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The N.A.C.A. apparatus for studying the formation and combustion of fuel sprays and the results from preliminary tests

Description: Described here is an apparatus for studying the formation and combustion of fuel sprays under conditions closely simulating those in a high speed compression-ignition engine. The apparatus consists of a single-cylinder modified test engine, a fuel injection system so designed that a single charge of fuel can be injected into the combustion chamber, an electric driving motor, and a high-speed photographic apparatus. The cylinder head of the engine has a vertical disk form of combustion chamber whose sides are glass windows. When the fuel is injected into the combustion chamber, motion pictures at the rate of 2000 per second are taken of the spray formation by means of spark discharges. When combustion takes place, the light of combustion is recorded on the same photographic film as the spray photographs. Included here are the results of some tests to determine the effect of air temperature, air flow, and nozzle design on the spray formation. The results show that the compression temperature has little effect on the penetration of the fuel spray, but does not affect the dispersion, that air velocities of about 300 feet per second are necessary to destroy the core of the spray, and that the effect of air flow on the spray is controlled to a certain extent by the design of the injection nozzle. The results on the combustion of the spray show that when ignition does not take place until after spray cut-off, the ignition may start almost simultaneously throughout the combustion chamber or at different points throughout the chamber. When ignition takes place before spray cut-off, the combustion starts around the edge of the spray and then spreads throughout the chamber.
Date: September 1, 1931
Creator: Rothrock, A. M.
Partner: UNT Libraries Government Documents Department

Preliminary tests on the vaporization of fuel sprays

Description: High-speed motion pictures were taken of fuel sprays injected into the combustion chamber of the N.A.C.A. combustion apparatus. Three fuels, ethyl alcohol, gasoline, and fuel oil, which differed considerably in volatility were tested. By maintaining the engine temperature below that required for ignition the spray could be studied from soon after the start of injection until 130 crank degrees later. The results show that the sprays vaporize appreciably so that it is possible for the ignition in high speed compression-ignition engines to take place from the vapor phase.
Date: February 1, 1932
Creator: Rothrock, A. M.
Partner: UNT Libraries Government Documents Department

Effect of high air velocities on the distribution and penetration of a fuel spray

Description: By means of the NACA Spray Photography Equipment high speed moving pictures were taken of the formation and development of fuel sprays from an automatic injection valve. The sprays were injected normal to and counter to air at velocities from 0 to 800 feet per second. The air was at atmosphere temperature and pressure. The results show that high air velocities are an effective means of mixing the fuel spray with the air during injection.
Date: May 1, 1931
Creator: Rothrock, A. M.
Partner: UNT Libraries Government Documents Department

Combustion in a high-speed compression-ignition engine

Description: An investigation conducted to determine the factors which control the combustion in a high-speed compression-ignition engine is presented. Indicator cards were taken with the Farnboro indicator and analyzed according to the tangent method devised by Schweitzer. The analysis show that in a quiescent combustion chamber increasing the time lag of auto-ignition increases the maximum rate of combustion. Increasing the maximum rate of combustion increases the tendency for detonation to occur. The results show that by increasing the air temperature during injection the start of combustion can be forced to take place during injection and so prevent detonation from occurring. It is shown that the rate of fuel injection does not in itself control the rate of combustion.
Date: January 1, 1933
Creator: Rothrock, A. M.
Partner: UNT Libraries Government Documents Department

Pressure fluctuations in a common-rail fuel injection system

Description: This report presents the results of an investigation to determine experimentally the instantaneous pressures at the discharge orifice of a common-rail fuel injection system in which the timing valve and cut-off valve were at some distance from the automatic fuel injection valve, and also to determine the methods by which the pressure fluctuations could be controlled. The results show that pressure wave phenomena occur between the high-pressure reservoir and the discharge orifice, but that these pressure waves can be controlled so as to be advantageous to the injection of the fuel. The results also give data applicable to the design of such an injection system for a high-speed compression-ignition engine.
Date: January 1, 1931
Creator: Rothrock, A. M.
Partner: UNT Libraries Government Documents Department

The NACA apparatus for studying the formation and combustion of fuel sprays and the results from preliminary tests

Description: This report describes the apparatus as designed and constructed at the Langley Memorial Aeronautical Laboratory, for studying the formation and combustion of fuel sprays under conditions closely simulating those occurring in a high-speed compression-ignition engine. The apparatus consists of a single-cylinder modified test engine, a fuel-injection system so designed that a single charge of fuel can be injected into the combustion chamber of the engine, an electric driving motor, and a high-speed photographic apparatus. The cylinder head of the engine has a vertical-disk form of combustion chamber whose sides are glass windows. When the fuel is injected into the combustion chamber, motion pictures at the rate of 2,000 per second are taken of the spray formation by means of spark discharges. When combustion takes place the light of the combustion is recorded on the same photographic film as the spray photographs. The report includes the results of some tests to determine the effect of air temperature, air flow, and nozzle design on the spray formation.
Date: January 1, 1933
Creator: Rothrock, A. M.
Partner: UNT Libraries Government Documents Department

