ALBERT

Description: An investigation to determine and correlate the experimental surface heat-transfer coefficients of finned cylinders with different air-stream cooling arrangements was conducted at the Langley Memorial Aeronautical Laboratory from 1932 to 1938. The investigation covered the determination of the effect of fin width, fin space, fin thickness, and cylinder diameter on the heat transfer. Wind-tunnel tests were made in the free air stream with and without baffles and also with various devices for creating a turbulent air stream. Tests were also made with blower.

Description: The cooling of a single-row radial air-cooled engine using several cowling arrangements has been studied in the NACA 20-foot wind tunnel. The results show the effect of the propeller and several cowling arrangements on cooling for various values of the indicated horsepower in the climb condition. A table giving comparative performance of the various cowling arrangements is presented. The dependence of temperature on indicated horsepower and pressure drop across the baffles is shown by charts. Other charts show the limiting indicated horsepower against the pressure drop across the engine and the heat dissipated at various values of the indicated horsepower.

Description: The results of tests made to determine the performance of a DePalma-Roots supercharger are presented. The performance of the DePalma supercharger with atmospheric pressure at the discharge was compared with that of a hypothetical NACA Roots-type supercharger of the same displacement. The tests were conducted at speeds from 1,000 to 6,000 r.p.m. and at pressure differences from 0 to 15 inches of mercury. The variation in clearance between the impeller tips and the impeller housing was determined for the DePalma supercharger at a speed of 2,000 r.p.m. and for the NACA supercharger at speeds from 500 to 3,000 r.p.m. with the pressure differences for each supercharger varying form 0 to 15 inches of mercury. The results indicate that, if warping and growing of the metals of the case and impellers are neglected, the most uniform clearances can probably be maintained for all operating conditions when the case and impellers are constructed of metals that have the same coefficient of expansion. The results also show that the discharge and intake openings of this model of the DePalma supercharger are too small, which lowers the volumetric efficiency and impairs the performance at all speeds and pressure differences. At high pressure difference the volumetric efficiency of the DePalma supercharger is greater when the discharge pressure surpasses atmospheric pressure than when the discharge pressure is atmospheric.

Description: An investigation was made to obtain information on the minimum quantity of air and power required to cool conventional air cooled cylinders at various operating conditions when using a blower. The results of these tests show that the minimum power required for satisfactory cooling with an overall blower efficiency of 100 percent varied from 2 to 6 percent of the engine power depending on the operating conditions. The shape of the jacket had a large effect on the cylinder temperatures. Increasing the air speed over the front of the cylinder by keeping the greater part of the circumference of the cylinder covered by the jacket reduced the temperatures over the entire cylinder.

Description: Several electrically heated finned steel cylinders enclosed in jackets were cooled by air from a blower. The effect of the air conditions and fin dimensions on the average surface heat-transfer coefficient q and the power required to force the air around the cylinders were determined. Tests were conducted at air velocities between the fins from 10 to 130 miles per hour and at specific weights of the air varying from 0.046 to 0.074 pound per cubic foot. The fin dimensions of the cylinders covered a range in pitches from 0.057 to 0.25 inch average fin thicknesses from 0.035 to 0.04 inch, and fin widths from 0.67 to 1.22 inches.

Description: Factors are obtained from semiempirical equations for correcting engine-cylinder temperatures for variation in important engine and cooling conditions. The variation of engine temperatures with atmospheric temperature is treated in detail, and correction factors are obtained for various flight and test conditions, such as climb at constant indicated air speed, level flight, ground running, take-off, constant speed of cooling air, and constant mass flow of cooling air. Seven conventional air-cooled engine cylinders enclosed in jackets and cooled by a blower were tested to determine the effect of cooling-air temperature and carburetor-air temperature on cylinder temperatures. The cooling air temperature was varied from approximately 80 degrees F. to 230 degrees F. and the carburetor-air temperature from approximately 40 degrees F. to 160 degrees F. Tests were made over a large range of engine speeds, brake mean effective pressures, and pressure drops across the cylinder. The correction factors obtained experimentally are compared with those obtained from the semiempirical equations and a fair agreement is noted.