The SSME HPFTP wavy interstage seal: Part 1

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The SSME HPFTP wavy interstage seal: Part 1 - Seal analysis

Scharrer, J.K. / Nunez, D.J.

The basic equations are derived for incompressible flow in an annular seal with a deformed surface (a wavy seal). The flow is assumed to be completely turbulent in the axial and circumferential directions with no separation, and is modeled by Hirs' turbulent lubrication equations. Linearized zeroth and first-order perturbation equations are developed for small motion about a centered position by an expansion in the eccentricity ratio. The zeroth-order continuity and momentum equations are solved exactly, yielding the axial and circumferential velocity components and the pressure distribution. The first-order equations are reduced to three ordinary, complex, differential equations in the axial coordinate Z. The equations are integrated to satisfy the boundary conditions and yield the perturbation pressure distribution. This resultant pressure distribution is integrated along and around the seal to yield the force developed by the seal and the corresponding dynamic coefficients. This analysis will be applied to the Space Shuttle Main Engine (SSME) High Pressure Fuel Turbopump (HPFTP) interstage seal. Rotordynamic coefficients will be developed for the wavy smooth, wavy rough, straight smooth, and straight rough seals. These coefficients will be used in Part 2 for the rotordynamic analysis.