Hydraulics of fuel-injection pumps for compression-ignition engines

Description: Formulas are derived for computing the instantaneous pressures delivered by a fuel pump. The first derivation considers the compressibility of the fuel and the second, the compressibility, elasticity, and inertia of the fuel. The second derivation follows that given by Sass; it is shown to be the more accurate of the two. Additional formulas are given for determining the resistance losses in the injection tube. Experimental data are presented in support of the analyses. The report is concluded with an application of the theory to the design of fuel pump injection systems for which sample calculations are included.
Date: January 1, 1932
Creator: Rothrock, A. M.
Partner: UNT Libraries Government Documents Department

Some characteristics of fuel sprays at low-injection pressures

Description: This report presents the results of tests conducted at the Langley Memorial Aeronautical Laboratory, Langley Field, Va., to determine some of the characteristics of the fuel sprays obtained from an 0.008-inch and a 0.020-inch open nozzle when injection pressures from 100 to 500 pounds per square inch were used. Fuel oil and gasoline were injected into air at densities of atmospheric land 0.325 pound per cubic foot. It was found that the penetration rate at these low pressures was about the same as the rate obtained with higher pressures. Spray cone-angles were small and individual oil drops were visible in all the sprays. Gasoline and fuel oil sprays had similar characteristics.
Date: November 1, 1931
Creator: Rothrock, A. M. & Waldron, C. D.
Partner: UNT Libraries Government Documents Department

Some characteristics of fuel sprays from open nozzles

Description: The penetration and cone-angle of fuel sprays from open nozzles were recorded with the NACA Spray Photography Equipment. The results show that for injection systems in which the rate of pressure rise at the discharge orifice is high, open nozzles give spray-tip velocities and penetrations which compare favorably with those of closed nozzles. The spray cone-angle was the same for all tests, although open nozzles having different orifice diameters were used, and one nozzle was used both as an open and as a closed nozzle. In designing a fuel system using open nozzles, particular care must be taken to avoid air pockets. The check valve should be placed close to the discharge orifice.
Date: November 1, 1930
Creator: Rothrock, A. M. & Lee, D. W.
Partner: UNT Libraries Government Documents Department

Effect of viscosity on fuel leakage between lapped plungers and sleeves and on the discharge from a pump-injection system

Description: Test data and analysis show that the rate of fuel leakage between a lapped plunger and sleeve varies directly with the density of the fuel, the diameter of the plunger, the pressure producing the leakage, and the cube of the mean clearance between the plunger and sleeve. The rate varies inversely as the length of the lapped fit and the viscosity of the fuel. With a mean clearance between the plunger and sleeve of 0.0001 inch the leakage amounts to approximately 0.2 percent of the fuel injected with gasoline and as low as 0.01 percent with diesel fuel oils. With this mean clearance an effective seal is obtained when the length of the lap is three times the diameter of the lap. The deformation of the sleeve and plunger under pressure is sufficient to change the rate of leakage appreciably from that which would be obtained if the clearance was constant under pressure.
Date: January 1, 1935
Creator: Rothrock, A. M. & Marsh, E. T.
Partner: UNT Libraries Government Documents Department

Effects of air-fuel spray and flame formation in a compression-ignition engine

Description: High-speed motion pictures were taken at the rate of 2,500 frames per second of the fuel spray and flame formation in the combustion chamber of the NACA combustion apparatus. The compression ratio was 13.2 and the speed 1,500 revolutions per minute. An optical indicator was used to record the time-pressure relationship in the combustion chamber. The air-fuel ratio was varied from 10.4 to 365. The results showed that as the air-fuel ratio was increased definite stratification of the charge occurred in the combustion chamber even though moderate air flow existed. The results also showed the rate of vapor diffusion to be relatively slow.
Date: January 1, 1937
Creator: Rothrock, A. M. & Waldron, C. D.
Partner: UNT Libraries Government Documents Department

Penetration and duration of fuel sprays from a pump injection system

Description: 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. The pump was used with and without a check valve. The results show that the penetration of the spray tip can be controlled by the dimensions of the injection tube, the area of the discharge orifice, and the injection-valve opening and closing pressures.
Date: January 1, 1934
Creator: Rothrock, A. M. & Marsh, E. T.
Partner: UNT Libraries Government Documents Department

