Effect of Turbulence on HCCI Combustion

Yu, Rixin; Bai, Xue‐Song; Vressner, Andreas; Hultqvist, Anders; Johansson, Bengt; Olofsson, Jörgen; Seyfried, Hans; Sjöholm, Johannes; Richter, Mattias; Aldén, Marcus

doi:10.4271/2007-01-0183

Cited by 34 publications

(24 citation statements)

References 16 publications

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“…for mass, momentum and energy) are spatially filtered, which results in unknown terms in the transport equations; these terms represent the effect of subgrid scale (SGS) on the resolved scale. In the present numerical solver [16,17,19] the SGS fluxes in the transport equations for scalars (the specific enthalpy, and the progress variable) are modelled using the Smagorinsky model [27], whereas the SGS stresses in the momentum equations are modelled using scale-similarity model [28].…”

Section: Description Of the Saci Les Modelmentioning

confidence: 99%

“…With large temperature stratification the combustion duration can be longer and the pressure-rise-rate can be lower for a given combustion phasing. One important role of turbulence played in HCCI engines is by modulating the temperature stratification in the engine cylinder; turbulence can affect the mixing of the intake gas with the residual gas and similarly it can affect the heat transfer between the intake gas and the hot residual gas, and between the cylinder/piston walls and the charge [17,18]. Under certain conditions, e.g.…”

Section: Introductionmentioning

confidence: 99%

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Large Eddy Simulation of Turbulent Combustion in a Spark-Assisted Homogenous Charge Compression Ignition Engine

Joelsson

Bai

2012

Combustion Science and Technology

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A large eddy simulation (LES) model was developed to simulate the combustion process in a spark-assisted homogeneous charge compression ignition (SACI) engine. First, an ignition and flame propagation model based on a reaction progress variable is presented. The reaction progress variable is defined based on the normalized cumulative heat release. Transport equation for the progress variable is derived where the source terms due to flame propagation and auto-ignition are modelled. The model is then applied to simulate the SACI combustion process with special focus on the interaction between the flame propagation introduced by the spark and the auto-ignition of the homogeneous charge. The engine simulated is a 0.5 litre experimental HCCI engine, with operation conditions ranging from spark-ignition controlled flame propagation to auto-ignition controlled HCCI combustion. In the first stage of SACI combustion, between the spark-ignition and the onset of HCCI auto-ignition, turbulence field governs the heat release rate and pressure-rise-rate in the cylinder. Increasing turbulence promotes the contribution of SI flame to the overall heat release. The second stage combustion, which is in the HCCI auto-ignition mode, is rather sensitive to the temperature field. The numerical results showed that with low initial temperature the SI flame mode prevails; with high initial temperature the HCCI mode prevails. With moderate initial temperature SI flame and HCCI ignition interact more closely, which results in higher sensitivity to the initial temperature and turbulence conditions. This may be the reason of having high cyclic variation found in the previous experiments. IntroductionIn light of today's public concern on green house gas (CO 2 ) emission and air pollution from combustion of fossil fuels, modern internal combustion engines are developed to have high efficient with low emissions. The benefits and shortfalls of the two major combustion concepts, spark ignition (SI) and compression ignition (CI), have over the past decades led to the development of homogenous charge compression ignition (HCCI) engines that can achieve high efficiency and low emissions of NOx and soot by using high compression ratio and excessive air or exhaust gas recirculation (EGR) in the fuel/air mixtures [1][2][3][4].In HCCI engines the combustion phasing is controlled by the auto-ignition of the lean charge. As the ignition delay time is sensitive to temperature of the charge the combustion phasing becomes rather sensitive to the initial flow and intake flow conditions. Furthermore, in HCCI engines the reaction fronts propagate at a velocity typically of an order of magnitude higher than the turbulent flame speed, the combustion duration in HCCI engine can be short if care is not taken to generate a suitable flow and temperature field in the cylinder. This is especially a serious problem when the engine runs at high load, where the pressure-rise-rate can be rather high, resulting in high noise level [5]. A recent review on HCCI combus...

