Combustion In Spark Ignition Engine Research Articles

Effect of Pressure and Dilution on Flame Front Displacement in Boosted Spark-Ignition Engine Combustion

The development of new types of engines (such as, the 'downsizing' engine) needs new characterizations and understandings of the combustion process inside the combustion chamber. Indeed, the usual turbulent premixed combustion models to represent as well as possible the combustion processes occurring in spark ignition (S.I) engine are based on the flamelet theory. But the operation mode for Boosting S.I engines are not usual for flame development: high pressure level and high dilution rate. Therefore, this paper investigates experimentally the local flame propagation of isooctane-air-diluents stoichiometric mixtures in a boosted S.I engine. The Mie scattering laser tomography technique is used to obtain the local flame front displacement in typical operating conditions of a 'downsizing' S.I. engine (i.e. high pressure level and high dilution rate). The turbulence and the flame front displacement characterizations are performed for the same burnt fraction angle (~5%) over the intake pressure and Exhaust Gas Recirculation (EGR) ranges: pressure = 0.70 to 1.50 bars and EGR = 10 to 35% by volume. Thank to the mean flame front displacement velocity (Sd) and the mean aerodynamic flow field (UGas) determined from the laser tomography images and Particle Image Velocimetry (PIV), turbulent burning velocity (ST) is estimated. Thus, the behaviour of the turbulent burning velocity should be analyzed in order to provide a more comprehension of the combustion in downsizing conditions and a database for testing various models of premixed turbulent combustion. A number of various empirical correlations for the combustion rate (ST/SL0), available in the literature, are then tested and compared with our experimental trends. The results show an increase in ST by pressure despite the decrease in the laminar burning velocity (SL0) and a decrease in ST by EGR. In spite of some discrepancies and that this empirical correlations are based on the flamelet theory, theory still liable to discussion in downsizing conditions, good agreement between correlation and experimental results are obtained.

A search for maximum efficiency and NOx reduction through spark-ignition engine design optimization at λ=1

In this study a multizone model of spark-ignition engine combustion is validated and used to predict the thermal efficiency and NO x emissions of the engine. The model is validated against an engine map obtained from an extensive series of experiments. An optimizing algorithm based on particle swarm concepts is applied to the model to find a trade-off between efficiency and NO x emissions using a predefined cost function. Optimization is performed for three cases, each of which progressively includes more variables for optimization. A further constrained optimization case is performed with constant values of several of the variables set at the average values found in the three prior cases. These variables are the ones that change over a small domain. The results show the potential improvement in efficiency while achieving remarkably low NO x emissions. They emphasize the importance of exhaust gas recirculation (EGR) at high compression ratio and high loads when the maximum in-cylinder pressures are very high. They also suggest some strategies for valve timings that use internal EGR (residual gas) and move towards different compression and expansion ratios (Atkinson cycle).

Development and validation of a multi-zone combustion model for performance and nitric oxide formation in syngas fueled spark ignition engine

The development of a zero-dimensional, multi-zone combustion model is presented for predicting the performance and nitric oxide (NO) emissions of a spark ignition (SI) engine. The model is validated against experimental data from a multi-cylinder, four-stroke, turbocharged and aftercooled, SI gas engine running with syngas fuel. This alternative fuel, the combustible part of which consists mainly of CO and H 2 with the rest containing non-combustible gases, has been recently identified as a promising substitute of fossil fuels in view of environmentally friendly engine operation. The basic concept of the model is the division of the burned gas into several distinct zones, unlike the simpler two-zone models, for taking into account the temperature stratification of the burned mixture during combustion. This is especially important for accurate NO emissions predictions, since NO formation is strongly temperature dependent. The multi-zone formulation provides the chemical species concentrations gradient existing in the burned zones, as well as the relative contribution of each burned zone to the total in-cylinder NO formation. The burning rate required as input to the model is expressed as a Wiebe function, fitted to experimentally derived burn rates. All model’s constants are calibrated at one operating point and then kept unchanged. Zone-resolved combustion related information is obtained, assisting in the understanding of the complex phenomena occurring during combustion in SI engines. Combustion characteristics of the lean-burn gas engine tested are provided for the complete load range, aiding the interpretation of its performance and knocking tendency. Computed NO emissions from the multi-zone model for various values of the engine load (i.e. air–fuel ratios) are presented and found to be in good agreement with the respective experimental ones, providing confidence for the predictive capability of the model. The superiority of the multi-zone model over its two-zone counterpart is demonstrated in view of its more realistic in-cylinder NO emissions predictions when compared to the available experimental data.

