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  Partner: UNT Libraries Government Documents Department
 Decade: 1930-1939
 Serial/Series Title: NACA Special Report
 Collection: Technical Report Archive and Image Library
Tandem Air Propellers

Tandem Air Propellers

Date: August 1, 1937
Creator: Lesley, E.P.
Description: Tests of 2-blade, adjustable-pitch, counterrotating tandem model propellers, adjusted to absorb equal power at maximum efficiency, were made at Stanford University. The characteristics, for 15 degrees, 25 degrees, 35 degrees, and 45 degrees pitch settings at 0.75 R of the forward propeller and for 8 1/2%, 15% and 30% diameter spacings, were compared with those of 2-blade and 4-blade propellers of the same blade form. The tests showed that the efficiency of the tandem propellers was from 0.5% to 4% greater than that of a 4-blade propeller and, at the high pitch settings, not appreciable inferior to that of a 2-blade propeller. It was found that the rear tandem propeller should be set at a pitch angle slightly less than that of the forward propeller to realize the condition of equal power at maximum efficiency. Under this condition the total power absorbed by the tandem propellers was from 3% to 9% more than that absorbed by the 4-blade propeller and about twice that absorbed by a 2-blade propeller.
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Tandem Air Propellers - II

Tandem Air Propellers - II

Date: October 1, 1939
Creator: Lesley, E. P.
Description: Tests of three-blade, adjustable-pitch counterrotating tandem model propellers, adjusted to absorb equal power at maximum efficiency of the combination, were made at Stanford University. The aerodynamic characteristics, for blade-angle settings of 15, 25, 35, 45, 55, and 65 degrees at 0.75R of the forward propeller and for diameters spacings of 8-1/2, 15 and 30% were compared with those of three-blade and six-blade propellers of the same blade form. It was found that, in order to realize the condition of equal power at maximum efficiency, the blade angles for the rear propeller must be generally less than for the forward propeller, the difference increasing the blade angle. The tests showed that, at maximum efficiency, the tandem propellers absorb about double the power of three-blade propellers and about 8% more power than six-blade propellers having the pitch of the forward propeller of the tandem combination. The maximum efficiency of the tandem propellers was found to be from 2-15% greater than for six-blade propellers, the difference varying directly with blade angle. It was also found that the maximum efficiency of the tandem propellers was greater than that of a three-blade propeller for blade angles at 0.75R of 25 degrees or more. The difference ...
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Wing-Nacelle-Propeller Tests - Comparative Tests of Liquid-Cooled and Air-Cooled Engine Nacelles

Wing-Nacelle-Propeller Tests - Comparative Tests of Liquid-Cooled and Air-Cooled Engine Nacelles

Date: January 1, 1934
Creator: Wood, Donald H.
Description: This report gives the results of measurements of the lift, drag, and propeller characteristics of several wing and nacelle combinations with a tractor propeller. The nacelles were so located that the propeller was about 31% of the wing chord directly ahead of the leading edge of the wing, a position which earlier tests (NASA Report No. 415) had shown to be efficient. The nacelles were scale models of an NACA cowled nacelle for a radial air-cooled engine, a circular nacelle with the V-type engine located inside and the radiator for the cooling liquid located inside and the radiator for the type, and a nacelle shape simulating the housing which would be used for an extension shaft if the engine were located entirely within the wing. The propeller used in all cases was a 4-foot model of Navy No. 4412 adjustable metal propeller. The results of the tests indicate that, at the angles of attack corresponding to high speeds of flight, there is no marked advantage of one type of nacelle over the others as far as low drag is concerned, since the drag added by any of the nacelles in the particular location ahead of the wing is very small. ...
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Engine Operation in Flight for Minimum Fuel Consumption

