复杂来流条件下设计参数对S弯喷管红外辐射特征影响

Influence of design parameters on infrared radiation characteristics of serpentine nozzles under complex flow conditions

为了获取在航空发动机混合室产生的复杂来流条件影响下,S弯喷管设计参数对其红外辐射特征的影响规律和产生机制,采用数值模拟方法计算了完全遮挡设计准则约束下不同宽高比和长径比S弯喷管的红外辐射特性,并分析了设计参数不同时复杂非均匀流动与红外辐射特性的耦合机理。研究结果表明,混合室中波瓣混合器诱导产生的流向涡会卷吸高温燃气冲击喷管壁面,使得S弯喷管上下壁面出现了大面积热斑,垂直探测面上的总红外特征水平相比水平探测面增大了1.22倍。随着出口宽高比增大,热斑面积由于流向涡贴壁现象的加剧而增大,而喷流长度由于大气掺混作用加强而减小,使得垂直探测面上的总红外特征水平几乎没有变化,水平探测面由于受热斑影响较小,总红外特征水平下降30.5%。当长径比较小时,由于壁面偏转曲率较大,S弯喷管内部出现了流动分离现象,壁面热斑强度大幅提升,使得水平和垂直探测面上的红外特征水平与未发生流动分离相比分别增加了23.5%和38.6%。随着长径比进一步增大,壁面热斑因内外涵气流充分掺混而扩大,总红外特征水平在水平和垂直探测面上分别增大了15.0%和29.4%。

To investigate the influence and generation mechanism of design parameters on the infrared radiation char⁃acteristics of serpentine nozzles under complex flow conditions generated in the mixing chamber of aviation engines,this study employs numerical simulation methods to calculate the infrared radiation characteristics of serpentine nozzles with different aspect ratios and length-diameter ratios.All serpentine nozzle models meet the constraint of completely shielding the high-temperature components.Additionally,the study analyzes the coupling mechanism between com⁃plex non-uniform flow and infrared radiation characteristics with different design parameters.The research findings indi⁃cate that the longitudinal vortex generated by the lobed mixer in the mixing chamber entrains high-temperature gas im⁃pacting the nozzle wall,leading to a large area of hot spots appearing on the upper and lower walls of the serpentine nozzle.On the vertical detection plane,the total infrared characteristic level increases by 1.22 times compared to that on the horizontal detection plane.As the aspect ratio increases,the hot spot area enlarges due to the intensified longi⁃tudinal vortex attachment,while the jet length decreases because of the enhanced atmospheric mixing.Conse⁃quently,the total infrared characteristic level on the vertical detection plane remains nearly unchanged,whereas that on the horizontal detection plane decreases by 30.5%due to the minor influence of hot spots.When the lengthdiameter ratio is small,flow separation occurs inside the serpentine nozzle due to the large curvature of the wall.The intensity of the hot spots on the wall surface significantly increases,causing the total infrared characteristic level on the horizontal and vertical detection planes to increase by 23.5%and 38.6%,respectively,compared to the cases with⁃out flow separation.With further increase in the length-diameter ratio,the hot spots on the wall expand due to the full mixing of the core flow and the bypass flow,resulting in 15.0%and 29.4%increase in total infrared characteristic level on the horizontal and vertical detection planes,respectively.