Showing papers on "Spark-ignition engine published in 1975"

Sustained arc ignition system

Abstract: Circuitry for maintaining an arc or spark across a spark gap for a desired length of time is disclosed. A high-voltage, direct-current (dc) source is connected in series with a secondary winding of a high voltage, step-up transformer or coil and a spark gap such as a spark plug for example. The high-voltage source may be on continuously or may be turned on and off by a control circuit such as a solid state switch which is, in turn, responsive to a timing device such as a set of ignition contact points or a magnetic pulse generator operating in synchronism with a spark ignition engine. The timing device also provides signals to a current switching circuit which interrupts current flow through a primary winding of the high-voltage coil at the prescribed time that a spark is desired at the spark gap. The control circuit may, if desired, include both a switch and a multivibrator if the timer is of the pulse-generating magnetic type.

Combustion, knock and emission characteristics of a natural gas fuelled spark ignition engine with particular reference to low intake temperature conditions

Abstract: For various fuel-air mixtures and different compression ratios, the intake temperature was varied over the entire range of 200 F (366 k) down to - 100 F (200 k) when employing a single cylinder spark ignited research engine fuelled with natural gas. Performance data such as knock and ignition limits, the nature and extent of exhaust emission and chamber pressure cyclic variation were obtained. Means were then suggested for the interpretation of the above mentioned data in terms of engine operation on liquefied natural gas. The experimental work confirmed in general the attractive features of the use of natural gas as a fuel in a spark ignition engine operated under extremely cold intake temperature conditions and that emissions of pollutants were not significantly increased.(a) /TRRL/

Characteristics of a plasma generated by combustion in a spark ignition engine

Abstract: Plasma probe measurements at dc and bulk absorption measurements at microwave frequencies have been made on a plasma generated by the combustion in a spark ignition engine. From these measurements, estimates of the charge concentration and characteristics of the space‐charge region formed around the plasma probe under the condition of positive‐ion collection have been deduced. The degree of ionization is estimated to be as high as 1 : 104 in the burned gases, depending on engine load. The charge species are concluded to consist primarily of electrons and positively charged ions. In addition, the applicability of various plasma probe theories predicting I‐V relationships has been investigated. The available data strongly indicate that the probe theory including the effect of flow of the ionized gases is the applicable one.

Computer simulation for combustion and exhaust emissions in spark ignition engine

Abstract: In order to predict the exhaust emission concentration without any measured pressure data or empirical burned mass fraction, a new method of combustion simulation was developed. It consists of two major parts: A flame propagation model, and an emission formation model. The flame propagation model, which is based on the burning velocity of the gaseous mixture, gives the pressure and temperature history in the cylinder and in the burned mass fraction for various parameters. In this model, the flame was assumed to propagate across the combustion cylinder as a spherical front centered around a spark plug; a heterogenous temperature field and uniform pressure in the cylinder were assumed. The cylinder consists, of unburned gas and numerous elements of burned gas which burned during successive small increments, of the crank angle. Using various values obtained with the flame propagation model, emission concentration were calculated in individual elements of burned gas, assuming partial equilibrium. Eleven chemical species were taken into consideration. Nine species, other than N and NO, were assumed to be equal to the equilibrium concentration throughout the time of interest. The formation of NO was assumed to be a nonequilibrium process controlled by chemical kinetics and to take place only in the post flame. Computer simulation developed here gives results consistent with the experimental data and it may be utilized for the practical design of a spark ignition engine.

On the problem of predicting burning rates in a spark ignition engine

Abstract: Formulation of a mathematical model for flame propagation in a spark ignited reciprocating engine has been described. The laminar burning velocity is calculated from Semenov's thermal model for the instantaneous unburned gas condition during combustion and is augmented for engine gas turbulence through an empirical function of the engine Reynolds parameter assuming wrinkled flame model. The turbulent flame velocity thus obtained is then corrected for flame transportation due to the expansion of the burning gases. /GMRL/

Simulation and Evaluation of a 4-Stroke Single-Cylinder Spark Ignition Engine

Abstract: This paper deals with the development and evaluation of a mathematical model for a 4-stroke, single-cylinder, spark ignition engine. The first part describes the development of the mathematical model and the computer program. The assumptions that were made in the model are also described. The instruments that were developed for the evaluation of the model are included in the second part, which also contains the evaluation of the results obtained from the model. /GMRL/

Rich-core stratified charge spark ignition engine with rich mixture scoop

Abstract: Creation of a swirling stratified air-fuel charge in an engine combustion chamber is aided by a curved vane or scoop fixedly mounted on the cylinder end and arranged to divide the vortex gas flow introduced through the intake passage into segregated peripheral and core portions. The scoop may also serve as a fuel vaporizing surface and collector for surface quench products. Various arrangements are disclosed for forming a rich mixture in the central core portion adjacent the spark plug to provide the ignition and combustion advantages of a stratified charge.

Spark ignition engine drive - ensures reduced pollution, high efficiency under partial load and high performance

Abstract: Spark ignition engine drive means comprises a gas tank and a petrol or methanol tank, the gas tank being replaceable by a carburetter which produces hot gas from liquid hydrocarbons. The quantity of fuel drawn off from the tanks is supplied by a regulator with associated petrol or methanol carburrettor with secondary air supply or fuel injector and gas mixer, the gas mixer being replaceable by a device for injecting gas directly into the combustion chamber. The exhaust has less obnoxious and polluting components than is usual. The drive gives high efficiency under partial load yet is capable of a general high performance. Fuel of high calorific value is used.

