Volumetric expander, process of starting the volumetric expander, closed-cycle plant, and process for converting thermal energy into electric energy using said plant

Expander according to clain 1, comprising:

• a plurality of pistons operating inside the casing, each being received in a respective shell defined inside the casing,
• wherein said pistons are angularly offset from each other with respect to the main axis of the main shaft
• a valve for each expansion chamber of each piston,
• a crank mechanism for each piston,
• wherein the transmission member for each piston comprises:
• at least one first toothed wheel fitted to the distributing body of the valve,
• at least one second toothed wheel fitted to the main shaft,
• at least one intermediate member configured for connecting the first and second toothed wheels,
• said transmission member being configured for:
• synchronizing—for each piston—at least the working fluid introduction and discharge conditions with respect to the expansion chamber with the rotation of the main shaft,
• synchronizing at least the working fluid introduction and discharge conditions of the different expansion chambers so that the introduction condition or discharge condition, respectively, of an expansion chamber is temporarily offset with respect to an introduction condition or discharge condition, respectively, of another expansion chamber.

Volumetric expander for a closed cycle plant comprising:

• at least one casing exhibiting at least one general inlet enabling introduction of a working fluid inside the casing and at least one general outlet enabling expulsion of the working fluid from said casing,
• a piston housed in said casing defining a variable volume expansion chamber,
• a main shaft connected to the piston and configured for turning around a main axis,
• at least one valve associated with the casing and configured for selectively opening and closing an inlet and outlet of said expansion chamber enabling at least:
• an introduction condition in which the working fluid is introduced into the expansion chamber,
• an expansion condition in which the working fluid expands in the expansion chamber, and
• a discharge condition in which the working fluid is discharged from said expansion chamber,
• wherein the casing internally defines a discharge chamber in direct fluid communication with the general outlet, the discharge chamber being further configured for being put in direct fluid communication with the outlet of the expansion chamber during said discharge condition,
• wherein the casing comprises at least one auxiliary inlet which is in direct communication only with the discharge chamber of the casing and, through this latter, with the general outlet, the auxiliary inlet being configured for enabling the working fluid to directly enter the casing.