A finite difference method for determining rotordynamic forces on an eccentric whirling labyrinth cavity has been developed. A coordinate-transformation was applied to the Reynolds time-averaged Navier-Stokes equations in order to use the modified bipolar coordinate system. The SIMPLER algorithm with QUICK differencing and the high Reynolds number k–ε turbulence model are used to compute the complex turbulent flowfield. A circular whirl orbit about the geometric center of the housing was specified for simplicity. The new model was tested against the rotordynamic force measurements, and close agreement was found. For the cases considered, the radial and tangential force components become rotor dynamically less desirable with increasing inlet swirl. Also, circumferential pressure variations are included for enhanced insight into the flowfield.

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A parametric study of geometrical effects on labyrinth seal leakage resistance was conducted wing a recently developed Navier-Stokes finite difference code. Previously unavailable design data in terms of a n effective cavity friction factor was obtained. Also, a new leahuge stability design approach was found, and the parametric study data was wed accordingly in designing a seal with nonuniform cavities for the new high-pressure oxygen turbo-pump of the space shuttle main engine. The leakage resistance showed signijicantly greater stability over a n extremely wide range of rotor axial position.Further, a n enhanced basic understanding of the effect of sharp knife comers on cavity friction factor is obtained from contours of intense turbulence generation. The location of these contours shows that it is the sharp streamline curvature at high velocity slightly upstream of the vena contracta which provides the primary intense turbulent friction. This is a departure from the previous belief that the large turbulent stresses near the edge of the vena contracta are primarily responsible. This finding is expected to be helpful in designing more advanced knife configurations.

A numerical study was undertaken to examine the effects of utilizing sharper edges for increasing the leakage resistance of advanced labyrinth seal configurations. Such an increase allows the designer to enlarge the extremely small knife clearance, providing a seal with less damage susceptibility at the same leakage rate. The maximum possible leakage resistance increase from changing three cavity edges to perfectly sharp ones was estimated from the present computations. In addition, previous measurements of the edge sharpness effect on the leakage through orifices are appropriately utilized to obtain a rough estimate of the resistance increase for generic seals. The latter allows consideration of a broader range of application. Further, turbulence energy generation contours reveal that only one particular cavity edge needs to be sharpened in order to obtain a significantly increased leakage resistance.