Showing papers on "Spark-ignition engine published in 1999"

Combustion characterization of natural gas in a lean burn spark-ignition engine

Abstract: Lean burn natural gas fuelled spark-ignition engines are particularly attractive regarding environmental performance. Nevertheless, few data exist concerning lean combustion in gas engines in terms of ignition delay, combustion duration and combustion rate. Such data are necessary when using thermodynamic models to predict energy and environmental performance. The present study proposes a contribution to such combustion characterization as a function of spark timing, air excess and engine load. This work is based on experimental cylinder pressure measurements in an open chamber engine on the one hand, and on a one-zone thermodynamic model used as a heat release analysis tool on the other hand. Results obtained, such as mass fraction burned, ignition delay and combustion duration, allow identification of the parameters used in the Wiebe function, a semi-empirical law that is frequently used to describe the combustion in predictive models.

Mechanisms of particulate matter formation in spark-ignition engines. 1: effect of engine operating conditions

Abstract: A combined experimental and modeling effort was performed in order to understand how particulate matter (PM) is formed in spark-ignition (SI) internal combustion engines. Parameters that affect global and local air/fuel ratios strongly affect PM. Minimum PM number and mass concentrations are emitted at a global air/fuel ratio within 10% of stoichiometric, and concentrations increase by as many as 3 orders of magnitude when the air/fuel ratio is either increased or decreased 30% from stoichiometric. Burning liquid fuel is a significant source of PM, as evidenced by the fact that open valve fuel injection increases PM concentrations by up to 3 orders of magnitude relative to closed valve injection. Coolant and oil temperatures, spark timing, and exhaust gas recirculation (EGR) affect PM through their effect on intake port and cylinder temperatures as well as through the effect on the availability of liquid fuel in the cylinder. Particle sizes as a function of engine operating conditions are discussed.

Vapor recovery control system for direct injection spark ignition engines

Abstract: A vapor recovery control system for a direct injection spark ignition engine is used to purge vapors in both a homogeneous air/fuel and stratified air/fuel mode. When purging vapors in a stratified mode, a portion of the cylinders receive purge vapors and operate in a homogeneous mode while the rest of the cylinders continue to operate in a stratified mode.

Control for direct fuel injection spark ignition internal combustion engine

Abstract: During a period from an engine start to activation of a catalytic emission control device, a direct injection spark ignition engine is operated in a stratified stoichiometric charge combustion mode under the control of an engine controller. In the stratified stoichiometric combustion mode, a fuel injection system carries out a direct cylinder injection on the compression stroke to produce a relatively rich stratified air fuel mixture closely around a spark plug, in a background of a relatively lean air fuel mixture produced homogeneously over the combustion chamber by a direct cylinder injection on the intake stroke or a port or passage injection on or before the intake stroke.

The effect of using 30% iso-butanol-gasoline blend on hydrocarbon emissions from a spark-ignition engine

Abstract: The level of hydrocarbon (HC) emissions, from a spark-ignition engine using a 30 % iso-butanol-gasoline blend was experimentally investigated. Experiments were conducted on a Hydra single-cylinder, spark-ignition, fuel-injection engine. HC emissions were measured as a function of fuel air equivalence ratio, ignition timing and engine speed. The effect of varying the temperature of cooling water on HC emissions was also investigated under three fuel air equivalence ratios (lean, stoichiometric, and rich). Results show that retarding ignition timing with respect to maximum break torque (MBT) has a great effect on HC emissions reduction, where for lean mixture, Phi 0.85, retarding ignition timing by 6 degrees from MBT reduces the exhaust HC emissions by 12 %. The level of HC emissions is also reduced by 30 % at MBT, as the cooling water temperature increase from 55 to 90 C. It is noticed that as the engine speed increases, the level of HC emissions decrease.

The Influence of Gasoline Formulation on Specific Pollutant Emissions

Abstract: Many recent works have dealt with the influence of fuel composition on regulated and specific pollutant emissions from spark ignition engines. While many qualitative correlations have been already proposed, only a few quantitative ones are known (benzene remains an exception). This paper describes qualitative and quantitative correlations between fuel composition and specific pollutant emissions (individual hydrocarbons, aldehydes, ketones, alcohols, and organic acids) of a spark ignition engine. The aim of this work was to find the precursors of the main specific pollutants. Then, for each of them, a multilinear equation has been calculated, illustrating the correlation between its concentration in exhaust gases and its content in the fuel. The results of these calculations point out which initial compound favors the formation of a determined pollutant. As lean conditions are probably going to be used in future commercial engines, the fuel effect has been studied for a broad range of equivalence...

