National Advisory Committee for Aeronautics (NACA) - 76 Matching Results

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Effect of Compressibility on Pressure Distribution over an Airfoil with a Slotted Frise Aileron

Description: Pressure distribution measurements were made over an airfoil with slotted Frise aileron up to 0.76 Mach at various angles of attack and aileron defections. Section characteristics were determined from these pressure data. Results indicated loss of aileron rolling power for deflections ranging from -12 Degrees to -19 Degrees. High stick forces for non-differential deflections incurred at high speed, which were due to overbalancing tendency of up-moving aileron, may precipitate serious control difficulties. Detailed results are presented graphically.
Date: July 1, 1944
Creator: Luoma, Avro A
Partner: UNT Libraries Government Documents Department

Knock-limited performance of several internal coolants

Description: The effect of internal cooling on the knock-limited performance of an-f-28 fuel was investigated in a CFR engine, and the following internal coolants were used: (1) water, (2), methyl alcohol-water mixture, (3) ammonia-methyl alcohol-water mixture, (4) monomethylamine-water mixture, (5) dimethylamine-water mixture, and (6) trimethylamine-water mixture. Tests were run at inlet-air temperatures of 150 degrees and 250 degrees F. to indicate the temperature sensitivity of the internal-coolant solutions.
Date: February 1, 1944
Creator: Bellman, Donald R. & Evvard, John C.
Partner: UNT Libraries Government Documents Department

Preignition-limited performance of several fuels

Description: Preignition-limited performance data were obtained on a supercharged CFR engine at two sets of operating conditions over a wide range of fuel-air ratios to determine the preignition characteristics for the following five fuels: s-3 reference fuel, s-3 plus 4 ml. tel per gallon, afd-33(140-p), benzene, and diisobutylene. Maximum thermal-plug temperatures at constant intake-air pressures were also determined to correlate the preignition characteristics of each fuel with its ability to increase general engine-temperature levels. Additional runs were made to compare the preignition-limited performance of triptane, triptane plus 4 ml. tel per gallon, and an-f-28r fuel.
Date: October 1, 1944
Creator: Male, Donald W. & Evvard, John C.
Partner: UNT Libraries Government Documents Department

Comparative tests of the strength and tightness of commercial flush rivets of one type and NACA flush rivets in machine-countersunk and counterpunched joints

Description: Report discusses an investigation that was conducted to compare the strength and tightness of machine-countersunk flush-riveted joints assembled with NACA flush rivets and a type of commercial flush rivet. A comparison was also generated between the strength and tightness of counterpunched flush-riveted joints assembled with the same types of rivet. NACA's flush-riveted joints tended to be stronger and tighter than the commercial joints.
Date: February 1, 1944
Creator: Mandel, Merven W.
Partner: UNT Libraries Government Documents Department

Some Notes on the Determination of the Stick-Free Neutral Point from Wind-Tunnel Data

Description: Two graphical methods are presented for determining the stick-free neutral point, and they are extensions of the methods commonly used to determine the stick-free neutral point. A mathematical formula for computing the stick-free neutral point is also given. These methods may be applied to determine approximately the increase in tail size necessary to shift the neutral point (stick fixed or free) to any desired location on an airplane having inadequate longitudinal stability.
Date: February 1, 1944
Creator: Schuldenfrei, Marvin
Partner: UNT Libraries Government Documents Department

Comparative Results of Tests on Several Different Types of Nozzles

Description: This paper presents the results of tests conducted to determine the effect of the constructional elements of a Laval nozzle on the velocity and pressure distribution and the magnitude of the reaction force of the jet. The effect was studied of the shapes of the entrance section of the nozzle and three types of divergent sections: namely, straight cone, conoidal with cylindrical and piece and diffuser obtained computationally by a graphical method due to Professor F. I. Frankle. The effect of the divergence angle of the nozzle on the jet reaction was also investigated. The results of the investigation showed that the shape of the generator of the inner surface of the entrance part of the nozzle essentially has no effect on the character of the flow and on the reaction. The nozzle that was obtained by graphical computation assured the possibility of obtaining a flow for which the velocity of all the gas particles is parallel to the axis of symmetry of the nozzle, the reaction being on the average 2 to 3 percent greater than for the usual conical nozzle under the same conditions, For the conical nozzle the maximum reaction was obtained for a cone angle of 25deg to 27deg. At the end of this paper a sample computation is given by the graphical method. The tests were started at the beginning of 1936 and this paper was written at the same time.
Date: May 1, 1944
Creator: Kisenko, M. S.
Partner: UNT Libraries Government Documents Department

