Abstract: Abstract: For the fire protection of large oil storage tanks, the CO2 fire extinguishing system can effectively overcome the problems of long fire response time and pollution of crude oil in the traditional air foam fire extinguishing system. However, the flow of CO2 in the pipelines is very complex, so it is necessary to study the flow characteristics of CO2. Through the combination of experiment and numerical simulation, the CO2 emission experimental device was built, and the flow model of the CO2 fire extinguishing pipeline was established using OLGA software. The experimental results were compared and analyzed to verify the model's reliability. On the basis of OLGA software, a long-distance fire pipeline of large oil storage tanks was established to simulate the change of CO2 flow parameters in the fire pipeline under different configuration conditions. The results show that the conveying distance, nozzle aperture, storage state of CO2 and diameter of the pipe will affect the flow characteristics of CO2. The shorter the conveying distance, the smaller the diameter and the larger the nozzle diameter, the higher the pressure relief rate of the pipeline, and the greater the temperature drop of the pipeline caused by the loss of gas flow energy and expansion; the change of pressure and temperature in the pipeline is positively correlated with the storage state of the extinguishing agent.

Key words: Key words: large oil storage tank, fire fighting pipeline, carbon dioxide, flow characteristics, numerical simulation, fire extinguishing agent