Multi-stage stirling cycle machine and a steady-state operating parameter control method therefor

A multi-stage Stirling cycle machine, which comprises at least one set of piston working units, wherein said one set of piston working units comprises:

• a first cylinder and one mechanical energy input piston that is axially movable in the first cylinder;
• a second cylinder and one mechanical energy transfer double-acting free piston that is axially movable in the second cylinder;
• a last stage cylinder and one mechanical energy output piston that is axially movable in the last stage cylinder;
• the first cylinder is connected to the second cylinder in the axial direction through a first cooler, a first regenerator and a first heater, the second cylinder is connected to the last stage cylinder in the axial direction through a second cooler, a second regenerator, and a second heater, constituting a Stirling working unit with two stages, the mechanical energy transfer double-acting free piston is input the mechanical energy from the connected one stage Stirling working unit, in addition to overcoming the mechanical loss of the reciprocating motion of the piston and the working gas, all the mechanical energy is output to the connected next stage Stirling working unit during a complete operating period, realizing that the mechanical energy transfer double-acting free piston can only reciprocate under the action of the pressure change of the working gas of the Stirling working unit on both sides so as to achieve the purpose of canceling the piston rod apparatus.