Showing papers on "Spark-ignition engine published in 1995"

Spark ignition engine exhaust system

Abstract: An exhaust system for a spark ignition engine on an automotive vehicle including an exhaust filter (30) disposed downstream of a spark ignition engine for condensing hydrocarbons in exhaust gases from the engine during a first time period after start of the engine, a bypass structure (56, 58, 60, 66, 68, 70) for bypassing at least a portion of exhaust gases around the exhaust filter (30) to heat the exhaust filter during a second time period after the first time period and evaporate the condensed hydrocarbons, and a catalytic converter (18) disposed downstream of the exhaust filter (30) to oxidise the evaporated hydrocarbons and reduce NOX in exhaust gases passing therethrough.

Identification and air-fuel ratio control of a spark ignition engine

Abstract: Accurate control of the air-fuel ratio in a spark-ignition engine is critical to satisfying future federal and California emissions regulations. The goal of this research is to explore the use of adaptive control as a means of precisely controlling the air-fuel ratio. A control-oriented, physics-based engine model, in which the sampling rate is based on crank-angle instead of time, has been utilized to construct a feedforward/feedback control scheme to regulate air-fuel ratio. The derived control law, however, requires the values of time constants, delay times, and other model parameters that must be experimentally determined. Since these parameters can possibly change over time, a method for estimating them online is preferred. A nonlinear least squares identification technique is used to accurately determine the model parameters using normal engine operating data. These parameter values are then employed in an estimator based controller to demonstrate cycle-to-cycle air-fuel ratio regulation on a single-cylinder laboratory engine (CFR) during various throttle transients. >

Engine with flow coupled spark discharge

Abstract: An improved spark ignition engine system producing a large continuous, centrally directed, flow coupled ignition spark discharge through combustion chamber (1), piston (4), inlet system (28/29), spark plug (5), and ignition spark discharge (26) design, and through the location and orientation, with respect to the mixture flow field, of a special design firing end and gap (7/9) of a spark plug fired with a spark discharge of hundreds of watts of power for hundreds of microseconds without spark segmentation or spark break-up by the flow field of up to about 20 m/sec flow velocity, with bulk flow occurring at the spark plug site at most engine speeds including low speeds to produce a very large centrally directed spark-initial flame front kernel which allows for substantial dilution of the mixture and significant reduction in engine cycle-to-cycle variation under most operating conditions of the engine including low speed light load.

Modeling and control of a spark ignition engine with variable cam timing

Abstract: A control scheme is designed to minimize emissions and respond to rapid throttle changes in a fuel injected, spark ignition engine equipped with variable cam timing. The model is derived from engine mapping data for an eight cylinder experimental engine mounted in a dynamometer test cell; it is fundamentally a nonlinear and multivariable model. The control scheme jointly manages fuel and cam position.

Analysis of fuel behavior in the spark ignition engine start-up process

Abstract: An analysis method for the characterization of fuel behavior during spark ignition engine start-up has been developed and applied to several sets of start-up data. The data sets were acquired from modem production vehicles during room temperature engine start-up. Two different engines, two control schemes, and two engine temperatures were investigated. The fuel accounting used was a cycle-by-cycle mass balance for the fuel, where the amount of fuel injected was compared with the amount burned or exhausted as unburned hydrocarbons. The difference was measured as \"fuel unaccounted for\". The calculation for the amount of fuel burned used an energy release analysis of the cylinder pressure data. The results include an overview of starting behavior and a fuel accounting for each data set. Differences between start-up strategies are discussed and areas for improvement are identified. Overall, starting occurred quickly, with combustion quality, manifold pressure and engine speed beginning to stabilize by the seventh cycle, on average. To facilitate this rapid starting at cold engine conditions, approximately five times the amount of fuel required for a stoichiometric mixture is injected during the first one or two cycles. A large portion of this fuel, equivalent to nearly ten injections at stoichiometric idle conditions, remains \"unaccounted for\" after ten cycles of this analysis. Close to 10% of the fuel injected during the initial overfueling that is \"unaccounted for\" at first, shows up later in underfueled cycles as burned fuel or as hydrocarbon emissions. Similar trends occurred with both engines, temperatures, and start-up strategies; although, during warm engine start-up conditions the overfueling is only 130% of stoichiometric, and the mass \"unaccounted for\" after ten cycles represents only one injection at idle. The most successful start-up strategies that were analyzed injected close to the stoichiometric requirement for each cycle after the initial overfueling. The stoichiometric requirement for a particular cycle is directly proportional to the manifold pressure at a given temperature and therefore it is recommended that methods for using manifold pressure in start-up strategies be investigated. 3 \"And to love life through labour is to be intimate with life's inmost secret.\" K.G.