Methods of Stress Calculation in Rotating Disks

Description: The paper describes nethods of computing the stresses in disks of a given profile as well as methods of choosing the disk profiles for a given stress distribution for turhines, turbo blowers, and so forth. A new method of in tegrating the differential equations of Stodola leads to a simplification of the computation for disks of hyperbolic profile.
Date: September 1, 1944
Creator: Tumarkin, S.
Partner: UNT Libraries Government Documents Department

DVL Angular Velocity Recorder

Description: In many studies, especially of nonstationary flight motion, it is necessary to determine the angular velocities at which the airplane rotates about its various axes. The three-component recorder is designed to serve this purpose. If the angular velocity for one flight attitude is known, other important quantities can be derived from its time rate of change, such as the angular acceleration by differentiations, or - by integration - the angles of position of the airplane - that is, the angles formed by the airplane axes with the axis direction presented at the instant of the beginning of the motion that is to be investigated.
Date: August 1, 1944
Creator: Liebe, Wolfgang
Partner: UNT Libraries Government Documents Department

The Surface Structure of Ground Metal Crystals

Description: The changes produced on metallic surfaces as a result of grinding and polishing are not as yet fully understood. Undoubtedly there is some more or less marked change in the crystal structure, at least, in the top layer. Hereby a diffusion of separated crystal particles may be involved, or, on plastic material, the formation of a layer in greatly deformed state, with possible recrystallization in certain conditions. Czochralski verified the existence of such a layer on tin micro-sections by successive observations of the texture after repeated etching; while Thomassen established, roentgenographically by means of the Debye-Scherrer method, the existence of diffused crystal fractions on the surface of ground and polished tin bars, which he had already observed after turning (on the lathe). (Thickness of this layer - 0.07 mm). Whether this layer borders direct on the undamaged base material or whether deformed intermediate layers form the transition, nothing is known. One observation ty Sachs and Shoji simply states that after the turning of an alpha-brass crystal the disturbance starting from the surface, penetrates fairly deep (approx. 1 mm) into the crystal (proof by recrystallization at 750 C).
Date: August 1, 1944
Creator: Boas, W. & Schmid, E.
Partner: UNT Libraries Government Documents Department

Heat Transfer in a Turbulent Liquid or Gas Stream

Description: The,theory of heat.transfer from a solid body to a liquid stream could he presented previously** only with limiting assumptions about the movement of the fluid (potential flow, laminar frictional flow). (See references 1, 2, and 3). For turbulent flow, the most important practical case, the previous theoretical considerations did not go beyond dimensionless formulas and certain conclusions as to the analogy between the friction factor and the unit thermal conductance, (See references 4, 5, 6, and 7,) In order to obtain numerical results, an experimental treatment of the problem was resorted to, which gave rise to numerous investigations because of the importance of this problem in many branches of technology. However, the results of these investigations frequently deviate from one another. The experimental results are especially dependent upon the overall dimensions and the specific proportions of the equipment. In the present work, the attempt will be made to develop systematically the theory of the heat transfer and of the dependence of the unit thermal conductance upon shape and dimensions, using as a basis the velocity distribution for turbulent flow set up by Prandtl and Von Karman.
Date: October 1, 1944
Creator: Latzko, H.
Partner: UNT Libraries Government Documents Department

Determination of the Actual Contact Surface of a Brush Contact

Description: The number of partial contact surfaces of a brush-ring contact is measured by means of a statistical method. The particular brush is fitted with wicks - that is, insulated and cemented cylinders of brush material, terminating in the brush surface. The number of partial contact surfaces can be computed from the length of the rest periods in which such wicks remain without current. Resistance measurements enable the determination of the size of the contact surfaces. The pressure in the actual contact surface of a recently bedded brush is found to be not much lower than the Brinell hardness of the brush.
Date: August 1, 1944
Creator: Holm, Ragnar
Partner: UNT Libraries Government Documents Department

