The Experimental Study Of Laser Induced Plasma Assisted Combustion Of Methane Gas

Laser induced plasma assisted combustion[LPAC]is a new combustion technique which can improve the lean burn limit and the flame stability. This technique has many advantages, such as non-invasive 、 plasma function area controlled exactly、and high efficiency. The article carried out the research on the mechanism of thermal effects and flow field structure of laser induced plasma assisted combustion. The mechanism of laser plasma has been analyzed.Firstly, this paper introduced the development of the LPAC, analyzed the research of the time evolution of the flow field structure and the temperature. Based on the Schlieren technique and optical emission spectroscopy, the methods were given to study the flow field structure and temperature, respectively. The sensitivity of emission spectroscopy to temperature was proved by OH and CH emission spectral fitting.Secondly, this article used the Schlieren technique to study the flow field structure in the still air and high speed air flow after the effect of laser plasma. The results are that in still air the flow field developed up and down evenly along with the laser vertical direction, but has a rapid expansion of development along the opposite of laser incident direction. But in the high speed air flow, the flow field structure developed more easily along the flow direction, it is more difficult to form the third wave lobe and the structure disperse more easily. The article studied the flow field structure of the methane diffusion gas and methane/nitrogen/oxygen premixed gas after laser induced plasma, analyzed the pulse rate needed in different conditions(the minimum lase pulse rate was 133 Hz while the velocity of methane gas was 23.6m/s).It was found that the development of initial flame kernel led to the formation of the flame.Finally, this paper had used the Mckenna flat burner to prove accuracy of the temperature measurement technique by optical emission spectroscopy. The time evolution of core temperature of methane/nitrogen/oxygen premixed gas had been obtained through CH emission. It was found that the temperature after the laser plasma can reach 3000K±300K, which can play a catalytic role in the chemical reaction, and the thermal effect was of great importance for the LPAC process.The achievement of the article is of great importance for the research of laser induced assisted combustion.