Cavitation Effects on Squeeze-Film Damper Performance

Abstract

Experimental observations on unpressurized dynamically loaded hydrodynamic bearings and squeeze-film dampers indicate that cavitation bubbles, once formed, do not completely redissolve upon the reappearance of positive pressures. Instead, one is left with a spongy compressible fluid. Assuming this to be a homogeneous gas-liquid mixture, with density and viscosity dependent on pressure, the load capacity of squeeze-film dampers is compared with that obtained using hitherto adopted cavitation models which assume an incompressible lubricant with the fluid-film pressures being set to the saturated vapor pressure (SVP) of the lubricant whenever the pressure falls below the SVP. To save computation effort, a short bearing approximation is derived for the compressible Reynolds equation, so that comparisons apply to narrow dampers only (i.e. to dampers with length-to-diameter ratios less than 0.25). It is shown that for circular orbit squeeze-film dampers, best agreement is obtained with the incompressible model where the SVP is taken as zero absolute, though depending on the orbit eccentricity and the value of a dimensionless parameter called the squeeze number, commonly used π and 2π film cavitation models may also give excellent agreement.

Presented at the 40th Annual Meeting in Las Vegas, Nevada May 6–9, 1985

Notes

Presented at the 40th Annual Meeting in Las Vegas, Nevada May 6–9, 1985