Research On Laser Particle Size Measurement Of Water Mist

In various fields of scientific and technological applications,the liquid water mist field formed by natural formation and artificial synthesis is widely used and is closely related to people's production and life.The characteristic indexes of water mist field mainly include particle size,concentration,speed,flow rate,pressure,etc.Among them,the particle size of water mist is the most important index.The droplet size is a dynamic process affected by two-phase flow and other environmental factors,so it is difficult to measure droplet size,which is generally expressed by equivalent particle size.The laser particle size analyzer has the characteristics of high accuracy and good repeatability,so it can realize the non-contact real-time online measurement of the mist field particle size.It is difficult to divide the sampling area in a large mist field,so the development of a miniaturized laser particle size meter which can place the whole instrument in the mist field is of great significance for the large mist field measurement.Based on the study of water mist field and fluid characteristics,the laser particle size measurement method is studied by using diffraction(scattering)method,and an online mist particle size meter prototype which can be placed in mist field is developed.Through the field test of particle plate sample and water mist field,the prototype has achieved the expected results.The main work of this dissertation is as follows.1.Based on the analysis of the water mist field characteristics,laser scattering principle and simplified diffraction measurement model,the main parameters of water mist laser particle size measurement are deduced and determined,and the design scheme is completed and optimized.A prototype of integral water mist laser particle size meter is developed.The hardware and software of the prototype are designed.Taking the small semiconductor laser as the light source,based on the self-designed and processed optical fiber collimation and signal acquisition optical path,and adopting the integrated structure,a light and small waterproof prototype with gas back-blowing function is designed and completed.The acquisition circuit of miniaturized package multi-element photodetector is designed,the signal conditioning,multiplexing and AD conversion are completed;The embedded technology and wireless transmission mode are adopted to realize remote control and data transmission,and the data is processed and finally displayed by the upper computer.2.The program design of the lower computer and the software design of the upper computer are completed,and the data processing algorithm is realized.The lower computer program carries out multiplexing and AD conversion of the adjusted 33 analog voltage signals,from which data acquisition is realized.Then the lower computer communicates through the serial port and sends the converted digital signal to the upper computer through the wireless transmission module.3.The prototype is used for debugging and experiments to achieve the standard particle board signal acquisition and verification;the prototype is placed in a dam simulation field to carry out the online measurement experiment,and the particle size distribution results of the mist field are obtained and analyzed.