MIXING ENHANCEMENT USING AXIAL FLOW

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Samples of axisymmetric tests

JSE applied to an annular jet composed of a helium-air mixture at Mach 0.9.

Jet Mach number=0.9  (NPR*=1.75)
Jet velocity=410 m/s
Jet Reynolds number =28,000  (based on annulus thickness)
Inner annulus diameter=0.5 in.
Outer annulus diameter=0.7 in.

See also results for a larger annular jet

jsm3001.jpg (32656 bytes)

Annular nozzle is convergent.

  jsm3009.jpg (38833 bytes)

Annular nozzle is convergent-divergent (Ae/Amin=1.25).   This is the JSE condition; the jet destabilization is obvious. This configuration could simulate the core exhaust of a turbofan or turbojet engine.

jpc06jpc07.gif (5319 bytes)

Centerline Mach number versus axial distance for the cases presented above.  Red: jet from convergent nozzle; Green: jet from convergent-divergent nozzle.  Faster decay of centerline Mach number indicates mixing enhancement.

*NPR=Nozzle pressure ratio:   total pressure over ambient pressure.  NPR=1.89 gives sonic fully-expanded Mach number