Showing papers on "Spark-ignition engine published in 2007"

Energy and exergy analyses of a gasoline engine

Abstract: SUMMARY This study presents comparative energy and exergy analyses of a four-cylinder, four-stroke spark-ignition engine using gasoline fuels of three different research octane numbers (RONs), namely 91, 93 and 95.3. Each fuel test was performed by varying the engine speed between 1200 and 2400 rpm while keeping the engine torque at 20 and 40 Nm. Then, using the steady-state data along with energy and exergy rate balance equations, various performance parameters of the engine were evaluated for each fuel case. It was found that the gasoline of 91-RON, the design octane rating of the test engine, yielded better energetic and exergetic performance, while the exergetic performance parameters were slightly lower than the corresponding energetic ones. Furthermore, this study revealed that the combustion was the most important contributor to the system inefficiency, and almost all performance parameters increased with increasing engine speed. Copyright # 2006 John Wiley & Sons, Ltd.

Neural Control of Fast Nonlinear Systems— Application to a Turbocharged SI Engine With VCT

Abstract: Today, (engine) downsizing using turbocharging appears as a major way in reducing fuel consumption and pollutant emissions of spark ignition (SI) engines. In this context, an efficient control of the air actuators [throttle, turbo wastegate, and variable camshaft timing (VCT)] is needed for engine torque control. This paper proposes a nonlinear model-based control scheme which combines separate, but coordinated, control modules. Theses modules are based on different control strategies: internal model control (IMC), model predictive control (MPC), and optimal control. It is shown how neural models can be used at different levels and included in the control modules to replace physical models, which are too complex to be online embedded, or to estimate nonmeasured variables. The results obtained from two different test benches show the real-time applicability and good control performance of the proposed methods.

Instructional Use of a Single-Zone, Premixed Charge, Spark-Ignition Engine Heat Release Simulation:

Abstract: Modeling and computer simulation of an internal combustion engine's operating processes offers a valuable tool for enhancing our understanding of real physical phenomena and contributes significantly to optimizing and controlling the engine's operation to meet different objectives. This paper illustrates the use of engine modeling in the educational setting through the development and use of a single-zone, premixed charge, spark-ignition engine heat release simulation. The paper begins by describing the operation of an engine. A heat release simulation is then discussed in depth, and a description is given of how it can be used to offer an understanding of thermodynamic fundamentals in an internal combustion engine. In particular, a comprehensive examination of the thermodynamic properties of the engine working fluid and in-cylinder gas-to-wall heat transfer demonstrates the need for accurate physical—chemical sub-models when performing a high-fidelity heat release analysis. Overall, this study demonstrat...

Thermodynamic analysis of spark‐ignition engine using a gas mixture model for the working fluid

Abstract: This paper presents thermodynamic analysis of spark-ignition engine. A theoretical model of Otto cycle, with a working fluid consisting of various gas mixtures, has been implemented. It is compared to those which use air as the working fluid with variable temperature specific heats. A wide range of engine parameters were studied, such as equivalence ratio, engine speed, maximum and outlet temperatures, brake mean effective pressure, gas pressure, and cycle thermal efficiency. For example, for the air model, the maximum temperature, brake mean effective pressure (BMEP), and efficiency were about 3000 K, 15 bar, and 32%, respectively, at 5000 rpm and 1.2 equivalence ratio. On the other hand, by using the gas mixture model under the same conditions, the maximum temperature, BMEP, and efficiency were about 2500 K, 13.7 bar, and 29%. However, for the air model, at lower engine speeds of 2000 rpm and equivalence ratio of 0.8, the maximum temperature, BMEP, and efficiency were about 2000 K, 8.7 bar, and 28%, respectively. Also, by using the gas mixture model under these conditions, the maximum temperature, BMEP, and efficiency were about 1900 K, 8.4 bar, and 27%, i.e. with insignificant differences. Therefore, it is more realistic to use gas mixture in cycle analysis instead of merely assuming air to be the working fluid, especially at high engine speeds. Copyright © 2007 John Wiley & Sons, Ltd.

Some aspects concerning the combination of downsizing with turbocharging, variable compression ratio, and variable intake valve lift:

Abstract: The inefficient running of the spark ignition engine at part loads due to the load control method but, mostly, their major weighting in the vehicle's operation time justifies the interest i...

