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Preliminary Results from Free-Jet Tests of a 48-Inch-Diameter Ram-Jet Combustor with an Annular-Piloted Baffle-Type Flameholder

Description: A ram-jet engine with an experimental 48-inch-diameter combustor was investigated in a free-jet facility. The combustor design comprised a large-volume annular pilot region and an array of sloping baffle- or gutter-type flameholders. The combustor was intended to operate at a fuel-air ratio of about 0.037. To promote combustion efficiency at such low fuel-air ratios, a divided-flow system was employed which bypassed a portion of the engine air around the combustion region. Three combustor lengths, three lengths of the shroud which separated the bypass air from the burning stream, and four fuel-distribution systems were investigated over a range of fuel-air ratios from 0.025 to 0.055 and a range of engine air flows from 40 to 110 pounds per second (combustor-outlet total pressures from 500 t o 1800 lb/sq ft abs). The highest efficiencies were obtained with a combustor length of 78 inches and a shroud length of 6 inches. At the lowest air flow, with combustor pressures of about 700 pounds per square foot absolute, a maximum efficiency of about 93 percent was obtained. The efficiency increased with combustor length, a typical increase being from 88 to 95 percent as the length increased from 60 to 96 inches. The length of the shroud separating the bypass air from the burning stream affected not only the efficiency level, but also the fuel-air ratio at which the maximum efficiency occurred. In general, a longer shroud caused the maximum efficiency to occur at lower f'uel-air ratios. Highest efficiencies usually resulted from the use of a fuel-injection system giving a uniform fuel profile. The efficiency at low fuel-air ratios could be considerably improved by the use of a radially nonuniform fuel profile which concentrated the fuel towards the outermost portion of the burning stream The total-pressure ratio across the combustor was about 0.86 at the ...
Date: May 11, 1955
Creator: Rayle, W. D.; Smith, I. D. & Wentworth, C. B.
Item Type: Report

Preliminary Data on Rain Deflection from Aircraft Windshields by Means of High-Velocity Jet-Air Blast

Description: A preliminary experimental investigation is being conducted to determine the feasibility of preventing rain from impinging on aircraft windshields by means of high-velocity jet-air blast. The results indicate that rain deflection by jet blast appears feasible for flight speeds comparable with landing and take-off speeds of interceptor-type jet aircraft; however, attainment of good visibility through the mist generated by raindrop breakup presents a problem. For the simulated windshield and the lower windshield angles used in the investigation, air-flow rates of the order of 3.3 pounds per minute of unheated air per inch of windshield span were required for adequate rain deflection at a free-stream velocity of 135 miles per hour. A method has been devised whereby it is possible to produce large-diameter water drops (1000 to 1500 p.) in a moving air stream, without breakup, at speeds in excess of 175 miles per hour.
Date: July 25, 1955
Creator: Ruggeri, Robert S.
Item Type: Report

Flight Instrument for Measurement of Liquid-Water Content in Clouds at Temperatures Above and Below Freezing

Description: A principle formerly used in an instrument for cloud detection was further investigated to provide a simple and rapid means for measuring the liquid-water content of clouds at temperatures above and below freezing. The instrument consists of a small cylindrical element so operated at high surface temperatures that the impingement of cloud droplets creates a significant drop in the surface temperature. ? The instrument is sensitive to a wide range of liquid-water content and was calibrated at one set of fixed conditions against rotating multicylinder measurements. The limited conditions of the calibration Included an air temperature of 20 F, an air velocity of 175 miles per hour, and a surface temperature in clear air of 475 F. The results obtained from experiments conducted with the instrument indicate that the principle can be used for measurements in clouds at temperatures above and below freezing. Calibrations for ranges of airspeed, air temperature, and air density will be necessary to adapt the Instrument for general flight use.
Date: March 5, 1951
Creator: Perkins, Porter J.
Item Type: Report

Investigation of Porous Gas-Heated Leading-Edge Section for Icing Protection of a Delta Wing

