A semi-empirical laminar-to-turbulent flame transition model coupled with G equation for early flame kernel development and combustion in spark-ignition engines

2019 ◽  
pp. 146808741986474 ◽  
Author(s):  
Seunghwan Keum ◽  
Guangfei Zhu ◽  
Ronald Grover ◽  
Wei Zeng ◽  
Christopher Rutland ◽  
...  
Keyword(s):  
Turbulent Flame ◽  
Transition Process ◽  
Spark Ignition ◽  
Transition Function ◽  
Spark Ignition Engine ◽  
Navier Stokes ◽  
Flame Kernel ◽  
Eddy Simulation ◽  
Flame Development ◽  
Semi Empirical

It has been reported that early combustion in a spark-ignition engine determines the subsequent combustion. Also, the early combustion has a very strong correlation with cycle-to-cycle variability, which limits engine operating range. As such, accurate modeling of the early flame development is very important in accurate simulation of spark-ignition engine combustion. During the early flame development, the flame kernel, initiated by spark, grows initially at laminar flame speed. As the kernel grows, the flame surface wrinkles due to surface instability and interacts with the flow turbulence as the flame transitions from laminar to turbulent flame. In this study, a semi-empirical model is proposed to simulate the laminar-to-turbulent flame transition process during early spark-ignition combustion. A hyperbolic tangent function was used to emulate the laminar-to-turbulent flame speed transition process. The proposed transition function was evaluated during early flame kernel development for both Reynolds-averaged Navier–Stokes and large eddy simulation models against combustion analysis data from high-speed optical particle image velocimetry. Difference in Reynolds-averaged Navier–Stokes and large eddy simulation transition function was analyzed and discussed.

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.

scholarly journals An Experimental and Simulation Study of Early Flame Development in a Homogeneous-charge Spark-Ignition Engine

2017 ◽  
Vol 72 (5) ◽  
pp. 32
Author(s):  
Y. Shekhawat ◽  
D.C. Haworth ◽  
A. d'Adamo ◽  
F. Berni ◽  
S. Fontanesi ◽  
...  
Keyword(s):  
High Speed ◽  
Spatial Scales ◽  
Model Development ◽  
Optical Diagnostics ◽  
Spark Ignition ◽  
Spark Ignition Engine ◽  
Eddy Simulation ◽  
Computational Mesh ◽  
Flame Development ◽  
The Times

An integrated experimental and Large-Eddy Simulation (LES) study is presented for homogeneous premixed combustion in a spark-ignition engine. The engine is a single-cylinder two-valve optical research engine with transparent liner and piston: the Transparent Combustion Chamber (TCC) engine. This is a relatively simple, open engine configuration that can be used for LES model development and validation by other research groups. Pressure-based combustion analysis, optical diagnostics and LES have been combined to generate new physical insight into the early stages of combustion. The emphasis has been on developing strategies for making quantitative comparisons between high-speed/high-resolution optical diagnostics and LES using common metrics for both the experiments and the simulations, and focusing on the important early flame development period. Results from two different LES turbulent combustion models are presented, using the same numerical methods and computational mesh. Both models yield Cycle-to-Cycle Variations (CCV) in combustion that are higher than what is observed in the experiments. The results reveal strengths and limitations of the experimental diagnostics and the LES models, and suggest directions for future diagnostic and simulation efforts. In particular, it has been observed that flame development between the times corresponding to the laminar-to-turbulent transition and 1% mass-burned fraction are especially important in establishing the subsequent combustion event for each cycle. This suggests a range of temporal and spatial scales over which future experimental and simulation efforts should focus.

