An optimum stepped piston for cylinders working with compressible fluid

A stepped piston, enclosed within a tight circular cylinder of uniform bore and subjected to unequal upstream and downstream boundary pressures, is analyzed for the case of a compressible fluid. Performance characteristics are given for small eccentricity and high boundary pressure ratio as a function of step size and location, and a design parameter that relates the leakage and the centering force is defined. It is shown that piston performance can be optimized by suitable step design.