平直型蒸发管不同出口结构性能数值研究

Numerical study on the performance of straight evaporation tube with different outlet forms

为提升平直型蒸发管的雾化能力,优化小型蒸发管燃烧室的工作性能,基于某型发动机燃烧室,利用数值模拟方法研究了不同蒸发管出口结构下的流量分配、流场、温度场及出口结构对燃烧室性能的影响。分析结果表明,平直型蒸发管流量主要取决于出口面积,采用扩张型出口,可以增加蒸发管流量,但是会造成更大的总压损失,导致出口流速下降和稳焰能力恶化。在出口面积和蒸发管流量一定的前提下,较小的扩张角能提升蒸发管平直段的流动速度,促进燃油雾化;但过大的扩张角则会导致流动分离,大部分燃油被卷入内圈,火焰筒内油气分布不均匀,主燃区燃烧不充分,高温区滞后。综合考虑油气混合、燃烧过程和壁面热防护的需要,蒸发管出口结构采用5°以下扩张角对燃烧室性能有利。

In order to enhance the atomization ability of straight evaporation tubes and optimize the working performance of small-scale evaporation tube combustion chambers,based on the combustion chamber of a certain type of engine,the flow rate distribution,flow field,temperature field and the influence of different evaporation tube outlet forms on the combustion chamber performance were studied through numerical simulation.The analysis results show that,the flow rate of the straight evaporation tube is mainly determined by the outlet area;the expansion outlet can increase the flow rate of the evaporation tube,but will cause larger total pressure loss,leading to a decrease in outlet flow velocity and flame stabilization ability.A small outlet expansion angle can increase the flow velocity inside the evaporation tube’s straight section,while a large outlet expansion angle will cause flow separation,resulting in most of the fuel being entrained into the inner circle,the fuel-air distribution inside the flame tube becoming uneven,and causing uncomplete combustion inside the main combustion zone.Comprehensively considering the fuel-air mixing process,the combustion process and the heat-protection needs of walls,an expansion angle not larger than 5°is beneficial to the overall performance of the combustion chamber.