The Basics of Controlling a Free Piston Stirling Engine

DOI : http://dx.doi.org/10.13005/bbra/2220

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This paper presents an algorithm to control the motion of the displacer and the working piston of a free-piston Stirling engine (FPSE). An active control method is used to correct the motion of the pistons, which allows to adjust the pressure in the gas spring (GS) of the displacer, compression space and the buffer chamber (BC) for each operating cycle. The pressure changes inside the spaces fit in a narrow range. They are aimed to compensate the working fluid (WF) flow-over between the inner spaces of FPSE due to leakages through the sealings. The proposed algorithm and means for its implementation allow to adjust the range of the displacer and working piston travel and keep the phase angle and average WF pressure in the inner spaces within a calculated range. Combination of these parameters ensures stability of the self-oscillating process in FPSE.

Free-piston Stirling engine; Working fluid; Algorithm; Displacer; Linear electric machine