Direct Injection Stratified Charge Engine Research Articles

Investigation on characteristics of ion current in a methanol direct-injection spark-ignition engine

Investigation on the characteristics of ion current in a direct-injection stratified-charge engine fueled with methanol was conducted. The test engine is a retrofitted 4-cylinder diesel engine with installation of a spark plug. Ion current was measured using the spark plug as ion sensor. Cylinder pressure was recorded and cylinder average temperature was calculated. The band-pass filtering and low-pass filtering method were chosen to extract the frequency and amplitude of ion current for the knock evaluation. Results shows that ion-current signals measured in the methanol engine under normal combustion conditions contain the front-flame stage and the post-flame stage. The characteristic parameters of ion current relate to the methanol engine operating conditions. The pattern of ion current shows high frequency oscillation under the knock conditions, and the amplitude of ion current frequency can reflect the knock intensity. The frequency of ion current signals under knock conditions is ∼7kHz. The knock evaluation index determined by band-pass filtering and low-pass filtering methods is in good agreement with the experimental results. Ion current method can effectively diagnose the knock of direct-injection methanol engines.

Suboptimal Control of Switched Systems With an Application to the DISC Engine

The growing stringency of fuel economy, emissions, and drivability requirements has led to proliferation of powertrain systems that have multiple discrete operating modes. Systematic approaches to the development of optimal and robust control systems for such powertrains are needed to contain their increased development times and costs. In this paper, we propose a new approach for controlling switched systems that is applicable to powertrain systems with multiple operating modes. Our approach reduces the complexity of computing a control law to a linear programming problem defined over a finite number of states in each operating mode. The methodology is designed to be suitable for practical applications while, under appropriate conditions, providing near-optimal performance. An application to the direct injection stratified charge engine with two distinct operating modes is given to illustrate our approach.

Hybrid Model Predictive Control of Direct Injection Stratified Charge Engines

This paper illustrates the application of hybrid modeling and model predictive control techniques to the management of air-to-fuel ratio and torque in advanced technology gasoline direct-injection stratified-charge (DISC) engines. A DISC engine is an example of a constrained hybrid dynamical system, because it can operate in two distinct modes (stratified and homogeneous) and because the mode-dependent constraints on the air-to-fuel ratio and on the spark timing need to be enforced during its operation to avoid misfire, knock, and high combustion variability. In this paper, we approximate the DISC engine dynamics as a two-mode discrete-time switched affine system. Using this approximation, we tune a hybrid model predictive controller with integral action based on online mixed-integer quadratic optimization, and show the effectiveness of the approach through simulations. Then, using an offline multiparametric optimization procedure, we convert the controller into an equivalent explicit piecewise affine form that is easily implementable in an automotive microcontroller through a lookup table of linear gains

Improvement of Stratified Combustion by a Large Amount of Hot EGR (Reduction of Unburned Hydrocarbons)

Unburned hydrocarbons from a direct injection stratified charge engine were greatly reduced by a large amount of hot EGR. A hydraulically controlled variable valve system was used to realize the hot EGR. Almost all the amount of required EGR gas for the NOx reduction was supplied directly from the previous cycle through the exhaust or inlet valves. Two kinds of recirculation were examined in this test. The first was the recirculation through the exhaust valves, which opened additionally during the suction stroke. Another was the recirculation through the inlet valves. The exhaust gas was pushed back to the port during the exhaust stroke through the additionally opened inlet valves and re-induced in the next cycle. Although both methods have the same ability to reduce HC emissions, required EGR was less in the latter method.

Analysis of Turbulent Combustion in Simplified Stratified Charge Conditions.

The stratified charge combustion system has been widely studied due to the significant potentials for low fuel consumption rate and low exhaust gas emissions. The fuel-air mixture formation process in a direct-injection stratified charge engine is influenced by various parameters, such as atomization, evaporation, and in-cylinder gas motion at high temperature and high pressure conditions. It is difficult to observe the in-cylinder phenomena in such conditions and also challenging to analyze the following stratified charge combustion. Therefore, the combustion phenomena in simplified stratified charge conditions aiming to analyze the fundamental stratified charge combustion are examined. That is, an experimental apparatus which can control the mixture distribution and the gas motion at ignition timing was developed, and the effects of turbulence intensity, mixture concentration distribution, and mixture composition on stratified charge combustion were examined. As a result, the effects of fuel, charge stratification, and turbulence on combustion characteristics were clarified.

Studies of NOx, CO, soot formation and oxidation from a direct injection stratified-charge engine using the k-ɛ turbulence model

In this investigation, a model has been developed to predict the performance and emissions—NOx, CO and soot—in a direct injection stratified-charge engine with a Texaco controlled combustion system. This model uses the k-ε turbulence model to determine characteristic velocities for heat transfer calculations and has only an empirical constant, by comparison with the Woschni equation in which separate constants are used for each process in the four-stroke cycle to determine the velocity for use in the Reynolds number. The modified Keck and Blizard model is used for combustion calculation by considering the rapid compression effects on the turbulence intensity. An extended Zel'dovich mechanism has been used to predict NOx emissions. To predict CO emissions, the Zeleknik and McBride models have been used. The model of Hiroyasu and Kodota has been used to predict the mass of soot formed and oxidized. Comparison of the model predictions with available experimental data shows a good agreement. Moreover, the program has a high flexibility for parametric studies to calculate the effect of engine parameters such as fuel-air ratio, engine speed, injection timing period and percentage of exhaust gas recirculation on the performance and emissions characteristics of the engine.

