Experimental Study On The Motion Of Ultra-fine Particle In Pipelines

Our living environment fills with a wide variety of ultra-fine particles.These particles not only affect the air quality, but also cause respiratory diseases andendanger human health.This paper mainly experimentally studied on the motion of ultra-fine particles inseveral typical flow fields. The main work and results are as follows:Firstly, FMPS3091was used to experimentally study on the motion of ultra-fineparticles in the straight pipes with the diameter is8mm. Compared to the previoustheoretical and experimental studies, the experiment results were found to bereasonable, which illustrated the accuracy and reliability of the experimental methodin this thesis. I found the penetration efficiency of particles increases with increasingthe particle diameter. This is because the smaller particles have higher diffusioncoefficient. The penetration efficiency of particles decreases with the increasingReynolds number, and this illustrates the increasing of Reynolds number can enhancethe deposition efficiency of particles. The effect of length of pipe on penetrationefficiency is very obvious.Secondly, FMPS3091was used to experimentally study on the motion ofultra-fine particles in the straight pipes with the diameter is6cm. The totalconcentration ratio of particles in the middle section of pipe is larger than that in theedge position, and this illustrates the deposition efficiency of particle in the edgepositions is larger than that in the middle section. The average particle size ofparticles in the middle section of pipe is less than that in the edge position, and thisillustrates the loss of the small particles in the edge position is more serious, resultingin the average particle size increases.Thirdly, FMPS3091was used to experimentally study on the motion ofultra-fine particles in the bend tubes with the diameter is6mm. The results show thatthe effect of Dean number on the penetration efficiency is dependent on the particlessize. Dean number has a stronger effect on the penetration efficiency for the smallparticles than that for the large particles. The turbulent motion has a main effect on the particles with diameters larger than100nm. There exists a critical value of Deannumber beyond which the penetration efficiency turns from increment to decrementwith increasing Dean number, and this critical value is dependent on particle size andbend length. The penetration efficiency decreases with increasing tube length. Thepenetration efficiency is obviously larger for large particles than that for smallparticles, and is larger in the turbulent flow than that in the laminar flow. Thedifference of penetration efficiency in the turbulent and laminar flows becomes smallwhen Schmidt number is larger than10000. The penetration efficiency increasesabruptly when Schmidt number changes from7500to25000. Finally, a theoreticalrelation between the penetration efficiency and Dean number, Schmidt number andbend length is derived.Finally, FMPS3091was used to experimentally study on the motion ofultra-fine particles in the square bend tubes with the side length of section is10mm.The results show that when the Dean number is small, the effect of particle size onthe penetration efficiency is not obvious. There exists a critical value of Deannumber around which the penetration efficiency is the largest, and the value isaround600. The penetration efficiency increases with the Schmidt number increasing,and the penetration efficiency get closer. When the Schmidt is less than20000, thepenetration efficiency increases obviously with increasing the Schmidt number.When the Schmidt is larger than20000, the change of penetration efficiency tends tobe smooth with increasing the Schmidt number. With increasing Dean number,turbulence intensity increases, the average particle size has also been increased.However, when the length of pipe increases, the increase in average particle diametertends to be smooth. This illustrates that the longer the pipe is, the effect of Deannumber on the average particle diameter is smaller.