Objective In order to analyze the failure mechanism of multiple types of flange sealing in hydrogen-blended natural gas transportation system.

Method A test platform for flange sealing performance with a multi-parameter monitoring unit was independently constructed based on the theory of gas permeation dynamics and material failure theory. The protruding flange and concave-convex flange were taken as the research objects, and bivariate parameters of hydrogen blending ratio (0-10%) and operating pressure (2-6 MPa) were set up using the orthogonal experimental design method; 100 groups of experiments were completed accordingly. Additionally, 40 groups of vibration leakage experiments were conducted on the basis of the hydrogen-doped experiments.

Result Experimental results indicated that leakage rates were significantly positively correlated with both operating pressure and hydrogen-blending ratio. Leakage was significantly exacerbated by vibration and was further increased with higher vibration frequencies. Considering the effects of hydrogen-blending ratio and operating pressure, a dimensionless evaluation model for flange sealing performance based on the Sherwood number was proposed. The coefficients of determination for the two flange sealing performance evaluation models were determined to be 0.97 and 0.99, respectively, with relative deviations less than 2%, meeting the accuracy requirements for engineering applications. Compared with the protruding flange, the pressure index, hydrogen-blending ratio index, and interaction term coefficients in the sealing performance evaluation model of the concave-convex flange were reduced by 8.24%, 17.30%, and 28.00% respectively, which quantitatively revealed the impact of flange structural differences on sealing performance.

Conclusion Case studies demonstrate that the established flange leakage prediction model exhibits strong predictive capability within the 0-10% hydrogen-blending ratio range, providing a crucial theoretical tool and safety assessment foundation for conducting research at higher-blending ratios.