DYNAMIC ANALYSIS OF GAS LUBRICATED RECIPROCATING RINGLESS PISTONS - BASIC MODELING

A mathematical model is developed for analyzing the dynamics of gas lu bricated ringless pistons. It takes into account the effects of piston -cylinder geometry, dynamic properties of piston and connecting rod, a nd operating conditions. A corresponding computer program is described which enables to obtain the piston trajectory and evaluate its stabil ity. Preliminary results are presented for a reference case of a cryoc ooler which uses a stirling cycle design where helium gas is compresse d by a motor driven piston. It is found that the connecting rod inerti a plays an important role in stabilizing the piston motion. It is also found that the stability of piston motion strongly depends on the the rmohydrodynamic condition of operation. Under isothermal condition the piston can be stable while under adiabatic condition its dynamic equi librium may be unstable.