Research On Gas Source Mobile Location Method And Application Based On Infrared Absorption Spectroscopy

Natural gas is a kind of clean burning energy that produces less than half the carbon dioxide（CO₂）of coal.Methane（CH₄）,which is the primary component of natural gas,has a global warming potential value of 28～86 times compared to carbon dioxide.The biggest man-made emission source is gas leaks from cracked pipelines.How to quickly find the leakage location of natural gas pipeline and reduce the probability of accidents is particularly important.With the requirements of energy security and environmental protection,traditional manual detection methods with low efficiency and small range have been unable to meet the daily detection requirements of gas pipeline leakages.In order to find practical,effective,sensitive and fast detection methods,this paper proposed two improved optimization algorithms,IPSO and NM-PSO,based on traditional particle swarm optimization（PSO）algorithm,and builds a ppbv-level vehicle-deployed mobile gas detection platform based on cavity enhanced infrared absorption spectroscopy with gas source location software to achieve leak detection and location of gas pipeline.The details are as follows.Firstly,the gas turbulent diffusion formula in windy condition is deduced in detail,and then source location inverse model is established.IPSO and NM-PSO algorithms are proposed to improve positioning accuracy under complex environmental factors.In order to solve the local optimal solution and premature particle convergence problems for PSO,IPSO algorithm adopts the way of the improved particle updating velocity formula.The simulation results show that the positioning accuracy increases by69.14%,61.43%,36.61%and 69.81%respectively under different source location positions,wind speeds,wind directions and moving speeds.NM-PSO algorithm is used to balance the ability between local search and global search.Through the cost function of four analogical leaks,the three algorithms（NM,PSO and NM-PSO）are compared from the perspective of iteration numbers,optimal value（mean value,deviation,confidence interval）and success rate.The results of 5000 independent tests show that the NM-PSO algorithm has good optimization ability and stable search ability.In order to realize the vehicle-deployed mobile leakage inspection of NG,a ppbv vehicle-deployed mobile gas detection platform based on cavity enhanced infrared absorption was built,including the cavity enhanced infrared absorption spectrum dual-gas sensor for monitoring CH₄/C₂H₆concentration change,the global positioning system（GPS）for position information,and the anemometer for wind and temperature information.The system structure of dual-gas sensor included optical,electrical and gas sampling systems.In order to meet the on-board requirements,the dual-gas sensor was integrated and its performance was evaluated.The linearity（R₂）of CH₄ sensor was0.997.The detection limit was 0.2 ppbv with an average time of 1s.Furthermore,the measurement range was determined to be 0.001-100 ppmv.At last,the response time was 8 s.While the linearity（R₂）of C₂H₆ sensor is 0.998.A detection limit of 10 ppbv was calculated by Allan variance with an averaging time of 1 s.The C₂H₆ detection range was 0.03-100 ppmv.The response time for C₂H₆ detection was evaluated,and an experimental response time of 8 s was achieved.In order to realize rapid classification,accurate positioning and visual display of natural gas leakage points,the system is described by modules according to the overall architecture of the gas source location software design.The data acquisition module realizes the access from the hardware equipment to the software data and the data parsing according to the format;The processing module is the core to realize pretreatment,baseline calculation,algorithm positioning and gas source leakage area calculation;The storage module is mainly able to store the parsed data and the important process values of the processing module;The display module realizes the diverse display of data and displays data in an intuitive and clear way.Finally,the simulated methane leakage source and natural gas leakage experiments were carried out to prove the stability of the whole mobile detection platform and the effectiveness of the mobile gas source location algorithm.Then,the area near the pipeline of Kunlun Gas Company in Wuchang District of Wuhan City was monitored,and several possible leakage sources were located and determined based on the mobile detection platform.As a new mobile detection and monitoring method for urban NG leakage,this technology solves the pain points and difficulties of long detection time,low efficiency and high risk of traditional hand-held leak detection method.In the future,this technology can also be applied to more urban environmental protection departments and relevant gas companies to deal with the threat of natural gas leakage.The innovation points of this article are as follows.（1）Aiming at the problems of local optimal solution and premature convergence of PSO,two mobile location methods of IPSO and NM-PSO algorithms are proposed,which improved the positioning accuracy,stability and optimization ability of PSO algorithm.（2）Aiming at the problem of low positioning accuracy of leakage source caused by complex environmental factors in vehicle-deployed mobile detection,a vehicle-deployed mobile gas detection platform based on infrared absorption spectroscopy is established.Combined with the gas source location software,accurate positioning of urban gas pipeline leakage is realized.