Morphology analysis on multi-jet flash-boiling sprays under wide ambient pressures

Research output: Contribution to journalArticle

Authors

  • Yanfei Li
  • Hengjie Guo
  • Xiao Ma
  • Yuliang Qi
  • Zhi Wang
  • Shijin Shuai

Colleges, School and Institutes

External organisations

  • Tsinghua University

Abstract

The main objective of this study is to investigate the effect of ambient pressure (Pamb) on the morphology of multi-jet flash boiling sprays and to promote the understanding on the collapse mechanism. With the high-speed imaging technique, the n-hexane spray process in a constant volume vessel was captured under the ambient pressures from 2 kPa to 101.3 kPa and the fuel temperatures (Tfuel) from 20 °C to 120 °C. The spray width within the axial distances of 20 nozzle diameters (do) could be increased by increasing Tfuel and/or decreasing Pamb. Beyond 20do, the change in spray width against superheated degree (ΔTSD) was fairly sensitive to Pamb. It decreased with the increase in ΔTSD at Pamb larger than 50 kPa, and increased with ΔTSD at Pamb less than 50 kPa. Based on the new understanding that the collapse in multi-jet flash-boiling sprays was induced by vapor condensation at the nozzle exit and the resultant local pressure drop (i.e. generation of low-pressure zone), the sensitivity of spray width on Pamb could be well explained as follows: relatively larger Pamb (>50 kPa for the used injector) would be conducive to the vapor coagulation and cause stronger vapor condensation (i.e. larger pressure drop) while the vapor dispersion may become dominant at lower Pamb (<50 kPa for the used injector), negatively influencing the intensity of vapor condensation.

Details

Original languageEnglish
Pages (from-to)38-47
Number of pages10
JournalFuel
Volume211
Early online date19 Sep 2017
Publication statusPublished - 1 Jan 2018

Keywords

  • Condensation, Flash boiling, Gasoline direct injection, Penetration length, Spray collapse, Superheated degree