Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “THROTTLING”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 505 records · Page 28
All sourcesNASA NTRSDOE OSTI
NASA NTRS1921

Airplane crashes: engine troubles : a possible explanation

The aim was to bring attention to what might be the cause of some aircraft accidents for which there was no satisfactory explanation. The author notes that in testing aircraft accidents at the Bureau of Standards, it happened frequently that the engine performance became erratic when the temperature of the air entering the carburetor was between 0 C and 20 C. Investigation revealed the trouble to have been caused by the formation and collection of snow somewhere between the entrance to the carburetor and the manifold, probably at the throttle. Proof scarcely less convincing was obtained during engine tests. The results of such engine tests are described. Granting that the loss of power and the sudden increases in power were caused by the condensation of moisture from the air and the subsequent formation of snow, two solutions proved effective. The removal of the moisture or an increase in temperature cured the problem.

ENGINE TROUBLE↗
NASA NTRS1922

The Use of Multiplied Pressures for Automatic Altitude Adjustments

The efficient performance of an airplane requires that certain adjustments be made as the density of the air through which the airplane passes changes. The safety of the over-dimensioned aircraft engine depends upon careful manipulation of spark advance and throttle opening and a proper control of a variable pitch propeller, if the maximum performance of the supercharged engine is to be obtained. It is evident that there is a real need for satisfactory devices to make such adjustments automatically. Discussed here is a method of automatic compensation which deserves consideration in the design of such devices. Existing schemes for automatic compensation all depend upon some contrivance which functions primarily because of changes in atmospheric pressure. In these devices a leak in the supposedly tight chamber means utter failure. The elimination of this source of danger is one of the aims of the method of altitude compensation described here. The change suggested is to make the source of operation the difference between atmospheric pressure and some multiple of atmospheric pressure instead of the difference between the atmospheric pressure and that of the gas confined in a tight chamber. The design of a device based on this method of altitude compensation is given.

Sparrow, Stanwood S↗
NASA NTRS1922

The "Universal propeller": built by Paragon Engineers, Inc., Baltimore, Md

At the request of the N.A.C.A. the "Universal Propeller" was operated and explained by the inventor, Mr. Spencer Heath, for the purpose of demonstrating the following features of design: 1) Elimination of continuously running gears, collars or bearings in the pitch control mechanism; 2) The use of engine power in place of manual labor in changing blade angle; 3) The absence of any structural limitation to the range of blade angles available and the possibility of limiting the blade travel between any two predetermined extreme positions; 4) Continuous indication on the instrument board of the blade position; 5) Automatic throttling of the engine while the propeller is passing through the position of neutral pitch.

PROPELLERS, CONTROLLABLE - PITCH↗
NASA NTRS1931

Penetration and Duration of Fuel Sprays from a Pump Injection System

High-speed motion pictures were taken of individual fuel sprays from a pump injection system. The changes in the spray-tip penetration with changes in the pump speed, injection-valve opening and closing pressures, discharge-orifice area, injection-tube length and diameter, and pump throttle setting were measured. In addition, the effects of the variables on the time lag and duration of injection can be controlled by the dimensions of the injection tube, the area of the discharge orifice, and the injection-valve opening and closing pressures.

Rothrock, A M↗
NASA NTRS1932

The Use of Large Valve Overlap in Scavenging a Supercharged Spark-ignition Engine Using Fuel Injection

This investigation was conducted to determine the effect of more complete scavenging on the full throttle power and the fuel consumption of a four-stroke-cycle engine. The NACA single-cylinder universal test engine equipped with both a fuel-injection system and a carburetor was used. The engine was scavenged by using a large valve overlap and maintaining a pressure in the inlet manifold of 2 inches of mercury above atmospheric. The maximum valve overlap used was 112 degrees. Tests were conducted for a range of compression ratios from 5.5 to 8.5. Except for variable speed tests, all tests were conducted at an engine speed of 1,500 r.p.m. The results of the tests show that the clearance volume of an engine can be scavenged by using a large valve overlap and about 2 to 5 inches of mercury pressure difference between the inlet and exhaust valve. With a fuel-injection system when the clearance volume was scavenged, a b.m.e.p. of over 185 pounds per square inch and a fuel consumption of 9.45 pound per brake horsepower per hour were obtained with a 6.5 compression ratio. An increase of approximately 10 pounds per square inch b.m.e.p. was obtained with a fuel-injection system over that with a carburetor.

