Calculation of high-pressure natural gas decompression wave velocity during pipeline fracture

Key words:  pipeline fracture  theoretical model  decompression wave velocity  three-characteristic line method  experimental verification

Abstract:

Solution of decompression wave velocity during pipeline fracture is the key problem in fracture control of natural gas transportation pipeline. Considering that the non-isentropic effect of small-diameter pipeline is obvious, the isentropic and the non-isentropic theoretical models were created respectively. Through deducing, the set of partial differential equations was inverted to the set of ordinary differential equations. Using P-R state equation, the calculation formulas for calculating compression factor and specific heat ratio were derived. Gas decompression wave velocity during the pipeline fracture process was solved by the three-characteristic line method，and the corresponding computer program was developed. The results show that the average relative deviation of the calculated value of specific heat ratio and its experimental value is 0. 617% , and the average difference of the compression factor is 0. 555%. The gas decompression wave velocity calculated agrees well with the measured data of full scale burst test. The influences of initial pressure, initial temperature，gas composition and diameter of pipeline on gas decompression wave velocity were analyzed.