| Along with the rapid development of social civilization and science and technology, humans began to conduct large-scale activities of material production, large quantities of industrial waste and domestic waste because of production, resulting in a serious environmental pollution, and air pollution is worth paying more attention. At present, the problem of air pollution in China is particularly serious, especially in northern cities, the phenomenon of high haze, PM2.5, etc., has been a wake-up call for people. Air pollution mainly comes from industrial waste gas, life coal, automobile exhaust gas. Among them, the main nitrogen oxide is one of the main gas state pollutants. In order to understand NO temporal and spatial distribution characteristics of vehicle exhaust and coal combustion gases, and further improve the control nitrogen oxide(NOx) emissions of combustion equipment. In this paper, the application of planar laser induced fluorescence(referred to as PLIF) method has been used to research distribution characteristics of the nitric oxide molecules in time and space of methane / air pre mixed flame plume.PLIF measurement method is mainly that laser is shaped to flaky beam, particles will be excited to high-energy state, by measuring fluorescence from the high-energy state transitions to lower energy state to obtain a section of the information, by changing the location of the excitation, so that we can obtain the fluorescence information of the arbitrary spatial position of the flow field. NO-PLIF(Planar Laser-Induced fluorescence of Nitric Oxide) technology is the use of PLIF technology to obtain the fluorescence information of NO molecules at any time, the space position of the flow field.In this paper, firstly we studied the theoretical formula of NO molecular transition energy levels. The relationship of NO-PLIF signal intensity with the incident laser energy, NO molecular number density, fluorescence radiation efficiency and detection system constant was determined; At the same time, we applied LIFBASE simulation software to simulate absorption coefficient of NO molecular X2∏'A2∑(0,0) transitions, determined the choice of NO molecular excitation wavelength range, and corrected laser wavelength offset within the scope of 1.9~4.2pm, selected transitions branch of the NO molecular was Q1(12)+Q12(20)+Q2(20)(226.033nm), at last we selected wavelength laser 226.029nm; According to the principle of prism splitting, the energy of the incident laser was determined, realized the real-time detection of laser energy; The incident laser energy was changed in 0.1~1.1m J, in order to verify the relationship of the NO-PLIF signal intensity and the incident laser energy was linear. It is proved that the laser energy was weak at this experimental time, and was weakly excited, satisfied the experimental conditions; Secondly, the optimal time delay of ICCD camera was 133 ns, the best gate width was 20 ns, the best total number was 20 times by controlling the variable method; Finally in the best experimental condition of NO-PLIF technology, changing the premixed gas equivalence ratio of 0.7~1.3, the intensity of NO-PLIF signal increased with the increasing of the equivalent ratio. Parallel on the burner surface orientation no distribution was uniform and at the same time, the application of rhodamine dye to stimulate the longitudinal distribution of the laser energy was modified. The modified different equivalence ratios NO-PLIF signal strength a slightly decreased with increasing height, indicating that at this time NO concentration reduced with high degree increasing. |
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