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.
 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. |
 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. |
 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.