Abstract: A combined numerical and experimental investigation was carried out for the self-starting characteristics of a 2D hypersonic inlet,with a special focus on the comparison between different scale models.The numerical results show that the self-starting capability is decreased when the model scale is reduced under the same unit Reynolds number condition,during which the corresponding self-starting Mach number may go up remarkably.It was also found that the inlet flow behaves similarly when the Reynolds numbers are close to each other even though the model scales are different in size,which demonstrates that the Reynolds number is a dominant factor characterizing the flow field.The experimental results obtained within the capability of the in-hand shock tunnel show that the agreement with that of the CFD simulation is reasonable. Furthermore,a kind of unexpected“self-starting”configuration was also observed experimentally under very low Reynolds number condition.It is argued,with the help of numerical simulation, that laminar flow is favourable for the occurrence unusual “self-starting”whereas turbulent flow is the opposite,although the mechanism needs to be clarified in the future.