Experimental Studies into the Effect that the Rotor Rotation and Flow Swirling Upstream of Seals Have on the Leakage Flowrate

The results from experiments for studying the effect of rotor rotation on the leakage through different types of seals are presented. It is shown from a comparative study of models involving a stalled rotor and rotor rotating with a 50 Hz frequency that the rotor rotation has hardly any effect on the leakage flowrate, so that the rotation may not be taken into account in calculations of leakage flowrate through the steam turbine end and diaphragm seals. The article presents results from experiments for studying the dependence of leakage flowrate on the flow parameters, namely, the change of the velocity vector axial and circumferential components in the annular inlet channel upstream of a single annular throttle orifice. During the experiments, the velocity axial and circumferential components were varied independently and in a very significant range. The accomplished studies have shown that the change of both the axial and circumferential velocity components has hardly any effect on the leakage flowrate. It can be concluded from an analysis of the obtained results that the influence of flow parameters upstream of the seal on the leakage flowrate is so insignificant that its neglect in the previously developed calculation procedures for determining the leakage flowrate in the steam turbine seals, which are still in use at present, is quite substantiated and justified. At present, studies are being carried out that allow the flow structure in different places of turbine machinery flow paths, including the turbine seals, to be analyzed by calculation. It should be noted that it is possible by using the modern calculation methods not only to determine the vortex structure in the seal neighborhood but also to estimate the leakage flowrate, leakage losses, and even the stage efficiency for different configurations of the chamber upstream of the seal. Nonetheless, care should be taken in dealing with practical recommendations on changing the seal configurations that are based solely on the calculation results. The soundness of such recommendations must be confirmed by the relevant experimental investigations.