A Leakage Rate Model for Nuclear Main Pump Standstill Seals Based on Percolation Theory

To address the lack of leakage rate model guidance for standstill seals and the limitations of most models due to neglecting asperity substrate deformation, this study proposes a new leakage rate model for nuclear main pump standstill seals based on percolation theory, effectively overcoming the common drawback of existing models that ignore the influence of substrate deformation on leakage rate. First, the substrate deformation of the maximum asperity at the sealing interface is analyzed, and a contact mechanics model and a porosity model are established to investigate the effects of substrate deformation, contact pressure and fractal parameters on the porosity of the sealing interface. Second, a leakage rate model for the sealing interface is developed based on percolation theory. Finally, an experimental setup for standstill seals is constructed to explore the normal load required for zero leakage at the sealing interface, thereby verifying the accuracy of the leakage rate model. The results show that porosity is independent of yield strength and decreases with increasing contact pressure. The reduction rate of porosity is faster when the fractal dimension is larger, and the fractal roughness and elastic modulus are smaller. Under these conditions, the influence of substrate deformation on porosity becomes significant and cannot be neglected. Conversely, when the fractal dimension is smaller, and the fractal roughness and elastic modulus are larger, the effect of substrate deformation on porosity is minimal and can be disregarded. As the contact load on the sealing interface increases, the leakage rate gradually decreases. The actual contact pressure required for zero leakage closely matches the theoretical value. This study offers new insights into the zero-leakage design of nuclear main pump standstill seals.