| Oil and natural gas are all indispensable energy sources in industry,but a large amount of toxic gas is generated when these energy sources are used in large quantities.There are lots of fatal accidents due to gas leaks each year.Although many kinds of monitoring systems have been used for gas leak detection,the industrial environment is complex,and the existing monitoring systems are still not accurate enough.By investigating the research status of gas detection and gas sensors at home and abroad,and combined with the actual industrial environment,the following related researches on the performance of gas sensor detection in the Industrial Internet of Things by obstacle models and constant temperature control methods have been done:(1)The influence of gas flow velocity fluctuation on the response of the gas sensor based on heater is analyzed,and the role of obstacles in reducing the gas flow velocity and improving the response performance of the sensor is proposed.The response of sensor with different sizes and shapes obstacles in the presence of gas flow velocity were simulated.Simulation results show that adding obstacle on the sensor can reduce the voltage response variation of gas sensor.Increasing the diameter of the obstacle can increase the reduction of the sensor response variation.Compared to the sensor response variation of 16.45% without obstacles,the sensor response variation of 11.37% with 0.5mm diameter obstacle is reduced a lot.And compared to the sensor response variation of 11.76% with 0.4mm diameter cylindrical obstacle,the response variation of sensor with 0.4mm edge-length prismatic obstacle is only 10.19%,which shows a better effect on detection accuracy.Secondly,it was verified through experiments that adding obstacles can indeed reduce the sensor response variation.The response variation of gas sensor with 0.5mm obstacle sensor under carbon dioxide gas flow rate of 80 sccm is only 82.01%,which is much less than the gas sensor response variation of 242.1% without obstacles.(2)A constant temperature control experiment of the MG811 gas sensor was tested,and the relationship between gas flow rate with 1% carbon dioxide gas concentration and sensor response under constant temperature control was analyzed.The results show that the effect of gas flow rate fluctuations on heater temperature can be compensated by constant temperature control,but the gas flow rate still affects the degree of physical or chemical reaction between gas and sensitive material of gas sensor.At gas flow rate of 80 sccm,the voltage response variation of the sensor is 25.23%(with constant temperature control)and 45.07%(without constant temperature control).By obtaining and analyzing relationship between gas sensor response and gas flow rate,if combined with gas flow sensor,the response accuracy of the gas sensor can be improved.(3)The influence of the cantilever beam spacing of the U-type heater on the heater temperature is analyzed.The results show that the larger the cantilever beam spacing is,the lower the energy-temperature conversion efficiency of the heater is.Simultaneously,the fluctuation of the gas flow rate has a greater impact on the energy-temperature conversion efficiency of the heater.Compared with heater of 5 μm cantilever spacing in natural convection,the energy-temperature conversion efficiency of the heater in environment of carbon dioxide flow rate of 0.5 m/s reduced by 45.66%.After the tip of heater improved to a serpentine structure,the energy-temperature conversion efficiency of the heater in natural convection environment is increased by 2.51%,and the energy-temperature conversion efficiency of the heater in carbon dioxide flow rate of 0.5m/s is increased by 2.21%.Then,from the simulation results of the temperature distribution of the snake heaters with three different structures,it was found that the temperature deviation of the variable electrode pitch planar heater is least affected by the gas flow rate,and the deviation of the sensor detection can be reduced well in the constant temperature control. |
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