SI2-1: Prediction of performance and pollutants in spark ignition engines using a 0D coherent flame model(SI: Spark-Ignition Engine Combustion,General Session Papers)

SI2-1: Prediction of performance and pollutants in spark ignition engines using a 0D coherent flame model(SI: Spark-Ignition Engine Combustion,General Session Papers)

SI2-3: Development and Application of Gasoline/EtOH Combustion Mechanism : Modeling of Direct Injection Ethanol Boosted Gasoline Engine(SI: Spark-Ignition Engine Combustion,General Session Papers)

SI2-3: Development and Application of Gasoline/EtOH Combustion Mechanism : Modeling of Direct Injection Ethanol Boosted Gasoline Engine(SI: Spark-Ignition Engine Combustion,General Session Papers)

SI1-1: The effect of early inlet valve closing on combustion within a direct injection spark ignition engine(SI: Spark-Ignition Engine Combustion,General Session Papers)

To develop an understanding of the combustion produced by two different valve strategies the techniques of combustion imaging, for flame front propagation, and laser Doppler anemometry, LDA, for the air flow and turbulence characteristics in the vicinity of the spark plug were applied in the optical engine configured to replicate the 2000 rpm 2.7 bar IMEP load point of a conventional thermodynamic engine for both valve strategies. A sequence of combustion images were taken at 4^0 CA intervals to span the entire combustion event with fifty images taken at each crankangle to produce a mean image for each crankangle in the sequence. A Matlab code, utilising the "jet" colormap, identified the minimum and maximum visible flame intensity levels and the intensity contour corresponding to the flame front overlaid with the combustion chamber outline. A radial coordinate system was applied which allowed the flame front propagation and velocity to be quantified in both the vertical and horizontal planes. Laser Doppler anemometry was applied to quantify the time resolved mean and fluctuating flow characteristics of the axial and cross flow components directly below the spark plug in the pent roof. The engine was motored, without fuel injection, to establish the flow field likely to exist at the time of spark and the appearance of the flame kernel.

SI1-4: High Compression Ratio Operation of SI Engines without Knocking by Controlling Piston Speed Near TDC(SI: Spark-Ignition Engine Combustion,General Session Papers)

SI1-4: High Compression Ratio Operation of SI Engines without Knocking by Controlling Piston Speed Near TDC(SI: Spark-Ignition Engine Combustion,General Session Papers)

SI1-3: Experimental analysis of the effect of Tumble motion on ignition and instabilities(SI: Spark-Ignition Engine Combustion,General Session Papers)

Many studies have already been conducted in order to improve knowledge on impacts of tumble motion on combustion processes. Furthermore, many studies have also been performed to study the links between flame kernel behaviour and combustion stability. But only a few experimental studies have concentrated on the links between local conditions during the ignition, including the spark itself, and flame kernel. With this study we aim at specifying the occurrence of combustion instabilities, as well as their key factors connected to air flow motion. Thus the current paper presents a study led on 4-valve spark ignition optical single cylinder engine. Different operating conditions were characterized using several optical and non optical diagnostics. The diagnostics used were PIV measurement in the combustion chamber, direct visualizations of the spark and flame visualizations. Additionally, recordings of the intensity and the voltage of the secondary side of the ignition coil, as well as in-cylinder pressure were acquired. The provided analysis confirmed the importance of the link existing between air flow motion prior to spark and combustion stability. Regarding the impact of tumble motion on combustion, it has been showed that the more velocity is obtained at the vicinity of the spark plug, the more cyclic fluctuation of air flow motion occurs. Nevertheless, analyses confirmed that stronger tumble motion is favourable to decrease in the ignition delay by convection of the spark and consecutive flame kernels further from spark plug electrodes, which is directly linked to the resulting ignition duration. Thus the air flow needed at the ignition timing has to be optimized for higher flow velocity, rather than higher flow reproducibility with lower flow velocity.

Effects of hydrogen addition on cycle-by-cycle variations in a lean burn natural gas spark-ignition engine

An experimental study aimed at examining the effects of hydrogen addition on cycle-by-cycle variation (CCV) in an SI engine was conducted on a 6-cylinder throttle body injection natural gas (NG) engine. Two types of fuels, CNG and 80/20 (in volume) CNG/hydrogen mixtures, were used for comparison purposes. The results showed that coefficient of variation (CoV) in both maximum pressure ( P max ) and indicated mean effective pressure (IMEP) could be reduced by hydrogen addition and that positive effect would be more obvious as the engine was further leaned out. The duration of flame development and propagation as well as the CCVs in flame propagation duration could be simultaneously reduced by hydrogen addition, all of which are beneficial to improve combustion stability and thought to be reasons for the reduction in CoV imep . Stability of combustion phasing that is crucial to the effectiveness of ignition timing optimization was also improved by hydrogen. Hydrogen addition was also proved to be good to the control of emission of NO x and unburned HC. Hence it is concluded that hydrogen addition is an effective and applicable approach to keep down CCVs in lean burn spark-ignition engines.