Engine Operation in Flight for Minimum Fuel Consumption

Date: November 1, 1939
Creator: Reuter, George
Description: Engine and airplane performance data have been gathered from various sources and analyzed to determine indications of the most economical methods of flight operation from a consideration of fuel expenditure. The analysis includes the influence of such facts as fuel-air ratio, engine speed, engine knock, altitude, cylinder cooling, spark timing, and limits of cruising brake mean effective pressure. The results indicate that the cheapest power is obtained with approximately correct mixture at low engine speed and highest permissible manifold pressure. If more power is desired, the methods of obtaining it are, in order of fuel economy: (a) increasing the engine speed and maintaining safe cylinder temperatures by cooling; (b) retarding the spark or cooling further to permit higher manifold pressure; and, (c) riching the mixture. The analysis further shows that the maximum time endurance of flight occurs at the air speed corresponding to minimum thrust horsepower required and with minimum practicable engine speed. Maximum mileage per pound of fuel is obtained at slightly higher air speed. The fuel-air ratio should be approximately the theoretically correct ratio in both cases. For an engine equipped with a geared supercharger, as in the example presented, and with knock as the limiting condition, a ...
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Experiments on the Recovery of Waste Heat in Cooling Ducts, Special Report

Experiments on the Recovery of Waste Heat in Cooling Ducts, Special Report

Date: May 1, 1939
Creator: Silverstein, Abe
Description: Tests have been conducted in the N.A.C.A. full-scale wind tunnel to investigate the partial recovery of the heat energy which is apparently wasted in the cooling of aircraft engines. The results indicate that if the radiator is located in an expanded duct, a part of the energy lost in cooling is recovered; however, the energy recovery is not of practical importance up to airplane speeds of 400 miles per hour. Throttling of the duct flow occurs with heated radiators and must be considered in designing the duct outlets from data obtained with cold radiators in the ducts.
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Investigation of an Electrically Heated Airplane Windshield for Ice Prevention, Special Report

Investigation of an Electrically Heated Airplane Windshield for Ice Prevention, Special Report

Date: March 1, 1939
Creator: Rodert, Lewis A.
Description: A study was made at the National Advisory Committee for Aeronautics Laboratory of the operation of an electrically heated glass panel, which simulated a segment of an airplane windshield, to determine if ice formations, which usually result in the loss of visibility, could be prevented. Tests were made in the 7- by 3-foot ice tunnel, and in flight, under artificially created ice-forming conditions. Ice was prevented from forming on the windshield model in the tunnel by 1.25 watts of power per square inch with the air temperature at 23 F and a velocity of 80 miles per hour. Using an improved model in flight, ice was prevented by 1.43 watts of power per square inch of protected area and 2 watts per inch concentrated in the rim, with the air temperature at 26 F and a velocity of 120 miles per hour. The removal of a preformed ice cap was effected to a limited extent in the tunnel by the use of 1.89 watts of power per square inch when the temperature and velocity were 25 F and 80 miles per hour, respectively. The results indicate that service tests with an improved design are justified.
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Large-Scale Boundary-Layer Control Tests on Two Wings in the NACA 20-Foot Wind Tunnel, Special Report

Large-Scale Boundary-Layer Control Tests on Two Wings in the NACA 20-Foot Wind Tunnel, Special Report

Date: April 1, 1935
Creator: Freeman, Hugh B.
Description: Tests were made in the N.A.C.A. 20-foot wind tunnel on: (1) a wing, of 6.5-foot span, 5.5-foot chord, and 30 percent maximum thickness, fitted with large end plates and (2) a 16-foot span 2.67-foot chord wing of 15 percent maximum thickness to determine the increase in lift obtainable by removing the boundary layer and the power required for the blower. The results of the tests on the stub wing appeared more favorable than previous small-scale tests and indicated that: (1) the suction method was considerably superior to the pressure method, (2) single slots were more effective than multiple slots (where the same pressure was applied to all slots), the slot efficiency increased rapidly for increasing slot widths up to 2 percent of the wing chord and remained practically constant for all larger widths tested, (3) suction pressure and power requirements were quite low (a computation for a light airplane showed that a lift coefficient of 3.0 could be obtained with a suction as low as 2.3 times the dynamic pressure and a power expenditure less than 3 percent of the rated engine power), and (4) the volume of air required to be drawn off was quite high (approximately 0.5 cubic ...
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Tests of Airfoils Designed to Delay the Compressibility Burble