A photographic study of combustion and knock in a spark-ignition engine

Description: Report presents the results of a photographic study of the combustion in a spark-ignition engine using both Schlieren and flame photographs taken at high rates of speed. Although shock waves are present after knock occurs, there was no evidence of any type of sonic or supersonic compression waves existing in the combustion gases prior to the occurrence of knock. Artificially induced shock waves in the engine did not in themselves cause knock. The photographs also indicate that, although auto-ignition ahead of the flame front may occur in conjunction with knock, it is not necessary for the occurrence of knock. There is also evidence that the reaction is not completed in the flame front but continues for some time after the flame front has passed through the charge.
Date: January 1, 1938
Creator: Rothrock, A. M. & Spencer, R. C.
Partner: UNT Libraries Government Documents Department

Distribution and regularity of injection from a multicylinder fuel-injection pump

Description: This report presents the results of performance test conducted on a six-cylinder commercial fuel-injection pump that was adjusted to give uniform fuel distribution among the cylinders at a throttle setting of 0.00038 pound per injection and a pump speed of 750 revolutions per minute. The throttle setting and pump speed were then varied through the operating range to determine the uniformity of distribution and regularity of injection.
Date: January 1, 1936
Creator: Rothrock, A. M. & Marsh, E. T.
Partner: UNT Libraries Government Documents Department

Effect of nozzle design on fuel spray and flame formation in a high-speed compression-ignition engine

Description: Fuel was injected from different type of injection nozzles into the combustion chamber of the NACA combustion apparatus, operated as a compression-ignition engine. High speed motion pictures were taken of the fuel sprays and combustion. Single-orifice nozzles of 0.008, 0.020, and 0.040 inch diameter, and multiorifice nozzles having 2, 6, and 16 orifices were tested. Nozzles having impinging jets and slit orifices were also included. The photographs indicate that the rate of vapor diffusion from the spray is comparatively slow and that this slow rate of diffusion for combustion chambers with little or no air flow prevents the compression-ignition engine from giving the high performance inherent in the high compression ratios. The sprays from the multiorifice nozzles destroyed the air movement to a greater extent than did those from single orifice nozzles. It is concluded that high performance cannot be realized until the methods of distributing the fuel are improved by means of the injection-nozzle design, air flow, or both.
Date: January 1, 1937
Creator: Rothrock, A. M. & Waldron, C. D.
Partner: UNT Libraries Government Documents Department

Effect of moderate air flow on the distribution of fuel sprays after injection cut-0ff

Description: High-speed motion pictures were taken of fuel sprays with the NACA spray-photographic apparatus to study the distribution of the liquid fuel from the instant of injection cut-off until about 0.05 second later. The fuel was injected into a glass-walled chamber in which the air density was varied from 1 to 13 times atmospheric air density (0.0765 to 0.99 pound per cubic foot) and in which the air was at room temperature. The air in the chamber was set in motion by means of a fan, and was directed counter to the spray at velocities up to 27 feet per second. The injection pressure was varied from 2,000 to 6,000 pounds per square inch. A 0.20-inch single-orifice nozzle, an 0.008-inch single-orifice nozzle, a multiorifice nozzle, and an impinging-jets nozzle were used. The best distribution was obtained by the use of air and a high-dispersion nozzle.
Date: January 1, 1935
Creator: Rothrock, A. M. & Spencer, R. C.
Partner: UNT Libraries Government Documents Department

The knocking characteristics of fuels in relation to maximum permissible performance of aircraft engines

Description: An analysis is presented of the relationship of various engine factors to knock in preignition in an aircraft engine. From this analysis and from the available experimental data, a method of evaluating the knocking characteristics of the fuel in an aircraft-engine cylinder is suggested.
Date: January 1, 1939
Creator: Rothrock, A. M. & Biermann, Arnold E.
Partner: UNT Libraries Government Documents Department

Correlation of knocking characteristics of fuels in an engine having a hemispherical combustion chamber

Description: Data are presented to show the effects of inlet-air pressure, inlet-air temperature, and compression ratio on the maximum permissible performance obtained with having a hemispherical-dome combustion chamber. The five aircraft-engine fuels used have octane numbers varying from 90 to 100 plus 2 ml of tetraethyl lead per gallon. The data were obtained on a 5 1/4-inch by 4 3/4-inch liquid-cooled engine operating at 2,500 r.p.m. The compression ratio was varied from 6.0 to 8.9. The inlet-air temperature was varied from 110 to 310 F. For each set of conditions, the inlet-air pressure was increased until audible knock occurred and then reduced 2 inches of mercury before data were recorded. The results for each fuel can be correlated by plotting the calculated end-gas density factor against the calculated end-gas temperature. Measurements of spark-plugs, cutting off the switch to one spark plug lowered the electrode temperature of that plug from a value of 1,365 F to a value of 957 F. The results indicate that the surface temperatures of combustion-chamber areas which become new sources of ignition markedly increase after ignition.
Date: July 1, 1940
Creator: Rothrock, A. M. & Biermann, Arnold E.
Partner: UNT Libraries Government Documents Department