Oxidation of the Piston Crevice Hydrocarbon During the Expansion Process in a Spark Ignition Engine

Abstract: Engine-out HC emissions were measured in SI engine experiments in which the piston topland crevice size was changed systematically. For a warmed-up engine, the HC emissions were found to be modestly sensitive to the piston crevice size-a 10% change in size results in approximately a 2% change in HC emissions. This low sensitivity is explained in terms of a crevice HC diffusion/oxidation model in the expansion process. When the piston crevice is sufficienlly small, however, the model shows that the HC emissions have a one-to-one correspondence with the crevice size.

Cycle-by-cycle variations in combustion and mixture concentration in the vicinity of spark plug gap

Abstract: The correlations between IMEP and pressures at referenced crank angles have different trends for different equivalence ratios. A fiber optic spark plug was used to detect the initial flame development which was then used to analyze the combustion cyclic variation. Rayleigh scattering measurements were applied to detect the air-fuel mixture fluctuations in the vicinity of spark plug gap for both homogeneous and inhomogeneous mixture preparations in a spark ignition engine. The variation in mixture concentration in the vicinity of spark plug gap was not confirmed as a major contributor to cycle-by-cycle variation in combustion for any of the homogeneous mixture cases or for the stoichiometric and lean mixtures of port injection. However, a leaner mixture of port injection did correlate with the cyclic variation in combustion. (AN).

Simulation of the mean flow in the cylinder of a motored 4-valved spark ignition engine

Abstract: The Computational Fluid Dynamics (CFD) code KIVA II has been applied to simulate the in-cylinder mean air motion (tumble) and turbulence levels in a motored 4-stroke single cylinder engine with pentroof combustion chamber geometry, having two inlet and two exhaust valves. In-cylinder flow during intake and compression strokes were simulated and a comparison between computational and experimental results were made. The mean turbulent kinetic energy and tumble ratio variation during the compression stroke obtained with CFD, have been compared with computational and experimental data from published literature. The simulation shows general similarity of flow structure and magnitude with published data on engines with similar geometry and initial flow conditions in the cylinder. 20 refs., 9 figs., 1 tab.

Misfire detection in a spark ignition engine

Abstract: A method for detecting misfire in a cylinder of an internal combustion engine through the ignition system of the engine. The present invention first predicts a time-to-fire measurement for an interrogating spark, then measures the actual time-to-fire measurement of the interrogating spark and then compares the predicted measurement and the actual measurement to determine whether misfire has occurred.

Post-Flame Oxidation and Unburned Hydrocarbon in a Spark-Ignition Engine

Abstract: : Many recent publications indicate that spark ignition (SI) engines equipped with the conventional port-injection fuel system (PIF) seem to have serious fuel-maldistribution problems, including the formation of liquid layers over the combustion chamber surfaces. It is reasonable to expect that such a maldistribution is an unfavorable condition for the flame propagation in the cylinder. The in-cylinder flame behaviors of a PIF-SI engine as fueled with gasoline are investigated by using the Rutgers high-speed spectral infrared imaging system. These results are then compared with those obtained from the same engine operated by gaseous fuels and other simple fuels. The results from the engine operated by gasoline reveal slowly burning fuel-rich local pockets under both fully warmed and room-temperature conditions. The local pockets seem to stem from the liquid layers formed over the surfaces during the intake period. The (invisible) post-flame oxidation of the rich pockets is observed to continue even after the exhaust valve opens. On the contrary, the same engine run with a gaseous fuel exhibits some predictable and 'clean' flame propagations. The new results obtained from the present study suggest that such a late oxidation of locally fuel-rich liquid pockets may be a significant cause for the emission of the engine-out unburned hydrocarbon (UHC). The sluggish consumption of the fuel there may also be a factor for reducing the thermal efficiency of the engine. A parametric study of this observation is performed to obtain a better understanding of the findings. (AN)

