An experimental study on premixed laminar and turbulent combustion of synthesized coalbed methane. (1st December 2015) - Zheng, Shizhuo
Abstract: Coalbed methane is an economic and sustainable alternative fuel for spark ignition engines. In a constant volume combustion bomb, an experimental study was conducted about laminar and turbulent burning characteristics of the premixed coalbed methane/air flames. The turbulent burning velocities of coalbed methane-air mixtures were obtained as well as unstretched laminar burning velocities and Markstein lengths of coalbed methane at different rms (root-mean-square) turbulent velocities of 0.03, 0.05, 0.1 m/s, equivalence ratios of 0.8–1.2, and pressures of 0.1, 0.3 MPa. The results reveal that the unstretched laminar burning velocities of the premixed coalbed methane/air mixtures decrease with the increase of N2 volumetric fractions and the initial pressures. The Markstein lengths increase with the rise of the N2 volumetric fractions and the equivalence ratios, but decrease with the increase of initial pressures. With the increase of rms turbulent velocity, the turbulent burning velocities of coalbed methane/air mixtures are promoted at the equivalence ratios ranging from 0.8 to 1.2. The ratio of turbulent burning velocity to laminar burning velocity decreases with the increase of the equivalence ratios, while it increases with the increase of N2 volumetric fractions in coalbed methane. Highlights: Laminar and turbulent burning velocities of the coalbed methane were obtained. The hydrodynamic instability tends to maintain the spherical turbulent flame. The peak turbulent burning velocity occurred at stoichiometric ratio. L b increases with the increase of R N 2 and the equivalence ratios. There is a linear relation between u t r ′ / u l and u ′ / u l .