A Laser Test System For Measuring Binary Gas Diffusion Coefficient And Simulation Under High Temperature And High Pressure

Nowadays,with strict environmental protection legislation and the increasingly fiercemarket competition,the electricity production always searches a more efficient and lowerpolluted way to use the fuels.To achieve this,on the one hand,we can establish precisemathematical models for numerical simulation to evaluate the efficiency of different coalboilers,on the other hand,we can develop more advanced technology,such as PFBB、IGCC,which both needs a basic physical quantities diffusion coefficient.Unfortunately,mostof the gas diffusion coefficients were measured at normal temperature and pressure,whichcan not be used to establish the kinetic models of coal combustion or gasification above1MPa.Measuring gas diffusion coefficients under high temperature and high pressure issignificant and helpful in sovling this problem.The methods and devices for measuring the gas diffusion coefficients are summarizedin this thesis,and the large transverse shearing laser interferometry combined with theimproved Loschmidt cell with a ball valve are choosen.A experimental system formeasuring gas diffusion coeffisions under high temperature and high pressure aredesigned.The eight major foreign binary gas diffusion models are analysised,and the FSGcombined with RSP model are used to calculate the diffusion coefficients of binary systemsO2-CO2、O2-CO、CO2-CO、O2-CH4、CO-H2at high pressure (0.1-5MPa), high temperature(less than1273K). The two-volume laser shearing interferometer gas diffusion model isestablished.Different gases under different conditions are simulated in matlab.With thecenterline method combined with the minimum mean-variance optimization principle theimages of the interference fringes are analyzed,by which the three-dimensionalconcentration distribution in the diffuse process is obtained furthermore.The results show that:the concentration errors of the laser shearing interferometer arebellow1.07%;the experiment system we set up has a good performance on sealing and realtime measuring.As the diffusion proceeds,the interference fringes first go density and thengo thin.The density of the fringes go thicker with the pressure increased.Differentconditions at different times,the fringes on CCD is very clear to distinguish.The three dimensional concentration distributions obtained through images processing have a goodagreement with the theoretical value,of which the maximum error is1.9%.