The Effect of Injection-Valve Opening Pressure on Spray-Tip Penetration

Description: The effect of various injection-valve opening pressures on the spray-tip penetration was determined for several injection pressure. A common-rail fuel injection system was used. For a given injection pressure a maximum rate of penetration was obtained with an injection-valve opening pressure equal to the injection pressure. As the excess of the injection pressure over the injection-valve opening pressure was increased for a given injection pressure, the effect of the injection-valve opening pressure on the spray-tip penetration was increased.
Date: July 1, 1931
Creator: Rothrock, A. M. & Marsh, E. T.
Partner: UNT Libraries Government Documents Department

Fuel spray and flame formation in a compression-ignition engine employing air flow

Description: The effects of air flow on fuel spray and flame formation in a high-speed compression-ignition engine have been investigated by means of the NACA combustion apparatus. The process was studied by examining high-speed motion pictures taken at the rate of 2,200 frames a second. The combustion chamber was of the flat-disk type used in previous experiments with this apparatus. The air flow was produced by a rectangular displacer mounted on top of the engine piston. Three fuel-injection nozzles were tested: a 0.020-inch single-orifice nozzle, a 6-orifice nozzle, and a slit nozzle. The air velocity within the combustion chamber was estimated to reach a value of 425 feet a second. The results show that in no case was the form of the fuel spray completely destroyed by the air jet although in some cases the direction of the spray was changed and the spray envelope was carried away by the moving air. The distribution of the fuel in the combustion chamber of a compression-ignition engine can be regulated to some extent by the design of the combustion chamber, by the design of the fuel-injection nozzle, and by the use of air flow.
Date: January 1, 1937
Creator: Rothrock, A. M. & Waldron, C. D.
Partner: UNT Libraries Government Documents Department

Fuel vaporization and its effect on combustion in a high-speed compression-ignition engine

Description: The tests discussed in this report were conducted to determine whether or not there is appreciable vaporization of the fuel injected into a high-speed compression-ignition engine during the time available for injection and combustion. The effects of injection advance angle and fuel boiling temperature were investigated. The results show that an appreciable amount of the fuel is vaporized during injection even though the temperature and pressure conditions in the engine are not sufficient to cause ignition either during or after injection, and that when the conditions are such as to cause ignition the vaporization process affects the combustion. The results are compared with those of several other investigators in the same field.
Date: January 1, 1933
Creator: Rothrock, A. M. & Waldron, C. D.
Partner: UNT Libraries Government Documents Department

The influence of directed air flow on combustion in spark-ignition engine

Description: The air movement within the cylinder of the NACA combustion apparatus was regulated by using shrouded inlet valves and by fairing the inlet passage. Rates of combustion were determined at different inlet-air velocities with the engine speed maintained constant and at different engine speeds with the inlet-air velocity maintained approximately constant. The rate of combustion increased when the engine speed was doubled without changing the inlet-air velocity; the observed increase was about the same as the increase in the rate of combustion obtained by doubling the inlet-air velocity without changing the engine speed. Certain types of directed air movement gave great improvement in the reproducibility of the explosions from cycle to cycle, provided that other variables were controlled. Directing the inlet air past the injection valve during injection increased the rate of burning.
Date: January 1, 1939
Creator: Rothrock, A. M. & Spencer, R. C.
Partner: UNT Libraries Government Documents Department

Some effects of injection advance angle, engine-jacket temperature, and speed on combustion in a compression-ignition engine

Description: An optical indicator and a high-speed motion-picture camera capable of operating at the rate of 2,000 frames per second were used to record simultaneously the pressure development and the flame formation in the combustion chamber of the NACA combustion apparatus. Tests were made at engine speeds of 570 and 1,500 r.p.m. The engine-jacket temperature was varied from 100 degrees to 300 degrees F. And the injection advance angle from 13 degrees after top center to 120 degrees before top center. The results show that the course of the combustion is largely controlled by the temperature and pressure of the air in the chamber from the time the fuel is injected until the time at which combustion starts and by the ignition lag. The conclusion is presented that in a compression-ignition engine with a quiescent combustion chamber the ignition lag should be the longest that can be used without excessive rates of pressure rise; any further shortening of the ignition lag decreased the effective combustion of the engine.
Date: January 1, 1936
Creator: Rothrock, A. M. & Waldron, C. D.
Partner: UNT Libraries Government Documents Department