Initial Flame Propagation Stabilized by the Analysis of G-equation

In order to meet recent stringent emission regulations, the exhaust catalyst should be heated as early as possible to activate the purifying reactions. In a direct injection spark-ignition engine, a combination of late fuel injection during the compression stroke and late ignition in the expansion stroke is a common strategy to quickly raise exhaust gas temperature for subsequent rapid activation of exhaust catalysts. However, this approach under cold start-up of an engine often results in incomplete and unstable combustion. In this study, to explore the conditions of stable ignition and combustion, the effect of injection timing on indicated mean effective pressure and early combustion duration (MBD0.5) are first investigated by an analysis of the pressure indicator diagram. As this analysis shows a strong correlation between indicated mean effective pressure and MBD0.5, the mechanism of initial flame propagation is investigated intensively using optical diagnostics. Namely, mean equivalence ratio of mixtures in the propagating flame front is measured by focusing on the ratio of C2* to CH* emission intensities. The flow velocity and turbulence intensity around the spark electrode are measured by the back-scattering laser Doppler anemometry. Two major conclusions are derived from this study: First, when the injection timing is retarded, the mean equivalence ratio increases as the time for the injected fuel to travel and diffuse is shortened. The most preferable mean equivalence ratio for fast initial combustion is found to lie in a range from 1.2 to 1.4. Second, when the second injection timing is retarded further, the mean equivalence ratio increases exceeding 1.4, and this results in slower and more fluctuated initial flame propagation. But, if the turbulent intensity is increased by means of the spray induced air motion, the slowed initial combustion can be recovered.

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Cycle Variation Analysis of Initial Flame Propagation Process in a Model Engine

10.4271/2004-01-3007 ◽

2004 ◽

Cited By ~ 1

Author(s):

Ken Naitoh

Keyword(s):

Flame Propagation ◽

Variation Analysis ◽

Propagation Process ◽

Cycle Variation ◽

Initial Flame ◽

Model Engine

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Numerical Simulation on the Working Process of a Lean Burn Natural Gas Engine

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.664.916 ◽

2013 ◽

Vol 664 ◽

pp. 916-922

Author(s):

Li Yan Feng ◽

Chun Huan Zhang ◽

Chang Jun Xiong

Keyword(s):

Natural Gas ◽

Flame Propagation ◽

Mixture Distribution ◽

Spark Ignition Engine ◽

Combustion System ◽

Working Process ◽

Lean Burn ◽

Natural Gas Engine ◽

Initial Flame ◽

Injection Strategies

The working process of a lean burn natural gas spark ignition engine was simulated with a 3-D CFD software package AVL-FIRE. Such simulations were made to analyze and understand the flow field, fuel/air mixture distribution, ignition and flame propagation. The simulations provide basis for the optimization of the combustion system of the engine. Two injection strategies for the pre-chamber enrichment were established and compared. The results indicate that with enrichment injection in the pre-chamber, the fuel/air equivalence ratio is precisely controlled in the range of 1.0 to 1.1, stable ignition in the pre-chamber is ensured, and fast initial flame propagation in main combustion chamber is realized.

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Effects of tumble and swirl flows on turbulence scale near top dead centre in a four-valve spark ignition engine

Proceedings of the Institution of Mechanical Engineers Part D Journal of Automobile Engineering ◽

10.1243/095440703322114988 ◽

2003 ◽

Vol 217 (7) ◽

pp. 607-615 ◽

Cited By ~ 12

Author(s):

K H Lee ◽

C S Lee

Keyword(s):

Flame Propagation ◽

Propagation Speed ◽

Spark Ignition ◽

Spark Ignition Engine ◽

Turbulence Scale ◽

Iccd Camera ◽

Spark Plug ◽

Swirl Flows ◽

Initial Flame ◽

Dead Centre

The in-cylinder flowfield and the turbulence scale at the ignition timing play an important role in enhancing the propagation speed of the initial flame and the engine combustion. The aim of this work is to investigate the effect of tumble and swirl flows on the turbulence scale near the top dead centre in a four-valve spark ignition (SI) engine by an experimental method. In this study, various flowfields such as tumble and swirl flows were generated by intake flow control valves. For investigation of the flowfields, the single-frame particle tracking velocimeter (PTV) and the twocolour particle image velocimeter (PIV) techniques were developed to clarify the in-cylinder flow pattern during the intake stroke and the turbulence intensity near the spark plug during the compression stroke respectively. In addition, the flame propagation was visualized by an ICCD camera, and its images were analysed to compare the flowfields. From these experimental results, the effects of tumble and swirl flows on the turbulence scale and the flame propagation speed were clarified.

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Effects of Inlet Pressure on Ignition of Spray Combustion

International Journal of Aerospace Engineering ◽

10.1155/2018/3847264 ◽

2018 ◽

Vol 2018 ◽

pp. 1-13 ◽

Cited By ~ 2

Author(s):

Jian Chen ◽

Jianzhong Li ◽

Li Yuan

Keyword(s):

Flame Propagation ◽

Temperature Rise ◽

Inlet Pressure ◽

Maximum Temperature ◽

Spray Combustion ◽

Ignition Process ◽

Outlet Temperature ◽

Maximum Temperature Rise ◽

Rise Rate ◽

Initial Flame

To evaluate the effects of inlet pressure on the ignition process of spray combustion, the images of the ignition process were recorded and the outlet temperatures were measured under inlet pressure of 0.04–0.16 MPa. The initial flame formation and flame propagation and the effects of the inlet pressure on the initial flame formation were observed. A variation of outlet temperature, flame propagation, initial time of outlet temperature rise, time of maximum temperature rise, and temperature rise rate was investigated. With increasing inlet pressure, the time of initial flame formation and time of maximum area growth rate of flame decrease and the centroid location move radially. The radial distances of the initial flame centroid gradually increased by about 13%, 5%, 6%, 12%, 57%, and 24%. The trace of flame centroid is determined from the distribution of fuel and is related to the initial SMD of the atomizer. The maximum temperature rise and temperature rise rate are determined by the rate of flame chemical reaction, rate of large drop evaporation, and fuel/air ratio. With increasing inlet pressure, the maximum temperature rise increased by 50%, 58%, 12%, 11%, and −9%, respectively. Meanwhile, the rate of the temperature rise increased by about 47%, 54%, 11%, 11%, and −7%, respectively.

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