| City gas is an important part of city energy structure and infrastructure,it provides high quality gas fuel for city industry,commerce and resident life.At the same time,all kinds of risk factors related to gas are increasing correspondingly.Gas leakage phenomenon caused by pipeline aging and valve falling off occurs from time to time.If it is not found in time,may cause a major fire explosion and other safety accidents.The Industrial and Commercial gas alarm plays an important role in the combustible gas leak detection,it can give the alarm to the gas leak,reminds the people to check immediately,is vital to the protection life and the property security.At present,Industrial gas alarms have been installed in chemical plants,paint spray houses and LPG stations where flammable gas leakage is likely to occur.However,because of the slow diffusion of gas and the influence of the shell of the alarm,the gas needs a certain diffusion time,which leads to the difference of the concentration inside and outside the alarm,and there is a lag in the alarm.Industrial and Commercial gas alarms are usually installed in factory buildings or duty rooms,the temperature,humidity,ventilation and the position,number and shape of the breathing holes of the alarm will influence the alarm time.Therefore,this paper assumes that the alarm is enveloped by a certain concentration of natural gas at the initial time,simulating the process of natural gas diffusing from the suction hole to the inner part of alarm,the alarm situation of alarm is analyzed.According to the different temperature,humidity,ventilation and the position,number and shape of the breathing holes in the alarm,the influence of different conditions on the alarm is studied.According to the simulation results,the design and installation of the breathing hole of the alarm are optimized to provide a reference for the daily maintenance of the alarm.In this paper,CFD simulation method is used to establish the physical model of industrial gas alarm.Based on the related gas diffusion equation,the mathematical model is established,the process of gas diffusion into the alarm is solved discretely.Finally,the gas diffusion in the alarm is analyzed by TECPLOT post-processing software.In this paper,first of all,the Industrial and Commercial gas alarm under normal circumstances for the numerical simulation,explore the gas diffusion caused by the slow delay of the alarm itself,when the volume fraction of natural gas outside the alarm is 2%,the time required for the sensor to reach the alarm concentration is 13s.Then we explore the influence of different external factors,including temperature,humidity and ventilation condition on the delay time of the alarm.When the wind in the horizontal direction is 1 m/s,the external force of the wind will cause the alarm lag phenomenon to be very serious,the time needed for the sensor to reach the alarm concentration is 35s,which is 22s later than that in the calm condition.Temperature and humidity have an effect on the diffusion coefficient and viscosity of natural gas,so they also have an effect on the alarm lag.Based on the above situation,this paper optimizes the design of the alarm hole,and explores the influence of the position,shape and number of the alarm hole on the alarm time,and obtains that when the alarm is provided with a circular suction hole on the side,it can effectively improve the influence of ventilation on the alarm time delay,when the wind speed is constant,the time needed for the alarm to reach the alarm concentration is 15s when the side of the alarm is equipped with six suction holes with a radius of 1mm,the alarm time is reduced by 20s as compared to the alarm time of only placing a suction hole in the bottom of the alarm.After that,this paper puts forward the optimization of the installation position of the industrial gas alarm,through setting different monitoring points in the space,explores the alarm time needed when the alarm is installed in different positions when gas leakage occurs,thus the best position of alarm installation can be obtained.Finally,this paper provides reasonable suggestions on the daily use and maintenance of the alarm,to ensure that the alarm is more sensitive and scientific in the use of the process,to be able to detect gas leakage in time,to avoid causing human and financial harm. |
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