Tests of Airfoils Designed to Delay the Compressibility Burble

Date: June 1, 1939
Creator: Stack, John
Description: Development of airfoil sections suitable for high-speed applications has generally been difficult because little was known of the flow phenomenon that occurs at high speeds. A definite critical speed has been found at which serious detrimental flow changes occur that lead to serious losses in lift and large increases in drag. This flow phenomenon, called the compressibility burble, was originally a propeller problem, but with the development of higher speed aircraft serious consideration must be given to other parts of the airplane. Fundamental investigations of high-speed airflow phenomenon have provided new information. An important conclusion of this work has been the determination of the critical speed, that is, the speed at which the compressibility burble occurs. The critical speed was shown to be the translational velocity at which the sum of the translational velocity and the maximum local induced velocity at the surface of the airfoil or other body equals the local speed of sound. Obviously then higher critical speeds can be attained through the development of airfoils that have minimum induced velocity for any given value of the lift coefficient. Presumably, the highest critical speed will be attained by an airfoil that has uniform chordwise distribution of induced velocity ...
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Wind-Tunnel Investigation of Air Inlet and Outlet Openings for Aircraft, Special Report

Wind-Tunnel Investigation of Air Inlet and Outlet Openings for Aircraft, Special Report

Date: October 1, 1938
Creator: Rogallo, Francis M. & Gauvain, William E.
Description: An investigation was made in the NACA 5-foot vertical wind tunnel of a large variety of duct inlets and outlets to obtain information relative to their design for the cooling or the ventilation systems on aircraft. Most of the tests were of openings in a flat plate but, in order to determine the best locations and the effects of interference, a few tests were made of openings in an airfoil. The best inlet location for a system not including a blower was found to be at the forward stagnation point; for one including a blower, the best location was found to be in the region of lowest total head, probably in the boundary layer near the trailing edge. Design recommendations are given, and it is shown that correct design demands a knowledge of the external flow and of the internal requirements in addition to that obtained from the results of the wind tunnel tests.
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Stability of Castering Wheels for Aircraft Landing Gears, Special Report

Stability of Castering Wheels for Aircraft Landing Gears, Special Report

Date: September 1, 1937
Creator: Kantrowitz, Arthur
Description: In many installations of castering rubber-tired wheels there is a tendency for the wheel to oscillate violently about the spindle axis. This phenomenon, popularly called 'shimmy,' has occurred in some airplane tail wheels and has been corrected in two ways: first by the application of friction in the spindles of the tail wheels; and, second, by locking the wheels while taxiing at high speeds. Shimmy is common with the large wheels used as nose wheels in tricycle landing gears and, since it is impossible to lock the wheels, friction in the nose-wheel spindle has been the sole means of correction. Because the nose wheel is larger than the conventional tail wheel and usually carries a greater load, the larger amounts of spindle friction necessary to prevent shimmy are objectionable. the present paper presents a theoretical and experimental study of the problem of the stability of castering wheels for airplane landing gears. On the basis of simplified assumptions induced from experimental observations, a theoretical study has been made of the shimmy of castering wheels. The theory is based on the discovery of a phenomenon called 'kinematic shimmy' and is compared quantitatively with the results of model experiments. Experimental checks, using a ...
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Notes on Factors Affecting Geometrical Arrangement of Tricycle-Type Landing Gear

Notes on Factors Affecting Geometrical Arrangement of Tricycle-Type Landing Gear

Date: April 1, 1937
Creator: Wenzinger, Carl J. & Kantrowitz, A. R.
Description: The effects of the geometrical arrangement of tricycle landing gears on various characteristics of an airplane equipped with such landing gear is discussed. The characteristics discussed include directional stability, overturning tendencies, steering and ground handling, shimmy, takeoff, and porpoising. The conclusions are summarized in a table.
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Investigation in the 7-By-10 Foot Wind Tunnel of Ducts for Cooling Radiators Within an Airplane Wing, Special Report

Investigation in the 7-By-10 Foot Wind Tunnel of Ducts for Cooling Radiators Within an Airplane Wing, Special Report

Date: July 1, 1938
Creator: Harris, Thomas A. & Recant, Isidore G.
Description: An investigation was made in the NACA 7- by 10-foot wind tunnel of a large-chord wing model with a duct to house a simulated radiator suitable for a liquid-cooled engine. The duct was expanded to reduce the radiator losses, and the installation of the duct and radiator was made entirely within the wing to reduce form and interference drag. The tests were made using a two-dimensional flow set-up with a full-span duct and radiator. Section aerodynamic characteristics of the basic airfoil are given and also curves showing the characteristics of the various duct-radiator combinations. An expression for efficiency, the primary criterion of merit of any duct, and the effect of the several design parameters of the duct-radiator arrangement are discussed. The problem of throttling is considered and a discussion of the power required for cooling is included. It was found that radiators could be mounted in the wing and efficiently pass enough air for cooling with duct outlets located at any point from 0.25c to 0.70c from the wing leading edge on the upper surface. The duct-inlet position was found to be critical and, for maximum efficiency, had to be at the stagnation point of the airfoil and to change ...
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The Transition Phase in the Take-Off of an Airplane, Special Report

