Interactions of flame propagation, auto-ignition and pressure wave during knocking combustion

2016 ◽  
Vol 164 ◽  
pp. 319-328 ◽  
Author(s):  
Jiaying Pan ◽  
Gequn Shu ◽  
Peng Zhao ◽  
Haiqiao Wei ◽  
Zheng Chen
Keyword(s):  
Flame Propagation ◽  
Pressure Wave ◽  
Auto Ignition

On the use of a tabulation approach to model auto-ignition during flame propagation in SI engines

2011 ◽  
Vol 88 (12) ◽  
pp. 4968-4979 ◽  
Author(s):  
Vincent Knop ◽  
Jean-Baptiste Michel ◽  
Olivier Colin
Keyword(s):  
Flame Propagation ◽  
Auto Ignition ◽  
Si Engines

A Comparative Study of Methane Combustion Characteristics with Different Additions in an Optical SI Engine

2021 ◽  
Author(s):  
Lin Chen ◽  
Xiao Zhang ◽  
Ren Zhang ◽  
Wanhui Zhao
Keyword(s):  
Natural Gas ◽  
Flame Propagation ◽  
Power Output ◽  
High Speed ◽  
Propagation Speed ◽  
Pressure Oscillation ◽  
Methane Combustion ◽  
Natural Gas Engines ◽  
Auto Ignition ◽  
Flame Propagation Speed

Abstract Natural gas is a promising fuel for IC engines with minimal modification, whereas its low power output and slow flame propagation speed remain a challenge for automobile manufacturers. To find a method of improving the natural gas engines, methane combustion with different additions was comparatively studied. High-speed direct photography and simultaneous pressure were performed to capture detailed combustion evolutions. First, the results of pure methane combustion confirm its good anti-knock property, and no pressure oscillation occurs even there is an end-gas auto-ignition, indicating that high compression ratio and high boosting are effective ways to improve the performance of natural gas engines. Second, adding heavy hydrocarbons can greatly improve engines' power output, but engine knock should be considered if low anti-knock fuel was used. Third, as a carbon-free and gaseous fuel, hydrogen addition can not only increase methane flame propagation speed but reduce cyclic variations. However, a proper fraction is needed under different load conditions. Last, oxygen-enriched combustion is an effective way to promote methane combustion. The heat release becomes faster and more concentrated, specifically, the flame propagation speed can be increased by more than 2 times under 27% oxygen concentration condition. The current study shall give insights into improving natural gas engines' performance.

The Reheat Concept: The Proven Pathway to Ultra-Low Emissions and High Efficiency and Flexibility

2007 ◽  
Author(s):  
Felix Gu¨the ◽  
Jaan Hellat ◽  
Peter Flohr
Keyword(s):  
Power Generation ◽  
Gas Turbine ◽  
Flame Propagation ◽  
High Efficiency ◽  
Flame Stabilization ◽  
Auto Ignition ◽  
Fuel Flexibility ◽  
Stage Combustion ◽  
Low Emission ◽  
Key Topics

Reheat combustion has proven now in over 80 units to be a robust, and highly flexible gas turbine concept for power generation. This paper covers three key topics to explain the intrinsic advantage of reheat combustion to achieve ultra-low emission levels. First, the fundamental kinetic and thermodynamic emission advantage of reheat combustion is discussed analyzing in detail the emission levels of the first and second combustor stages, optimal firing temperatures for minimal emission levels, as well as benchmarking against single-stage combustion concepts. Secondly, the generic operational and fuel flexibility of the reheat system is emphasized, which is based on the presence of two fundamentally different flame stabilization mechanisms, namely flame propagation in the first combustor stage and auto-ignition in the second combustor stage. Finally, the present fleet status is reported by highlighting the latest combustor hardware upgrade and its emission performance.

Numerical Investigation of Fuel Property Effects on Mixed-Mode Combustion in a Spark-Ignition Engine

2019 ◽  
Author(s):  
Chao Xu ◽  
Pinaki Pal ◽  
Xiao Ren ◽  
Sibendu Som ◽  
Magnus Sjöberg ◽  
...  
Keyword(s):  
Heat Release ◽  
Flame Propagation ◽  
Heat Release Rate ◽  
Release Rate ◽  
Octane Number ◽  
Mixed Mode ◽  
Spark Ignition ◽  
Spark Ignition Engine ◽  
Chemical Effect ◽  
Auto Ignition

