Study On Smoke Concentration Measurement By Pulse Laser

Laser is vulnerable to be scattered and absorbed by smoke while it propagates in aerosols. Basing on the characteristics of the laser, this paper builds an experimental platform for detecting smoke laser scattering characteristics and measuring concentration.The characteristics of four typical smokes by pulse laser transmission were studied experimentally. Create a mathematical model of pulse laser transmission in smoke based on laser transmission theory and Monte Carlo method. Put forwards a method of distinguishing smoke type and calculating the smoke concentration.In this paper, there are several aspects following researched:(1) Basing on Mie scattering theory, establish a Monte Carlo simulation model. It contains photon transmission model, smoke density meter model and so on as the core of pulse laser transmitted in smoke.(2) Build an experimental system by pulse laser to detect smoke concentration. It mainly consists of pulse laser emission system, smoke box, pulse laser receiver system and so on. Use the mode of “a transmitter four receivers” for experimental research to detect four typical smokes.(3) Test scattering characteristics of four typical smokes and calculate the relative intensity ratio. The results show that: the relative intensity ratio of scattered light relates to smoke species, and has nothing to do with the concentration of smoke. When the smoke species is unknown, it is feasible to distinguish smoke species by the relative intensity ratio.Testing the transmission characteristics of four typical smokes to get real-time optical density of smoke.(4) Combining theory with experiment, using MATLAB software to simulate smoke scattering and transmission characteristics by Monte Carlo simulation method. Obtain the transmission characteristics of smoke by pulse laser. Comparing simulation results with experimental values to analyze error. Experimental results agree with simulation results well. It illustrates that the experimental program is feasible and the experimental system is reliable.(5) Use the transmission characteristics in smoke by pulse laser to calculate smoke optical density. Give the empirical formula between optical density and the mass concentration of smoke of a characteristic parameter.(6) According to the experimental scheme proposed in this paper, multi-angle detecting smoke density by pulse laser can distinguish the species of smoke. In particular,when smoke species is unknown, as long as there are more than two angles matched, you can determine the species of smoke and the concentrations. Using laser scattering method to express smoke concentration is fast and real-time, and it lays the groundwork for detecting transmission characteristics and measuring smoke concentration by laser.