An Experimental Investigation of Early Flame Development in an Optical Spark Ignition Engine Fueled With Natural Gas

2018 ◽  
Vol 140 (8) ◽  
Author(s):  
Cosmin E. Dumitrescu ◽  
Vishnu Padmanaban ◽  
Jinlong Liu
Keyword(s):  
Natural Gas ◽  
Flame Propagation ◽  
Combustion Engine ◽  
Turbulent Flame ◽  
Spark Ignition ◽  
Spark Ignition Engine ◽  
Piston Bowl ◽  
Pressure Trace ◽  
Flame Development ◽  
Flame Region

Improved internal combustion engine simulations of natural gas (NG) combustion under conventional and advanced combustion strategies have the potential to increase the use of NG in the transportation sector in the U.S. This study focused on the physics of turbulent flame propagation. The experiments were performed in a single-cylinder heavy-duty compression-ignition (CI) optical engine with a bowl-in piston that was converted to spark ignition (SI) NG operation. The size and growth rate of the early flame from the start of combustion (SOC) until the flame filled the camera field-of-view were correlated to combustion parameters determined from in-cylinder pressure data, under low-speed, lean-mixture, and medium-load conditions. Individual cycles showed evidence of turbulent flame wrinkling, but the cycle-averaged flame edge propagated almost circular in the two-dimensional (2D) images recorded from below. More, the flame-speed data suggested different flame propagation inside a bowl-in piston geometry compared to a typical SI engine chamber. For example, while the flame front propagated very fast inside the piston bowl, the corresponding mass fraction burn was small, which suggested a thick flame region. In addition, combustion images showed flame activity after the end of combustion (EOC) inferred from the pressure trace. All these findings support the need for further investigations of flame propagation under conditions representative of CI engine geometries, such as those in this study.

A comparison of butanol and ethanol flame development in an optical spark ignition engine

Fuel ◽  
2016 ◽  
Vol 170 ◽  
pp. 27-38 ◽  
Author(s):  
Ben G. Moxey ◽  
Alasdair Cairns ◽  
Hua Zhao
Keyword(s):  
Spark Ignition ◽  
Spark Ignition Engine ◽  
Flame Development ◽  
Ethanol Flame

G-equation based ignition model for direct injection spark ignition engines

2021 ◽  
pp. 146808742110139
Author(s):  
Arun C Ravindran ◽  
Sage L Kokjohn ◽  
Benjamin Petersen
Keyword(s):  
Heat Release ◽  
Direct Injection ◽  
Turbulent Flame ◽  
Spark Ignition ◽  
Discharge Process ◽  
Flame Kernel ◽  
Turbulent Flame Speed ◽  
Direct Injection Spark Ignition ◽  
Kernel Growth ◽  
Spark Energy

To accurately model the Direct Injection Spark Ignition (DISI) combustion process, it is important to account for the effects of the spark energy discharge process. The proximity of the injected fuel spray and spark electrodes leads to steep gradients in local velocities and equivalence ratios, particularly under cold-start conditions when multiple injection strategies are employed. The variations in the local properties at the spark plug location play a significant role in the growth of the initial flame kernel established by the spark and its subsequent evolution into a turbulent flame. In the present work, an ignition model is presented that is compatible with the G-Equation combustion model, which responds to the effects of spark energy discharge and the associated plasma expansion effects. The model is referred to as the Plasma Velocity on G-surface (PVG) model, and it uses the G-surface to capture the early kernel growth. The model derives its theory from the Discrete Particle Ignition (DPIK) model, which accounts for the effects of electrode heat transfer, spark energy, and chemical heat release from the fuel on the early flame kernel growth. The local turbulent flame speed has been calculated based on the instantaneous location of the flame kernel on the Borghi-Peters regime diagram. The model has been validated against the experimental measurements given by Maly and Vogel,1 and the constant volume flame growth measurements provided by Nwagwe et al.2 Multi-cycle simulations were performed in CONVERGE3 using the PVG ignition model in combination with the G-Equation-based GLR4 model in a RANS framework to capture the combustion characteristics of a DISI engine. Good agreements with the experimental pressure trace and apparent heat-release rates were obtained. Additionally, the PVG ignition model was observed to substantially reduce the sensitivity of the default G-sourcing ignition method employed by CONVERGE.

