Aero-spike expansion using diffuser

Douglas

Dear All,

I am carrying out an analysis of a mach3 linear aero-spike nozzle of throat 0.01m.

The problem I am having is when I attach a diffuser, of 0.015m throat (i.e. an ejector system) to the downstream section of the nozzle and run for 10bar gauge. The flow exiting the aero-spike will not expand, as the pressure in the test section will not decrease as expected.

I have tried varying the throat and the length of the diffuser but to no avail. I know that the aero-spike has been design correctly as the flow expands as expected without the diffuser.

The reasons for the ejector system are to gain a velocity of mach3 in the test section using a gauge pressure of 10bar. This is instead of using the aero-spike alone with a gauge pressure of 34bar for full expansion.

Thanks for any assistance. Doug.