A Numerical Study on the Effect of the Equivalence Ratio of Hydrogen/Air or Methane/Air Mixtures on Minimum Ignition Energy in Spark Ignition Process

The paper describes a numerical study of the combustion of hydrogen enriched methane and biogases containing hydrogen in a Controlled Auto Ignition engine (CAI). A single cylinder CAI engine is modelled with Chemkin to predict engine performance, comparing the fuels in terms of indicated mean effective pressure, engine efficiency, and pollutant emissions. The effects of hydrogen and carbon dioxide on the combustion process are evaluated using the GRI-Mech 3.0 detailed radical chain reactions mechanism. A parametric study, performed by varying the temperature at the start of compression and the equivalence ratio, allows evaluating the temperature requirements for all fuels; moreover, the effect of hydrogen enrichment on the auto-ignition process is investigated. The results show that, at constant initial temperature, hydrogen promotes the ignition, which then occurs earlier, as a consequence of higher chemical reactivity. At a fixed indicated mean effective pressure, hydrogen presence shifts the operating range towards lower initial gas temperature and lower equivalence ratio and reduces NOx emissions. Such reduction, somewhat counter-intuitive if compared with similar studies on spark-ignition engines, is the result of operating the engine at lower initial gas temperatures.

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A Numerical Study on Effects of Electrode Gap and Heat Loss on Flame Kernel Formation in Spark Ignition Process for Methane/Air Mixtures

TRANSACTIONS OF THE JAPAN SOCIETY OF MECHANICAL ENGINEERS Series B ◽

10.1299/kikaib.77.177 ◽

2011 ◽

Vol 77 (773) ◽

pp. 177-185

Author(s):

Shinji NAKAYA ◽

Mitsuhiro TSUE ◽

Michikata KONO ◽

Daisuke SEGAWA ◽

Toshikazu KADOTA

Keyword(s):

Heat Loss ◽

Numerical Study ◽

Spark Ignition ◽

Ignition Process ◽

Electrode Gap ◽

Flame Kernel

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Numerical Investigation of Mixing Characteristic for CH4/Air in Rotating Detonation Combustor

Applied Sciences ◽

10.3390/app10041298 ◽

2020 ◽

Vol 10 (4) ◽

pp. 1298

Author(s):

Shan Jin ◽

Qingyang Meng ◽

Zhiming Li ◽

Ningbo Zhao ◽

Hongtao Zheng ◽

...

Keyword(s):

Mass Flow ◽

Flow Rate ◽

Pressure Loss ◽

Equivalence Ratio ◽

Numerical Study ◽

Ignition Energy ◽

Flow Rates ◽

Mass Flow Rates ◽

Critical Ignition ◽

Rotating Detonation

The mixing process of fuel and oxidizer is a very critical factor affecting the real operating performance of non-premixed rotating detonation combustor. In this paper, a two-dimensional numerical study is carried out to investigate the flow and mixing characteristics of CH4/air in combustor with different injection structures. On this basis, the effect of CH4/air mixing on the critical ignition energy for forming detonation is theoretically analyzed in detail. The numerical results indicate that injection strategies of CH4 and air can obviously affect the flow filed characteristic, pressure loss, mixing uniformity and local equivalence ratio in combustor, which further affect the critical ignition energy for forming detonation. In the study for three different mass flow rates (the mass flow rates of air are 12.01 kg/s,8.58 kg/s and 1.72 kg/s, respectively), when air is radially injected into combustor (fuel/air are injected perpendicular to each other), although the mixing quality of CH4 and air is improved, the total pressure loss is also increased. In addition, the comparative analysis also shows that the increase of mass flow rate of CH4/air can decrease the difference of the critical ignition energy for forming detonation at a constant total equivalence ratio. The ignition energy decreases with the decrease of the total flow rate and then increases gradually.

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