Abstract In the present study, mixed-mode combustion of an E30 fuel in a direct-injection spark-ignition engine is numerically investigated at a fuel-lean operating condition using multidimensional computational fluid dynamics (CFD). A fuel surrogate matching Research Octane Number (RON) and Motor Octane Number (MON) of E30 is first developed using neural network based non-linear regression model. To enable efficient 3D engine simulations, a 164-species skeletal reaction mechanism incorporating NOx chemistry is reduced from a detailed chemical kinetic model. A hybrid approach that incorporates the G-equation model for tracking turbulent flame front, and the multi-zone well-stirred reactor model for predicting auto-ignition in the end gas, is employed to account for turbulent combustion interactions in the engine cylinder. Predicted in-cylinder pressure and heat release rate traces agree well with experimental measurements. The proposed modelling approach also captures moderated cyclic variability. Two different types of combustion cycles, corresponding to purely deflagrative and mixed-mode combustion, are observed. In contrast to the purely deflagrative cycles, mixed-mode combustion cycles feature early flame propagation followed by end-gas auto-ignition, leading to two distinctive peaks in heat release rate traces. The positive correlation between mixed-mode combustion cycles and early flame propagation is well captured by simulations. With the validated numerical setup, effects of NOx chemistry on mixed-mode combustion predictions are investigated. NOx chemistry is found to promote auto-ignition through residual gas recirculation, while the deflagrative flame propagation phase remains largely unaffected. Local sensitivity analysis is then performed to understand effects of physical and chemical properties of the fuel, i.e., heat of evaporation (HoV) and laminar flame speed (SL). An increased HoV tends to suppress end-gas auto-ignition due to increased vaporization cooling, while the impact of HoV on flame propagation is insignificant. In contrast, an increased SL is found to significantly promote both flame propagation and auto-ignition. The promoting effect of SL on auto-ignition is not a direct chemical effect; it is rather caused by an advancement of the combustion phasing, which increases compression heating of the end gas.

scholarly journals Effects of Flame Propagation Velocity and Turbulence Intensity on End-Gas Auto-Ignition in a Spark Ignition Gasoline Engine

Energies ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 5039
Author(s):  
Lei Zhou ◽  
Xiaojun Zhang ◽  
Lijia Zhong ◽  
Jie Yu
Keyword(s):  
Flame Propagation ◽  
Turbulence Intensity ◽  
Propagation Velocity ◽  
Gasoline Engine ◽  
Pressure Oscillation ◽  
Spark Ignition ◽  
Flame Propagation Velocity ◽  
Eddy Simulation ◽  
Auto Ignition ◽  
Large Eddy

Knocking is a destructive and abnormal combustion phenomenon that hinders modern spark ignition (SI) engine technologies. However, the in-depth mechanism of a single-factor influence on knocking has not been well studied. Thus, the major aim of the present study is to study the effects of flame propagation velocity and turbulence intensity on end-gas auto-ignition through a large eddy simulation (LES) and a decoupling methodology in a downsized gasoline engine. The mechanisms of end-gas auto-ignition as well as strong pressure oscillation are qualitatively analyzed. It is observed that both flame propagation velocity and turbulence have a non-monotonic effect on knocking intensity. The competitive relationship between flame propagation velocity and ignition delay of the end gas is the primary reason responding to this phenomenon. A higher flame speed leads to an increase in the heat release rate in the cylinder, and consequently, quicker increases in the temperature and pressure of the unburned end-gas mixture are obtained, leading to end-gas auto-ignition. Further, the coupling of a pressure wave and an auto-ignition flame front results in super-knocking with a maximum peak of pressure of 31 MPa. Although the turbulence indirectly influences the end-gas auto-ignition by affecting the flame propagation velocity, it can accelerate the dissipation of radicals and heat in the end gas, which significantly influences knocking intensity. Moreover, it is found that the effect of turbulence is more pronounced than that of flame propagation velocity in inhibiting knocking. It can be concluded that the intensity of the pressure oscillation depends on the unburned mixture mass as well as the local thermodynamic state induced by flame propagation and turbulence, with mutual interactions. The present work is expected to provide valuable perspective for inhibiting super-knocking of an SI gasoline engine.

Damköhler Number Analysis on the Effect of Ozone on Auto-Ignition and Flame Propagation in Internal Combustion Engines

2018 ◽  
Author(s):  
Seunghwan Keum ◽  
Tang-Wei Kuo
Keyword(s):  
Flame Propagation ◽  
Ozone Concentration ◽  
Internal Combustion Engines ◽  
Internal Combustion ◽  
Combustion Engines ◽  
Damkohler Number ◽  
Damköhler Number ◽  
Ozone Sensitivity ◽  
Auto Ignition ◽  
Ozone Addition

Ozone assisted combustion has shown promise in stabilizing combustion and extending operating range of internal combustion engines. However, it has been reported that sensitivity of ozone quantity on combustion varies significantly dependent on combustion modes. For example, auto-ignition driv3en combustion in homogeneous charge compression ignition (HCCI) engine was found to be highly sensitive to the ozone concentration, and up to 100 PPM was found to be sufficient to promote combustion. On the other hand, flame propagation in spark-ignited (SI) engine has been reported to be much less sensitive to the ozone amount, requiring ozone concentration about 3000∼6000 PPM to realize any benefit in the flame speed. A better understanding on the ozone sensitivity is required for combustion device design with ozone addition. In this study, a Damköhler number analysis was performed to analyze the vast difference in the ozone sensitivity between auto-ignition and flame propagation. The analysis showed that, for ozone to be effective in flame propagation, the contribution of ozone on chemistry should be large enough to overcome the diffused radical from the oxidation layer. It is expected that similar analysis will be applicable to any additives to provide an understanding of their effect.

scholarly journals Relationship of flame propagation and combustion mode transition of end-gas based on pressure wave in confined space

2020 ◽  
Vol 214 ◽  
pp. 371-386 ◽  
Author(s):  
Xiaojun Zhang ◽  
Haiqiao Wei ◽  
Lei Zhou ◽  
Xiaodong Cai ◽  
Ralf Deiterding
Keyword(s):  
Flame Propagation ◽  
Pressure Wave ◽  
Mode Transition ◽  
Confined Space ◽  
Combustion Mode ◽  
Relationship Of
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