Comparison of experimental and theoretical results for leakage, pressure gradients, and rotordynamic coefficients for tapered annular gas seal.
A brief review of current annular seal theory and a discussion of the predicted effect on stiffness of tapering the seal stator are presented. An outline of Nelson's analytical computational method for determining rotordynamic coefficients for annular compressible flow seals is included. Modifications to increase the maximum rotor speed of an existing air seal test apparatus at Texas A & M University are described. Experimental results, including leakage, entrance loss coefficients, pressure distributions, and normalized rotordynamic coefficients, are presented for four convergent tapered, smooth rotor, smooth stator seals. A comparison of the test results shows that an inlet to exit clearance ratio of 1.5 to 2.0 provides the maximum direct stiffness, a clearance ratio of 2.5 provides the greatest stability, and a clearance ratio of 1.0 provides the least stability. The experimental results are compared to theoretical results from Nelson's analysis with good agreement. Test results for cross coupled stiffness show less sensitivity of fluid prerotation than predicted. (A)
author list (cited authors)
Elrod, D. A., & Childs, D. W.