Study on flame characteristics of low heat value gas

•At equivalent ratio of 1, thetensile flame propagation rate isfastest.•The laminar burning rate of the rich mixture is slightly higher than the lean mixture.•The turbulent flame velocity decreases with the increase of the nitrogen fraction.•The impact of hydrogen ratio on the rapid burning time of mean cycle is small.•Different ignition positions have a great influence on flame morphology. The flame combustion characteristics of low heat value gas are studied by simulation and experimental methods. The flame radius, the stretched flame velocity, and laminar burning velocity at various ratios of nitrogen and fuel/air equivalence ratios are obtained. The turbulent flame propagation rate, the flame development time and rapid burning time of the mean cycle, and the flame surface wrinkle at various hydrogen fractions are also analysed. The influence of different ignition positions on the flame surface wrinkle is studied. The results show that the flame propagation speed is the fastest under the stoichiometric equivalence ratio. With the increase of the volumefraction of nitrogen, the flame propagation speed and the flame surface wrinkles decrease, and the flame development time of the mean cycle increases rapidly. With the increase of the hydrogen fraction, the turbulent flame rate and the flame surface wrinkle gradually increase, while the flame development time of the mean cycle reduces. The increase of nitrogen and hydrogen contents has noobvious effect on the rapid burning time of the mean cycle. The ignition position has a great influence on combustion efficiency and development form of the flame surface.