Investigation on the effect of concentration of methane in biogas when used as a fuel for a spark ignition engine

The influence of reduction in the concentration of CO 2 in biogas on performance, emissions and combustion in a constant speed spark ignition (SI) engine was studied experimentally. A lime water scrubber was used to lower carbon dioxide (CO 2) levels from 41% in biogas to 30% and 20%. The tests covered the range of equivalence ratios from rich to the lean operating limit at a constant speed of 1500 rpm and at compression ratio of 13:1 with a masked valve to enhance swirl. With a reduction in the CO 2 level there was a significant improvement in the performance and reduction in emissions of hydrocarbons (HC) particularly with lean mixtures. The lean limit of combustion also gets extended. Heat release rates indicated enhanced combustion rates, which are mainly responsible for the improvement in thermal efficiency. A reduction in the CO 2 level by 10% seemed to be sufficient for reducing HC levels and the NO levels were also not significantly raised. The spark timings were to be retarded by about 5° when the CO 2 concentration was decreased by 10%.

Combustion in a high-speed rotary valve spark-ignition engine

The current paper describes a study of combustion in the Bishop rotary valve engine by means of computation simulations. The combustion model was developed for this research at speeds up to 18 000 r/min and the results from the simulation were compared with experimental data. Sensitivity studies were performed in order to investigate the parametric effects on the combustion simulation of the engine. The major finding of this study was that convection of the flame kernels occurs and has a strong influence on the performance of the engine. The results indicated some insights as to how the combustion process of the engine can be improved.

Improvement of Spark-Ignition (SI) Engine Combustion and Emission during Cold Start, Fueled with Methanol/Gasoline Blends

A three-cylinder, with a bore of 68.5 mm port fuel injection, engine was adopted to study the combustion and emission characteristics of a methanol/gasoline-fueled engine during cold start and warm up. The cylinder pressure analysis indicates that engine combustion is improved with the methanol addition into gasoline. With the increase of the methanol fraction, the flame developing period and the fast burning period are shortened and the indicated mean effective pressures become higher during the first 50 cycles. Meanwhile, a novel quasi-instantaneous measurement system was designed to measure engine emissions during this process. With the increase of the methanol fraction (below 30%), the unburned hydrocarbon and carbon monoxide (CO) are decreased obviously. The measured results show that the hydrocarbon is reduced about 40% at 5 °C and 30% at 15 °C during the cold-start and warm-up period; CO is reduced nearly 70% when the engine is fueled with M30 (30% methanol in volume), and a higher difference in the exhaust gas temperature of about 140 °C is achieved at 200 s after starting than fueled with gasoline.

Towards large eddy simulation of combustion in spark ignition engines

Internal combustion engine simulations are commonly performed using the RANS (Reynolds averaged Navier–Stokes) approach. It gives a correct estimates of global quantities but is by nature not adapted to describe phenomena strongly linked to cyclic variations. On the other hand, large eddy simulation (LES) is a promising technique to determine successive engine cycles. This work demonstrates the feasibility of LES engine cycles simulation by using a flame surface density (FSD) approach. This approach, presented in a first section, combines an Eulerian spark ignition model derived from the RANS AKTIM model [J.M. Duclos, O. Colin, Arc and Kernel Tracking Ignition Model for 3D SI Engines Calculations, Comodia, Nagoya, Japan, 2001, pp. 343–350] and a Coherent Flame Model (CFM) [S. Candel, T. Poinsot, Combust. Sci. Tech. 70 (1990) 1–15; O. Colin, A. Benkenida, C. Angelberger, Oil & Gas Sci. Techn.— Rev. IFP 58 (1) (2003) 47–32] describing the flame propagation. The CFM model, commonly used in RANS simulations, is here formulated in a LES context. In a second part, the whole ignition-combustion model is validated against an experiment relative to the turbulent ignition and flame propagation of a stoichiometric propane-air mixture [B. Renou, A. Boukhalfa, Combust. Sci. Tech. 162 (2001) 347–371]. Finally, LES engine cycles simulations are performed on a real engine configuration. First, the sensitivity of the model to the LES combustion filter size Δ ˆ is examined, showing a weak dependence of the modelling approach to Δ ˆ . Then results are compared to those obtained with the algebraic model for the FSD proposed by Boger et al. [M. Boger, D. Veynante, H. Boughanem, A. Trouvé, Proc. Combust. Inst. 27 (1998) 917–925] and the need for non-equilibrium combustion models is demonstrated.

