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Due to environmental and legislative concerns, less polluting and more efficient vehicle powertrain systems must be developed. A first step is a simple, low cost system such as the presented Engine Stop-Start (ESS) system. A 1.9 liter four-cylinder spark-ignition engine with a four-speed automatic transmission was modified to enable fuel off-on transitions during decelerations and stops. Additional hardware includes a 7 kW electric motor-generator, a power electronics module with an inverter and a DCDC converter, a 36 Volt nominal battery system, and minor modifications to the transmission. A control scheme was developed which takes advantage of the system's fuel saving potential while minimally affecting driveability. Tests have shown EPA City fuel economy gains of approximately 12-14 percent while maintaining the same emissions classification. The EPA Highway fuel economy was increased by approximately 1 percent.

1D wave action simulation has been used to construct models of a number of turbocharged spark ignition engines. This paper describes how the models have been applied in the development of those engines. The simulation has been used to optimise a number of components including the inlet and exhaust manifolds, the valve timing and the turbo match. The models have been validated against test data. The method of modelling unsteady flow is described and the behaviour of the turbocharger in unsteady flow investigated.

This paper introduces the preliminary simulation of a four-stroke spark ignition engine. An arbitrary heat release formula was used to predict the cylinder pressure, which was used to find out the indicated work done. The heat transfer from the cylinder, friction and pumping losses also were taken into account to predict the brake mean effective pressure, brake thermal efficiency and brake specific fuel consumption. Most of the parameters that can affect the performance of the four stroke spark ignition engines such as equivalence ratios, spark timing, heat release rate, compression ratios, compression index and expansion index are studied. The use of a real combustion curve has a profound influence on the similarity of the pressure-volume profile to that seen for the real engine. The modeling process is obviously getting closer to reality and is now worth pursuing as a design aid.

The large number of mechanical, electro-magnetic and oleo-dynamic systems for variable valve actuation developed by automotive suppliers demonstrates the great interest that is being devoted to their potential application on internal combustion engines. In the paper, a possible strategy to realize an original engine load control by means of both intake and exhaust variable valve timing (VVT) is briefly presented and the thermodynamic analysis of the performance obtainable with this solution is carried out. The peculiarity of this strategy is that it is possible to directly recirculate the desired mass of exhaust gas with less limitation with respect to the external duct architecture.

Today it is relatively common for modern SI engines to have dual continuously controlled camshaft phasing. To achieve less fuel consumption and emissions the optimal valve timing has to be chosen for every operating point. Conventional grid measurement leads to unacceptably long duration of measurement. This paper shows that statistical experimental methods - like Design of Experiments (DoE) - can shorten test expenses and development time by more than the factor of ten without quality loss. Different layout strategies are applied and compared using the same data set. Using this method the complex relationships of full variable valve trains can be treated, which was not possible until now.

The paper is focused on possibilities to increase low or medium speed torque developed by a twin turbocharged engine, under full load operation. Sequential operation mode is analyzed from the point of view of compressor and possibilities to control transition area. A modality to reduce actual technological complications for a sequential turbocharger operation (STO) is presented by the proposal of a new simplified configuration and a new binary Controlled Blow-off Valve (CBV). More, a new turbocharger topology schema, able to operate in series or parallel connection of the compressors (SPCO) is presented. Comparison with the sequential turbocharger operation mode (STO) reveals the SPCO's mechanism, which can increase in a decisive way the low, and medium speed torque, increase turbochargers' life and simplify the transition operation mode. Solutions presented for a V6 spark ignition engine may be used without any hesitation for all twin turbo engines, including diesel.

For years, secondary air injection Systems have been used to reduce hydrocarbon exhaust emissions for a short period after engine cold start. In the beginning, passive secondary air systems were used, with the airflow driven by the pressure pulsations in the exhaust system. Since 1990, for most applications, active secondary air systems (i. e., systems where air is injected into the hot exhaust gases by a pump) have been employed. Secondary air injection into the hot exhaust gases is realized by a d-c motor driven turbine pump, i. e. a secondary air pump, and a control valve. Numerous factors, including raw engine emissions during cold start and warm up, driveability requirements and the need to adapt to different emissions legislation, dictate the use of secondary air injection systems. The development of other exhaust aftertreatment systems, e. g., close-coupled or heated catalysts as well as packaging and cost factors will influence the market penetration of secondary air systems.

