A Study of Boundary Layer and Mass Bleed in a Short Length Supersonic Diffuser for a Gas Dynamic Laser
NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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This research was conducted to study the effect of boundary layer and mass bleed on the starting i.e., establishment of supersonic flow and running of a short length supersonic diffuser for a gas dynamic laser. A one-dimensional diffuser geometry which diffused the flow by an isentropic turn was laid out by the method of characteristics. Extensive boundary layer bleed holes and slots were incorporated in the diffuser walls. Self-actuating, one-way valves installed in the walls bled excess flow during starting. Schlieren flow visualization was obtained through opposite glass diffuser walls. The diffuser was started and Mach 3.5 flow established in a diffuser with a contraction ratio of 1.69. This geometry would not start without utilizing boundary layer and mass bleed. A mode of operation called self bleed was discovered. The lower static pressure in the diffuser entrance, via suitable ducting, was used to bleed the boundary layer in the diffuser throat. This method reduced the minimum operating stagnation pressure 17.0 without utilizing vacuum tanks or pumps. Testing confirmed that boundary layer bleed in the diffuser throat significantly lowers operating stagnation pressure.
- Lasers and Masers
- Fluid Mechanics