Determination of the Stresses Produced by the Landing Impact in the Bulkheads of a Seaplane Bottom

Description: The present report deals with the determination of the impact stresses in the bulkhead floors of a seaplane bottom. The dynamic problem is solved on the assumption of a certain elastic system, the floor being assumed as a weightless elastic beam with concentrated masses at the ends (due to the mass of the float) and with a spring which replaces the elastic action of the keel in the center. The distributed load on the floor is that due to the hydrodynamic force acting over a certain portion of the bottom. The pressure distribution over the width of the float is assumed to follow the Wagner law. The formulas given for the maximum bending moment are derived on the assumption that the keel is relatively elastic, in which case it can be shown that at each instant of time the maximum bending moment is at the point of juncture of the floor with the keel. The bending moment at this point is a function of the half width of the wetted surface c and reaches its maximum value when c is approximately equal to b/2 where b is the half width of the float. In general, however, for computing the bending moment the values of the bending moment at the keel for certain values of c are determined and a curve is drawn. The illustrative sample computation gave for the stresses a result approximately equal to that obtained by the conventional factory computation.
Date: January 1, 1944
Creator: Darevsky, V. M.
Partner: UNT Libraries Government Documents Department

Gas Jets

Description: A brief summary of the contents of this paper is presented here. In part I the differential equations of the problem of a gas flow in two dimensions is derived and the particular integrals by which the problem on jets is solved are given. Use is made of the same independent variables as Molenbroek used, but it is found to be more suitable to consider other functions. The stream function and velocity potential corresponding to the problem are given in the form of series. The investigation on the convergence of these series in connection with certain properties of the functions entering them forms the subject of part II. In part III the problem of the outflow of a gas from an infinite vessel with plane walls is solved. In part IV the impact of a gas jet on a plate is considered and the limiting case where the jet expands to infinity changing into a gas flow is taken up in more detail. This also solved the equivalent problem of the resistance of a gaseous medium to the motion of a plate. Finally, in part V, an approximate method is presented that permits a simpler solution of the problem of jet flows in the case where the velocities of the gas (velocities of the particles in the gas) are not very large.
Date: August 1, 1944
Creator: Chaplygin, S.
Partner: UNT Libraries Government Documents Department

The Effect of Piston-Head Temperature on Knock-Limited Power

Description: To determine the effect of piston-head temperature on knock-limited power. Tests were made in a supercharged CFR engine over a range of fuel-air ratios from 0.055 to 0.120, using S-3 reference fuel, AN-F-28, Amendment-2, aviation gasoline, and AN-F-28 plus 2 percent xylidines by weight. Tests were run at a compression ratio of 7.0 with inlet-air temperatures of 150 F and 250 F and at a compression ratio of 8.0 with an inlet-air temperature of 250 F. All other engine conditions were held constant. The piston-head temperature was varied by circulation of oil through passages in the crown of a liquid-cooled piston. This method of piston cooling decreased the piston-head temperature about 80 F. The data are not intended to constitute a recommendation as to the advisability of piston cooling in practice.
Date: July 1, 1944
Creator: Imming, Harry S.
Partner: UNT Libraries Government Documents Department

The Frictional Force with Respect to the Actual Contact Surface

Description: Hardy's statement that the frictional force is largely adhesion, and to a lesser extent, deformation energy is proved by a simple experiment. The actual contact surface of sliding contacts and hence the friction per unit of contact surface was determined in several cases. It was found for contacts in normal atmosphere to be about one-third t-one-half as high as the macroscopic tearing strength of the softest contact link, while contacts annealed in vacuum and then tested, disclosed frictional forces which are greater than the macroscopic strength.
Date: August 1, 1944
Creator: Holm, Ragnar
Partner: UNT Libraries Government Documents Department

