基于离散等收缩比的前体/进气道流向双乘波一体化设计

前体/进气道一体化设计是高超声速飞行的关键技术,一体化设计的核心是前体与进气道在基准流场上的气动融合.针对腹部进气布局中前体压缩后的非均匀流影响进气道性能的问题,文章基于局部收缩比处处一致的思想,提出了离散等收缩比设计方法,实现了乘波前体/内转式进气道流向气动融合与遵循气动规律的变截面流道设计.将进气道的三维流场分解成一簇具有相同收缩比的三维流管,视每根流管侧壁为轴对称流场;以锥导乘波前体压缩后的非均匀流作为来流条件,以总压恢复为目标对每根流管进行优化设计;通过匹配激波反射位置将流管重新组合起来,流管的对应边界组成内转式变截面进气道.该设计方法适配任何已知的非均匀来流,可灵活控制唇口位置,且适用于任意形状之间的变截面转换.数值研究表明,依托该方法设计的一体化构型性能符合预期,出口流场均匀,具有优越的抗反压能力,且非设计点流场波系结构良好.离散等收缩比设计方法为腹部进气布局中前体/进气道一体化气动融合设计提供了新思路

Self-similar unstart characteristics of supersonic contraction duct with an expansion corner

Inlet unstart is detrimental to hypersonic airbreathing flights. By unstart, we mean the separation-induced collapse of a supersonic duct flow. The unstart characteristics of a two-dimensional contraction duct with an expansion corner are numerically investigated to develop a universal prediction method and to determine the unstart mechanism. The unstart boundaries under varying contraction angles, entrance heights, and Reynolds numbers are obtained by translating the cowl plate. A self-similar empirical equation of unstart boundary that unifies multiple variables is proposed through similarity analysis. To estimate the unstart boundaries of large-angle ducts, the alternative area ratio is presented. Three types of unstarts are identified according to the distribution of the unstart boundaries and the evolution mechanism of separation region: the long-cowl, transitional, and short-cowl unstart. The long-cowl unstart stems from the mass flow limit at the throat, while the other two unstarts stem from the separation region growth. The wall pressure criteria for unstart are correlated with the dimensionless cowl length and the characteristic separation scale in the critical state to facilitate unstart detection. Moreover, the self-similar compression intensity is proposed to characterize the maximum pressure increase induced by the unit effective area contraction in the started state