The Design And Analyses Of Pipeline Type Negative Pressure Proportioner

Fire fighting of metro stations,tunnels and air-raid shelters is disturbing people all the time.At present,the place we mentioned put out a fire by setting box type fire extinguisher system.The box type fire extinguisher system is made up of foamite,tanks,proportioners and an electronic control unit.The property of box type fire extinguisher system is depended on the proportioners.In other words,Proportioners are the key part of whole system.However,domestic proportioners have many problems.First,domestic proportioners can’t create enough negative pressuer.Second,when we use the domestic proportioners,water and foamite can’t mix very well.Third,domestic proportioners can’t atomization foamite.Fourth,domestic proportioners don’t have enough gunshot.In a word,is difficult to use the domestic proportioner.There is still a huge gap between domestic proportioners and import proportioners.In China,there is still lack of standards of proportioners designing.A theory of proportioners designing was brought forward in this thesis.Properties of the proportioner is improved by using theoretical analysis,numerical simulation and making experiments.There are some conclusions from this thesis:(1)By reading a lot of papers,this thesis brings forward design requirements of the proportioner,including input diameter,output diameter and throat diameter.Input angle and output angle are optimized.Changed initial structure of the proportioner to advance structure.Therefor the product can create enough negative pressuer.The advance structure has longer gunshot than the initial structure.Advance structure also mix water and foamite well.The mathematic relation of negative pressuer and input pressure was calculated,as well as the the local head loss coefficient.(2)Initial structure of the proportioner and advance structure of the proportioner are analysed by using fluid dynamics software.Obtained pressure change,speed change and exit velocity curve of flow field characteristic parameters.The simulation results show that the negative pressure of the improved structure is lower than the initial structure,the range is far from the initial structure,and the energy conversion efficiency is higher than the initial structure.(3)Initial structure of the proportioner and advance structure of the proportioner are analysed by using fluid-solid coupling simulation software.(4)The stress and deformation are satisfied with the stress law.Both of the structures have nice performance.(5)Solved the problem of negative pressuer lower than-0.098 MPa during fluid dynamics simulation,by using cavitation modles.The result of FEM simulation was proved.(6)Based on the result of experiment,the advance structure limits the negative pressure rate faster and it has lower critical pressure,less energy loss.Therefor,the advance structure is better than the initial structure,and provides reference for optimization design.