Flight Investigation of Pentaborane Fuel in 9.75-inch-diameter Ram-jet Engine With Downstream Fuel Injection Page: 2 of 29
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NACA RM E55G01 CONFIDENTIAL
NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS
RESEARCH MEMORANDUM
FLIGHT INVESTIGATION OF PENTABORANE FUEL IN 9.75-INCH-DIAMETER
RAM-JET ENGINE WITH DOWNSTREAM FUEL INJECTION
By John H. Disher and Merle L. Jones
SUMMARY
The third flight test of pentaborane fuel in a 9.75-inch-diameter
air-launched ram-jet engine with a design free-stream Mach number of 1.8
was made. The ram jet used for this test was equipped with a revised
spray-bar - flameholder configuration. This change was designed to pre-
vent burning upstream of the flameholder and thereby prevent fuel-spray-
bar plugging, which was suspected to have occurred during the previous
flight.
After release from the carrier airplane at an altitude of 33,600
feet and a free-stream Mach number of 0.51, the engine accelerated to a
maximum Mach number of 2.06 in 34.1 seconds. A maximum acceleration of
7.2 g's was reached at the same instant. The propulsive thrust (thrust
minus drag) coefficient reached a maximum value of 0.573 at a free-stream
Mach number of 1.77, while the actual propulsive-thrust specific fuel
consumption (based on the actual combustion efficiency) reached a minimum
value of 2.44 pounds per hour per pound thrust minus drag at a free-stream
Mach number of about 1.8. The calculated values of ideal propulsive-
thrust specific fuel consumption (based on 100-percent combustion effi-
ciency) of pentaborane for the actual propulsive thrust were essentially
the same as the actual values at free-stream Mach numbers greater than
1.7, indicating combustion efficiencies in the order of 100 percent for
that portion of the flight. The calculated values of ideal propulsive-
thrust specific fuel consumption of octene-1 for the actual propulsive
thrust were about 33 percent higher than those for pentaborane in the
Mach number range from 1.7 to 2.06. The average equivalence ratio of
pentaborane during this period was 0.33.
INTRODUCTION
Pentaborane is being evaluated as a ram-jet fuel by the NACA Lewis
laboratory, through a series of test-stand and flight tests in coopera-
tion with the Bureau of Aeronautics, Department of the Navy, as part of
Project Zip. The flight tests are conducted by launching fin-stabilized,- 05 * * * .. *" * : ....
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Disher, John H. & Jones, Merle L. Flight Investigation of Pentaborane Fuel in 9.75-inch-diameter Ram-jet Engine With Downstream Fuel Injection, report, April 22, 1957; (https://digital.library.unt.edu/ark:/67531/metadc52871/m1/2/: accessed April 18, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.