Description: A tip section of a delta wing having an NACA 0004-65 airfoil section and a 600 leading-edge sweepback was equipped with a porous leading-edge section through which hot gas was 'bled for anti-icing. Heating rates for anti-icing were determined for a wide range of icing conditions. The effects of gas flow through the porous leading-edge section on airfoil pressure distribution and drag in dry air were investigated. The drag increase caused by an ice formation on the unheated airfoil was measured for several icing conditions. Experimental porous surface- to free-stream convective heat-transfer coefficients were obtained in dry air and compared with theory. Adequate icing protection was obtained at all icing conditions investigated. Savings in total gas-flow rate up to 42 percent may be obtained with no loss in anti-icing effectiveness by sealing half the upper-surface porous area. Gas flow through the leading-edge section had no appreciable effect on airfoil pressure distribution. The airfoil section drag increased slightly (5-percent average) with gas flow through the porous surface. A heavy glaze-ice formation produced after 10 minutes of icing caused an increase in section drag coefficient of 240 percent. Experimental convective heat-transfer coefficients obtained with hot-gas flow through the porous area in dry air and turbulent flow were 20 to 30 percent lower than the theoretical values for a solid surface under similar conditions. The transition region from laminar to turbulent flow moved forward as the ratio of gas velocity through the porous surface to air-stream velocity was increased.
Date: January 19, 1955
Creator: Bowden, Dean T.
Item Type: Report

Investigation of Power Requirements for Ice Prevention and Cyclical De-Icing of Inlet Guide Vanes with Internal Electric Heaters

Description: An investigation was conducted to determine the electric power requirements necessary for ice protection of inlet guide vanes by continuous heating and by cyclical de-icing. Data are presented to show the effect of ambient-air temperature, liquid-water content, air velocity, heat-on period, and cycle times on the power requirements for these two methods of ice protection. The results showed that for a hypothetical engine using 28 inlet guide vanes under similar icing conditions, cyclical de-icing can provide a total power saving as high as 79 percent over that required for continuous heating. Heat-on periods in the order of 10 seconds with a cycle ratio of about 1:7 resulted in the best over-all performance with respect to total power requirements and aerodynamic losses during the heat-off period. Power requirements reported herein may be reduced by as much as 25 percent by achieving a more uniform surface-temperature distribution. A parameter in terms of engine mass flow, vane size, vane surface temperature, and the icing conditions ahead of the inlet guide vanes.was developed by which an extension of the experimental data to icing conditions and inlet guide vanes, other than those investigated was possible.
Date: December 1, 1950
Creator: VonGlahn, Uwe & Blatz, Robert E.
Item Type: Report

Boundary-Layer-Transition Measurements in Full-Scale Flight

Description: Chemical sublimation has been employed for boundary-layer-flow visualization on the wings of a supersonic fighter airplane in level flight at speeds near a Mach number of 2.0. The tests have shown that laminar flow can be obtained over extensive areas of the wing with practical wing-surface conditions. In addition to the flow visualization tests, a method of continuously monitoring the conditions of the boundary layer has been applied to flight testing, using heated temperature resistance gages installed in a Fiberglas "glove" installation on one wing. Tests were conducted at speeds from a Mach number of 1.2 to a Mach number of 2.0, at altitudes from 35,000 feet to 56,000 feet. Data obtained at all angles of attack, from near 0 deg to near 10 deg, have shown that the maximum transition Reynolds number on the upper surface of the wing varies from about 2.5 x 10(exp 6) at a Mach number of 1.2 to about 4 x 10(exp 6) at a Mach number of 2.0. On the lower surface, the maximum transition Reynolds number varies from about 2 x 10(exp 6) at a Mach number of 1.2 to about 8 x 10(exp 6) at a Mach number of 2.0.
Date: July 28, 1958
Creator: Banner, Richard D.; McTigue, John G. & Petty, Gilbert, Jr.
Item Type: Report