SI engines with gasoline direct injection are currently the focus of development for almost all car manufacturers. After the introduction of DISI engines, first to the Japanese market and after a short time delay also in Europe, a broad variety of technical solutions for efficient stratified concepts can be stated. The targets of the development activities in this field are defined by legislation and customer's demands. The potential reduction of fuel consumption with stratified operation has to be combined with a further improvement of the full load potential of the DISI engine. A substantial part of the development activities are the fulfillment of current and future emission standards. Therefore, in order to realize a highly efficient lean operation, new technologies and strategies in the field of exhaust gas aftertreatment and vehicle application are required.

Gasoline direct injection is one of the best way to reduce fuel consumption of spark ignited engines. Stratified combustion has the advantage of drastically increasing the SI engine efficiency. However, whereas future pollution standards become more restricting, it makes after-treatment of NOx emissions more difficult, especially since NOx traps require very low sulfur level in fuel. Thus, engines working with this type of combustion are expensive to be after-treated and actual consumption benefits on the urban cycles are significantly lower than theoretical expectations without any pollution constraint. Homogeneous stoechiometric conditions present lots of advantages. After-treatment can be easily achieved without too expensive systems and applications of this combustion mode on current naturally aspirated engines show high volumetric efficiency and compression ratio in comparison with intake port injection.

The stochastic properties of continuous time model parameters obtained through discrete least squares estimation are examined. Particular attention is given to the application of estimating the fuel evaporation dynamics of a V-8 SI engine. The continuous time parameter distributions in this case are biased. The bias is shown to be a function of both measurement noise and sampling rate selection. Analysis and experimental results suggest that for each particular model, there is a corresponding optimum sampling rate. A bias compensation formula is proposed that improves the accuracy of least squares estimation without iterative techniques.

Strict legislation standards for automotive emission limits (e.g. ULEV, SULEV), which target for HC conversion rates beyond 99 %, impose the necessity to dramatically shorten catalyst Light-Off time and increase catalytic efficiency through improved catalytic converter heat-up. Especially, in early design stages, modeling thermal energy management is crucial to predict wether emissions standards can be met. The CAE method (Computer Aided Engineering) presented in this study gives the flexibility composing the frontal exhaust system from modular numerical models, which describe heat transfer in single exhaust components, as e.g. takedown-pipes, flexible coupling element (FCE), flanges and conversion characteristics in catalytic converter. Each module upstream of the converter internally couples the energy equations of 1Dgas to 1D/2D-solid-structure, including heat transfer mechanism as radiation, natural and forced convection.

To meet the recent emission standard and fuel economy, it is required to scale down engine component sizes. For the ignition system, we would like to reduce the physical size of an ignition coil as well. However the present direct-ignition (DI) engine requires long spark duration time, and which makes difficult to reduce the physical size of the ignition coil. NTK developed a special method to achieve the goal. The presented paper introduces size reduction of the ignition coil and shortening the spark duration time for good ignition performance with the carbon fouling detection capability. Occurrence of the carbon fouling accompanies abnormal spark around the spark nose area always. Accordingly, this paper describes also a method detecting the abnormal spark, by using discharge current method or spark plug voltage. Furthermore, this paper describes the method of early detection of misfire and evasive control by detecting the abnormal spark.

A misfire detection study on a prechamber equipped spark ignition gas combustion engine is presented. The study shows that the logarithm of the absolute valued ion current can be linearly weighted in order to detect misfire over a broad load range with only one threshold. Results also show that a very low complexity misfire detector can achieve good performance when a linear weighting technique is applied to the squared rotational speed samples. The detection performance based on the combination of rotational speed and ionization measurements is also presented.

A spray model for pressure-swirl atomizers that is based on a linearized instability analysis of liquid sheets has been combined with an ignition and combustion model for stratified charge spark ignition engines. The ignition model has been advanced, such that the presence of dual spark plugs can now be accounted for. Independent validation of the spray model is achieved by investigating a pressure-swirl injector inside a pressure bomb containing air at ambient temperature. In a second step, the complete model is used to estimate the performance of a small marine DISI Two-Stroke engine operating in stratified charge mode. Simulation results and experimental data are compared for several different injection timings and the agreement is generally good such that there is confidence in the predictive quality of the combustion model. Finally the model is applied in a conceptual study to investigate possible benefits of split injections.

