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Icing limit and wet-surface temperature variation for two airfoil shapes under simulated high-speed flight conditions

Description: Report presenting a study of the wet-surface temperature and stream conditions that result in ice-free surfaces for bodies in flight through icing clouds and a comparison of these experimental results with calculated results using the analytical method. Two symmetrical airfoil models were used in the investigation and testing occurred for a range of Mach numbers and pressure altitudes. Results regarding chordwise variation of pressure distribution, chordwise variation of recovery factor, results with the diamond airfoil and circular-arc airfoil, and the experimental and analytical results are presented.
Date: February 1955
Creator: Coles, Willard D.
Partner: UNT Libraries Government Documents Department

Experimental determination of thermal conductivity of low-density ice

Description: From Summary: "The thermal conductivity of low-density ice has been computed from data obtained in an experimental investigation of the heat transfer and mass transfer by sublimation for an iced surface on a flat plate in a high-velocity tangential air stream. The results are compared with data from several sources on the thermal conductivity of packed snow and solid glaze ice. The results show good agreement with the equations for the thermal conductivity of packed snow as a function of snow density. The agreement of the curves for packed snow near the solid ice regime with the values of thermal conductivity, of ice indicates that the curves are applicable over the entire-ice-density range."
Date: March 1954
Creator: Coles, Willard D.
Partner: UNT Libraries Government Documents Department

Investigation of far noise field of jets 2: comparison of air jets and jet engines

Description: Report presenting a comparison of the noise generation of air jets and turbojet engines under similar free-flight conditions. Results regarding a comparison of the sound power, afterburner data, spectrum measurements, noise data for engine thrust, and frequency distribution for the two engines are provided.
Date: January 1956
Creator: Coles, Willard D. & Callaghan, Edmund E.
Partner: UNT Libraries Government Documents Department

Full-scale investigation of several jet-engine noise-reduction nozzles

Description: A number of noise-suppression nozzles were tested on full-scale engines. In general, these nozzles achieved noise reduction by the mixing interference of adjacent jets, that is, by using multiple-slot-nozzles. Several of the nozzles achieved reductions in sound power of approximately 5 decibels (nearly 70 percent) with small thrust losses (approx. 1 percent). The maximum sound-pressure level was reduced by as much as 18 decibels in particular frequency bands. Some of the nozzles showed considerable spatial asymmetry; that is, the sound field was not rotationally symmetrical. A method of calculating the limiting frequency effected by such nozzles is presented. Furthermore data are shown that appear to indicate that further reductions in sound power will not be easily achieved from nozzles using mixing interference as a means of noise suppression.
Date: January 1, 1958
Creator: Coles, Willard D & Callaghan, Edmund E
Partner: UNT Libraries Government Documents Department

Full-scale investigation of several jet-engine noise-reduction nozzles

Description: A number of nozzles which use the mixing interference of adjacent jets for noise suppression were investigated. Reductions in sound power of nearly 70 percent (5 db) with thrust losses of 1 percent were achieved. A method of calculating the limiting frequency affected by this type of suppression nozzle, that is , multiple-slot nozzles, is presented. Data are shown which indicate that further large reductions in sound power are not likely with mixing-interference nozzles.
Date: April 1, 1957
Creator: Coles, Willard D & Callaghan, Edmund E
Partner: UNT Libraries Government Documents Department

Experimental investigation of sublimation of ice at subsonic and supersonic speeds and its relation to heat transfer

Description: From Summary: "An experimental investigation was conducted in a 3.84- by 10-inch tunnel to determine the mass transfer by sublimation, heat transfer, and skin friction for an iced surface on a flat plate for Mach numbers of 0.4, 0.6, and 0.8 and pressure altitudes to 30,000 feet. Measurements of rates of sublimation were also made for a Mach number of 1.3 at a pressure altitude of 30,000 feet. The results show that the parameters of sublimation and heat transfer were 40 to 50 percent greater for an iced surface than was the bare-plate heat-transfer parameter. For iced surfaces of equivalent roughness, the ratio of sublimation to heat-transfer parameters was found to be 0.90. The sublimation data obtained at a Mach number of 1.3 showed no appreciable deviation from that obtained at subsonic speeds. The data obtained indicate that sublimation as a means of removing ice formations of appreciable thickness is usually too slow to be of mach value in the de-icing of aircraft at high altitudes."
Date: March 1954
Creator: Coles, Willard D. & Ruggeri, Robert S.
Partner: UNT Libraries Government Documents Department

Effect of exhaust-nozzle ejectors on turbojet noise generation

Description: From Summary: "Engine noise levels and jet-velocity profiles have been obtained with several turbojet exhaust-nozzle ejectors. An insignificant reduction in total sound power was realized. At subsonic nozzle pressure ratios, total sound power from exhaust-nozzle ejectors or bypass exit configurations can be calculated from primary-jet parameters only."
Date: October 1955
Creator: North, Warren J. & Coles, Willard D.
Partner: UNT Libraries Government Documents Department

