中介机匣是航空发动机中连接低压压气机与高压压气机的过渡通道，决定了高压压气机进口流场的品质，是影响高压压气机性能的关键因素。以民用大涵道比涡扇发动机中介机匣为对象，采用数值模拟的方法对其中的基本流场特征及流动机理进行细致分析；同时，考虑发动机运行的实际工况，针对不同来流马赫数和进气节流比的情况，对中介机匣流动损失开展了对比研究。结果表明:大径向落差中介机匣主要的损失来自于端壁型线曲率及由此带来的压力梯度。支板的下壁面高损失区的影响范围明显高于上壁面损失区，下壁面型线曲率是影响中介机匣性能的关键因素。相同的来流马赫数情况下，中介机匣总压损失系数均随着进气节流比的降低呈递增趋势。相同进气节流比情况下，当来流Ma数低于0.3时，中介机匣损失水平相对较低；然而，随着出口马赫数的增大，中介机匣总压损失随来流马赫数的增加呈现先降低后增加的趋势。

The intermediate duct is the transition channel connecting the low-pressure compressor and the high-pressure compressor in the aero-engine, which determines the quality of the inlet flow field of the high-pressure compressor and is a key factor affecting the performance of the high-pressure compressor. Taking the intermediate duct of a civil high bypass ratio turbofan engine as an object, the basic flow field characteristics and flow mechanism of the intermediate duct are analyzed in detail by means of numerical simulation. Furthermore, considering the actual operational conditions of the engine, a comparative study was carried out on the influence of the incoming Mach number and the intake throttle ratio on the flow loss of the intermediate duct. The results show that the main loss of the intermediate duct with large radial drop comes from the curvature of the endwall contour and the resulting pressure gradient. The impact region of high losses on the lower surface of the struts is markedly larger than that on the upper surface, with the curvature of the lower surface contour being a key factor affecting the performance of the intermediate duct. Under the same incoming Mach number conditions, the total pressure loss coefficient of the intermediate duct exhibits an increasing trend with decreasing inlet throttle ratios. For identical intake throttle ratios, when the incoming Mach number is below 0.3, the level of losses in the intermediate duct remains relatively low. However, as the incoming Mach number increases, the total pressure loss in the intermediate duct follows a pattern of initial decrease followed by an increase with rising incoming Mach numbers.