The long-distance natural gas pipeline is characterized by large diameter and fast flow,and the uneven mixing of hydrogen gas will increase the risks of metal hydrogen embrittlement,seal leakage and unstable operation of equipment in the pipeline transportation system.According to the operating conditions of a long?distance natural gas pipeline in China,numerical simulation was used to study the flow field characteristics and mixing effect of four types of static mixers (SK,SX,SL,HEV) when hydrogen doping is transported(the ratio of hydrogen doping is 3%).The results show that all four types of static mixers have disturbing mixing effects on natural gas with hydrogen addition,and the value of the mixed non?uniformity COV decreases with the increase of flow rate,while the pressure loss increases with the increase of flow rate.The mixing characteristics and effects of SK, SX,SL and HEV type mixers vary significantly under the operating conditions of 3% hydrogen doping ratio,4.22 MPa hydrogen doping pressure,and flow rates ranging from 13×108 Nm3/a to 36×108 Nm3/a.The COV value should be reduced to less than 5% at different mixing distances.It can be optimally or innovatively designed with a relatively simple structure, short mixing distance, low non?uniformity, excellent turbulence characteristics,good shear characteristics, and moderate pressure drop as a large-caliber long-distance natural gas main pipeline hydrogen mixer.
