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MESPI applied to a coaxial jet with primary flow composed of a helium-air mixture at Mach 0.9.
Jet Mach number=0.9
Jet velocity=465 m/s
Jet Reynolds number =180,000

These experiments suggest that the exhaust of a turbofan engine can mix faster by making a minor change in the shape of the fan duct.  See also experiments at larger bypass ratio.

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Jet + air coflow at NPR*=1.71 (Mach 0.91) from a convergent nozzle. Bypass ratio**=1.35. Centerline Mach number = 0.73 at x/D=8.

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Jet + air coflow at NPR=1.71 (Mach 0.91) from a convergent-divergent nozzle (Ae/Amin=1.25).   This is the MESPI condition; the jet destabilization is obvious in the picture.  Bypass ratio=1.20.   Centerline Mach number = 0.58 at x/D=8.

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Jet + air coflow at NPR=1.71 (Mach 0.91) from a recessed convergent-divergent nozzle (Ae/Amin=1.35).   It is apparent that MESPI still works even with the coflow exhausting upstream of the jet exit.  Bypass ratio**=1.20.   Centerline Mach number = 0.52 at x/D=8.

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

**Bypass ratio= Coflow mass flow rate over jet mass flow rate.

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