Combustion Characteristics and Heat Release Analysis of a Spark-Ignited Engine Fueled with Natural Gas−Hydrogen Blends

Abstract: Combustion characteristics and heat release analysis of a spark-ignited engine fueled with natural gas−hydrogen blends were investigated. For the same excess air ratio and at the optimum ignition timing setting, the natural gas combustion gives higher values of peak cylinder pressure and peak heat release rate in the case of the rich mixture combustion. In the case of the stoichiometric mixture combustion and the lean mixture combustion, the natural gas−hydrogen blend with a 10% hydrogen fraction gives the highest value of the peak cylinder pressure and the peak heat release rate. The initial combustion duration and the total combustion duration decrease with the increase of hydrogen fraction in the natural gas−hydrogen blend. The addition of hydrogen into natural gas decreases the ignition delay. Although the optimum ignition timing is retarded with the increase of the hydrogen fraction in the natural gas−hydrogen blends, the heat release process is not postponed.

Exhaust emissions and energy release rates from a controlled spark ignition engine using ethanol blends

Abstract: Although alcohols have been considered and used as fuels for internal combustion engines for decades, their use in automotive transportation systems has been rather limited. In the past few years, ethanol has received varying amounts of attention in the United States owing to the increasing cost of gasoline fuel and legislative mandates in some states requiring the sale of alcohol-blended gasoline for light-duty vehicles. This may, in the end, help the agricultural economy in the United States. If alcohol blends are to be used in spark ignition (SI) engines designed to operate on gasoline, then it is important that engines be tuned for the fuel that is being utilized at that instant. This requires knowledge of the combustion characteristics of alcohol blends so that the engine control system can make appropriate changes according to the quality of the blend. The present investigation was conducted to evaluate the combustion and exhaust emissions characteristics of ethanol-gasoline blends in a two-valve automotive SI engine. Ethanol blends improved the specific energy consumption relative to pure gasoline fuel. At stoichiometric air-fuel ratio, the alcohol blends improved exhaust CO emissions marginally. However, there were consistent reductions in NO x levels, particularly with the E-85 blend. The use of E-85 in the engine also resulted in a reduction in HC levels relative to neat gasoline, but E-85 produced significantly higher levels of acetaldehydes by comparison with neat gasoline and lower ethanol blends, particularly at lighter engine loads. The E-85 blend required a longer time to develop and set up the flame in the combustion chamber relative to neat gasoline. This was particularly true at lower engine loads, probably owing to cooling effects of the inducted charge. However, the rapid combustion duration did not exhibit much difference between the blends and gasoline.

Cycle-to-cycle oscillations of heat release in a spark ignition engine

Abstract: Fluctuations of combustion were studied using experimental time series of internal pressure in one of four cylinders in a spark ignition engine. Employing standard statistical methods like histograms and return maps, cycle-to-cycle variations of heat release were analyzed. A substantial difference in system behavior corresponding to quality of combustion was observed with a changing spark advance angle. Examining recurrence plots for a higher spark advance angle formation of specific patterns of vertical lines characteristic to intermittent behavior was found.

Thermal and Flow Fields Modeling of Fast Spark Discharges in Air

Abstract: In this study, a two-dimensional axisymmetric computational model of spark discharge in air is presented to provide a better understanding of the dynamics of the process. Better understanding of the modeling issues in spark discharge processes is an important issue for the automotive spark plug community. In this work we investigate the evolution of the shock front, temperature, pressure, density, geometry, and flow history of a plasma kernel using various assumptions that are typically used in spark discharge simulations. A continuum, inviscid, heat conducting, single fluid description of the flow is considered with radiative losses. Assuming local thermal equilibrium, the energy input due to resistive heating is determined using a specified current profile and temperature-dependent gas electrical conductivity in the gap. The spark discharge model focuses on the early time flow physics, the relative importance of conduction and radiation losses, the influence of thermodynamic model choice and ambient pressure effects.

