Experimental and numerical research of hydrogen-blended natural gas leakage and diffusion in utility tunnels

The safety of hydrogen-blended natural gas (HBNG) in underground utility tunnels continues to receive attention. In this study, an experiment platform for the leakage near-field of the utility tunnel is designed based on the similarity theory. The reliability of CFD numerical simulation in the leakage near field is verified by experiments. For the leakage process of HBNG, the increase of hydrogen blending ratio (HBR) enhances the diffusion in the horizontal direction. The gas concentration in the measurement points tend to a maximum value with increasing leakage time during the leakage process in the ventilated condition. The study carried out CFD numerical simulations of HBNG leakage in the entire utility tunnel. It was found that some changes in leak location do not affect the stabilized concentration during ventilation. The alarm time is linearly related to the horizontal distance of the alarm from the leak source. Based on the numerical simulation results, a simple model of HBR, alarm location and alarm trigger time was obtained. The model can provide some references for the location and number of alarms in the utility tunnel.