超声速气流中电火花塞直接点燃煤油过程试验研究

ExperimentalStudyonSparkIgnitionProcessofKerosenein

关键词:  超燃冲压发动机  凹腔  火花塞点火  煤油  喷注方案中图分类号:V231.1文献标识码:A文章编号:1001-4055(2015)12-1839-07DOI:10.13675/j.cnki.tjjs.2015.12.012

Key words:  Scramjet  Cavity  Sparkignition  Kerosene  Injectionscheme

摘要:

在来流总温1486K，总压1.6MPa，马赫数2.52的条件下，采用两级串联凹腔构型燃烧室，开展了电火花塞直接点燃航空煤油的试验研究。利用高速摄影相机进行观测，对比了不同煤油喷注方案和点火位置对火核生成和火焰传播的影响。通过上游凹腔前壁面水平喷注煤油、下游凹腔点火的方案可靠性高，在煤油与空气混合气的当量比为0.04～0.063均可实现煤油成功点火和稳定燃烧；串联凹腔构型可以提高点火性能的主要原因有两方面:一是下游凹腔有稳定火焰作用，火焰在边界层内逆流传播实现对上游凹腔的能量反馈；二是煤油蒸发、混合距离长，通过近壁区进入下游凹腔，形成了更为适宜的点火环境。

Abstract:

Experimentalinvestigationsonsparkignitionofliquidkeroseneinascramjetcombustorwithtwo-stagedcavitieswereconductedattheinflowconditionsofMa=2.52，T0=1486K，p0=1.6MPa.Highspeedphotographywasusedtorecordertheflamepropagationprocesses，tocomparetheeffectsofkeroseneinjectionschemesandignitionpositionsontheformationofflamecoreandflamepropagation.Whenkerosenewasinjectedfromtheleadingedgeoftheupstreamcavity(overallequivalentratio=0.04～0.063)andignitedbythesparkinthedownstreamcavity，itwillleadtoareliableignitionwithlargemarginofflamestability.Thecombustorconfigurationwithtwo-stagecavitiescanimprovetheignitionability.Firstly，thedownstreamcavitystabilizestheflame，andthentheflamepropagatesupstreamthroughboundarylayerandprovidesenergyfortheignitioninupstreamcavity.Secondly，thekeroseneinjectedatupstreamcavitypassesalongdistanceinnearwallareaforevaporationandmixingwiththefreshairbeforeitisentrainedintothedownstreamcavity，andproduceabetterignitionenvironmentindownstreamcavity.