Showing papers on "Spark-ignition engine published in 1991"

Decomposed Methanol as a Fuel—A review

Abstract: The use of decomposed methanol, i.e., hydrogen and carbon monoxide, in spark-ignition engines is reviewed. The emphasis is on onboard decomposition and the paper docs not deal with engines fueled by stored hydrogen. The paper concentrates mostly on the experimental work performed using catalytically decomposed methanol, where the methanol is used as a hydrogen carrier. The greatest potential for this type of engine, besides the low energy consumption, lies in the low emissions of nitrogen oxides when running at lean air/fuel ratios. An active and selective catalyst for the decomposition reaction is essential for the utilization of this concept. A literature review on catalyst investigations is included. Neat methanol engines arc not readily started at low ambient temperatures. The possibility of using decomposed methanol as a cold start fuel for methanol engines is reviewed. Decomposed methanol has been proposed as a fuel for gas turbines. A brief review of this subject is also included.

A model for flame kernel development in a spark-ignition engine

Abstract: A First-Law-based model for the growth of the spark-generated flame kernel in a spark-ignition engine has been developed and applied. The purpose of the study was to show how the basic physics relevant to the early stages of flame growth—electrical energy deposition, chemical energy release, and heat losses to the spark plug—can explain the observed kernel behavior under real engine operating conditions. The primary focus was on how the heat losses to the spark plug electrodes, insulator and ground case effect the rate of flame kernel development and its variation, cycle-by-cycle. It is shown that the heat loss rate from the kernel to the spark plug, and the electrical power fed into the kernel from the discharge positive column, are comparable in magnitude and vary significantly cycle-by-cycle. For flame kernels which remain centered on the plug electrodes and have a high contact area with the plug, the heat losses are higher and spark energy deposited is lower than for the cycles where the kernel is convected away from the electrodes by the flow. With higher heat losses, which can be comparble in magnitude to the combustion energy release for kernels up to a about 1.5 mm radius, the kernel grows significantly more slowly. The model also shows that excessive heat loss to the spark plug can lead to misfire.

A Numerical Study of Fuel Evaporation and Transportation in the Intake Manifold of a Port-Injected Spark-Ignition Engine:

Abstract: The paper presents a computer simulation of mixture preparation in the inlet port of a port-injected spark-ignition engine operating at low load and low speed. The solution of the models at success...

The Effect of Piston Temperature on Hydrocarbon Emissions from a Spark-Ignited Direct-Injection Engine

Abstract: Light-load unburned hydrocarbon emissions were studied experimentally in a spark-ignited direct-injection engine burning gasoline where the piston temperature was varied The test engine was a single-cylinder Direct-Injection Stratified-Charge (DISC) engine incorporating a combustion process similar to the Texaco Controlled Combustion System At a single low load operating condition, the piston temperature was varied by 50 K by controlling the cooling water and oil temperature The effect of this change on unburned hydrocarbon emissions and heat release profiles was studied It was found that by carefully controlling the intake air temperature and pressure to maintain constant in- cylinder conditions at the time of injection, the change in piston temperature did not have a significant effect on the unburned hydrocarbon emissions from the engine It was concluded that fuel wetting of the piston surface is not a significant source of hydrocarbon emissions from engines of this type when burning gasoline (A) For the covering abstract of the conference see IRRD 852385

In-cylinder fuel distribution in a port-injected model engine using Rayleigh scattering

Abstract: The spatial and temporal variation of the fuel concentration (air/fuel ratio) in a model engine was quantified by laser Rayleigh scattering. Fuel was simulated by gaseous Freon-12 injected at various timings and quantities into the intake port. The results showed that the fuel concentration in the engine cylinder was strongly dependent on the injection timing and duration and that the Rayleigh system was able to identify spatial variations of the order of one air/fuel ratio at realistic mixture strengths.

Spark-ignition engine

Abstract: A spark-ignition engine (10) is disclosed that incorporates a relatively unlimited number of spark sources within each combustion chamber (26), without conventional spark plugs being required. The engine (10) includes a planar circuit module (38) clampingly located between a cylinder assembly (12) and a head assembly (24) of the engine. The module (38) includes an electrically insulative substrate (58); a pair of electrode members (42); a foil circuit (50) on the substrate (58) for connecting the electrode members (42) to a pulser (22) that generates a high voltage intermittent electric signal for producing spark ignition of the fuel within a combustion chamber (26) of the engine (10); first and second seals (72) for connecting the substrate (58) to the cylinder assembly (12) and the head assembly (24). Also disclosed is a kit for replacing spark plugs in an internal combustion engine (10) the kit including the circuit module (38) and in one version, injector assemblies (90) for use in place of the spark plugs.

