Development of a Species-Based Extended Coherent Flamelet Model (SB-ECFM) for Gasoline Direct Injection Engine (GDI) Simulations

2018 ◽  
Author(s):  
O. Colin ◽  
S. Chevillard ◽  
J. Bohbot ◽  
P. K. Senecal ◽  
E. Pomraning ◽  
...  
Keyword(s):  
Reference Model ◽  
Mixture Fraction ◽  
Direct Injection ◽  
Gasoline Direct Injection ◽  
Current Work ◽  
Flamelet Model ◽  
Progress Variable ◽  
Auto Ignition ◽  
Mass Fractions ◽  
The Difference

The current work presents a recent development of the Extended Coherent Flamelet Model (ECFM) for 3D combustion modeling in spark-ignited gasoline engines. The reference-based ECFM model, originally published in 2003, computes the conditional unburned and burned gas species mass fractions from both real species and species tracers. This current work is motivated by two limitations of the reference-based model. First, the difference between convection of species tracers and convection of real species leads to small discrepancies between the two, due to high velocity gradients during gas exchange. This can lead to inaccurate estimation of the progress variable and consequently to negative conditional mass fractions in the burned gases after ignition. Second, the reference-based ECFM model assumes implicitly that the unburned and burned states correspond to the same mixture fraction. This assumption is valid for low stratification cases, but it can lead to substantial conditioning errors for highly stratified systems like gasoline direct injection (GDI) engines. To address these shortcomings, a new species-based ECFM (SB-ECFM) implementation is presented. In this species-based model, the unburned and burned gas states are entirely defined by the transported species in each zone. It is shown that SB-ECFM more reliably defines conditional quantities and the progress variable. This enhancement allows the use of a second-order central scheme in space when using full decoupling of auto-ignition and premixed flame progress variables as proposed in Robert et al., Proc. Comb. Inst, 2015, while the reference model is limited to the first-order upwind scheme in this case. Finally, simulations of a GDI engine are presented at different loads and rpm conditions. It is shown that, with the higher order scheme, SB-ECFM demonstrates very good agreement with measured pressure.

scholarly journals Numerical Simulation of Knock Combustion in a Downsizing Turbocharged Gasoline Direct Injection Engine

2019 ◽  
Vol 9 (19) ◽  
pp. 4133 ◽  
Author(s):  
Wang ◽  
Zhang ◽  
Wang ◽  
Han ◽  
Chen
Keyword(s):  
Direct Injection ◽  
Combustion Process ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Gasoline Direct Injection ◽  
Valve Lift ◽  
Fuel Droplets ◽  
Gasoline Direct Injection Engine ◽  
Auto Ignition ◽  
Combustion Simulation

Engine knock has become the prime barrier to significantly improve power density and efficiency of the engines. To further look into the essence of the abnormal combustion, this work studies the working processes of normal combustion and knock combustion under practical engine operating conditions using a three-dimensional computation fluid dynamics (CFD) fluid software CONVERGE (Version 2.3.0, Convergent Science, Inc., Madison, USA). The results show that the tumble in the cylinder is gradually formed with the increase of the valve lift, enhances in the compression stroke and finally is broken due to the extrusion of the piston. The fuel droplets gradually evaporate and move to the intake side under the turbulent and high temperature in the cylinder. During the normal combustion process, the flame propagates faster on the intake side and it facilitates mixture in cylinder combustion. During the knock combustion simulation, the hotspots near the exhaust valve are observed, and the propagating detonation wave caused by multiple hotspots auto-ignition indicates significant effects on knock intensity of in-cylinder pressure.

Simulation-Aided Development of Prechamber Ignition System for a Lean-Burn Gasoline Direct Injection Motor-Sport Engine

2020 ◽  
Vol 142 (8) ◽  
Author(s):  
Muhammed Fayaz Palakunnummal ◽  
Priyadarshi Sahu ◽  
Mark Ellis ◽  
Marouan Nazha
Keyword(s):  
Thermal Efficiency ◽  
Direct Injection ◽  
Fuel Mixture ◽  
Gasoline Direct Injection ◽  
Lean Burn ◽  
Ignition System ◽  
Motor Sport ◽  
Auto Ignition ◽  
Computational Fluid Dynamics Cfd ◽  
Sport Events

Abstract Due to recent regulation changes to restricted fuel usage in various motor-sport events, motor-sport engine manufacturers have started to focus on improving the thermal efficiency and often claim thermal efficiency figures well above equivalent road car engines. With limited fuel allowance, motor-sport engines are operated with a lean air–fuel mixture to benefit from higher cycle efficiency, requiring an ignition system that is suitable for the lean mixture. Prechamber ignition is identified as a promising method to improve lean limit and has the potential to reduce end gas auto-ignition. This paper analyses the full-load performance of a motor-sport lean-burn gasoline direct injection (GDI) engine and a passive prechamber is developed with the aid of a computational fluid dynamics (CFD) tool. The finalized prechamber design benefited in a significant reduction in burn duration, reduced cyclic variation, knock limit extension, and higher performance.

