当量比对氢燃料超燃燃烧室流场结构和燃烧模态影响研究

Investigation for Effects of Equivalence Ratio onFlow Structure and Combustion Mode in aHydrogen Fueled Scramjet Combustor

关键词:  超燃冲压发动机  氢气  燃烧模态  差分干涉  平面激光诱导荧光系统

Key words:  Scramjet  Hydrogen  Combustion mode  Interferometry  Planer laser-induced fluorescence

摘要:

为了考察氢气当量比对超燃燃烧室流场结构和燃烧模态的影响，采用试验方法和多种测量手段对其进行了研究。试验在中国空气动力研究与发展中心1kg/s脉冲直连式风洞设备上开展，采用纹影、差分干涉、自发光照相和PLIF (Planar Laser-Induced Fluorescence) 等光学测量手段观察了流场内激波串结构和火焰传播与稳定的形态，并进一步结合壁面压力数据分析了发动机的燃烧模态。研究表明:在来流为马赫数2.0，总温950 K，总压0.8 MPa的条件下，随着氢气当量比的增加，激波串头部的位置不断向隔离段上游推进，同时燃烧流场结构由稳定逐渐转变为振荡，发动机的燃烧模态经历了超燃、过渡和亚燃。当氢气当量比≤0.233时，发动机燃烧模态为超燃，燃烧流场结构稳定，火焰连续分布于凹槽下部剪切层内；当氢气当量比在0.233～0.279时，燃烧反压开始扰入隔离段内，发动机燃烧转变为过渡模态；当氢气当量比大于0.279时，发动机燃烧模态为亚燃，燃烧流场结构振荡且火焰分布为不连续的破碎状，燃烧反压逐渐前扰至隔离段中部位置。因此，氢气当量比对超燃冲压发动机燃烧流场结构和燃烧模态有较大影响。

Abstract:

In order to investigate the effects of hydrogen equivalence ratio on flow structure and combustion mode in the scramjet combustor， the experiments were conducted in CARDC’s 1kg/s direct-connected supersonic combustion wind tunnel. Schlieren， interferometry， flame emission and PLIF (Planar Laser-Induced Fluorescence) were used for better understanding the reacting flow field structure， flame development and stable status， the wall pressure measurement data was also used to analyze the combustion mode. The results were obtained under the inflow condition of Mach number 2.0， total temperature 950K and total pressure 0.8MPa. When the hydrogen equivalence ratio increased， the head of shock train moved upstream to the isolator entrance， the combustion flow structure status changed from stable to oscillation gradually， the combustion mode changed from supersonic combustion， dual-mode combustion to subsonic combustion. When the hydrogen equivalence ratio was not larger than 0.233， the combustion mode was supersonic combustion， the combustion flow structure was stable and the flame located in the cavity below shear layer. When the hydrogen equivalence ratio was between 0.233 and 0.279， the combustion induced back pressure began to disturb into the isolator and the combustion mode was dual-mode combustion. When the hydrogen equivalence ratio was larger than 0.279， the combustion mode was subsonic combustion， the combustion flow structure was unstable and the flame distribution was discontinuously broken status， the back pressure had disturbed near the center of the isolator. So， the hydrogen equivalence ratio had a great effect on flow structure and combustion mode.