Schey, Oscar W↗
NASA NTRS1932

Comparative Performance of a Powerplus Vane-type Supercharger and an N.A.C.A. Roots-type Supercharger

This report presents the results of tests of a Power plus supercharger and a comparison of its performance with the performance previously obtained with an N.A.C.A. Roots-type supercharger. The Powerplus supercharger is a positive displacement blower of the vane type having mechanically operated vanes, the movement of which is controlled by slots and eccentrics. The supercharger was tested at a range of pressure differences from 0 to 15 inches of mercury and at speeds from 500 to 2,500 r.p.m. The pressure difference across the supercharger was obtained by throttling the intake of a depression tank which was interposed in the air duct between the supercharger and the Durley orifice box used for measuring the air. The results of these tests show that at low pressure differences and at all speeds the power required by the Powerplus supercharger to compress a definite quantity of air per second is considerably higher than that required by the Roots. At pressure differences from 10 to 14 inches of mercury and at speeds over 2,000 r.p.m. the power requirements of the two superchargers are practically the same. At a pressure difference of 15 inches of mercury or greater and at a speed of 2,500 r.p.m. or greater the performance of the Powerplus supercharger is slightly better than that of the Roots. Because the Powerplus supercharger cannot be operated at a speed greater than 3,000 r.p.m. as compared with 7,000 r.p.m. for the Roots, its capacity is approximately one-half that of the Roots for the same bulk. The Powerplus supercharger is more complicated and less reliable than the Roots supercharger.

Schey, Oscar W↗
NASA NTRS1937

Discharge characteristics of a double injection-valve single-pump injection system

The discharge characteristics of two similar injection valves operated by a single-cylinder fuel-injection pump were determined with an apparatus that measured the quantity of fuel discharged from each valve during every 0.5 degrees of pump rotation. It was found that similar discharges took place from the two valves at all pump speeds when the valve-opening pressures, the nozzle-orifice diameters, and the injection-tube lengths were the same for both valves. Under these conditions, the effects of changing the pump speed, the pump throttle setting, or the nozzle orifice diameter were very similar to those occurring with a single-injection valve. By a proper selection of discharge-orifice areas and valve-opening pressures it was possible to obtain a great many combinations of discharge quantities, discharge rates, and injection timings for the two valves. A series of tests using injection tubes of unequal lengths for the two valves showed that under these conditions the injection timing and the fuel quantity discharged from each valve varies widely and erratically with changes in the pump speed.

Lee, Dana W↗
NASA NTRS1951

Investigation of Altitude Starting and Acceleration Characteristics of J47 Turbojet Engine

An investigation was conducted on an axial-flow-compressor type turbojet engine in the NACA Lewis altitude wind tunnel to determine the operational characteristics of several ignition systems, cross-fire tube configurations and fuel systems over a range of simulated flight conditions. The opposite-polarity-type spark plug provided the most satisfactory ignition. Increasing the cross-fire-tube diameter improved intercombustor flame propagation. At high windmilling speeds, accelerations to approximately 6200 rpm could be made at a preset constant throttle position. The use of a variable-area nozzle reduced acceleration time.

IGNITION SYSTEMS↗
NASA NTRS1953

Investigation of acceleration characteristics of a single-spool turbojet engine

Operation of a single-spool turbojet engine with constant exhaust-nozzle area was investigated at one flight condition. Data were obtained by subjecting the engine to approximate-step changes in fuel flow, and the information necessary to show the relations of acceleration to the sensed engine variables was obtained. These data show that maximum acceleration occurred prior to stall and surge. In the low end of the engine-speed range the margin was appreciable; in the high-speed end the margin was smaller but had not been completely defined by these data. Data involving acceleration as a function of speed, fuel flow, turbine-discharge temperature, compressor-discharge pressure, and thrust have been presented and an effort has been made to show how a basic control system could be improved by addition of an override in which the acceleration characteristic is used not only to prevent the engine from entering the surge region but also to obtain acceleration along the maximum acceleration line during throttle bursts.