Heavy-Duty Spark Ignition Engines Fueled With Methane

Abstract: Pollution reduction in urban areas is a major driving force to upgrade mass transportation systems. Options to the urban planner include electric traction and combustion engine upgrade. Electric traction centralizes the emission source, usually removed from urban areas, but requires substantial capital costs and lead time for the transportation infrastructure. Engine emission improvement is possible through both fuel changes and engine upgrade. Natural gas engines are a viable option for clean-operating urban buses. In the near term, conversion of existing diesel bus engines to spark-ignited natural gas is an attractive solution in terms of capital costs and lead time. This paper contains the analysis required to transform diesel engines into spark-ignited natural gas engines. Experimental data are shown for both a turbocharged and a naturally aspirated conversion. Emission data are presented showing the natural gas conversion to meet present EEC emission requirements.

Liquid Cooled Turbocharged Propulsion System for HALE Application

Abstract: An unmanned air vehicle (UAV) capable of sustained flight in the upper limits of the tropopause is a relatively new technology which has seen increasing interest during the past decade. Mission lengths for High Altitude Long Endurance (HALE) applications are typically measured in days rather than hours with operating altitudes ranging from 50,000 to 100,000 feet. An Otto cycle propulsion system offers significant performance advantages over other cycles. This paper provides a technical assessment of a liquid cooled turbocharged, reciprocating engine concept capable of meeting the requirements for a HALE vehicle. A properly designed spark ignition engine with a two or three stage series turbocharger system utilizing state-of-the-art aerodynamic design can meet the challenges presented at these altitudes. Several records for long endurance and high altitude flight have already been set with this type of propulsion system. A comparison with other candidate engines will also be made. The ability to operate with low brake specific fuel consumption (BSFC) across a broad operating range will be identified. With sufficiently high exhaust gas temperatures, the addition of a power turbine for turbocompounding can further reduce the BSFC and brake specific air consumption (BSAC). A version of the turbocharged spark ignition engine is capable of providing high thermal efficiency with the least BSAC and minimum turbomachinery weight.Copyright © 1991 by ASME

Mixture strength measurements in the combustion chamber of si engine via rayleigh scattering (2nd report, results for liquid fuel injection)

Abstract: An experimental study was made of the fundamental aspect of the mixture formation in the combustion chamber of an automotive spark ignition engine with multipoint fuel injection. The mixture formation process during the intake stroke of an engine was simulated by the intermittent injection of gasoline or Freon-113 into the steady flow of dust-free dry air through an intake port. The time histories of the vapor concentration at several locations in the transparent combustion cylinder were determined with the application of the laser Rayleigh scattering. The measured results were expressed in terms of the peak vapor concentration at the location of interest, the period of time between the initiation of the liquid fuel injection and vapor arrival, and the duration for the vapor to be observed over a wide range of injection pressures, injection durations, intake valve temperatures, intake valve lifts and intake air flow rates

The Use of Gas Dynamics to Link In-Cylinder and Exhaust System Unburnt Hydrocarbon Measurements on a Spark Ignition Engine

Abstract: The paper reviews the ideas on the sources of unburnt hydrocarbons in spark ignition engines. Time resolved measurements made in-cylinder and in the exhaust system in previous investigations have revealed large differences between the cylinder and the exhaust system. It is not possible to distinguish between reductions by mixing and oxidation. The object of the present paper is to investigate the links between the two sets of measurements using a new development of engine gas dynamics. An outline is given of the authors' measurements and the new aspects of the gas dynamics model. The key idea of the latter is the introduction of "the path line streams". A recent study using this method is described and the results discussed. It explains the role of mixing at entry to the exhaust valve annulus and the post flame oxidation process. It is concluded that the new technique has extensive possibilities in the understanding of the problem of unburnt hydrocarbons from reciprocating engines. (A) For the covering abstract of the conference see IRRD 852385.