The Transition Phase in the Take-Off of an Airplane, Special Report

Date: December 1, 1937
Creator: Wetmore, J. W.
Description: An investigation was undertaken to determine the character and importance of the transition phase between the ground run and steady climb in the takeoff of an airplane and the effects of various factors on this phase and on the airborne part of the takeoff as a whole. The information was obtained from a series of step-by-step integrations, which defined the motion of the airplane during the transition and which were based on data derived from actual takeoff tests of a Verville AT airplane. Both normal and zoom takeoffs under several loading and takeoff speed conditions were considered. The effects of a moderate wind with a corresponding wind gradient and the effect of proximity of the ground were also investigated. The results show that, for normal takeoffs, the best transition was realized at the lowest possible takeoff speed. Moreover, this speed gave the shortest overall takeoff distance for normal takeoffs. Zoom takeoffs required a shorter overall takeoff run than normal takeoffs, particularly with a heavy landing, if the obstacle to be cleared was sufficiently high (greater than 50 feet); no advantage was indicated to the airplane with a light loading if the height to be cleared was less. The error resulting ...
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The Torsional and Bending Deflection of Full-Scale Duralumin Propeller Blades under Normal Operating Conditions, Special Report

The Torsional and Bending Deflection of Full-Scale Duralumin Propeller Blades under Normal Operating Conditions, Special Report

Date: March 1, 1938
Creator: Hartman, Edwin P. & Biermann, David
Description: The torsional deflection of the blades of three full-scale duralumin propellers operating under various loading conditions was measured by a light-beam method. Angular bending deflections were also obtained as an incidental part of the study. The deflection measurements showed that the usual present-day type of propeller blades twisted but a negligible amount under ordinary flight conditions. A maximum deflection of about 1/10th of a degree was found at V/nD of 0.3 and a smaller deflection at higher values of V/nD for the station at 0.70 radius. These deflections are much smaller than would be expected from earlier tests, but the light-beam method is considered to be much more accurate than the direct-reading transit method used in the previous tests.
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Tests in the Variable-Density Tunnel of Seven Tapered Wings Having N.A.C.A. 230 Mean Lines, Special Report

Tests in the Variable-Density Tunnel of Seven Tapered Wings Having N.A.C.A. 230 Mean Lines, Special Report

Date: August 1, 1937
Creator: Anderson, Raymond F.
Description: At the request of the Materiel Division of the Army Air Corps, seven tapered wings having sections based on the N.A,C.A. 230 mean line were tested in the variable-density wind tunnel, The characteristics of the wings are given.
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Correction of Profile-Drag Results from Variable-Density Tunnel and the Effect on the Choice of Wing-Section Thickness

Correction of Profile-Drag Results from Variable-Density Tunnel and the Effect on the Choice of Wing-Section Thickness

Date: March 1, 1938
Creator: Jacobs, Eastman N.
Description: Profile-drag coefficients published from tests in the N.A.C.A. variable-density tunnel (Technical Reports Nos. 460, 537, 586, and 610, references 1 to 4) have tended to appear high as compared with results from the N.A.C.A. full-scale tunnel (Technical Report No. 530, reference 5) and from foreign sources (references 6 to 8). Such discrepancies were considered in Technical Report No. 586, and corrections for turbulence and tip effects were derived that tended to reduce the profile-drag coefficients, particularly for the thicker airfoils. The corrected profile-drag coefficients, designated by the lower-case symbol cdo as contrasted with the older CDO, have been employed in the airfoil reports published since Technical Report No. 460, but even these corrected results continued to appear high, particularly for the thicker sections. The important practical result is that a smaller increase of drag with airfoil thickness is indicated, which may be of primary importance to the airplane designer in choosing the optimum airfoil sections for actual wings. Further investigations of this subject were, of course, undertaken, one of the most important being an investigation of three symmetrical sections N.A.C A. 0009, 0012, and 0018 under conditions of low turbulence in the full-scale tunnel. Preliminary results from this investigation also ...
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Full-Scale Wind-Tunnel Investigation of Wing-Cooling Ducts Effects of Propeller Slipstream, Special Report