A Learning Algorithm for Optimal Internal Combustion Engine Calibration in Real Time

Abstract: Advanced internal combustion engine technologies have increased the number of accessible variables of an engine and our ability to control them. The optimal values of these variables are designated during engine calibration by means of a static correlation between the controllable variables and the corresponding steady-state engine operating points. While the engine is running, these correlations are being interpolated to provide values of the controllable variables for each operating point. These values are controlled by the electronic control unit to achieve desirable engine performance, for example in fuel economy, pollutant emissions, and engine acceleration. The state-of-the-art engine calibration cannot guarantee continuously optimal engine operation for the entire operating domain, especially in transient cases encountered in driving styles of different drivers. This paper presents the theoretical basis and algorithmic implementation for allowing the engine to learn the optimal set values of accessible variables in real time while running a vehicle. Through this new approach, the engine progressively perceives the driver’s driving style and eventually learns to operate in a manner that optimizes specified performance indices. The effectiveness of the approach is demonstrated through simulation of a spark ignition engine, which learns to optimize fuel economy with respect to spark ignition timing, while it is running a vehicle.Copyright © 2007 by ASME

Spray Development, Flow Interactions and Wall Impingement in a Direct-Injection Spark-Ignition Engine

Abstract: Levels of liquid fuel impingement on in-cylinder surfaces in direct injection spark ignition engines have typically been higher than those in port-fuel injection engines due to in-cylinder injection and higher injection pressures. The result is typically an increase in the levels of un-burned hydrocarbons and smoke emissions which reduce the potential fuel economy benefits associated with direct injection engines. Although different injection strategies can be used to reduce these effects to some extent, full optimisation of the injection system and combustion process is only possible through improved understanding of spray development that can be obtained from optical engine investigations under realistic operating conditions. To this extent, the spray formation from a centrally mounted multihole injector was studied in a single-cylinder optical directinjection spark-ignition engine under part-load conditions (0.5 bar intake plenum pressure) at 1500 RPM. A highspeed camera and laser illumination were used to obtain Mie-scattering images of the spray development on different in-cylinder planes for a series of consecutive engine cycles. The engine temperature was varied to reflect cold-start (20 °C) and fully warm (90 °C) engine conditions. A multicomponent fuel (commercial gasoline) and a singlecomponent fuel (iso-octane) were both tested and compared to investigate the effects of fuel properties on spray formation and wall impingement. An experimental arrangement was also developed to detect in-cylinder liquid fuel impingement using heat flux sensors installed on the cylinder liner. Two different injection strategies were tested; a typical single-injection strategy in the intake stroke to promote homogeneous mixture formation, as well as a triple-injection strategy around the same timing to assess the viability of using multiple-injection strategies to reduce wall impingement and improve mixture preparation. A sweep of different locations around the cylinder bore revealed the locations of highest fuel impingement levels which did not correspond directly to the nominal spray plume trajectories as a result of spray-flow interactions. These results were analysed in conjunction with the observed effects from the parallel imaging investigation.

Single nozzle injection of gasoline and anti-knock fuel

Abstract: Fuel management system for operation of a spark ignition engine. The system includes a source of gasoline and a source of anti-knock fuel. A proportioning valve receives the gasoline and the anti-knock fuel to discharge a mixture having a controlled gasoline/anti-knock fuel ratio. A single high pressure pump receives the mixture and delivers the mixture to an injector. A fuel management control system controls the proportioning valve and the injector for injection of the mixture into a cylinder of the engine to control knock. A preferred anti-knock fuel is ethanol.

The Experimental Validation of a New Thermodynamic Method for TDC Determination

Abstract: In-cylinder pressure analysis is becoming more and more important both for research and development purpose and for control and diagnosis of internal combustion engines; directly measured by means of a combustion chamber pressure transducers or evaluated by analysing instantaneous engine speed [1,2,3,4], incylinder pressure allows the evaluation of indicated mean effective pressure (IMEP), combustion heat release, combustion phase, friction pressure, etc...It is well known to internal combustion engine researchers that for a right evaluation of these quantities the exact determination of Top Dead Centre (TDC) is of vital importance: a 1° error on TDC determination can lead to evaluation errors of about 10% on the IMEP and 25% on the heat released by the combustion. In this paper the authors present the experimental validation of an original thermodynamic method for the correct evaluation of the “loss angle”, i.e. the angular phase shift between the TDC location and the pressure peak location. The validation has been carried out on a spark ignition engine comparing the results of the thermodynamic method, whose input is the in-cylinder pressure acquired in a “motored” cylinder (i.e. without combustion), with those obtained from a commercial available TDC sensor. The comparative tests aimed to characterize the precision of the proposed method.