The Impact of Gland-Injected Secondary Flow on the Performance of Various Types of Labyrinth Seals

Abstract This study presents a novel labyrinth seal design with a thin circumferential slot in the outer bushing that allows for the controlled injection of just a small amount of the same working fluid, diverted from the discharge or suction line, to minimize leakage flow rate. A numerical analysis is carried out to investigate the effect of blowing rate and labyrinth seal geometry on leakage characteristics for various seal configurations. The findings indicate a linear relationship between the pressure drop across the seal and axial leakage velocity. Increasing the blowing rate moves the linear relationship upward, improving sealing effectiveness without mechanical contact. Among the geometries tested, grooved shaft and grooved casing designs demonstrated greater leakage control, although up-the-step and down-the-step seals displayed intrinsic pressure gradients due to asymmetry. The seal aspect ratio has been found to have an important impact on the optimum blowing rate, with higher ratios requiring less injection to produce zero leakage. Under optimum blowing conditions, leakage is decreased by up to 21% for grooved shaft seal at pressure difference of 0.733 MPa, and total leakage suppression is possible at a dimensionless blowing velocity of 0.055, (3.47 m/s) The proposed solution shows great potential for increasing efficiency and reliability in pump and turbomachinery sealing applications.