Full-Scale Wind-Tunnel Investigation of Wing-Cooling Ducts Effects of Propeller Slipstream, Special Report

Date: March 1, 1939
Creator: Nickle, F. R. & Freeman, Arthur B.
Description: The safety of remotely operated vehicles depends on the correctness of the distributed protocol that facilitates the communication between the vehicle and the operator. A failure in this communication can result in catastrophic loss of the vehicle. To complicate matters, the communication system may be required to satisfy several, possibly conflicting, requirements. The design of protocols is typically an informal process based on successive iterations of a prototype implementation. Yet distributed protocols are notoriously difficult to get correct using such informal techniques. We present a formal specification of the design of a distributed protocol intended for use in a remotely operated vehicle, which is built from the composition of several simpler protocols. We demonstrate proof strategies that allow us to prove properties of each component protocol individually while ensuring that the property is preserved in the composition forming the entire system. Given that designs are likely to evolve as additional requirements emerge, we show how we have automated most of the repetitive proof steps to enable verification of rapidly changing designs.
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Full-Scale Wind-Tunnel Investigation of Wing Cooling Ducts, Special Report

Full-Scale Wind-Tunnel Investigation of Wing Cooling Ducts, Special Report

Date: October 1, 1938
Creator: Nickle, F. R. & Freeman, Arthur B.
Description: The systematic investigation of wing cooling ducts at the NACA laboratory has been continued with tests in the full-scale wind tunnel on ducts of finite span. These results extend the previous investigation on section characteristics of ducts to higher Reynolds numbers and indicate the losses due to the duct ends. The data include comparisons between ducts completely within the ring and the conventional underslung ducts. Methods of flow regulation were studied and data were obtained for a wide range of internal duct resistance. The results show satisfactory correlation between the finite span and the previously measured section characteristics obtained with full-span ducts. The effects of the various design parameters on the duct characteristics are discussed. The cooling power required for the internal duct installation is shown to be only a small percentage of the engine power.
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The Effect of Lateral Inclination of the Thrust Axis and of Sweepback of the Leading Edge of the Wing on Propulsive and Net Efficiencies of a Wing-Nacelle-Propeller Combination

The Effect of Lateral Inclination of the Thrust Axis and of Sweepback of the Leading Edge of the Wing on Propulsive and Net Efficiencies of a Wing-Nacelle-Propeller Combination

Date: April 1, 1935
Creator: Wood, Donald H. & Windler, Ray
Description: This report describes and gives the results of tests made to determine the effect of lateral inclination of the propeller thrust axis to the direction of flight. A wing-nacelle-propeller combination with the nacelle axis located successively parallel to and at 15 degrees to the perpendicular to the leading edge of a wing was tested with the combination at several angles of yaw. Tests of the wing alone at the same angles of yaw were also made. The data are presented in the usual graphic form. An increase in propulsive efficiency with increase in angle of the thrust axis was found. The change in net efficiency, found by charging the whole nacelle drag to the power unit, was negligible, however, within the range of the tests.
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An Investigation of the Drag of Windshields in the 8-Foot High-Speed Wind Tunnel

An Investigation of the Drag of Windshields in the 8-Foot High-Speed Wind Tunnel

Date: June 1, 1939
Creator: Robinson, Russell G. & Delano, James B.
Description: The drag of closed-cockpit and transport-type windshields was determined from tests made at speeds from 200 to 440 miles per hour in the NACA 8-foot high-speed wind tunnel. This speed range corresponds to a test Reynolds number range of 2,510,000 to 4,830,000 based on the mean aerodynamic chord of the full-span model (17.29 inches). The shapes of the windshield proper, the hood, and the tail fairing were systematically varied to include common types and a refined design. Transport types varied from a reproduction of a current type to a completely faired windshield. The results show that the drag of windshields of the same frontal area, on airplanes of small to medium size, may account for 15% of the airplane drag or may be reduced to 1%. Optimum values are given for windshield and tail-fairing lengths; the effect, at various radii is shown. The longitudinal profile of a windshield is shown to be most important and the transverse profile, to be much less important. The effects of retaining strips, of steps for telescoping hoods, and of recessed windows are determined. The results show that the drag of transport-type windshields may account for 21% of the fuselage drag or may be reduced ...
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Profile-Drag Investigation of an Airplane Wing Equipped with Rubber Inflatable De-Icer