Crevice Flow and Combustion Visualization in a Direct-Injection Spark-Ignition Engine Using Laser Imaging Techniques

Abstract: Crevice flows of hydrocarbon fuel (both liquid and vapor) have been observed directly from fuel-injector mounting and nozzle-exit crevices in an optically-accessible single-cylinder direct-injection two-stroke engine burning commercial gasoline. Fuel trapped in crevices escapes combustion during the high-pressure portions of the engine cycle, exits the crevice as the cylinder pressure decreases, partially reacts when mixed with hot combustion gases in the cylinder, and contributes to unburned hydrocarbon emissions. High-speed laser Mie-scattering imaging reveals substantial liquid crevice flow in a cold engine at light load, decreasing as the engine warms up and as load is increased. Single-shot laser induced fluorescence imaging of fuel (both vapor and liquid) shows that substantial fuel vapor emanates from fuel injector crevices during every engine cycle and for all operating conditions. Early in the crevice-flow process, some of the emerging fuel vapor (imaged by laser-induced fluorescence) burns as a rich diffusion flame (imaged by flame luminosity), but most of the crevice flow fails to burn as the cylinder pressure and temperature fall. Crevice HC`s are a significant (but not the predominant) source of hydrocarbon emissions in this two-stroke engine, since most of the crevice flow hydrocarbons are retained as residual fuel in the combustion chamber. Similarmore » laser-imaging techniques are applicable to four-stroke spark-ignition engines, where crevice flows are believed to be the dominant hydrocarbon-emissions source.« less

Analytical Scaling Model for Hydrocarbon Emissions From Fuel Absorption in Oil Layers in Spark Ignition Engines

Abstract: Cyclic absorption and desorption of fuel by the lubricating oil layer on the cylinder wall has been suggested as a significant source of unburned hydrocarbon emissions from spark ignition engines. A simple analytical model describing this dynamic process as unsteady one-dimensional cyclic absorption and desorption of a dilute amount of gas in a thin liquid layer on an impervious wall has been developed. A general solution for a periodic variation in fuel concentration in the gas phase is obtained, and three distinct limits for the net absorption of hydrocarbons are shown to exist depending on the relative time scales for the hydrocarbon concentration forcing function, the diffusion in the liquid and in the gas phase. A general criterion for when gas-phase convection species transfer resistance must be taken into account is also derived. Focus was given to the relative importance of the gas-phase and liquid-phase diffusion rates, and the scaling of the hydrocarbon absorption phenomena with realist...

Stratified charge spark ignition engine

Abstract: Each cylinder has two intake valves 18 and each intake valve 18 is supplied by two intake port channels 22, 32. Channel 22 supplies a fuel and air mixture while channel 32 supplies air or recirculated exhaust gases. The two channels supplying each intake valve are separately connected to respective intake manifolds 24, 34 controlled by respective flow regulating valves (28, 38, Fig. 1) The channel 32 directs a gas flow across the roof 17 of the combustion chamber 10 and the channel 22 directs a gas flow towards the centre of the combustion chamber. The flow from the channel 32 serves to separate the flow from the channel 22 from the roof 17 of the combustion chamber as the two flows enter the combustion chamber, the two flows tumbling in unison to produce envelope stratification within the combustion chamber. A partition 22a in the channel 22 provides a gas flow into the combustion chamber between the other two flows and contains substantially no fuel from the injector 46.

Cylinder injection type spark ignition engine

Abstract: PURPOSE: To control injection timing and ignition timing by being matched to the change delay of an intake air condition control value when the fuel injection pattern of an cylinder injection-type spark ignition engine is switched so as to optimize combustion during a switching period. CONSTITUTION: Injection timing and ignition timing out of a swirl ratio, an EGR rate, the injection timing and the ignition timing which are changed when a fuel injection pattern is switched among compression stroke ignition, two-time ignition and intake stroke ignition according to a load change, are delayed to be moved to values after changed by being matched to the delay of changes in the swirl ratio and the EGR rate.