Oppenheimer, Frank L↗
NASA NTRS1951

Experimental Investigation of a 16-inch Impulse-type Supersonic-compressor Rotor

Performance data and characteristics of a 16-inch impulse-type supersonic-compressor rotor are presented. The experimental portion of this investigation was conducted in Freon-12. A peak pressure ratio of 3.6 was obtained with an adiabatic efficiency of 0.80 at design conditions. Performance was continuous from impulse operation, at open throttle, to shock-in-rotor operation at the stall condition.

COMPRESSOR FLOW THEORY AND EXPERIMENT↗
NASA NTRS1921

Comparison of hecter fuel with export aviation gasoline

Among the fuels which will operate at compression ratios up to at least 8.0 without preignition or "pinking" is hecter fuel, whence a careful determination of its performance is of importance. For the test data presented in this report the hecter fuel used was a mixture of 30 per cent benzol and 70 per cent cyclohexane, having a low freezing point, and distilling from first drop to 90 per cent at nearly a constant temperature, about 20 degrees c. below the average distillation temperature ("mean volatility") of the x gasoline (export grade). The results of these experiments show that the power developed by hecter fuel is the same as that developed by export aviation gasoline at about 1,800 r.p.m. at all altitudes. At lower speeds differences in the power developed by the fuels become evident. Comparisons at ground level were omitted to avoid any possibility of damaging the engine by operating with open throttle on gasoline at so high a compression. The fuel consumption per unit power based on weight, not volume, averaged more than 10 per cent greater with hecter than with x gasoline. The thermal efficiency of the engine when using hecter is less than when using gasoline, particularly at higher speeds. A generalization of the difference for all altitudes and speeds being 8 per cent. A general deduction from these facts is that more hecter is exhausted unburnt. Hecter can withstand high compression pressures and temperature without preignition. (author)

Dickinson, H C↗
NASA NTRS1921

General Theory of the Steady Motion of an Airplane

The writer points out briefly the history of the method proposed for the study of steady motion of an airplane, which is different from other methods now used. M. Paul Painleve has shown how convenient the drag-lift curve was for the study of airplane steady motion. The author later added to the drift-lift curve the curve called the "speed curve" which permits a direct checking of the speed of the airplane under all flying conditions. But the speed curve was plotted in the same quadrant as the drag-lift curve. Later, with the progressive development of aeronautical science, and with the continually increasing knowledge concerning engines and propellers, the author was brought to add the three other quadrants to the original quadrant, and thus was obtained the steady motion chart which is described in detail in this report. This charts permits one to read directly for a given airplane its horizontal speed at any altitude, its rate of climb at any altitude, its apparent inclination to the horizon at any moment, its ceiling, its propeller thrust, revolutions, efficiency, and power absorbed, that is the complete set of quantities involved in the subject, and to follow the variations of all these quantities both for variable altitude and for variable throttle. The chart also permits one to follow the variation of all of the above in flight as a function of the lift coefficient and of the speed. The author also discusses the interaction of the airplane and propeller through the slipstream and the question of the properties of the engine-propeller system and its dependence upon the properties of the engine considered alone and of the propeller considered alone. There is also a discussion of a standard atmosphere.

De Bothezat, George↗
NASA NTRS1921

Performance of a Liberty 12 airplane engine

In cooperation with the Engineering Division of the Air Service of the United States Army, a Liberty-12 engine has been tested at the Bureau of Standards. The program of tests was planned to yield that information considered most important in determining the value of the engine for aviation. Full power runs were made at the ground, at 25,000 feet, and at several intermediate altitudes. To determine the mechanical efficiency of the engine, friction horsepower was measured at the ground and at 15,000 feet. As a basis for predicting engine performance with a propeller, a series of tests was made in which the dynamometer load and engine throttle were adjusted at each speed to simulate the engine load which would be imposed at that speed by a propeller operating under normal full load at 1,700 r.p.m. Among the quantities calculated from the test measurements are: brake horsepower; break mean effective pressure; fuel consumption; mixture ratio; mechanical, thermal, and volumetric efficiency; and the percentage of the heat in the fuel appearing in the jacket water and in the exhaust. Jacket water temperature, oil temperature, manifold pressure, etc., are recorded to show the conditions under which the test was made.

