ABSTRACT
It should be noted here that the radius at which the dynamic "stator seal" is placed can, in itself, become a design issue. If we assume a fixed clearance between the seal elements (independent of radius), then the seal annular area becomes a function of radius. Therefore, seal leakage will vary directly with the radius on which the seal is placed. It would obviously be desirable to minimize this leakage, as it decreases turbine efficiency. On the other hand, the reader will note that as the seal radius is reduced, the pressure-area force on the first rotor disk underside will increase, because a larger area will be "pressure controlled" by the first rotor blade outlet hub pressure. An exercise for the interested reader is to vary the radius of the stator seal and reproduce the data in Fig. 28 to observe the effect of varying seal placement on the overall turbine axial thrust.