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Section: Description Of the Saci Les Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Large Eddy Simulation of Turbulent Combustion in a Spark-Assisted Homogenous Charge Compression Ignition Engine

Joelsson

Bai

2012

Combustion Science and Technology

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“…Homogeneous charge compression ignition (HCCI) engines have been an active research area recently (Zhong et al, 2005;Naiki, Iida, & Lhomme, 2010;Yu et al, 2007;Janhunen, 2012;Yun, Wermuth, & Najt, 2011) due to their advantages in reducing emissions levels. Regulatory bodies, such as those in Europe, the United States and Japan, are imposing stringent vehicle emissions quality standards (Wesselink, Buijsman, & Annema, 2006;EPA, 2000;Popp, 2004).…”

Section: Introductionmentioning

confidence: 99%

Effect of Different Heat Transfer Models on a Diesel Homogeneous Charge Compression Ignition Engine

Hairuddin

Yusaf²,

Wandel³

2013

Int J Automot Mech Eng

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Homogeneous charge compression ignition (HCCI) engine technology is relatively new and has not matured sufficiently to be commercialized compared with conventional engines. It can use spark and compression ignition engine configurations, capitalizing on the advantages of both: high engine efficiency with low emissions levels. However, the combustion behavior in an HCCI engine is difficult to predict because it has no spark plug or injector. The chemical kinetics mechanism influences the combustion with some heat losses to the cylinder wall. The effect of different heat loss models in a diesel HCCI engine has to be investigated further. A single-zone thermodynamics model was used in this study along with three different heat loss models: Woschni, modified Woschni, and Hohenberg correlations. It was found that the difference in heat loss models leads to a big difference in the heat flux, and the modified Woschni model has the highest heat flux among these models. The effects of the different scaling factor and characteristic velocity were also investigated. The study concluded that the modified Woschni model produced more accurate results, while the Woschni and Hohenberg models require more tuning of constants before they can be used in a diesel HCCI engine.

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“…b-pdf) as well as transported pdfs [29] have been used to simulate the ignition in engines. Yu et al [30][31][32] conducted several LES studies based on a three-dimensional chemistry table. For the subgrid treatment they employed a twodimensional pdf build by assuming independent Gaussian distributions for the total enthalpy and the reaction progress variable.…”

Section: Introductionmentioning

confidence: 99%

“…In [30][31][32] a detailed reaction mechanism is coupled with the LES code using a progress variable approach. Within these consecutive works the authors investigated the sensitivity of the HCCI combustion with respect to an initially imposed turbulence level and temperature inhomogeneity.…”

Section: Introductionmentioning

confidence: 99%

Understanding the Influences of Thermal and Mixture Inhomogeneities on the Auto-Ignition Process in a Controlled Auto-Ignition (CAI) Engine Using LES

Yildar

Kuenne

et al. 2017

Oil & Gas Science and Technology - Rev. IFP Energies nouvel

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-This work applies Large Eddy Simulation (LES) to the combustion process within a CAI engine. The chemical reaction is treated with a pre-tabulation approach based on homogeneous reactor simulations. At this juncture, a five-dimensional chemistry database is employed where the thermochemical properties are a function of the unburnt gas temperature, the air-fuel ratio, the exhaust gas ratio, the pressure, and the reaction progress variable. Statistical quantities are gathered for 20 simulated cycles and the averaged pressure curves get compared to measurements. The simulation data are then used to provide further insight into the auto-ignition process. It will be shown how thermochemical states are distributed within the cylinder and how the ignition quality depends on them. A statistical analysis is conducted to identify manifolds in the multi-dimensional scalar space along which the conditions leading to ignition evolve. Furthermore the strong influence in between consecutive cycles caused by the exhaust gas is investigated to identify the mechanism of cycle-to-cycle variations.

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Effect of Turbulence on HCCI Combustion

Cited by 34 publications

References 16 publications

Large Eddy Simulation of Turbulent Combustion in a Spark-Assisted Homogenous Charge Compression Ignition Engine

Large Eddy Simulation of Turbulent Combustion in a Spark-Assisted Homogenous Charge Compression Ignition Engine

Effect of Different Heat Transfer Models on a Diesel Homogeneous Charge Compression Ignition Engine

Understanding the Influences of Thermal and Mixture Inhomogeneities on the Auto-Ignition Process in a Controlled Auto-Ignition (CAI) Engine Using LES

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