Mechanisms of Particulate Matter Formation in Spark-Ignition Engines. 3. Model of PM Formation

Abstract: A combined experimental and modeling effort was performed in order to understand how particulate matter (PM) is formed in spark-ignition (SI) internal combustion engines. Application of the model allows quantification of the amount of PM nucleated at sites of burning liquid fuel (either droplets or pools) and in homogeneous gas-phase chemical reactions. Moreover, it quantifies PM growth by condensation and absorption/adsorption of hydrocarbon (HC) vapors as well as PM reduction by oxidation both in the cylinder and in the exhaust pipe. Model parameters, fit by comparison to experimental data, show the strong dependence of PM formation on the presence of liquid fuel in the cylinder and HCs in the exhaust, temperatures in the intake port and cylinder, air/fuel ratio, and propensity of the fuel molecule to break down into soot precursors. PM emissions calculated by the 13-parameter model compare to 84 experimental data sets with an R 2 correlation coefficient of 0.81, demonstrating good correlation. The effe...

Fuel injection control system for direct injection-spark ignition engine

Abstract: A fuel injection control system for a direct injection-spark ignition engine determines an injection pulse width corresponding to a given quantity of fuel with which an injector is kept open, controls the injector to spray a given quantity of fuel in a compression stroke while the engine operates in a zone of lower engine loads specified for lean stratified charge combustion so that the fuel is stratified around an ignition plug to cause lean stratified charge combustion so as thereby to provide an air-fuel ratio greater than a stoichiometric air-fuel ratio, executes fuel injection feedback control to control a quantity of fuel injection based on an air-fuel ratio detected by an oxygen sensor, causes the injector to spray a given quantity of fuel through a plurality of intake stroke split injection in a specified engine operating zone in which the fuel injection feedback control is performed to maintain at least a stoichiometric air-fuel ratio while the engine operates with lower loads, learns a fuel injection quantity characteristic of the injector with respect to injection pulse width for each intake stroke split injection based on a value controlled by the fuel injection feedback control during execution of the intake stroke split injection to determine a leaning correction value, and makes the learning correction value reflect on the control of the quantity of fuel in a minute injection zone specified within the specified engine operating zone for the lean stratified charge combustion.

Droplet Sizing by Mie Scattering Interferometry in a Spark Ignition Engine

Abstract: A theoretical explanation is given of a technique based on Mie scattering interferometry (MSI), obtained by defocusing of the collecting optics, to size droplets. The originality of this study is the development of a droplet sizing method by planar laser light scattering for the case of a scattering angle range close to 90°. The feasibility of this method and its limitations are fully described. The dependence on intensity levels and refractive index variations can be neglected. After discussion of some practical details about particle size, imaging and camera constraints, the results obtained in the combustion chamber of a spark ignition (SI) engine, near the spark plug, prior to ignition and for different injection timings are described and discussed. It can be concluded that the implementation of the MSI method in this experimental set-up has been realized successfully to provide droplet distributions in an SI engine. To allow the easier use of the technique, image processing software will be developed in the Matlab environment.

Mode control system for direct injection spark ignition engines

Abstract: A mode control system for a direct injection spark ignition engine is controlled to operate in either homogeneous air/fuel modes or stratified air/fuel modes. When transitioning from homogeneous to stratified mode, the throttle is used to adjust manifold pressure to a level where it is possible to operate in a stratified mode with a torque equal to that of the homogeneous model. When transitioning from a stratified to a homogeneous model, the throttle is used to adjust manifold pressure to a level where it is possible to operate in a homogeneous model with a torque equal to that of the stratified mode. During the transition, other engine operating conditions are used to assist in controlling engine torque.

Formaldehyde formation in the endgas of Otto engines: Numerical simulations and quantitative concentration measurements

Abstract: Formaldehyde is an important intermediate species formed during combustion processes, e.g. inside IC engines. It disappears rapidly during the excitation phase of the ignition process and can be measured by means of laser induced fluorescence (LIF) with high sensitivity. Due to its important role during the combustion of hydrocarbon fuels an accurate knowledge of formaldehyde concentration fields may improve the detailed understanding of the variety of gasdynamical and chemical processes associated with the auto-ignition of the endgas. However, LIF as one of the preferred methods in combustion diagnostics cannot quantitatively determine species concentrations as long as the collisional quenching rates are unknown. The approach taken in this study allows an online calibration of the LIF technique applied io formaldehyde concentration measurements during the ignition phase inside an optically accessible research engine. The method is based on simultaneously recording the LIF signal distribution alo...

Combustion and Fuels

Abstract: The fundamental difference between spark ignition (SI) and compression ignition (CI) engines lies in the type of combustion that occurs, and not in whether the process is idealised as an Otto cycle or a Diesel cycle. The combustion process occurs at neither constant volume (Otto cycle), nor constant pressure (Diesel cycle). The difference between the two combustion processes is that spark ignition engines usually have pre-mixed flames while compression ignition engines have diffusion flames. With pre-mixed combustion the fuel/air mixture must always be close to stoichiometric (chemically correct) for reliable ignition and combustion. To control the power output a spark ignition engine is throttled, thus reducing the mass of fuel and air in the combustion chamber; this reduces the cycle efficiency. In contrast, for compression ignition engines with fuel injection the mixture is close to stoichiometric only at the flame front. The output of compression ignition engines can thus be varied by controlling the amount of fuel injected; this accounts for their superior part load fuel economy.

