Modeling And Control Of The Ventilation System In The Independent Gas Cabin Of The Utility Tunnel

With the continuous development of China’s economy, the rational use of the land space is also on the agenda. The utility pipe can make a reasonable arrangement, and make the operation and maintenance of municipal pipelines more convenient. In China, there is concern in the security level for the utility pipe with the gas pipeline.Statistics show that in the actual construction of the utility pipe, there are independent gas cabins reserved. But in many security considerations, no gas pipeline truly will run in the indepentdent cabin. In these case, this paper carried out the research on the ventilation control system of independent cabin, aiming to provide some relevant advice and basis for treatment about ventilation after gas leakage. First of all, we will complete the analysis of the characteristics of ventilation in the gas cabin through online information research, and these will be the basis for CFD simulation;secondly, we use the CFD method to completes the research of the gas leakage diffusion under the condition of ventilation, including normal ventilation and emergency ventilation under different ventilation frequency; Then, after finishing the analysis of the factors influencing the ventilation efficiency of independent cabin accidents through the simulation results, and considering the gas leakage divided according to ventilation control scheme. When it’s normal ventilation in theindependent cabin, if the gas start leakage, the concentration of the leak hole upwind monitored will quickly reduce. The leaking gas will be driven to downwind. There are explosive space about the length of the 55m in 30s, and it’s around 1/4 of the fire district. With the time passing by, the explosion of space will become increasingly longer. the leakage concentration should be reduced by accident ventilation quickly; The measured variation of concentration are familiar in every monitor downwind, and they are always rising rapidly, then decreased slowly.The influence factors of gas leakage ventilation efficiency include pressure in pipeline and the rate of accident ventilation. Among them, the greater the pressure, the faster the velocity of gas leakage, leakage is greater. The change in the first monitor point downwind determines the changes of leaking downwind of all monitor points, so the first monitor point is representative; Finally, using the theory of pattern recognition, ventilation control scheme are made in the gas cabin. The gas concentration is divided into three categories: no leakage, dangerous leakage and leakage of dangerous weakened, three categories above correspond to the following three kinds of ventilation: normal ventilation. Strengthen emergency ventilation and minimum accident ventilation, which the strengthen emergency has a ventilation of 24time/h, the minimum accident ventilation has a ventilation of 12time/h. Finally we got two decision function partition above three categories.