Profile-Drag Investigation of an Airplane Wing Equipped with Rubber Inflatable De-Icer

Date: December 1, 1939
Creator: Rodert, Lewis A. & Jones, Alun R.
Description: The National Advisory Committee for Aeronautics has made profile-drag measurements in flight of a wing which was equipped with a rubber inflatable de-icer and to which various stimulated ice formations were attached. Tuft observations at the stalling speed of the wing with the various drag conditions were made in order to determine the influence on the maximum lift coefficient. The de-icer installation caused an increase of from 10-20% in the profile drag of the plain wing and reduced CL(sub max) about 6%. Simulated ice, when confined to the leading-edge region of the de-icer, had no measurable influence upon the profile drag at the cruising speed. This ice condition, however, reduced the value of CL(sub max) to about three-fourths that of the plain wing. Simulated ice in the form of a ridge along the upper and lower de-icer cap-strips increased the profile drag by about 360% at cruising speed. This condition reduced the CL(sub max) to approximately one-half that of the plain wing value.
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Radiator Design and Installation

Radiator Design and Installation

Date: May 1, 1939
Creator: Brevoort, M.J. & Leifer, M.
Description: The fundamental principles of fluid flow, pressure losses, and heat transfer have been presented and analyzed for the case of a smooth tube with fully developed turbulent flow. These equations apply to tubes with large length-diameter ratios where the f1ow is at a high Reynolds Number. The error introduced by using these equations increases as the magnitude of the tube length and the air-flow Reynolds Number approaches the values encountered in modern radiator designs. Accordingly, heat-transfer tests on radiator sections were made and the results are presented in nondimensional form to facilitate their use and for comparison with other heat-transfer data. In addition, pressure losses were measured along smooth tubes of circular, square, and rectangular cross section and the results were also correlated and are presented in nondimensional form. The problem of a radiator design for a particular installation is solved, the experimental heat-transfer and pressure-loss data being used, on a basis of power chargeable to the radiator for form drag, for propelling the weight, and for forcing the air through the radiator. The case of an installation within a wing or an engine nacelle is considered. An illustration of radiator design is carried through for an arbitrary set of ...
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Resume of Present Data on Load Distribution on Slots and Flaps, Special Report

Resume of Present Data on Load Distribution on Slots and Flaps, Special Report

Date: April 1, 1934
Creator: Wenzinger, Carl J.
Description: This report covers a study of the generally available data on load distribution on slots and flaps. The study was made by the National Advisory Committee for Aeronautics at the request of the Material Division, Army Air Corps to furnish information applicable to design criteria for slots and flaps of various types. The data are presented in three main sections: slots (Handley page type), auxiliary airfoils (fixed), and flaps.
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Preliminary Tests of Blowers of Three Designs Operating in Conjunction with a Wing-Duct Cooling System for Radial Engines, Special Report

Preliminary Tests of Blowers of Three Designs Operating in Conjunction with a Wing-Duct Cooling System for Radial Engines, Special Report

Date: June 1, 1939
Creator: Biermann, David & Valentine, E. Floyd
Description: This paper is one of several dealing with methods intended to reduce the drag of present-day radial engine installations and improve the cooling at zero and low air speeds, The present paper describes model wind-tunnel tests of blowers of three designs tested in conjunction with a wing-nacelle combination. The principle of operation involved consists of drawing cooling air into ducts located in the wing root at the point of maximum slipstream velocity, passing the air through the engine baffles from rear to front, and exhausting the air through an annular slot located between the propeller and the engine with the aid of a blower mounted on the spinner. The test apparatus consisted essentially of a stub wing having a 5-foot chord and a 15-foot span, an engine nacelle of 20 inches diameter enclosing a 25-horsepower electric motor, and three blowers mounted on propeller spinners. Two of the blowers utilize centrifugal force while the other uses the lift from airfoils to force the air out radially through the exit slot. Maximum efficiencies of over 70 percent were obtained for the system as a whole. Pressures were measured over the entire flight range which were in excess of those necessary to cool ...
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