DRIFT STABILIZER FOR RECIPROCATING FREE-PISTON DEVICES

摘要

A free-piston device (30) has a stabilized piston drift. A piston (32) having a frequency of reciprocation over a stroke length and with first and second sides facing first and second variable volumes (36, 38), respectively, for containing a working fluid defining an acoustic wavelength at the frequency of reciprocation. A bypass tube waveguide (50) connects the first and second variable volumes (36, 38) at all times during reciprocation of the piston (32). The waveguide (50) has a relatively low impedance for steady flow and a relatively high impedance for oscillating flow at the frequency of reciprocation of the piston (32), so that steady flow returns fluid leakage from about the piston (32) between the first and second volumes (36, 38) while oscillating flow is not diverted through the waveguide (50). Thus, net leakage about the piston (32) is returned during each stroke of the piston (32) while oscillating leakage is not allowed and pressure buildup on either the first or second side of the piston (32) is avoided to provide a stable piston location.