Investigation on Leakage Characteristics of Two Kinds of Injection-type Shaft Seals Using CFD

Abstract

Recently, injection-type shaft seals (non-contact type seals) started replacing their counterparts called mechanical seals (contact-face type seals) in power plant feedwater pumps. Both of these seals have primary function of preventing the fluid inside the pump pressure casing from leaking to outside of the pump. Mechanical seals are reported to fail rapidly and abruptly in especially power plant feedwater pumps because of increased speeds and the feedwater temperatures. If mechanical seals fail, most often the pump must be shut-down immediately and put the pump reliability in question. Hence, the injection-type shaft seals were introduced in order to avoid reliability problems associated with mechanical seals and save maintenance costs of feedwater pumps. Therefore, in this paper we investigated the performance of injection-type shaft seals particularly with labyrinth and plain annuls designs. Research findings show that design parameters such as seal clearance and diameter play an important role in determining the injection-type shaft seal's leakage, while drain temperature was un-affected by these design parameters.