Numerical analysis of gas tightness of seals in pSOFCs based on Lattice Boltzmann Method simulation

Abstract

To better understand the leakage mechanism of compressive seals in planar solid oxide fuel cells (pSOFCs), a theoretical method of leakage prediction is proposed that combines three numerical techniques. The Lattice-Boltzmann method was introduced to simulate the nonlinear flow in rough wall interfacial gaps due to its flexibility when dealing with flow problems related to complex boundaries. A numerical three-dimensional (3D) rough-surface generation technique was applied for the geometry configuration of interface gaps, and finite element analysis was adopted for micro-contact mechanics of single asperities to determine the gap height under stress. Based on this method, the 3D flow characteristics of the gas in interface gaps were numerically studied, and two important dimensionless flow factors (the flow factor Φσ of roughness and the flow factor Φh of height) were proposed. All numerical results were fitted as dimensionless criteria for calculating the interface leakage rate. These criteria can be directly used to predict the leakage rate of a given compressive seal under specific working conditions without relying on any experimental empirical formula. Furthermore, leakage rate predictions were compared to existing experimental data and good agreement was obtained, corroborating the accuracy of the method. In addition, the effects of influencing parameters on leakage according to the rate-temperature relationship were discussed. Several important conclusions were drawn to guide the design of compressive seals for pSOFC.