Fast Response CO2 Sensor for Automotive Exhaust Gas Analysis

Abstract: A fast response sensor for measuring carbon dioxide concentration has been developed for laboratory research and tested on a spark ignition engine. The sensor uses the well known infra-red absorption technique with a miniaturized detection system and short capillary sampling tubes, giving a time constant of approximately 5 milliseconds; this is sufficiently fast to observe changes in CO2 levels on a cycle-by-cycle basis under normal operating conditions. The sensor is easily located in the exhaust system and operates continuously. The sensor was tested on a standard production four cylinder spark-ignition engine to observe changes in CO2 concentration in exhaust gas under steady state and transient operating conditions. The processed sensor signal was compared to a standard air-to-fuel ratio (AFR) sensor in the exhaust stream and the results are presented here. The high frequency response CO2 measurements give new insights into both engine and catalyst transient operation. Copyright © 1999 Society of Automotive Engineers, Inc.

In-cylinder pressure estimation using structural vibration measurements of spark ignition engines

Abstract: The knowledge of in-cylinder pressure of spark ignition engines can be used for various tasks in engine management, e.g. misfire detection, optimal spark timing, etc. Unfortunately direct measurement is still to expensive. We present a novel approach to reconstruct the in-cylinder pressure of a spark ignition engine from measurements of structural vibrations. A method for identifying the transfer function from pressure to vibration is presented. Once the transfer function is known, the pressure can be reconstructed from measurements of vibration. Real data experiments show the capability of the proposed methods.

Development and Validation of a Model for Mechanical Efficiency in a Spark Ignition Engine

Abstract: A set of models for the prediction of mechanical efficiency as function of the operating conditions for an automotive spark ignition engine is presented. The models are embedded in an integrated system of models with hierarchical structure for the analysis and the optimal design of engine control strategies. The validation analysis has been performed over a set of more than 400 steady-state operating conditions, where classical engine variables and pressure cycles were measured. Models with different functional structures have been tested; parameter values and indices of statistical significance have been determined via nonlinear and step-wise regression techniques. The Neural Network approach (Multi Layer Perceptrons with BackPropagation) has been also used to evaluate the feasibility of using such an approach for fast black-box modelization. The proposed regression models, characterized by a very limited computational demand, exhibit excellent performance over a large set of experimental data, with less than ten parameters but requiring a rather complex engine geometrical and operative description. On the other hand, the Neural Network model has been developed considering as independent variables only four measurable engine parameters and the training has been performed using a reduced set of experimental data. The results presented show a relevant precision improvement with respect the available models cited in literature. The different model structures developed are suitable for several uses, both for off-line and on-line applications.

Local mixture injection to extend the lean limit of spark-ignition engines

Abstract: The effect of charge stratification by direct, in-cylinder injection of a small quantity of propane-air mixture in a single-cylinder, propane-fuelled, spart-ignition engine, has been determined in terms of in-cylinder pressure, flame visualisation and exhaust emissions. The operating conditions ranged from low load to wide open throttle at 1000 and 1500 rpm, and with quiescent and swirling in-cylinder flows. The effects of injection-driven flow and turbulence on combustion have been considered independently of mixture strength by assessing the consequences of injecting a local mixture of an equivalence ratio equal to that of the port-induced charge.

Cylinder injection type internal combustion engine

Abstract: PROBLEM TO BE SOLVED: To attain good lean-burning not depending on the engine speed at low and medium load driving even of a flat type piston in a spark ignition engine to inject fuel directly to a cylinder in an internal combustion engine. SOLUTION: An internal combustion engine is provided with an ignition plug 6 and a fuel injection valve 5 to inject fuel directly in a cylinder. A cylinder center axis is defined as Z axis, an axis crossing with the Z axis vertically and passing through a gravitational point of the cylinder and a point directly under the fuel ignition valve 5 is defined as X axis, and an axis passing through the gravitational point of the cylinder, which is perpendicular to the X axis and the Z axis is defined as Y axis. At that time, airflow turning around the center of the axis is formed in a cylinder 1. Injected fuel 16 is set so that the fuel injection quantity control can be carried out. In this case, air-fuel ratio becomes higher than stoichiometric air-fuel ratio under an atomization state where the spray angle perpendicular to the XZ plane becomes narrower than the spray angle parallel to the XZ plane in the low and medium load driving. Fuel is injected during the periods from the latter half of the intake stroke to the former half of the compression stroke.