Combustion characteristics of a two-stroke spark ignition UAV engine fuelled with gasoline and kerosene (RP-3)

2018 ◽  
Vol 91 (1) ◽  
pp. 163-170 ◽  
Author(s):  
Rui Liu ◽  
Xiaoping Su ◽  
Xiaodong Miao ◽  
Guang Yang ◽  
Xuefei Dong ◽  
...  
Keyword(s):  
Spark Ignition ◽  
Combustion Characteristics ◽  
Spark Ignition Engine ◽  
Bench Test ◽  
Potential Hazard ◽  
Content Type ◽  
Combustion Performance ◽  
Development Period ◽  
Flame Development ◽  
Load Conditions

Purpose The purpose of this paper is to compare the combustion characteristics, including the combustion pressure, heat release rate (HRR), coefficient of variation (COV) of indicated mean effective pressure (IMEP), flame development period and combustion duration, of aviation kerosene fuel, namely, rocket propellant 3 (RP-3), and gasoline on a two-stoke spark ignition engine. Design/methodology/approach This paper is an experimental investigation using a bench test to reflect the combustion performance of two-stroke spark ignition unmanned aerial vehicle (UAV) engine on gasoline and RP-3 fuel. Findings Under low load conditions, the combustion performance and HRR of burning RP-3 fuel were shown to be worse than those of gasoline. Under high load conditions, the average IMEP and the COV of IMEP of burning RP-3 fuel were close to those of gasoline. The difference in the flame development period between gasoline and RP-3 fuel was similar. Practical implications Gasoline fuel has a low flash point, high-saturated vapour pressure and relatively high volatility and is a potential hazard near a naked flame at room temperature, which can create significant security risks for its storage, transport and use. Adopting a low volatility single RP-3 fuel of covering all vehicles and equipment to minimize the number of different devices with the use of a various fuels and improve the application safeties. Originality/value Most two-stroke spark ignition UAV engines continue to combust gasoline. A kerosene-based fuel operation can be applied to achieve a single-fuel policy.

Experimental and Theoretical Analysis of Flame Development and Misfire Phenomena in a Spark-Ignition Engine

1992 ◽  
Author(s):  
Josef Hacohen ◽  
Michael R. Belmont ◽  
Richard W.F. Thurley ◽  
Jim C. Thomas ◽  
E. Layton Morris ◽  
...  
Keyword(s):  
Theoretical Analysis ◽  
Spark Ignition ◽  
Spark Ignition Engine ◽  
Flame Development

scholarly journals LES study on mixing and combustion in a Direct Injection Spark Ignition engine

2018 ◽  
Vol 73 ◽  
pp. 32
Author(s):  
Nicolas Iafrate ◽  
Anthony Robert ◽  
Jean-Baptiste Michel ◽  
Olivier Colin ◽  
Benedicte Cuenot ◽  
...  
Keyword(s):  
Ignition Time ◽  
Direct Injection ◽  
Combustion Process ◽  
Spark Ignition ◽  
Spark Ignition Engine ◽  
Pollutant Emissions ◽  
Spark Ignition Engines ◽  
Eddy Simulation ◽  
Mixture Preparation ◽  
The Impact

Downsized spark ignition engines coupled with a direct injection strategy are more and more attractive for car manufacturers in order to reduce pollutant emissions and increase efficiency. However, the combustion process may be affected by local heterogeneities caused by the interaction between the spray and turbulence. The aim for car manufacturers of such engine strategy is to create, for mid-to-high speeds and mid-up-high loads, a mixture which is as homogeneous as possible. However, although injection occurs during the intake phase, which favors homogeneous mixing, local heterogeneities of the equivalence ratio are still observed at the ignition time. The analysis of the mixture preparation is difficult to perform experimentally because of limited optical accesses. In this context, numerical simulation, and in particular Large Eddy Simulation (LES) are complementary tools for the understanding and analysis of unsteady phenomena. The paper presents the LES study of the impact of direct injection on the mixture preparation and combustion in a spark ignition engine. Numerical simulations are validated by comparing LES results with experimental data previously obtained at IFPEN. Two main analyses are performed. The first one focuses on the fuel mixing and the second one concerns the effect of the liquid phase on the combustion process. To highlight these phenomena, simulations with and without liquid injection are performed and compared.

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