Investigation Of Streamwise Vortex Enhanced H₂/Air Mixing In A Gaseous Hydrogen Fueled Ramjet

Air-Turbo-Ram Engine is regarded as one of the most prospective engines for a hypersonic vechicle .The technical barrier of hydrogen fueled ram-combustor research is how to improve the fuel distribution and enhance the fuel/air mixing. Although some research has recently been performed in the area of enhanced H₂/Air mixing, poor combustion of gaseous hydrogen is still not resolved. This paper discuses the physical mechanism of streamwise vortex enhanced H₂/Air mixing and deals with a practical study for the hydrogen fueled dump combustor and bluffbody flameholder combustor.In the research of dump combustor,the concept of gaseous hydrogen injected traversely into the subsonic air flow is put forward. Streamwise Vortex produced by traverse jets improved H₂/AIr mixing. The cold and combustion experiments and numerical modelling have been carried out.The effect of the geometric and jet flow variables on the jet penetration depth and trajectory is investigated. Rresults show that the penetration depth depends mainly upon the product of squre root of the momentum ratio and the ratio of orifices spacing and duct height. A new well-definition is suggested --Vortex Jet Trajectory defined by the locus of streamwise vortex core. Then the reason that the jet concenration trajectory is below the jet velocity trajectory is explained. The mixing of traverse jet and coming flow depends upon the scope and strength of streamwise vortex. A criterion of optimization mixing is put forward. According with this criterion the streamwise vortex core should be located in the center of duct cross section in order to achieve the best mixing to achieve . Gaseous hydrogen fueled combustor model with quartz glass windows was designed.Vanous traverse H₂ injection model experiments were carried out. Experimental results indicate that only the model according with the demands of the optimization critertion can be reached high combustion efficiency.Large total presure loss has been found in the experiment of dump combustor with straight pipes injection.In this paper numerical study is conducted on the influence of temperature ratio on the penetration depth of two dimensional confined Jet flow and it is found that the jet to main flow temperature ratio is a important parameter independent of momentum rato. The physical mechanisim can be explained by using the concept of thermal drag.Gaseous hydrogen concentrated in the recirculation zone behind the V-gutter lead to a bad combustion. A new concept flameholder - SVGs was designed to produce streamwise vortex for the enhancement of mixing. Research clarified the complex flow fields produced by SVGs. The flow structure behind SVGs can be divided into two parts, one is spanwise recirculation flow, the other is streamwise vortex formed by the stream flowing across sweep slope. Experimental results show that the mixing of SVGs with square injector hole is the best, SVGs with circular hole is the better, V-gutter is the worst.