Effect of Conical Spray and Multi-Hole Spray on Gasoline Engine Mixture Formation and Combustion Performance Based on Different Injection Strategies

2020 ◽  
Vol 143 (6) ◽  
Author(s):  
Shengli Wei ◽  
Zhiqing Yu ◽  
Zhilei Song ◽  
Fan Yang ◽  
Chengcheng Wu
Keyword(s):  
Gasoline Engine ◽  
Direct Injection ◽  
Mixture Distribution ◽  
Gasoline Direct Injection ◽  
Injection Timing ◽  
Mixture Formation ◽  
Injection Strategy ◽  
Gdi Engine ◽  
The Difference ◽  
Injection Strategies

Abstract This article presents a numerical investigation carried out to determine the effects of second and third injection timing on combustion characteristics and mixture formation of a gasoline direct injection (GDI) engine by comparing conical spray against multihole spray. The results showed that at the engine 80% full load of 2000 r/min, the difference in mixture distribution between the two sprays was obvious with double and triple injection strategies. With the second injection timing from 140 deg CA delay to 170 deg CA, the in-cylinder pressure, the in-cylinder temperature, and the heat release rate of the conical spray increased by 20.8%, 9.8%, and 30.7% and that of the multihole spray decreased by 30.7%, 13.6%, and 37.8%. The delay of the injection time reduced the performance of the engine with the multihole spray, and the performance of the multihole spray was obviously in the simulation of the triple injection strategy. However, for the conical spray, the application of the triple injection strategy increased the temperature and the pressure compared with the double injection strategy.

Flamelet Studies of Reduced and Detailed Kinetic Mechanisms for Methane/Air Diffusion Flames

2000 ◽  
Author(s):  
Foluso Ladeinde ◽  
Xiaodan Cai ◽  
Balu Sekar
Keyword(s):  
Dissipation Rate ◽  
Diffusion Flames ◽  
Mixture Fraction ◽  
Intermediate Species ◽  
Flamelet Model ◽  
Mass Fractions ◽  
Kinetic Mechanisms ◽  
Moderate Effect ◽  
Extinction Strain Rate ◽  
Air Diffusion

We adopt a steady-state flamelet model in this paper to study the performance of reduced and detailed kinetic mechanisms for methane/air diffusion flames. Through the numerical calculations, we investigate the sensitivity of the main and intermediate species mass fractions to the mixture fraction dissipation rate, χ. Our results seem to suggest a weak to moderate effect of χ on the calculated species mass fraction. It has also been shown in this paper that the current flamelet calculations fail to predict the extinction strain rate.

Development of a Multi-Phase Flamelet Generated Manifold for Spray Combustion Simulations

2020 ◽  
Author(s):  
Xu Zhang ◽  
Ran Yi ◽  
C. P. Chen
Keyword(s):  
Mixture Fraction ◽  
Diffusion Reaction ◽  
Spray Combustion ◽  
Direct Integration ◽  
Interphase Heat Transfer ◽  
Similarity Reduction ◽  
Progress Variable ◽  
Flamelet Generated Manifold ◽  
Significant Difference ◽  
Mass Fractions

Abstract In this study, a model flame of quasi-1D counterflow spray flame has been developed. The two-dimensional multiphase convection-diffusion-reaction (CDR) equations have been simplified to one dimension using similarity reduction under the Eulerian framework. This model flame is able to directly account for non-adiabatic heat loss as well as multiple combustion regimes present in realistic spray combustion processes. A spray flamelet library was generated based on the model flame. To retrieve data from the spray flamelet library, the enthalpy was used as an additional controlling variable to represent the interphase heat transfer, while the mixing and chemical reaction processes were mapped to the mixture fraction and the progress variable. The spray-flamelet/progress-variable (SFPV) approach was validated against the results from the direct integration of finite-rate chemistry as a benchmark. The SFPV approach gave a better performance in terms of temperature predictions, while the conventional gas-phase flamelet/progress-variable (FPV) approach over-predicted by nearly 20%. In terms of species mass fractions, there was no significant difference between the two, both showing good agreements with the direct integration of chemistry (DIC) model.

