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Old 30th Jun 2009, 02:07
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Brian Abraham
 
Join Date: Aug 2003
Location: Sale, Australia
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Out of interest I ran the figures for the CF6 through NASAs educational software and it came up with the following
Code:
ALTITUDE	SPEED	CORE	FUEL FLOW	GROSS	RAM	NET
	(MPH)	FLOW (LB/S)	(PPH)	THRUST	DRAG	THRUST

0	0	254	13820	45,171	0	45,171
0	170	262	14062	47,415	8,716	38,699
3,000	282	251	13511	47,256	14,146	33,109
35,000	.85M	103	6501	23,183	11,382	11,801
It should be noted that the air meeting the compressor face is not at free stream velocity (speed of the aircraft). The inlet is designed to slow the airflow so that it is presented to the compressor at a speed of .5M or less, to avoid choking the compressor. The ram drag above, is the drag associated with slowing down the free stream air as the air is brought inside the inlet. Even the SR-71 at 3.2M has the air delivered to the compressor at approx .5M.

Of interest also is the J-58 installed in the SR-71. At 3.2M, 54% of the thrust is provided by the differential pressure between the internal and external surfaces of the inlet spike. Of the remainder, 17% is provided by the engine and 29% by the ejector (the afterburner, which is in ram jet mode at this speed - air being tapped off the 4th stage compressor, diverted around the turbine, and injected into the afterburner)

I've tried reformatting with little luck - hope you can make sense of it.

Last edited by Brian Abraham; 30th Jun 2009 at 02:42.
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