Journal of Central South University | 2021
Combustion characteristics of supersonic strut-cavity combustor under plasma jet-assisted combustion
Abstract
Plasma jet has been widely used in supersonic combustor as an effective ignition and combustion assisted method, but currently it is mostly combined with the traditional wall fuel injection method, while the application combined with the central fuel injection method is less. In order to expand the combustion range, the plasma jet was introduced into a strut-cavity combustor with an alternating-wedge. The effects of total pressure of strut fuel injection, total pressure of cavity fuel injection, total pressure of plasma jet injection and plasma jet media on the combustion characteristics were analyzed in supersonic flow by numerical calculations in a three-dimensional domain. The combustion field structure, wall pressure distribution, combustion efficiency and distribution of H2O at the exit of the combustor with different injection conditions were analyzed. The results show that the combustion efficiency decreases with the increase of the strut fuel injection total pressure. However, the combustion area downstream increases when the total pressure of the strut fuel injection increases within the proper range. The combustion range is expanded and the combustion efficiency is improved when the cavity fuel injection total pressure is increased within the range of 0.5–2.0 MPa, but a sharp drop in combustion efficiency can be found due to limited fuel mixing when the total injection pressure of the cavity fuel is excessively increased. With the increased total injection pressure of the plasma jet, the height of the cavity shear layer is raised and the equivalence ratio of the gas mixture in the cavity is improved. When the total pressure of the plasma jet is 1.25 MPa, the combustion efficiency reaches a maximum of 82.1%. The combustion-assisted effect of different plasma jet media is significantly different. When the medium of the plasma jet is O2, the combustion-assisted effect on the combustor is most significant. 等离子体射流作为一种有效的点火助燃方式在超声速燃烧室中得到了广泛的应用, 但是目前大 都是与传统的壁面燃料喷注方式相结合, 而与中心燃料喷注方式的结合较少。为了扩大燃烧范围, 本 文将等离子体射流引入了带有交替尾缘结构的支板-凹腔燃烧室中。通过三维数值计算, 研究了超声 速气流中支板燃料喷注总压、凹腔燃料喷注总压、等离子体射流喷注总压和等离子体射流介质对燃烧 特性的影响, 分析了不同喷注条件下的燃烧场结构、壁压分布、燃烧效率和燃烧室出口水组分的分布 情况。研究结果表明:燃烧效率随着支板燃料喷注总压的增加而降低, 但当在合适的范围内增加支板 燃料喷注总压时, 燃烧室下游的燃烧区域也有所增加。当凹腔燃料喷注总压在0.5~2.0 MPa 的范围内 增加时, 燃烧室的燃烧区域和燃烧效率都有明显提升;但过度地增加凹腔燃料喷注总压, 由于燃料的 混合受限, 燃烧效率急剧下降。随着等离子体射流喷注总压的增加, 凹腔剪切层的高度抬升, 凹腔内 的混气当量比也得到改善, 有效地促进了燃烧。当等离子射流的喷注总压为1.25 MPa 时, 燃烧效率 达到最高的82.1%。不同等离子射流介质的助燃效果有着显著的差异。当等离子射流的介质为O2 时, 对燃烧室的助燃作用最为明显。