The Wall Interference of a Wind Tunnel of Elliptic Cross Section

Description: The wall interference is obtained for a wind tunnel of elliptic section for the two cases of closed and open working sections. The approximate and exact methods used gave results in practically good agreement. Corresponding to the result given by Glauert for the case of the closed rectangular section, the interference is found to be a minimum for a ratio of minor to major axis of 1:square root of 6 This, however, is true only for the case where the span of the airfoil is small in comparison with the width of the tunnel. For a longer airfoil the favorable ellipse is flatter. In the case of the open working section the circular shape gives the minimum interference.
Date: November 1, 1944
Creator: Tani, Itiro & Sanuki, Matao
Partner: UNT Libraries Government Documents Department

Researches on the Piston Ring

Description: In internal combustion engines, steam engines, air compressors, and so forth, the piston ring plays an important role. Especially, the recent development of Diesel engines which require a high compression pressure for their working, makes, nowadays, the packing action of the piston ring far more important than ever. Though a number of papers have been published in regard to researches on the problem of the piston ring, none has yet dealt with an exact measurement of pressure exerted on the cylinder wall at any given point of the ring. The only paper that can be traced on this subject so far is Mr. Nakagawa's report on the determination of the relative distribution of pressure on the cylinder wall, but the measuring method adopted therein appears to need further consideration. No exact idea has yet been obtained as to how the obturation of gas between the piston and cylinder, the frictional resistance of the piston, and the wear of the cylinder wall are affected by the intensity and the distribution of the radial pressure of the piston ring. Consequently, the author has endeavored, by employing an apparatus of his own invention, to get an exact determination of the pressure distribution of the piston ring. By means of a newly devised ring tester, to which piezoelectricity of quartz was applied, the distribution of the radial pressure of many sample rings on the market was accurately determined. Since many famous piston rings show very irregular pressure distribution, the author investigated and achieved a manufacturing process of the piston ring which will exert uniform pressure on the cylinder wall. Temperature effects on the configuration and on the mean spring power have also been studied. Further, the tests were performed to ascertain how the gas tightness of the piston ring may be affected by the ...
Date: February 1, 1944
Creator: Ehihara, Keikiti
Partner: UNT Libraries Government Documents Department

The Theory of a Free Jet of a Compressible Gas

Description: In the present report the theory of free turbulence propagation and the boundary layer theory are developed for a plane-parallel free stream of a compressible fluid. In constructing the theory use was made of the turbulence hypothesis by Taylor (transport of vorticity) which gives best agreement with test results for problems involving heat transfer in free jets.
Date: March 1, 1944
Creator: Abramovich, G. N.
Partner: UNT Libraries Government Documents Department

An Experimental Investigation of the Flow of Air in a Flat Broadening Channel

Description: The wide use of diffusers, in various fields of technology, has resulted in several experimental projects to study the action and design of diffusers. Most of the projects dealt with steam (steam turbine nozzles). But diffusers have other applications - that is, ventilators, smoke ducts, air coolers, refrigeration, drying, and so forth. At present there is another application for diffusers in wind-tunnel design. Because of higher requirements and increased power of such installations more attention must be paid to the correctness of work and the decrease in losses due to every section of the tunnel. A diffuser, being one of the component parts of a tunnel , can in the event of faulty construction introduce considerable losses. Therefore, in the design of the new CAHI wind tunnel, it was suggested that an experimental study of diffusers be made, with a view to applying the results to wind tunnels. The experiments conducted by K. K. Baulin in the laboratories of CAHI upon models of diffusers of different cross sections, lengths, and angles of divergence, were a valuable source of experimental data. They were of no help, however, in reaching any conclusion regarding the optimum shape because of the complexity and diversity of the factors which all appeared simultaneously, thereby precluding the.study of the effects of any one factor separately. On the suggestion of the director of the CAHI,Prof. B. N. Ureff, it was decided to experiment on a two-dimensional diffuser model and determine the effect, of the angle of divergence. The author is acquainted with two experimental projects of like nature: the first was conducted with water, the other with air. The first of these works, although containing a wealth of experimental data, does not indicate the nature of flow or its relation to the angle of divergence. The second work ...
Date: January 1, 1944
Creator: Vedernikoff, A. N.
Partner: UNT Libraries Government Documents Department