In order to meet the flow requirements of Mach number range of modal translation (incoming Mach number 2.2-3.2) for the 2D curved surface variable inlet

in view of three adjustment schemes of cowl translation

rotation and translation + rotation

based on theoretical analysis and the flow field of the reference inlet

an accurate prediction method of flow coefficient was proposed

and verified by numerical calculation

and the overall performance was obtained. The results showed that their flow coefficients were exactly equal to the predicted values and did not require repeated trial-calculation

which met the design expectations and could be extended to the axisymmetric inlet. In relation to the reference inlet

the flow coefficient and compression efficiency increased simultaneously as the cowl moved forward. The total pressure recovery coefficient of the exit was equal and the pressure ratio was increased by 14.6% at incoming Mach number 2.5. Under the condition of reducing the same flow coefficient

the backward movement of the cowl made the pressure ratio and compression efficiency lower

the total pressure recovery coefficient of the exit was basically equal and the pressure ratio was reduced by 12.9% at incoming Mach number 2.5

while the rotation of the cowl further reduced the pressure ratio by 9.1%

and the performance of cowl back movement scheme was better.