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1955-01-01
Technical Paper
550254
Joern Schmey, Ralph M. Guerke
ORIGINS of propeller noise and possible means for its reduction both within and external to turboprop aircraft are discussed here. Decreasing the tip speed and increasing the number of blades of turboprop propellers result in quieter performance within the aircraft but with a heavy weight penalty. Changes in certain aircraft design parameters, such as increasing clearance between fuselage wall and propeller tips, can also reduce internal noise and vibration. Improvements in external turboprop noise can be achieved by use of quiet-type propellers, increased rate and angle of climb, preferential runways, adequate airport zoning, and sound-dissipating foliage and ground covers.
1955-01-01
Technical Paper
550265
F. B. Stulen
VARIOUS structural problems encountered in the design of high-speed turboprop propellers are discussed in this paper. Formulas for a number of design factors are also given here. These include: 1. Blade efficiency. 2. Power capacity. 3. Advance/diameter ratio. 4. Limiting tip speed. 5. Periodic lift. 6. Propeller normal force and moment. The paper also describes two types of vibration occurring with turboprop installations: 1. First-ordered aerodynamically excited vibration. 2. Subsonic stall flutter. The author shows how these vibrations may be accurately predicted and controlled by proper design of the propeller blades.
1955-01-01
Technical Paper
550269
Robert Meagher, R. L. Johnson, K. G. Parthemore
A BETTER knowledge of the nature and causes of preignition and of its frequency during normal engine operation has been obtained by instrumenting a 9/1-compression-ratio engine on a test stand and an engine in an automobile with rate of change of pressure pickups. Photographic records of the oscilloscope traces produced by this instrumentation have enabled the determination of: 1. The relative tendency for preignition or postignition to occur and the relation of these phenomena to engine or car operating conditions. 2. The physical causes of the noises accompanying the several types of preignition. 3. The effect of retarded spark timing on deposit-induced preignition. 4. The significance of the “key-off” method of fuel rating.
1955-01-01
Technical Paper
550294
David C. Apps, George M.Vanator
TIRE thump has gained prominence as passenger cars have become quieter and roads smoother. Studies at the CM Proving Ground dating back to 1940 have shown thump to be a very complex example of the simple phenomenon that combining two closely spaced frequency components will produce a certain beat. Here the authors detail what has been learned about the physical characteristics of car and tire which go into producing thump of various frequencies and loudnesses. They also describe a newly developed portable instrument which measures the depth of modulation of the beat between two frequencies, thus serving as a uniform standard of tire thump severity.
1955-01-01
Technical Paper
550177
G. E. SANDERSON
1955-01-01
Technical Paper
550186
CHARLES B. BRAHM
1955-01-01
Technical Paper
550127
LEWIS C. KIBBEE
1955-01-01
Technical Paper
550046
S. R. PRANCE
1955-01-01
Technical Paper
550073
W. H. SKIDMORE
SUMMARY This paper is based on a prior paper by the same author entitled “Fragility Rating For Aircraft Equipment”. The analogy between accelerations caused by vibration and shock is discussed. Testing to establish a fragility rating is discussed and a rating is established for a Klystron based upon tests discussed in a companion paper. Comparative fragility data is presented, showing a wide scope of fragility, size, weight and loading.
1955-01-01
Technical Paper
550070
JOHN CAMMARATA, VINCENT ATALESE
1955-01-01
Technical Paper
550072
J. T. MDLLER
SUMMARY This paper describes the procedure used to determine vibration and shock response characteristics of a klystron. Suggestions to use these data as a basis for a proposed fragility rating.
1955-01-01
Technical Paper
550066
R. H. BOLT
1955-01-01
Technical Paper
550064
KARL D. SWARTZEL, MURRAY KAMRASS
Analysis of the effects of noise on the activities of human beings is usually difficult and uncertain. Recently developed means of evaluating these effects are reviewed. The analysis hinges on the use of the “Speech Interference Level”, a nearly non-subjective criterion which is particularly useful. Calculations based on measurements of noise levels near a J-47 turbojet engine, and on recently collected data for sound attenuation in the atmosphere are used as examples. Data are presented in a novel form utilizing overlays to show the ground intersection of equal speech interference surfaces when a hypothetical airplane is flying at specified altitudes. With a map of appropriate scale, the overlays may be used to study the effect of such flights on any ground area. The data are also presented in the form of hemispherical domes or igloos of specified Speech Interference Level around a point on the ground. Assumptions are described and discussed.
1954-10-01
Magazine
1954-09-01
Magazine
1954-04-01
Magazine
1954-01-01
Technical Paper
540285
John M. Tyler, Edward C. Perry
AN analysis of jet engine noise as a function of jet engine design characteristics is presented in this paper along with some thoughts as to possible means for reducing the noise of jet transports for the future. The authors present a summary of (a) scale-model noise work, (b) full-scale jet engine noise measurements in test cells and free field, and (c) a discussion of information gleaned from comparisons of scale-model work with full-scale engine work. This paper received the Wright Brothers Medal for 1954.
1954-01-01
Technical Paper
540230
D.B. Callaway
RESULTS of an Armour Research Foundation program, promoted by ATA interest in truck exhaust noise problems, are described here. It is shown that exhaust-noise measurements can be made using an octave band analyzer, and values thus obtained agree quite well with listening tests. Highway truck noises are recorded on magnetic tape, which is then fed into the analyzer at leisure. Test-stand measurements, however, give good results only when the exhaust is the main source of truck noise.
1954-01-01
Technical Paper
540061
L. H. FRAILING
1954-01-01
Technical Paper
540062
M. KAMINS, W. B. LOVE
1954-01-01
Technical Paper
540063
ROBERT J. SAXON
1954-01-01
Technical Paper
540064
R. R. PETERSON
1954-01-01
Technical Paper
540045
FRED M. GLASS
1954-01-01
Technical Paper
540144
W. H. SKIDMORE
Summary Some things are more fragile than others. It seems possible to classify things according to some fragility index just as one might classify by color, by weight or by any other common sorting characteristic. Such an index or rating would be extremely useful to packaging engineers and depending upon its nature and accuracy, might be interesting and useful to design engineers. Based on masses mounted on springs, it is possible to calculate useful values of numbers of “g's” and undamped periods for things having simple systems, and a fragility rating composed of these two components is proposed. To obtain this rating experimentally on more complex assemblies may appear costly although economies might still be effected in some broader aspects to justify destructive testing. This paper also poses some of the problems attendent to the determination and use of such a rating.
1954-01-01
Technical Paper
540156
F. B. STULEN
1953-10-01
Magazine
1953-01-01
Technical Paper
530263
M.C. Turkish
THE author shows how the success of a valve-spring design is intrinsically related to both the cam design and the valve gear dynamics obtained at high engine speeds. Good valve gear dynamics, which is characterized by minimum vibration, he says, minimizes hydraulic lifter pump-up tendency and greatly simplifies the job of making a satisfactory spring design. He shows that the use of the smooth-acceleration curve is very helpful in producing good valve gear dynamics, and that it is to be recommended over other types. The author also discusses the use of dual springs and cyclo-pelting and presetting of springs. Discussion of this and other papers on “Valve Gear Problems in Modern Overhead-Valve Engines” starts on page 714.
1953-01-01
Technical Paper
530168
E. V. Murphree, A. R. Cunningham, J. P. Haworth, A. F. Kaulakis
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