Knocking combustion observed in a spark-ignition engine with simultaneous direct and Schlieren high-speed motion pictures and pressure records
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MOVING-PICTURE (HIGH-SPEED)↗
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Turbulent flame propagation and combustion in spark ignition engines
Pressure measurements synchronized with high-speed motion-picture records of flame propagation have been made in a transparent-piston engine. The data show that the initial expansion speed of the flame front is close to that of a laminar flame. As the flame expands, its speed rapidly accelerates to a quasi-steady value comparable with that of the turbulent velocity fluctuations in the unburned gas. During the quasi-steady propagation phase, a significant fraction of the gas behind the visible front is unburned. Final burnout of the charge may be approximated by an exponential decay in time. The data have been analyzed in a model-independent way to obtain a set of empirical equations for calculating mass burning rates in spark-ignition engines. The burning equations contain three parameters: the laminar burning speed, a characteristic speed (uT), and a characteristic length (lT). The laminar burning speed is known from laboratory measurements. Tentative correlations relating uT and lT to engine geometry and operating variables have been derived from the engine data.
Beretta, G. P.↗
Thermodynamic analysis of turbulent combustion in a spark ignition engine. Experimental evidence
A method independent of physical modeling assumptions is presented to analyze high speed flame photography and cylinder pressure measurements from a transparent piston spark ignition research engine. The method involves defining characteristic quantities of the phenomena of flame propagation and combustion, and estimating their values from the experimental information. Using only the pressure information, the mass fraction curves are examined. An empirical burning law is presented which simulates such curves. Statistical data for the characteristics delay and burning angles which show that cycle to cycle fractional variations are of the same order of magnitude for both angles are discussed. The enflamed and burnt mass fractions are compared as are the rates of entrainment and burning.
Beretta, G. P.↗
End-zone Water Injection as a Means of Suppressing Knock in a Spark-ignition Engine
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ENGINES-WATER INJECTION↗
An analytical investigation of NO sub x control techniques for methanol fueled spark ignition engines
A thermokinetic SI engine simulation was used to study the effects of simple nitrogen oxide control techniques on performance and emissions of a methanol fueled engine. As part of this simulation, a ring crevice storage model was formulated to predict UBF emissions. The study included spark retard, two methods of compression ratio increase and EGR. The study concludes that use of EGR in high turbulence, high compression engines will both maximize power and thermal efficiency while minimizing harmful exhaust pollutants.
Browning, L. H.↗
Infrared radiation from explosions in a spark-ignition engine
This report presents the results of an investigation to determine the variations in intensity and spectral distribution of the radiant energy emitted by the flames during normal and knocking explosions in an engine. Radiation extending into the infrared was transmitted by a window of fluorite, placed either near the spark plug or over the detonation zone at opposite ends of the combustion chamber. Concave, surface-silvered mirrors focused the beam, first at the slit of a stroboscope which opened for about 2 degrees of crank angle at any desired point in the engine cycle, and then upon the target of a sensitive thermocouple for measuring radiation intensity. Spectral distribution of the radiant energy was determined by placing over the window, one at a time, a series of five filters selected with a view to identifying, as far as possible without the use of a spectrograph, the characteristic emissions of water vapor, carbon dioxide, and incandescent carbon.
Marvin, Charles F , Jr↗
Investigation of the potential for improving efficiency of a spark ignition engine operating on natural gas
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Oneal, G. B.↗
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↗
Preliminary evaluation of the performance of a uniflow two-stroke-cycle spark-ignition engine combined with a blowdown turbine and a steady-flow turbine
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Sather, Bernard I↗
Performance of a Fuel-Injection Spark-Ignition Engine Using a Hydrogenated Safety Fuel
This report presents the performance of a single-cylinder test engine using a hydrogenated safety fuel. The safety fuel has a flash point of 125 degrees f. (Cleveland open-dup method), which is high enough to remove most of the fire hazard, and an octane number of 95, which permits higher compression ratios to be used than are permissible with most undoped gasolines.
Schey, Oscar W↗
The Influence of Directed Air Flow on Combustion in Spark-Ignition Engine
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.
Rothrock, A M↗
Measurement of Knock Characteristics in Spark-ignition Engines
This paper presents a discussion of three potential sources of error in recording engine knocking which are: the natural oscillation of the membrane, the shock process between test contacts, and the danger of burned contacts. Following this discussion, the paper calls attention to various results which make the bouncing-pin indicator appear fundamentally unsuitable for recording knock phenomena.