The influence of ethanol content in gasoline on speciated emissions from a direct injection stratified charge (DISC) SI engine is assessed. The engine tested is a commercial DISC one that has a wall guided combustion system. The emissions were analyzed using both Fourier transform infrared (FTIR) spectroscopy and conventional emission measurement equipment. Seven fuels were compared in the study. The first range of fuels was of alkylate type, designed to have 0, 5, 10 and 15 % ethanol in gasoline without changing the evaporation curve. European emissions certification fuel was tested, with and without 5 % ethanol, and finally a specially blended high volatility gasoline was also tested. The measurements were conducted at part-load, where the combustion is in stratified mode. The engine used a series engine control unit (ECU) that regulated the fuel injection, ignition and exhaust gas recirculation (EGR).

Piston-wetting effects are investigated in an optical direct-injection spark-ignition (DISI) engine. Fuel spray impingement on the piston leads to the formation of fuel films, which are visualized with a laser-induced fluorescence (LIF) imaging technique. Oxygen quenching is found to reduce the fluorescence yield from liquid gasoline. Fuel films that exist during combustion of the premixed charge ignite to create piston-top pool fires. These fires are characterized using direct flame imaging. Soot produced by the pool fires is imaged using laser elastic scattering and is found to persist throughout the exhaust stroke, implying that piston-top pool fires are a likely source of engine-out particulate emissions for DISI engines.

The recent emergence of production Gasoline Direct Fuel Injection (GDFI) engines into the world markets offers the promise of both improved fuel economy and emissions for 4-stroke Spark Ignition (SI) engines. However with all new technologies there are new challenges that accompany them. The subjects of fuel and intake system and combustion chamber deposits in Port Fuel Injected (PFI) SI engines are well researched and documented. Today only a small amount of specific research exists for GDFI engines [1,2,3,4]. In any case, based on available PFI deposit literature it is possible to make a number of observations about the likely GDFI fuel and intake system deposit issues and their effect on fuel economy, exhaust emissions and performance during a lifetime of service.

A systematic experimental investigation was undertaken to compare the fuel consumption and exhaust emissions of a production SI engine fueled by either gasoline or compressed natural gas (CNG). The investigation was carried out on a two-liter four-cylinder engine featuring a fast-burn pent-roof chamber, one centrally located spark plug, four valves per cylinder and variable intake-system geometry. The engine was originally designed at Fiat to operate with unleaded gasoline and was then converted at Politecnico di Torino to run on CNG. A Magneti Marelli IAW electronic module for injection-duration and spark-advance setting was used to obtain a carefully controlled multipoint sequential injection for both fuels.

Experimental investigations relating to the use of producer gas in a spark ignition engine are reported in the proposed paper. The experimental setup consists of a single cylinder diesel engine converted to operate on a spark ignition engine mode coupled to a swinging field electrical dynamometer. A downdraft closed top charcoal gasifier has been used to generate the producer gas. After cooling and cleaning, it is fed to a venturi type gas carburetor, which ensures proper mixing of gas and air before it enters the engine. Testing of the converted engine was carried out under gasoline mode at a specified compression ratio. However subsequent tests on producer gas operation were performed at different compression ratios. The significant outcome of the present investigations include the satisfactory conversion of diesel engine to a spark ignition mode for neat producer gas operation and satisfactory operation of gas carburetor designed and developed for the purpose.

Modelling small and large scale fluctuations of fuel distribution is of high interest for stratified direct injection spark ignition (DISI) engines. Homogeneous combustion models need to be extended or replaced in order to account for these fluctuations. They are presently neglected in most engine simulations. Effects of mean fuel/air equivalence ratio gradient have been recently included in previous homogeneous mixture approaches. To account for local fluctuations of mixture composition, the new model ECFM-Z has been developed on the basis of recent Direct Numerical Simulation results and Coherent Flame Surface modelling. The model has been implemented in a CFD code (KMB) The influence of mixture fraction is integrated in the Extended Coherent Flame Surface combustion model. The model is based on a conditional approach. Unburnt hydrocarbons produced by lean flame local extinctions are taken into account.