6. It was shown that, during starting, an isentropic diffuser would experience a detached shock and consequent losses. In order to swallow the shock, a fixed- geometry diffuser must be overspeeded.

However, as shown in Fig. 6.9, as the design Mach number increases, the required overspeeding increases very rapidly, so that even if the aircraft could be infinitely overspeeded, the design Mach number would be limited to a finite value. Assuming one-dimensional flow and constant y (1.4), determine the absolute maximum design Mach number for which an otherwise isentropic diffuser of fixed geometry may be expected to start, any amount of overspeed being possible.