Schutz, R↗
Free-piston Stirling hydraulic engine and drive system for automobiles
The calculated fuel economy for an automotive free piston Stirling hydraulic engine and drive system using a pneumatic accumulator with the fuel economy of both a conventional 1980 spark ignition engine in an X body class vehicle and the estimated fuel economy of a 1984 spark ignition vehicle system are compared. The results show that the free piston Stirling hydraulic system with a two speed transmission has a combined fuel economy nearly twice that of the 1980 spark ignition engine - 21.5 versus 10.9 km/liter (50.7 versus 25.6 mpg) under comparable conditions. The fuel economy improvement over the 1984 spark ignition engine was 81 percent. The fuel economy sensitivity of the Stirling hydraulic system to system weight, number of transmission shifts, accumulator pressure ratio and maximum pressure, auxiliary power requirements, braking energy recovery, and varying vehicle performance requirements are considered. An important finding is that a multispeed transmission is not required. The penalty for a single speed versus a two speed transmission is about a 12 percent drop in combined fuel economy to 19.0 km/liter (44.7 mpg). This is still a 60 percent improvement in combined fuel economy over the projected 1984 spark ignition vehicle.
Beremand, D. G.↗
Advanced Technology Spark-Ignition Aircraft Piston Engine Design Study
The advanced technology, spark ignition, aircraft piston engine design study was conducted to determine the improvements that could be made by taking advantage of technology that could reasonably be expected to be made available for an engine intended for production by January 1, 1990. Two engines were proposed to account for levels of technology considered to be moderate risk and high risk. The moderate risk technology engine is a homogeneous charge engine operating on avgas and offers a 40% improvement in transportation efficiency over present designs. The high risk technology engine, with a stratified charge combustion system using kerosene-based jet fuel, projects a 65% improvement in transportation efficiency. Technology enablement program plans are proposed herein to set a timetable for the successful integration of each item of required advanced technology into the engine design.
Stuckas, K. J.↗
The spark-ignition aircraft piston engine of the future
The advanced technology, spark ignition, aircraft piston engine design study was conducted to determine the improvements that could be made by taking advantage of technology that could reasonably be expected to be made available for an engine intended for production by January 1, 1990. Two engines were proposed to account for levels of technology considered to be moderate risk and high risk. The moderate risk technology engine is a homogeneous charge engine operating on avgas and offers a 40% improvement in transportation efficiency over present designs. The high risk technology engine, with a stratified charge combustion system using kerosene-based jet fuel, projects a 65% improvement in transportation efficiency. Technology enablement program plans are proposed herein to set a timetable for the successful integration of each time of required advanced technology into the engine design.
Stuckas, K. J.↗
Emissions and new technology programs for conventional spark-ignition aircraft engines
A long-range technology plan in support of general aviation engines was formulated and is being implemented at the Lewis Research Center. The overall program was described, and that part of the program that represents the in-house effort at Lewis was presented in detail. Three areas of government and industry effort involving conventional general-aviation piston engines were part of a coordinated overall plan: (1) FAA/NASA joint program, (2) NASA contract exhaust emissions pollution reduction program, and (3) NASA in-house emissions reduction and new technology program.
Wintucky, W. T.↗
Computed and measured turbulence in axisymmetric reciprocating engines
The turbulent flowfield of a spark-ignition engine affects strongly the combustion characteristics of the engine. The flowfield depends on the design of the combustion chamber and the intake system. The present investigation is concerned with the effect of chamber design, and engine operating conditions on top dead center turbulence prior to ignition. It is shown that many of the trends which were identified in earlier studies can be obtained from a single model. The employed model takes into account a two-dimensional axisymmetric flowfield. Attention is given to governing equations, boundary and initial conditions, a comparison of the computed results with measurements, and the effect of swirl and squish.
Grasso, F.↗
Further Studies of Flame Movement and Pressure Development in an Engine Cylinder
This report describes an investigation using a stroboscopic apparatus for observing flame movement through a large number of small windows distributed over the head of a spark-ignition engine in following flame spread with combustion chambers of different shapes at two engine speed and for a variety of spark-plug locations including single and twin ignition. The principal factors influencing flame movement in the engine are discussed, and the lack of reliable information regarding their separate effects upon the structure of the flame and its speed of propagation are emphasized.
Marvin, Charles F , Jr↗