Simulation Model for a Crankcase-Compression Two-Stroke Spark-Ignition Engine Including Intake and Exhaust Systems

Abstract: A model is presented to simulate the power cycle and gas exchange process in a crankcase-compression two-stroke spark-ignition engine which includes intake and exhaust systems. Chemical equilibrium and a two-zone combustion model with a spherical flame front are assumed for the power cycle and generalized non-steady gas dynamic expressions, including variable composition, variable specific heats, friction and heat transfer, are assumed for the gas exchange process in the intake and exhaust systems. For the scavenge process in the cylinder, a thermal mixing model is used to calculate the pressure changes. Experiments with a small high-speed engine showed that the model gave good predictions of the pressure changes during the gas exchange process and the air flow rate. The power predictions followed the experimental trend, but the quantitative results were not so good as the air flow predictions. Despite the limitations of the power predictions, the method offers the designer a tool for improving the perfor...

Two-cycle jet ignition engine with prechamber in piston

Abstract: A two-cycle spark ignition engine is provided with jet ignition means including a prechamber formed within the piston and connected by a restricted passage with the main combustion chamber. At piston bottom dead center, the prechamber connects with an auxiliary inlet from which it receives a rich air-fuel mixture. At piston top dead center, the prechamber communicates with a spark plug that initiates combustion in the rich mixture, causing a flame jet to shoot through the restricted passage to the main combustion chamber, igniting and burning the lean mixture therein. A lean air-fuel mixture may be provided in the main chamber by any of several means, including direct or manifold injection, carburetion or carry-over from the rich mixture in the prechamber. Both uniflow scavenged and loop scavenged arrangements are disclosed.

Operation of a homogeneous exhaust manifold reactor

Abstract: The thermal exhaust manifold reactor, used to reduce carbon base emissions in the exhaust of an Otto cycle engine, is a thermally insulated chamber replacing the exhaust manifold on the engine; when fresh air is added upstream of the reactor, homogeneous reactions can oxidize the emissions. The objective of the present work was to systematically investigate reactor operation in order to provide meaningful information for future reactor designs. The unique approach of simulating the spark ignition engine exhaust using a steady flow hot gas generator is implemented to eliminate the effects of the engine operation parameters. The main criterion for reactor design is its effectiveness in promoting self ignition of the mixture of engine exhaust and secondary air. It is demonstrated experimentally that the ignition is thermal in nature, which amplifies the importance of heat loss from and flow patterns within the reactor, and the optimum gas composition for promoting ignition is given. Furthermore, a correlation of these data, in terms of Damkohler's first similarity group, demonstrates the mechanism of stable and efficient reactor operation and establishes the principles of effective fluid mechanic design.

Evaluation of prechamber spark ignition engine concepts

Abstract: The report reviews the performance, emission, and operational characteristics of prechamber (or divided chamber), spark ignition engine concepts, including an analysis and evaluation of the applicability of these concepts to new automotive and stationary engines and retrofit installations. Relative to conventional automotive engines, prechamber engines exhibit very low carbon monoxide emissions accompanied by some reduction in the emission of nitrogen oxides. However, the hydrocarbon emission from prechamber engines is similar to that of conventional engines employing non-catalytic emission control systems, indicating a need for aftertreatment devices such as lean thermal reactors or catalytic converters. The fuel consumption of vehicles equipped with prechambers is similar to or slightly better than that of equivalent conventional vehicles at comparable levels of emission control.

Internal combustion spark ignition engine

Abstract: The disclosure concerns an internal combustion spark ignition engine including a cylinder; a reciprocating piston in said cylinder and defining a combustion chamber therewith; dividing means for dividing the combustion chamber into a main and an auxiliary section, said auxiliary section being in communication with only the main section, an orifice in said dividing means for connecting the said sections, the volumes of the main and auxiliary sections and the size of the orifice being selected to be such that, during a compression cycle, part of the combustible mixture of air and fuel enters into the auxiliary section in such a manner as to cause great turbulence therein, and a spark plug provided in the auxiliary section for causing ignition.

Off-stoichiometry operation of an si engine - a model of formation and control of nitric oxide.

Abstract: The highest concentrations of NO appear in the exhaust of a spark ignition engine when it is operated slightly on the lean side of stoichiometry. A suggested method of control therefore is to run the engine at an off-stoichiometric air/fuel ratio where the nitric oxide emission is low. The oxygen atom concentration in the combustion chamber of an engine can be higher than the equilibrium concentration, particularly in the lean mixture region. Such higher concentrations of (0) can yield higher concentrations of NO. This paper desceibes a model which takes account of this super-concentration of oxygen atoms in the flame front in order to predict NO emission levels. Comparisons are made with measured results and the agreement found to be good. The combustion duration period is considered as a critical parameter in the control of NO in the lean mixture range. /GMRL/

A Technique for the Measurement of Fuel Maldistribution in a Spark-Ignition Engine

Abstract: The infra-red radiation from combustion processes occurs mainly in C02 and H20 bands and, for the case of liquid fuels, in a continuum from the flame carbon. For combustion close to the stoichiometric air/fuel ratio, both the C02 and H20 levels reach a peak, as does the combustion temperature, so a sharp peak in the radiation is observed. The current technique relies on monitoring the infra-red emission from each CYLINDE~ I

Spark-ignition engine for lean air-fuel mixture

Abstract: A spark-ignition-type internal combustion engine having a main combustion chamber, an auxiliary combustion chamber, and a spark plug disposed in the passage interconnecting those chambers and wherein the spark plug is positioned in an enlarged portion of the passage.