(2-09) Analysis of Turbulent Combustion in Idealized Stratified Charge Conditions((SI-3)S. I. Engine Combustion 3-Flow and Combustion)

The stratified charge combustion system has been widely studied due to the significant potentials for low fuel consumption and low exhaust gas emissions. The mixture formation process for a direct-injection stratified charge engine is influenced by various parameters such as the atomization, the fuel evaporation, and the in-cylinder gas motion at high temperature and high pressure conditions. It is difficult to observe the in-cylinder phenomena in such conditions and also challenging to analyze the following stratified charge combustion. Therefore, the combustion phenomena in idealized stratified charge conditions aiming to analyze the fundamental stratified charge combustion are examined. That is, an experimental apparatus which can control the mixture distribution and the gas motion at ignition timing was developed, and the effects of turbulence intensity, mixture concentration distribution, and mixture composition on stratified charge combustion were examined. The schematic of experimental setup is shown in Fig. 1. Three volumes separated by two partitions were evacuated and then three premixtures were charged simultaneously through pressure regulators. After the charging was completed, the gas motion generator was operated to control turbulence at spark timing. After partitions were removed, ignition was made. As a result, it was found that in stratified charge combustion using propane-air mixture, when the overall equivalence ratio, φo, is unity, no advantages by charge stratification is found, but when φo is set at 0.8 combustion is enhanced by additive effects combining turbulence with charge stratification, and that combustion is enhanced by strong turbulence in slightly stratified charge fields using methane-air mixture, but extending stratification brings unfavorable results compared with the homogeneous condition.

Combustion and emissions in a methane DI stratified charge engine with hydrogen pre-mixing

Characteristics of combustion and emissions in a methane direct injection stratified charge engine premixed with hydrogen lean mixture were analyzed. Results showed the combustion system achieved a higher thermal efficiency due to higher flame propagation velocity and lower exhaust emissions. An increase in the amount of premixed hydrogen stabilizes the combustion to reduce HC and CO exhaust emission, and increases the degree of constant volume combustion and NO x exhaust emission. The increase in NO x emission can be maintained at a lower level with retarded ignition timing without deteriorating the improved thermal efficiency.

Analysis of mixture formation on combustion chamber wall of direct injection stratified charge engine

Analysis of mixture formation on combustion chamber wall of direct injection stratified charge engine

Numerical Investigation of the Combustion Process in a Direct-Injection Stratified Charge Engine

Abstract A numerical study of the turbulent combustion in a direct-injection stratified charge engine is presented. The focus of the present paper is incorporating detailed reaction schemes as well as coupling the turbulent flow characteristics to chemical reactions. In the present application most of the combustion occurs in diffusion flames, and the combustion takes place in the flamelet regime for turbulent combustion. The present model extends the flamelet model for turbulent diffusion flames to conditions of internal engine combustion. The computations are performed using the KIVA-II code that is modified to include the present combustion model. Results are presented for three different engine load conditions. For comparison, there are numerical integrations with simplified chemistry as well as measurements of both the pressure history and the chemical composition of the exhaust gas. The discrepancies between measurements and calculations with the simplified model are greatly improved, for instance, ...

Effects of local premixing on direct-injection stratified-charge combustion in a constant volume bomb.

The direct-injection stratified-charge engine is considered to be a promising alternative to convectional spark-ignition engines. It has the favourable features of high thermal efficiency, low carbon monoxide and nitric oxide emission levels as well as multifuel capability. It has, however, the unfavourable feature of a high unburned hydrocarbon emission level, especially during light-load operations. In order to conquer this problem, the locally near-premixed direct-injection stratified-charge combustion system was examined in this study, using a pancake type constant volume bomb. A mixing promoting projection was attached to he inner circumference of the bomb to make locally near-premixed mixture. Experimental analyses were made on combustion pressure histories and on stratification processes. Some improvements on the maximum combustion pressure, combustion duration and unburned hydrocarbon emission level were obtained by this new system compared to the basic direct-injection stratified-charge combustion.

Spray Photographs, Poppet Lift, and Injection Pressure of an Oscillating Poppet Injector

Sprays from an injector with a conical oscillating poppet and supplied with fuel at injection rates similar to those used in direct-injection stratified-charge engines have been characterized. Instantaneous injection pressure and poppet lift were measured and short-exposure backlit photographs were taken at several times during injection. Spray axial tip penetration and velocity were determined from the photographs. The experiments were conducted in a constant-volume pressure vessel. The gas was nitrogen and the liquid was hexane. The gas temperature was either 25° or 55°C. The experiments included a systematic variation of the ambient pressure, pump speed and injected liquid volume. It was found that the structure of the spray was strongly affected by the chamber pressure. The hollow cone collapsed and injection duration, spray axial initial velocity and tip penetration decreased with increasing chamber pressure. Increasing pump speed decreased both injection duration and number of oscillations.