Design Of Remote Detection System For Infrared Gas CH₄ On The NDIR Technology

Nowadays,it will meet a new round of energy transformation characterized by low-carbon and non-carbon in the world.Natural gas,as an important clean energy,is becoming an important force to promote the global energy transformation.The main component of natural gas is methane.As a kind of flammable gas,methane can form explosive mixture with air when its content exceeds 5%.Therefore,detecting the concentration of methane is very vital in the process of natural gas exploitation,transportation and power generation.1.Based on the research of gas concentration sensors in the country,a CH₄ gas concentration detector with high precision,low cost and long-distance transmission was designed according to the infrared spectrum absorption theory and with differential absorption detection technology in the paper.In the design of optical path system,LightTools optical software was used to complete the simulation analysis of ray tracing map,illumination grating distribution and scatter surface map for direct absorption chamber and ship reflection absorption chamber,then reasonable chamber structure was selected to improve the stability of the system.2.In the hardware circuit design,the infrared light source was modulated by microprocessor to make the detector receive the changing optical signal.The tiny electrical signal of the detector was extracted from the noise by signal conditioning module,which can filter and amplify the tiny signal.Until the signal being adjusted to the range of input voltage,the analog-to-digital conversion module can collect it.The microprocessor will calculate the concentration of discrete voltage signals based on the fitted function relations and transmit gas concentration to PC through remote communication module.3.Owe to the change of detection environment temperature will greatly fluctuate the test data and reduce the reliability of concentration data.So the Grey Wolf Optimization?GWO-BP?neural network algorithm was proposed to compensate the temperature of the detection environment.By comparing the absolute error between the measured data and the predicted value of the compensated GWO-BP neural network,it was proved that the GWO-BP neural network algorithm can eliminate the detection deviation caused by the change of detection environment temperature to a certain extent and improve the detection accuracy of CH₄ gas concentration detector.