LEAKAGE FROM LABYRINTH SEALS UNDER STATIONARY AND ROTATING CONDITIONS

Although the leakage flow through labyrinth seals under stationary con ditions has been examined by many investigators a reliable prediction of the effect of various labyrinth parameters on leakage rate has not been reported so far. The theoretical models for the seals proposed in most of the previous literature provided results with considerable di fferences and contradictions in some cases. The structure of the lamin ar incompressible flow and the performance of a number of seals of var ious shapes for both stationary and rotating conditions are investigat ed in this paper. The theoretical treatment is based on the formulatio n of three-dimensional axisymmetric momentum and continuity equations for labyrinth shapes having small height to radius ratio as is always the case in turbomachinery, rotodynamic pumps and many hydraulic devic es. It is found in this paper that shaft rotation is only beneficial f or the up-the-step seal, has no effect on grooved shaft and grooved ca sing seals and has an adverse effect on the down-the-step seal. It is also found that the use of a smaller clearance size at the entrance ma kes some improvement in the performance of the grooved shaft and down- the-step seals depending on the value of the height to width ratio of the seal. Copyright (C) 1996 Elsevier Science Ltd