Estimation of the natural gas leakage source with different monitoring sensor networks in an underground utility Tunnel: From the perspectives of energy security

Utility tunnels could make full use of underground space and are important for the energy security of the city. The natural gas pipelines were integrated into utility tunnels and have potential leakage risk. Due to the hazardous gas leakage, a fire or explosion will release energy and may cause fatalities and economic loss. In this study, we set up 10 m full scaled experimental utility tunnel mockup and applied CFD simulation combined with the adjoint method to optimize gas-monitoring sensor networks in utility tunnels for estimation of the natural gas leakage source. The CFD method was first validated by the full scaled experimental data. And networks with different number of sensors based on the existing gas-monitoring system were analyzed and used to identify the leakage source location. Then two new gas-monitoring sensor networks were proposed to achieve long distance estimation of the leakage source. For the existing gas-monitoring sensor network, it was found that four monitoring sensors could identify the leakage source accurately with errors within five meters. For the new gas-monitoring sensor network, three monitoring sensors could identify the location of the leakage source accurately and could achieve long distance leakage source identification of 75 m. This study provided useful methods for identifying the natural gas leakage source inversely and optimizing gas-monitoring sensor networks in the utility tunnels.