Abstract: In order to satisfy the working requirement of Xiamen Turbine Ejector Ramjet （XTER） combined cycle engine， a three-dimensional inward-turning quadir-ducts combined inlet with three modes （i.e.， turbojet， ejector and ramjet modes） and working speed range at Ma_∞=0.0~6.0 was designed in this work. The flow and performance of the combined inlet in mode transition process from the ejector mode to the ramjet mode are analyzed numerically， considering both fixed Mach number mode transition （Ma_∞=4.0） and interval Mach number mode transition （Ma_∞=3.0~4.0）. The results show that the inlet works properly and the captured mass flow rate of the inlet transits smoothly from the ejector duct to the ramjet duct for both types of mode transition. At fixed Mach number mode transition， the total mass flow rate coefficient of the inlet decreases from 0.92 to 0.91 due to the adjustment of the splitters， and the Mach number at throat reduces from 2.47 to 1.99. The total pressure recovery coefficient at the exit of the ejector duct decreases from 0.28 to 0.13 with closing of the splitters， while the total pressure recovery coefficient at the exit of the ramjet duct rises from 0.27 to 0.48. At interval Mach number mode transition， the total mass flow rate coefficient of the inlet rises from 0.89 to 0.91， and the Mach number at throat increases from 1.63 to 1.99. The total pressure recovery coefficient of the ejector duct decreases from 0.60 to 0.13， while the total pressure recovery coefficient of the ramjet duct decreases from 0.55 to 0.48. In general， the anti-back pressure capability of the ramjet duct is gradually enhanced during both types of mode transition processes， but considering both the flow feature and the performance of each duct， selecting the interval Mach number mode transition can efficiently improve the aerodynamic performance of the combined inlet.

Key words: Turbine based combined cycle;Inward-turning inlet;Mode transition;Numerical simulation;Performance analysis

摘要： 为满足XTER组合循环发动机的工作需求，设计了一种具备涡轮、引射火箭、冲压三种模态，工作速域Ma_∞=0.0~6.0的三维内转四通道组合进气道。重点对比分析了引射火箭至冲压的模态转换过程在固定马赫数转级（Ma_∞=4.0）和区间马赫数转级（Ma_∞=3.0~4.0）模式下的流动与性能特性。结果表明：该进气道在两种转级模式中均正常工作，进气道的捕获流量均能实现由引射火箭通道向冲压通道平稳过渡。固定马赫数转级时，由于分流板的调节，进气道总流量系数由0.92降至0.91，喉道马赫数从2.47降至1.99。引射火箭通道出口总压恢复系数随分流板的逐渐关闭从0.28下降至0.13，冲压通道出口总压恢复系数从0.27升至0.48。区间马赫数转级时，进气道总流量系数从0.89上升至0.91，喉道马赫数从1.63增至1.99。引射火箭通道的出口总压恢复系数随分流板的逐渐关闭从0.60下降至0.13，冲压通道出口的总压恢复系数从0.55下降至0.48。两种转级模式下，冲压通道的抗反压能力均逐渐增强，但结合通道内流动特性与各项性能参数，选择区间马赫数下转级可提高该组合进气道的综合气动性能。

关键词: 涡轮基组合动力;内转进气道;模态转换;数值模拟;性能分析