Experimental and numerical study on laminar burning characteristics of premixed methane–hydrogen–air flames Erjiang Hu, Zuohua Huang*, Jiajia He, Chun Jin, Jianjun Zheng State Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University, Xi’an 710049, People’s Republic of China article info Article history: Received 15 January 2009 Received in revised form 25 March 2009 Accepted 26 March 2009 Available online 25 April 2009 Keywords: Methane Hydrogen Laminar burning velocity Markstein length Sensitivity analysis Flame structure abstract An experimental and numerical study on laminar burning characteristics of the premixed methane–hydrogen–air flames was conducted at room temperature and atmospheric pressure. The unstretched laminar burning velocity and the Markstein length were obtained over a wide range of equivalence ratios and hydrogen fractions. Moreover, for further understanding of the effect of hydrogen addition on the laminar burning velocity, the sensitivity analysis and flame structure were performed. The results show that the unstretched laminar burning velocity is increased, and the peak value of the unstretched laminar burning velocity shifts to the richer mixture side with the increase of hydrogen fraction. Three regimes are identified depending on the hydrogen fraction in the fuel blend. They are: the methane-dominated combustion regime where hydrogen fraction is less than 60%; the transition regime where hydrogen fraction is between 60% and 80%; and the methane-inhibited hydrogen combustion regime where hydrogen fraction is larger than 80%. In both the methane-dominated combustion regime and the methane-inhibited hydrogen combustion regime, the laminar burning velocity increases linearly with the increase of hydrogen fraction. However, in the transition regime, the laminar burning velocity increases exponentially with the increase of hydrogen fraction in the fuel blends. The Markstein length is increased with the increase of equivalence ratio and is decreased with the increase of hydrogen fraction. Enhancement of chemical reaction with hydrogen addition is regarded as the increase of H, O and OH radical mole fractions in the flame. Strong correlation is found between the burning velocity and the maximum radical concentrations of H and OH in the reaction zone of the premixed flames. ª 2009 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved. 1. Introduction With the depletion of crude oil reverses and the strengthening of automotive emission legislations, the development of alternative fuel engines has attracted more and more atten- tion in engine community. Natural gas is a clean fuel in which methane is its major component, is considered to be one of the favorable fuels for engines. The natural-gas-fuelled engines have been realized in the spark-ignition engines. However, due to the slow burning velocity of natural gas and its poor lean-burn capability, the natural gas spark-ignited engine still remains its disadvantages like low thermal effi- ciency, large cycle-by-cycle variation, and poor lean-burn capability, and these will decrease the engine power output and increase the fuel consumption [1,2]. One of the effective methods to solve the problem of slow burning velocity of * Corresponding author. Tel.: þ86 29 82665075; fax: þ86 29 82668789. E-mail address: zhhuang@mail.xjtu.edu.cn (Z. Huang). Available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/he 0360-3199/$ – see front matter ª 2009 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.ijhydene.2009.03.058 international journal of hydrogen energy 34 (2009) 4876–4888