Sparrow, S W↗
NASA NTRS1923

Performance of Maybach 300-horsepower airplane engine

This report contains the results of a test made upon a Maybach Engine in the altitude chamber of the Bureau of Standards, where controlled conditions of temperature and pressure can be made the same as those of the desired altitude. The results of this test lead to the following conclusions: from the standpoint of thermal efficiency the full-load performance of the engine is excellent at densities corresponding to altitudes up to and including 15,000 feet. The brake mean effective pressure is rather low even at wide-open throttle. This tends to give a high weight per horsepower, in as much as the weight of many engine parts is governed by the size rather than the power of the engine. At part load the thermal efficiency of the engine is low. Judged on a basis of performance the engine's chief claim to interest would appear to lie in the carburetor design, which is largely responsible excellent full-load efficiency and for its poor part-load efficiency.

Sparrow, S W↗
NASA NTRS1923

Performance of B. M. W. 185-Horsepower Airplane Engine

This report deals with the results of a test made upon a B. M. W. Engine in the altitude chamber of the Bureau of Standards, where controlled conditions of temperature and pressure can be made to simulate those of the desired altitude. A remarkably low value of fuel consumption - 041 per B. H. P. hour - is obtained at 1,200 revolutions per minute at an air density of 0.064 pound per cubic foot and a brake thermal efficiency of 33 per cent and an indicated efficiency of 37 per cent at the above speed and density. In spite of the fact that the carburetor adjustment does not permit the air-fuel ratio of maximum economy to be obtained at air densities lower than 0.064, the economy is superior to most engines tested thus far, even at a density lower than 0.064, the economies superior to most engines tested thus far, even at a density (0.03) corresponding to an altitude of 25,000 feet. The brake mean effective pressure even at full throttle is rather low. Since the weight of much of the engine is governed more by its piston displacement than by the power developed, a decreased mean effective pressure usually necessitates increased weight per horsepower. The altitude performance of the engine is, in general, excellent, and its low fuel consumption is the outstanding feature of merit.

Sparrow, S W↗
NASA NTRS1924

A study of longitudinal dynamic stability in flight

This investigation was carried out by the aerodynamic staff of the National Advisory Committee for Aeronautics for the purpose of studying experimentally the longitudinal dynamic stability of airplanes in flight. The airplanes selected for this purpose were a standard rigged VE-7 advanced-training airplane and a JN4H with special tail surfaces. The airplanes were caused to oscillate by means of the elevator, then the longitudinal control was either locked or kept free while the oscillation died out. The magnitude of the oscillation was recorded either by a kymograph or an airspeed meter. The results show that the engine speed has as much effect on the period and damping as the airspeed, and that, contrary to theory as developed for small oscillations, the damping decreased at the higher airspeeds with closed throttle.

Norton, F H↗
NASA NTRS1925

Investigation of Slipstream Velocity

These experiments were made at the request of the Bureau of Aeronautics, Navy Department, to investigate the velocity of the air in the slipstream in horizontal and climbing flight to determine the form of expression giving the slipstream velocity in terms of the airspeed of the airplane. The method used consisted in flying the airplane both on a level course and in climb at full throttle and measuring the slipstream velocity at seven points in the slipstream for the whole speed range of the airplane in both conditions. In general the results show that for both condition, horizontal and climbing flights, the slipstream velocity v subscript 3 and airspeed v can be represented by straight lines and consequently the equations are of the form: v subscript s = mv+b where m and b are constant. (author)

Crowley, J W , Jr↗
NASA NTRS1928

Friction of Aviation Engines

The first portion of this report discusses measurements of friction made in the altitude laboratory of the Bureau of Standards between 1920 and 1926 under research authorization of the National Advisory Committee for Aeronautics. These are discussed with reference to the influence of speed, barometric pressure, jacket-water temperature, and throttle opening upon the friction of aviation engines. The second section of the report deals with measurements of the friction of a group of pistons differing from each other in a single respect, such as length, clearance, area of thrust face, location of thrust face, etc. Results obtained with each type of piston are discussed and attention is directed particularly to the fact that the friction chargeable to piston rings depends upon piston design as well as upon ring design. This is attributed to the effect of the rings upon the thickness and distribution of the oil film which in turn affects the friction of the piston to an extent which depends upon its design.

Sparrow, S W↗