Research On TDLAS-based Natural Gas Telemetry System

With the reform of China’s energy structure,the proportion of natural gas in national production and life has gradually increased.However,accidents caused by natural gas leakage have occurred frequently,which has already restricted the further popularization of natural gas.The main component of natural gas is methane.The amount of methane gas in mixture of natural gas and oxygen is an important factor causing natural gas explosion accidents.Therefore,the development of equipment capable of monitoring natural gas leakage in real time has important practical significance for safeguarding people’s lives and property.The paper first introduced the domestic and international research status of commonly used natural gas detection methods and lock-in amplification technology.By comparing the advantages and disadvantages of various methods,a natural gas telemetry system based on infrared absorption principle was designed to realize the natural gas monitoring function well.The system used distributed feedback semiconductor laser(DFB LD)as the laser monochromatic light source,combining digital lock-in amplification technology to analysis the application of harmonic detection in natural gas telemetry.Secondly,with the study of hardware circuit design and program design of natural gas telemetry system,the paper focused on the key technologies such as laser drive circuit,laser temperature control circuit and digital phase-locked amplification technology based on FPGA in natural gas telemetry system.At the same time,the signal processing circuits such as A/D signal acquisition module and band pass filter was designed.An inverse algorithm calculating natural gas concentration was designed by the Nios Ⅱ soft core integrated in the FPGA to calculate the natural gas concentration in the natural gas telemetry system.Finally,we conducted a methane gas absorption experiment with the harmonic detection method used in the natural gas telemetry system,and carried out experiments on repeatability and stability of the system hardware circuit as well as the stability of the system program.The experimental results were consistent with the theoretical analysis,indicating the sensitivity of the system in natural gas telemetry was 0.0010uw/ppm and the resolution 20ppm.