Exploring the application of pressure balance concept on flow-induced force minimization for the tooth-on-rotor type labyrinth seal in turbomachines

Although labyrinth seals primarily suppress the clearance leakage in turbomachines, its complicated internal flow also generates significant flow-induced force (tangential force) exciting the rotor vibration. This problem is particularly severe for the tooth-on-rotor type labyrinth seal. To counter this problem, this study explores the application of pressure balance concept on tangential force minimization, thereby proposing a pressure balanced type labyrinth seal. On the outer side of the tooth-on-rotor type, one central chamber and several pressure balance pipes are designed. These pressure balance pipes enable the flow transfer between the innermost seal cavity and outermost central chamber. Based on the computational fluid dynamic method, the performance of the pressure balanced type is obtained. Compared with the tooth-on-rotor type, the pressure balanced type further reduces the leakage through increasing the kinetic energy dissipation and flow resistance. The pressure difference between both sides of the eccentricity direction is reduced. The tangential force is minimized form the root. The pressure balanced type's tangential force is independent of preswirl ratio. This is highly important for high/ultra-high speed turbomachines. The effect of pressure difference on the tangential force is also largely reduced. This study demonstrates the effectiveness of the pressure balance concept on tangential force minimization, and provides a useful alternative for modern seal design.