Screen-type noise reduction devices for ground running of turbojet engines

Description: Report presenting testing of the use of screens placed across the jet as a means of suppressing jet noise during ground running, which was somewhat offset by increased noise levels ahead of the engine. Air-jet tests showed negligible reduction in sound generation with additional screens. The large reductions obtained by using screens show that noise generated inside the engine by the turbine or combustion contribute only a minor part of the total noise.
Date: July 1957
Creator: Coles, Willard D. & North, Warren J.
Partner: UNT Libraries Government Documents Department

Laboratory investigation of icing in the carburetor and supercharger inlet elbow of an aircraft engine 3: heated air as a means of de-icing the carburetor and supercharger inlet elbow

Description: Report discussing the use of a twin-barrel injection carburetor and a supercharger inlet elbow to establish the relation between wet- and dry-bulb temperatures of the de-icing air and time required to recover from air-flow loss due to icing. The tests were performed at several power conditions, icing conditions, temperatures, and dry and humidified air. De-icing time was found to be a function of the nature of the ice formation and of the wet-bulb temperature of the de-icing air.
Date: December 1945
Creator: Lyons, Richard E. & Coles, Willard D.
Partner: UNT Libraries Government Documents Department

Far Noise Field of Air Jets and Jet Engines

Description: An experimental investigation was conducted to study and compare the acoustic radiation of air jets and jet engines. A number of different nozzle-exit shapes were studied with air jets to determine the effect of exit shape on noise generation. Circular, square, rectangular, and elliptical convergent nozzles and convergent-divergent and plug nozzles were investigated. The spectral distributions of the sound power for the engine and the air jet were in good agreement for the case where the engine data were not greatly affected by reflection or jet interference effects. Such power spectra for a subsonic or slightly choked engine or air jet show that the peaks of the spectra occur at a Strouhal number of 0.3.
Date: January 1, 1957
Creator: Callaghan, Edmund E & Coles, Willard D
Partner: UNT Libraries Government Documents Department

Near Noise Field of a Jet-Engine Exhaust

Description: From Summary: "Aircraft structures located in the near noise field of a jet engine are subjected to extremely high fluctuating pressures that may cause structural fatigue. Studies of such structures have been limited by lack of knowledge of the loadings involved. The acoustic near field produced by the exhaust of a stationary turbojet engine having a high pressure ratio was measured for a single operating condition without burning. The maximum overall sound pressure without afterburning was found to be about 42 pounds per square foot along the jet boundary in the region immediately downstream of the jet-nozzle exit."
Date: 1957
Creator: Howes, Walton L.; Callaghan, Edmund E.; Coles, Willard D. & Mull, Harold R.
Partner: UNT Libraries Government Documents Department

Icing-protection requirements for reciprocating-engine induction system

Description: From Summary: "Despite the development of relatively ice-free fuel-metering systems, the widespread use of alternate and heated-air intakes, and the use of alcohol for emergency de-icing, icing of aircraft-engine induction systems is a serious problem. Investigations have been made to study and to combat all phases of this icing problem. From these investigations, criterions for safe operation and for design of new induction systems have been established. The results were obtained from laboratory investigations of carburetor-supercharger combinations, wind-tunnel investigations of air scoops, multicylinder-engine studies, and flight investigations. Characteristics of three forms of ice, impact, throttling, and fuel evaporation were studied."
Date: June 20, 1949
Creator: Coles, Willard D.; Rollin, Vern G. & Mulholland, Donald R.
Partner: UNT Libraries Government Documents Department

Acoustic, thrust, and drag characteristics of several full-scale noise suppressors for turbojet engines

Description: From Introduction: " Considerable analytical and experimental research has been done to find means of reducing the noise levels of the turbojet transports. Noise levels can be decreased by engine redesign to reduce the jet-exit velocity (ref. 1), proper flight-climb techniques (ref. 2), and the use of noise-suppression exhaust nozzles (refs. 3 to 5). The present report is concerned with the last method."
Date: April 1958
Creator: Ciepluch, Carl C.; North, Warren J.; Coles, Willard D. & Antl, Robert J.
Partner: UNT Libraries Government Documents Department

Near noise field of a jet-engine exhaust 2: cross correlation of sound pressures

Description: Pressure cross correlations were obtained over a range of jet velocities both longitudinally and laterally for the overall sound pressure and for several frequency bands. The region of positive correlation was found to increase with distance downstream of the nozzle exit and was greater for lateral than for longitudinal correlations. In general, little change in the correlation curves was found as a function of jet velocity or frequency band width. Measurements made with a fixed and a movable microphone in a plate showed correlations similar to the free-field results. The results are interpreted in terms of pressure loads on surfaces.
Date: September 1956
Creator: Callaghan, Edmund E.; Howes, Walton L. & Coles, Willard D.
Partner: UNT Libraries Government Documents Department