of under-expanded nature in the gasoline-like fuel (n-hexane) flash-boiling jet under the GDI engine condition, and further reveal the significant influence factors. The experimental examination was carried in a constant volume vessel with ambient pressure ranging from 0.1 bar to 1.0 bar and fuel temperatures from 30℃ to 170℃. In order to capture the flow details in the jet, a high-brightness light source was used in the optical imaging. The shock structure of under-expanded nature was observed in close nozzle region under those conditions above 130℃, and the shock structure was in good agreement with the previous simulation results under the same conditions. The size of the wave structure was increase with the ambient pressure decrease or fuel temperature increase. In other words, the wave structure was increase with the superheated degree. A close-up examination of the shock structure over different ambient pressure with similar superheated degree (different fuel temperatures) found that the higher ambient pressure would compress the size of the shock structure. In addition, the higher injection pressure was found to increase the size of the shock structure. Except for superheated degree, there might be a pressure ratio (injection-to-ambient) to affect the under-expanded features in flash-boiling jets, which was the main control parameter for the under-expanded gas jet. And this similarity between flash-boiling jet and gas jet still needs further theoretical examination.
- Citation
- Li, Y., Zhang, J., Ma, X., and Shuai, S., "Characterizing shock waves induced by phase change of superheated liquid jets ," SAE Technical Paper 2022-01-0594, 2022, .