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National Advisory Committee for Aeronautics, Research Memorandum - Subsonic Flight Investigation of Rectangular Ram Jet Over Range of Altitudes

A flight investigation was conducted on a rectangular ram Jet
incorporating a V-shaped gutter—type flame holder over a range of
fuel-air ratios from 0.019 to 0.112, oombustion—chanber—inlet veloc-
ities from 59 to 101 feet per second, and pressure altitudes from
1500 to 29,200 feet.

The maximum combustion efficiency obtained. was approximately
84 percent at a. fuel-air ratio of 0.069 and a pressure altitude of
1500 feet. An. increase in altitude resulted in a pronounced decrease
in combustion efficiency. The highest pressure altitude at which
ignition was possible with the spark plug and ignition cone was
22,500 feet. Above 11,000 feet, an increase in altitude increased
the value of fuel—air ratio at which lean blow-out occurred. Rough
engine operation was encountered only at altitudes above 20,000 feet
as the fuel-air ratio approached the lean or rich blow-out limits.

As part of a research program for the study of ram. Jets,
a flight investigation is being conducted at the NASA Cleveland
laboratory on a rectangqu ram ,jet installed in a short-span wing
mounted beneath the fuselage of a twin—engine, fighter-type air-
plane. This type of power plant was designed for installation
within the wings of a high-speed airplane or missile.

The purpose of the investigation is to determine the perform-
ance and operational characteristics of a rectangular ram Jet over
a range of altitudes at subsonic velocities. During a test—stand
investigation (reference 1), a similar engine operated satisfacto-
rily over a range of fuel-air ratios from 0.025 to 0.083. Owing to
the comparatively low inlet—air velocities available, only a limited
amount of data could be obtained on ignition, blow-out, and combus—
tion efficiency. The flight investigation reported herein was made
at pressure altitudes from 1500 to 29,200 feet in order to determine
the effect of altitude on ignition, lean and rich blow-out limits,
and combustion efficiency.