Numerical simulation on the flow passage of the ram-rotor test system was carried out under different back pressure and rotational speeds by using FLUENT software. Results show that characteristic curves of the ram-rotor are steep. Steady operation range of the ram-rotor is narrow

and relative mass flow rate range of the ram-rotor is from 26.57% to 1.96%. At high back pressure or low rotational speed

the flow in the vane passage is not sensitive to the low pressure zone located at the leading edge of the ram-rotor. Back pressure and rotational speed have little impact on flow loss of the vane segment. With back pressure rising

flow in the ram-rotor segment experiences such four compression processes as oblique shock

λ-shape shock/shock train

λ-shape shock/normal shock and λ-shape shock. With the increasing of rotational speed

the shock wave incident location on the shroud approaches downstream passage gradually

which causes high total pressure ratio and large loss. The support segment experiences minimum loss condition when back pressure rises. As rotational speed increases

total pressure recovery coefficient in the support segment changes from 0.944 to 0.875

which means high flow loss.