Abstract: Lean burn of compressed natural gas (CNG) can improve its combustion efficiency and lower its combustion temperature, so it is very important to study the control parameters which affect the lean burn of CNG. In this paper, the effects of different air excess factors (AEFs) and different ignition energies on CNG combustion are analyzed by a constant volume bomb combustion test based on schlieren method. The results show that under the same ignition energy, flame propagation speed decreases as AEF increases, and at lean limit point (an AEF of 1.7), the success rate of ignition diminishes with the reduction of ignition energy. In addition, it can be seen from the quantitative analysis on flame propagation that the stronger turbulence can better promote the increase of flame propagation speed

Key words: CNG, constant volume bomb, ignition energy, air excess factor, flame propagation