CFD Study of Heat Transfer in a Spark-Ignition Engine Combustion Chamber

Abstract The objective of this study is the thermal investigation of a typical spark-ignition (SI) engine combustion chamber with particular focus in determination of the locations where the heat flux and heat transfer coefficient are highest. This subject is an important key for some design purposes especially thermal loading of the piston and cylinder head. To this end, CFD simulation using the KIVA-3V CFD code on a PC platform for flow, combustion, and heat transfer in a typical SI engine has been performed. Some results including the temporal variation of the area-averaged heat flux and heat transfer coefficient on the piston, combustion chamber, and cylinder wall are presented. Moreover, the temporal variation of the local heat transfer coefficient and heat flux along a centerline on the piston as well as a few locations on the combustion chamber wall are shown. The investigation reveals that during the combustion period, the heat flux and heat transfer coefficient vary substantially in space and time due to the transient nature of the flame propagation. For example, during the early stages of the flame impingement on the wall, the heat flux undergoes a rapid increase by as much as around 10 times the preimpingement level. In other words, the initial rise of the heat flux at any location is related to the time of the flame arrival at that location.

E224 オンボード計測による火花点火燃焼の解釈(計測2)

E224 オンボード計測による火花点火燃焼の解釈(計測2)

SYSTEM IDENTIFICATION OF THE CRANKSHAFT DYNAMICS IN A 5 CYLINDER INTERNAL COMBUSTION ENGINE

Future emission regulations for internal combustion engines has lead to an increasing interest in control of the combustion process in order to maximize efficiency while keeping the emission levels at a minimum. One possibility to indirectly measure the combustion process quality is by using a crankshaft mounted torque sensor and use model based signal processing techniques to calculate individual cylinder measures of combustion quality. Since the crankshaft is a flexible device the model must be dynamic. In this contribution we present methodology and results of applying system identification techniques for modeling the crankshaft dynamics. Data is collected from an experimental 5 cylinder spark ignited combustion engine and sampled every 1 degree of the crankshaft revolution. For a fixed engine speed the sampling will be almost identical to time based sampling. Data sets from 7 different engine speeds with static operating conditions are used which results in a data set with 7 different sampling frequencies. A frequency domain approach is adopted to estimate a single parametric continuous time model for all engine speeds. The estimated model is evaluated in two soft sensing applications.

INNOVATIVE MODULAR VALVE TRAINS FOR 2015 LOGISTIC BENEFITS BY EMVT

In this paper the way to a 5-day-car with respect to a modular valve train systems for spark ignited combustion engines is shown. The necessary product diversity is shift from mechanical or physical components to software components. Therefore, significant improvements of logistic indicators are expected and shown. The working principle of a camless cylinder head with respect to an electromagnetical valve train (EMVT) is explained and it is demonstrated that shifting physical diversity to software is feasible. The future design of combustion engine systems including customisation can be supported by a set of assistance tools which is shown exemplary.

06/00283 Investigating the effects of LPG on spark ignitionengine combustion and performance: Bayraktar, H. and Durgun, O. Energy Conversion and Management, 2005, 46, (13–14), 2317–2333

06/00283 Investigating the effects of LPG on spark ignitionengine combustion and performance: Bayraktar, H. and Durgun, O. Energy Conversion and Management, 2005, 46, (13–14), 2317–2333

Investigating the effects of LPG on spark ignition engine combustion and performance

Abstract A quasi-dimensional spark ignition (SI) engine cycle model is used to predict the cycle, performance and exhaust emissions of an automotive engine for the cases of using gasoline and LPG. Governing equations of the mathematical model mainly consist of first order ordinary differential equations derived for cylinder pressure and temperature. Combustion is simulated as a turbulent flame propagation process and during this process, two different thermodynamic regions consisting of unburned gases and burned gases that are separated by the flame front are considered. A computer code for the cycle model has been prepared to perform numerical calculations over a range of engine speeds and fuel–air equivalence ratios. In the computations performed at different engine speeds, the same fuel–air equivalence ratios are selected for each fuel to make realistic comparisons from the fuel economy and fuel consumption points of view. Comparisons show that if LPG fueled SI engines are operated at the same conditions with those of gasoline fueled SI engines, significant improvements in exhaust emissions can be achieved. However, variations in various engine performance parameters and the effects on the engine structural elements are not promising.

Phenomenological model for determining velocity field of LPG jet in combustion chamber of direct injection S.I. engine

A phenomenological model has been established to predict the velocity distribution of LPG (Liquefied Petroleum Gas) jet in combustion chamber of spark ignition (SI) engine. A shaped coefficient \(\beta\) governing the similarity of velocity profiles of LPG jets has been defined based on the theoretical and experimental analyses of turbulent diffusion jets. The results show that \(\beta\) is constant for steady jet but it is not the case for unsteady one. The model will enable us to calculate the velocity profiles of LPG jet after ending injection. This is necessary for research of stratified combustion in direct injection LPG SI engines.