Method of operating a piston expander of a steam engine

A method of operating a piston expander, including the steps of:

• introducing live steam from a steam feed into a cylinder space via an inlet valve;
• expanding the live steam, introduced into the cylinder space, during a power stroke in which a piston moves from an upper dead center position into a lower dead center position;
• after the piston reaches the lower dead center position, conveying the expanded steam out of an outlet opening and into a steam discharge, whereby compressed residual steam is retained within the cylinder space and is not exhausted;
• subsequently closing said outlet opening at least 45° before the piston, in an exhaust stroke when the piston moves from the lower dead center position to the upper dead center position, reaches the upper dead center position, wherein in a time frame between closing of said outlet opening and closing of the inlet valve, a steam mixture is produced by means of the introduction of the live steam into the cylinder space, and wherein the steam mixture has a pressure that corresponds approximately to a pressure of the live steam;
• and
• recompressing the residual steam remaining in the cylinder by movement of the piston after the outlet opening is closed,
• wherein said conveying step comprises opening said outlet opening at a crank angle of from 25° to 15° prior to the lower dead center position, and wherein said closing step comprises closing said outlet opening at a crank angle of from 25° to 15° after the lower dead center position.