Towards large eddy simulation of combustion in spark ignition engines

2007 ◽  
Vol 31 (2) ◽  
pp. 3059-3066 ◽  
Author(s):  
S. Richard ◽  
O. Colin ◽  
O. Vermorel ◽  
A. Benkenida ◽  
C. Angelberger ◽  
...  
Keyword(s):  
Large Eddy Simulation ◽  
Spark Ignition ◽  
Spark Ignition Engines ◽  
Eddy Simulation ◽  
Large Eddy

Large-eddy simulation of the flow in a direct injection spark ignition engine using an open-source framework

2020 ◽  
pp. 146808742090362
Author(s):  
Mateus Dias Ribeiro ◽  
Alex Mendonça Bimbato ◽  
Maurício Araújo Zanardi ◽  
José Antônio Perrella Balestieri ◽  
David P Schmidt
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Large Eddy Simulation ◽  
Open Source ◽  
Direct Injection ◽  
Spark Ignition ◽  
Spark Ignition Engines ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Direct Injection Spark Ignition

Direct injection spark ignition engines aim at reducing specific fuel consumption and achieving the strict emission standards in state of the art internal combustion engines. This can be achieved by research comprising experimental methods, which are normally expensive and limited, and computational fluid dynamics methods, which are often more affordable and less restricted than their experimental counterpart. In the latter approach, the costs are mainly related to the acquisition, usage, and maintenance of computational resources, and the license cost when commercial computational fluid dynamics codes are used. Therefore, in order to make the research of direct injection spark ignition engines and their internal processes more accessible, this article proposes a novel open-source and free framework based on the OpenFOAM computational fluid dynamics library for the simulation of the internal flow in direct injection spark ignition engines using a large-eddy simulation closure for modeling the turbulence within the gas phase. Finally, this framework is tested by simulating the Darmstadt engine in motored operation, validating the results with experimental data compiled by the Darmstadt Engine Workshop.

Laminar-to-turbulent flame transition and cycle-to-cycle variations in large eddy simulation of spark-ignition engines

2020 ◽  
pp. 146808742096234
Author(s):  
Yunde Su ◽  
Derek Splitter ◽  
Seung Hyun Kim
Keyword(s):  
Large Eddy Simulation ◽  
Early Stage ◽  
Turbulent Flame ◽  
Transition Process ◽  
Spark Ignition ◽  
Transition Model ◽  
Flame Kernel ◽  
Eddy Simulation ◽  
Proposed Model ◽  
Large Eddy

This paper investigates the effect of laminar-to-turbulent flame transition modeling on the prediction of cycle-to-cycle variations (CCVs) in large eddy simulation (LES) of spark-ignition (SI) engines. A laminar-to-turbulent flame transition model that describes the non-equilibrium sub-filter flame speed evolution during an early stage of flame kernel growth is developed. In the present model, the flame transition is characterized by the flame kernel size at which the flame transition ends, defined here as the flame transition scale. The proposed model captures the effects that variations in a turbulent flow field have on the evolution of early-stage burning rates, through variations in the flame transition scale. The proposed flame transition model is combined with the front propagation formulation (FPF) method and a spark-ignition model to predict CCVs in a gasoline direct injection SI engine. It is found that multi-cycle LES with the proposed flame transition model reproduces experimentally-observed CCVs satisfactorily. When the transition model is not considered or when variations in the transition process are neglected, CCVs are significantly under-predicted for the case considered here. These results indicate the importance of modeling the laminar-to-turbulent flame transition and the effect of turbulence on the transition process, when predicting CCVs, under certain engine conditions. The LES results are also used to analyze sources for variations in the flame transition. It is found, for the present engine case, that the most important source is the cycle-to-cycle variation in the turbulence dissipation rate, which is used to measure the strength of turbulence in the proposed model, near a spark plug. The large-scale velocity field and the variations of the laminar flame speed due to the mixture composition and thermal stratification are also found to be important factors to contribute to the variations in the flame transition.

Validation of Species-Based Extended Coherent Flamelet Model in a Large Eddy Simulation of a Homogeneous Charge Spark Ignition Engine

2020 ◽  
Author(s):  
Y. See ◽  
M. Wang ◽  
J. Bohbot ◽  
O. Colin
Keyword(s):  
Large Eddy Simulation ◽  
Computational Cost ◽  
Spark Ignition ◽  
Spark Ignition Engine ◽  
Cylinder Pressure ◽  
Flamelet Model ◽  
Progress Variable ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Homogeneous Charge

