Nozzle Atomization In Supersonic Flow Experiments And Theoretical Studies,

In general, technology and scientific challenges towards the sucessful development of liquid hydrocarbon-fueled scramjets include (1) a deeper fuel penetration into the air stream tor better mixing; (2) generation of smaller liquid fuel droplets for faster evaporation; (3) a appropriate flame stabilization mechanism for piloting and sustaining combustion; and (4) a substantial reduction in drag losses associated with processes of mixing and flameholding. Therefore the properties and mechanism of the liquid hydrocarbon atomization in supersonic How and cavity-based fuel injector/flameholder configurations are of particular interest.First, in this paper the experimental system was built and five direct-injectors were designed. These direct-injectors varied with exit-length or exit-diameter or exit-angle etc. The atomization modes of the direct-injectors include pressure atomization and effervescent atomization.Second, the experiment investigating of flowrate characteristics and atomization characteristics of the injector was processed. Flowrate characteristics experiment primarily toe use on investigation of the influences to the flowrate and the flowrate coefficient. Alomization characteristics experiment primarily focuse on investigation of the influences to ihe liquid penetration height and the rules of the spray.The main achievements are shown as follows:(1) First, the flowrate of direct-injector increases with the increasing injection pressure,and the Flowrate coefficient increase with the descreasing L/D ratio but is little influenced by injection pressure. Second, the flowrate coefficient of direct-injector is much influenced by exit-angle, and decrease with the decreasing exit-angle. Third, under the constant gas pressure the liquid flowrate in effervescent atomization increase with the decreasing ALR (the gas to liquid mass ratio) and the gas flowrate in effervescent atomization increase with the increasing ALR; At last the Flowrate coefficient of effervescent is very small, usually it is below 0.3.(2)The atomization characteristics experiment shows: First, spray penetration increase with increasing the injection pressure, discharge mass and the spray angle. Second, the relationship between the penetration height to the direct-injector'exit-diameter ratio and the liquid jet to supersonic stream momentum ratio is linearity.Third, it was found that gas barbotage might not have a strong effect on the penetration height. At last the atomization level of the effervescent atomization-injector is truely higher thanthe direct-injector under the same condition.(3) First, the critical discharge coefficient formula of the effervescent atomization and the penetration correlation for the pressure atomization were constructed. Second, the influences of cavity flame-holders in the supersonic combustion were analysed. At last the machanism of secondary breakup of the liquid droplets in the supersonic flow was researched into.