Three passive control methods of dynamic total pressure distortion have been developed in a 2–D diffuser in this paper: a fore–positioned shock stabilizing rod on a porous plate (model Q), a mid–positioned shock stabilizing rod on a porous plate (model Z), a porous plate (model K) and the original model without any control.

From the experiment results, we observe that the PCSB (Passive Control of Shock wave / Boundary layer) technique used in the diffuser is effective to decrease the dynamic distortion. We conclude that:

a) Different flow regions and their characteristic frequencies in the diffuser have been found.

b) The interaction between the terminal shock wave and the boundary layer produces the peak value of the dynamic distortion.

c) The steady total pressure varies inversely with the dynamic components of the total pressure along the height at the exit of the diffuser.

d) The effects of different positions of the shock stabilizing rod on the dynamic distortion are relative to the upstream total pressure of the diffuser.

e) New explanation about the production of the distortion has been given.

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