Abstract The Species-Based Extended Coherent Flamelet Model (SB-ECFM) was developed and previously validated for 3D Reynolds-Averaged Navier-Stokes (RANS) modeling of a spark-ignited gasoline direct injection engine. In this work, we seek to extend the SB-ECFM model to the large eddy simulation (LES) framework and validate the model in a homogeneous charge spark-ignited engine. In the SB-ECFM, which is a recently developed improvement of the ECFM, the progress variable is defined as a function of real species instead of tracer species. This adjustment alleviates discrepancies that may arise when the numerical treatment of real species is different than that of the tracer species. Furthermore, the species-based formulation also allows for the use of second-order numeric, which can be necessary in LES cases. The transparent combustion chamber (TCC) engine is the configuration used here for validating the SB-ECFM. It has been extensively characterized with detailed experimental measurements and the data are widely available for model benchmarking. Moreover, several of the boundary conditions leading to the engine are also measured experimentally. These measurements are used in the corresponding computational setup of LES calculations with SB-ECFM. Since the engine is spark ignited, the Imposed Stretch Spark Ignition Model (ISSIM) is utilized to model this physical process. The mesh for the current study is based on a configuration that has been validated in a previous LES study of the corresponding motored setup of the TCC engine. However, this mesh was constructed without considering the additional cells needed to sufficiently resolve the flame for the fired case. Thus, it is enhanced with value-based Adaptive Mesh Refinement (AMR) on the progress variable to better capture the flame front in the fired case. As one facet of model validation, the ensemble average of the measured cylinder pressure is compared against the LES/SB-ECFM prediction. Secondly, the predicted cycle-to-cycle variation by LES is compared with the variation measured in the experimental setup. To this end, the LES computation is required to span a sufficient number of engine cycles to provide statistical convergence to evaluate the coefficient of variation (COV) in peak cylinder pressure. Due to the higher computational cost of LES, the runtime required to compute a sufficient number of engine cycles sequentially can be intractable. The concurrent perturbation method (CPM) is deployed in this study to obtain the required number of cycles in a reasonable time frame. Lastly, previous numerical and experimental analyses of the TCC engine have shown that the flow dynamics at the time of ignition is correlated with the cycle-to-cycle variability. Hence, similar analysis is performed on the current simulation results to determine if this correlation effect is well-captured by the current modeling approach.

scholarly journals Numerical Analysis of End-Gas Autoignition and Pressure Oscillation in a Downsized SI Engine Using Large Eddy Simulation

Energies ◽  
2019 ◽  
Vol 12 (20) ◽  
pp. 3909 ◽  
Author(s):  
Zhong ◽  
Liu
Keyword(s):  
Large Eddy Simulation ◽  
Gasoline Engine ◽  
Numerical Models ◽  
Pressure Oscillation ◽  
Spark Ignition ◽  
Gasoline Engines ◽  
Eddy Simulation ◽  
Auto Ignition ◽  
Large Eddy ◽  
Primary Reference

Knock and super-knock are abnormal combustion phenomena in engines, however, they are hard to study comprehensively through optical experimental methods due to their inherent destructive nature. In present work, the methodology of large eddy simulation (LES) coupled with G equations and a detailed mechanism of primary reference fuel (PRF) combustion is utilized to address the mechanisms of knock and super-knock phenomena in a downsized spark ignition gasoline engine. The knock and super-knock with pressure oscillation are qualitatively duplicated through present numerical models. As a result, the combustion and onset of autoignition is more likely to occur at top dead center (TDC), which causes end gas at a higher temperature and pressure. It is reasonable to conclude that the intensity of knock is not only proportional to the mass fraction of mixtures burned by the autoignition flame but the thermodynamics of the unburned end-gas mixture, and the effect of thermodynamics is more important. It also turns out that two auto-ignitions occur in conventional knock conditions, while only one auto-ignition takes place in super-knock conditions. However, the single autoignition couples with the pressure wave and they reinforce each other, which eventually evolves into detonation combustion. This work gives the valuable insights into knock phenomena in spark ignition gasoline engines.

Large-eddy simulation analysis of knock in a direct injection spark ignition engine

2018 ◽  
Vol 20 (7) ◽  
pp. 765-776 ◽  
Author(s):  
Anthony Robert ◽  
Karine Truffin ◽  
Nicolas Iafrate ◽  
Stephane Jay ◽  
Olivier Colin ◽  
...  
Keyword(s):  
Large Eddy Simulation ◽  
Simulation Analysis ◽  
Direct Injection ◽  
Spark Ignition ◽  
Spark Ignition Engine ◽  
Eddy Simulation ◽  
Oscillation Analysis ◽  
Spark Timing ◽  
Large Eddy ◽  
Direct Injection Spark Ignition

Downsized spark ignition engines running under high loads have become more and more attractive for car manufacturers because of their increased thermal efficiency and lower CO2 emissions. However, the occurrence of abnormal combustions promoted by the thermodynamic conditions encountered in such engines limits their practical operating range, especially in high efficiency and low fuel consumption regions. One of the main abnormal combustion is knock, which corresponds to an auto-ignition of end gases during the flame propagation initiated by the spark plug. Knock generates pressure waves which can have long-term damages on the engine, that is why the aim for car manufacturers is to better understand and predict knock appearance. However, an experimental study of such recurrent but non-cyclic phenomena is very complex, and these difficulties motivate the use of computational fluid dynamics for better understanding them. In the present article, large-eddy simulation (LES) is used as it is able to represent the instantaneous engine behavior and thus to quantitatively capture cyclic variability and knock. The proposed study focuses on the large-eddy simulation analysis of knock for a direct injection spark ignition engine. A spark timing sweep available in the experimental database is simulated, and 15 LES cycles were performed for each spark timing. Wall temperatures, which are a first-order parameter for knock prediction, are obtained using a conjugate heat transfer study. Present work points out that LES is able to describe the in-cylinder pressure envelope whatever the spark timing, even if the sample of LES cycles is limited compared to the 500 cycles recorded in the engine test bench. The influence of direct injection and equivalence ratio stratifications on combustion is also (MAPO) analyzed. Finally, focusing on knock, a Maximum Amplitude Pressure Oscillation analysis (MAPO) is conducted for both experimental and numerical pressure traces pointing out that LES well reproduces experimental knock tendencies.

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