Analysis of the GDI Spray Dynamics Through Multidimensional Modeling and Flow Visualization in an Optically Accessible SI Engine

2014 ◽  
Author(s):  
Michela Costa ◽  
Ugo Sorge ◽  
Paolo Sementa ◽  
Alessandro Montanaro
Keyword(s):  
Direct Injection ◽  
Gasoline Direct Injection ◽  
Si Engine ◽  
Engine Model ◽  
Working Cycle ◽  
3D Engine ◽  
Experimental Side ◽  
The Difference ◽  
Wall Interaction ◽  
Injection Strategies

Present work is aimed at studying into detail mixture formation and combustion in a gasoline direct injection (GDI) engine working under stoichiometric mixture conditions. The study is performed both numerically and experimentally. From the experimental side, the engine, optically accessible, is characterized by collecting, for various injection strategies, in-cylinder pressure cycles and digital images. From the numerical side, a 3D engine model is developed, that includes proper sub-models for the spray dynamics and the spray-wall interaction. This last phenomenon is studied into detail by resorting to a preliminary 3D simulation of the spray impingement realized in a proper experiment, where the engine injector is mounted at a certain distance from a cold or hot wall. An interesting comparison between numerical and experimental images of the in-cylinder spray dynamics is presented, that also allows individuating the difference in the wallfilm deposition under various injection strategies. This opens the way to understand the difference in the combustion development arising as injection is anticipated or retarded in the engine working cycle.

Influence of Humid Air on Gaseous Combustion of Gasturbines

2005 ◽  
Author(s):  
Yue Wang ◽  
Gang Xu ◽  
Chaoqun Nie ◽  
Yunhan Xiao ◽  
Weiguang Huang ◽  
...  
Keyword(s):  
Mixture Fraction ◽  
Pollutant Emission ◽  
No Production ◽  
Humid Air ◽  
Flamelet Model ◽  
Chemical Mechanisms ◽  
Flow Recirculation ◽  
Chemical Reaction Mechanism ◽  
The Difference ◽  
Hot Zone

Combustion with humid air is a key process of humid air turbine (HAT) cycle. In the present study, the influence of humid air on gas turbine combustion was studied both experimentally and numerically. Performance of a full-scale can-type combustor equipped with a diffusion burner was investigated when burning propane and syn-gas with various humidity of intake air. The results indicate that the effect of humid air on pollutant emission depends on fuel type due to the difference of chemical mechanisms. For the syn-gas flames, moisture addition can effectively reduce NO emission without increasing CO. A numerical model was developed to simulate the 3D flow field in the combustor when burning syn-gas. The mixture fraction approach and the laminar flamelet model were applied to simulate the diffusion flame. The thermochemical quantities of the flamelets were computed by adopting a detailed chemical reaction mechanism for the H2-CO-N2-O2 system. The numerical results show that an oval hot zone above 2100 K is formed near the axis of the combustor due to flow recirculation. The hot zone mainly accounts for the thermal NO in the syn-gas flames. With the moisture addition into intake air, the volume of this zone is substantially decreased, and, therefore, the NO production is suppressed. This explains the NO reduction due to humid air observed in the experiment.

Homogeneous auto-ignition — the future of gasoline direct injection?

MTZ worldwide ◽  
2002 ◽  
Vol 63 (10) ◽  
pp. 15-17 ◽  
Author(s):  
Günter Karl Fraidl ◽  
Walter F. Piock ◽  
Alois Fürhapter ◽  
Eduard M. Unger ◽  
Thomas Kammerdiener
Keyword(s):  
Direct Injection ◽  
Gasoline Direct Injection ◽  
Auto Ignition ◽  
The Future

scholarly journals A combustion model sensitivity study for CH4/H2 bluff-body stabilized flame

2007 ◽  
Vol 221 (11) ◽  
pp. 1377-1390 ◽  
Author(s):  
M Hossain ◽  
W Malalasekera
Keyword(s):  
Bluff Body ◽  
Mixture Fraction ◽  
Sensitivity Study ◽  
Combustion Model ◽  
Flamelet Model ◽  
Combustion Models ◽  
Mass Fractions ◽  
Experimental Values ◽  
Constituent Mass ◽  
Laminar Flamelet

The objective of the current work is to assess the performance of different combustion models in predicting turbulent non-premixed combustion in conjunction with the k-∊ turbulence model. The laminar flamelet, equilibrium chemistry, constrained equilibrium chemistry, and flame sheet models are applied to simulate combustion in a CH4/H2 bluff-body flame experimentally studied by the University of Sydney. The computational results are compared to experimental values of mixture fraction, temperature, and constituent mass fractions. The comparison shows that the laminar flamelet model performs better than other combustion models and mimics most of the significant features of the bluff-body flame.

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