雾化角对液体火箭发动机燃烧室压力振荡的影响

Effects of Spray Angle on the Pressure Oscillations in the Combustion Chamber of LOX/RP-1 Liquid Rocket Engine

针对液氧/煤油火箭发动机模型燃烧室实现了三维非稳态两相燃烧过程的数值模拟,得到的燃烧室截面平均压力和平均速度与实验吻合。在初边值条件不施加任何扰动的情况下,得到了燃烧室压力自激振荡过程,并研究了液氧和煤油喷嘴雾化角对燃烧室压力振荡的影响。计算结果表明:当雾化角为40°或120°时,由于燃料与氧化剂喷雾锥重叠区域较小或较大,导致了推进剂混合很差或很好,不易在燃烧室头部出现局部爆炸性的可燃混气团,致使燃烧室压力振荡强度较弱;而当雾化角为中间值65°时,易于出现爆炸性的可燃气团并导致剧烈的压力振荡,使燃烧室中出现燃烧不稳定性。因此,雾化角的合理设计是抑制燃烧不稳定性的一种途径。

To investigate the effects of spray angle on the pressure oscillations,the three-dimensional transient two-phase reacting flow in the thrust chamber of LOX/RP-1 liquid rocket engine was numerically studied in this paper.The averaged velocity and pressure are consistent with experimental data and self-triggered pressure oscillations are obtained without any artificial excitations.It is shown that the intensity of pressure oscillations in the case with 40 or 120 degree spray angles are weaker than that in the case with 65 degree spray angles and severe combustion instability occurs in the latter case.Further analysis indicates that when the spray angle is smaller or larger,it is not easy to form the explosive combustible mixtures in the head regions of combustion chambers due to poor or well mixing.However,the explosive combustible mixtures are prone to form in the region where LOX and RP-1 spray angles falling in between 40 and 120 degree overlap,which will result in severe pressure oscillations and ultimately trigger combustion instability.Hence,spray angle is a key factor to control combustion instability.