MIXING ENHANCEMENT USING
it is ...
Investigation of fundamental physics
of a turbofan engine (low bypass ratio)
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.
+ 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
**Bypass ratio= Coflow mass flow rate
over jet mass flow rate.
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