Free piston device

Patent metadata

Field	Value
Publication number	US-10472995-B2
Application number	US-201615580960-A
Country	US
Kind code	B2
Filing date	Jun 9, 2016
Priority date	Jun 9, 2015
Publication date	Nov 12, 2019
Grant date	Nov 12, 2019

Abstract

A free piston device, comprises a housing with a cylindrical inner wall having a first wall opening and a second wall opening; a cylindrical piston movable in axial direction and rotatable around its longitudinal axis; the piston comprising a first skirt forming a first chamber, said first skirt having at least a first opening in the form of a hole through the wall of the skirt for allowing passage of a fluid directly into or out of said chamber; control means for controlling axial and angular movement of said piston; sensing means for providing signals related to the axial position and/or the angular position of the piston; a digital control unit for rotating the piston around its longitudinal axis in synchronism with its axial movement.

First claim

The invention claimed is:

1. A free piston device comprising:
a housing having a cylindrical inner wall defining a cylindrical cavity, the cylindrical inner wall having a first wall opening connectable to a first channel and a second wall opening connectable to a second channel;
a cylindrical piston arranged in said cylindrical cavity and being movable in axial direction and being rotatable around its longitudinal axis;
the cylindrical piston comprising a central element, and a first skirt having a cylindrical wall defining a first cylindrical space closed at one end by a first face of said central element,
the first face, and at least part of the cylindrical wall of the first skirt, and a transverse wall section of an element mounted inside the housing or a transverse wall section being part of the housing forming a first chamber inside said first skirt, said transverse wall section being positioned inside the cylindrical space of the first skirt,
said first skirt having at least a first skirt opening in the form of a first hole through the cylindrical wall of the first skirt for allowing passage of a fluid directly into or out of said first chamber;
first control means for controlling movement of said piston in axial direction along its longitudinal axis;
second control means for controlling movement of the piston in angular direction around its longitudinal axis;
sensing means adapted for providing a first signal related to the axial position and a second signal related to the angular position of the piston relative to the housing;
a digital control unit for controlling the first and/or the second control means or rotating the piston around its longitudinal axis and/or for moving the piston along its longitudinal axis, based on at least the first and the second signal, in a manner wherein the axial movement is synchronized with the longitudinal movement such that the first skirt opening is in fluid connection with the first wall opening at a first moment in time when the piston is in a first axial position, and such that the first skirt opening is in fluid connection with the second wall opening at a second moment in time when the piston is in a second axial position different from the first axial position.

2. The free piston device according to claim 1 , wherein the sensing means further comprises a first pressure sensor arranged for measuring a pressure inside the first chamber and wherein the digital control unit is further adapted for controlling the first and/or second control means by also taking into account a signal obtained from the first pressure sensor.

3. The free piston device according to claim 1 , wherein the first and second control means comprise at least one electromagnetic rotor assembly mounted to the piston and at least one electromagnetic stator assembly mounted to the housing.

4. The free piston device according to claim 3 , wherein:
the free piston device is a free piston expander;
the first channel is configured for providing a fluid having a first pressure to the first chamber;
the free piston device is adapted for allowing the fluid in the first chamber to expand during a first time period, by allowing the piston to move away from the first transverse wall section, thereby increasing the volume in the first chamber;
the second channel is configured for receiving a fluid having a second pressure lower than the first pressure, from the first chamber;
the rotor assembly and stator assembly being configured for functioning as a linear generator for converting the axial movement of the piston due to the fluid expansion into electrical power.

5. The free piston device according to claim 1 , wherein the element comprising the transverse wall section is mounted inside the housing.

6. The free piston device according to claim 1 , wherein the element is the stator assembly, having an outer diameter corresponding to an inner diameter of the cylindrical wall of the first skirt.

7. The free piston device according to claim 1 , wherein the piston further comprises a second skirt having a cylindrical wall defining a second cylindrical space closed at one end by a second face of the central element,
the second face of said central element, and at least part of the cylindrical wall of the second skirt, and a second transverse wall section of an element mounted inside the housing or a transverse wall section being part of the housing forming a second chamber inside said second skirt, said second transverse wall section being positioned inside the cylindrical space of the second skirt,
said second skirt having at least a first skirt opening in the form of a second hole through the cylindrical wall of the second skirt for allowing passage of a fluid directly into or out of said second chamber;
wherein the digital control unit is adapted for controlling the first and/or the second control means for rotating the piston around its longitudinal axis and/or for moving the piston along its longitudinal axis, based on at least the first and the second signal, in a manner wherein the axial movement is synchronized with the longitudinal movement,
such that the first skirt opening is in fluid connection with the first wall opening of the housing and the second skirt opening is in fluid connection with the second wall opening of the housing at a first moment in time when the piston is in a first axial position,
and such that the first skirt opening is in fluid connection with the second wall opening of the housing and the second skirt opening is in fluid connection with the first wall opening of the housing at a second moment in time when the piston is in a second axial position different from the first axial position.

8. The free piston device according to claim 1 , further comprising a means for moving the piston in an axial direction towards the first transverse wall section, said means comprising at least one of the following components: a gas spring, a mechanical spring.

9. The free piston device according to claim 4 , wherein:
the piston further comprising a second skirt having a cylindrical wall closed at one end by said center element,
a second face of the center element, and at least part of the cylindrical wall of the second skirt, and a second transverse wall section of a second element mounted inside the housing or a second transverse wall section being part of the housing forming a second chamber inside the second skirt, said second transverse wall section being positioned inside the cylindrical space of the second skirt,
said second skirt having at least a first opening in the form of a first hole through the cylindrical wall of the second skirt for allowing passage of a fluid directly into or out of said second chamber;
the free piston device is adapted for allowing the fluid in the second chamber to expand during a second time period, by allowing the piston to move away from the second transverse wall section, thereby increasing the volume in the second chamber;
the digital control unit being further configured for controlling the first and/or the second control means for rotating the piston around its longitudinal axis and/or for moving the piston along its longitudinal axis, based on at least the first and second signal and optionally also based on the signal from the first pressure sensor and/or the signal from the second pressure sensor, in a manner wherein the axial movement is synchronized with the longitudinal movement such that the opening of the second skirt is in fluid connection with the first wall opening at a third moment in time when the piston is in a third axial position, and such that the opening of the second skirt is in fluid connection with the second wall at a fourth moment in time whe

Assignees

• Univ Gent

Inventors

• Gusev Sergei

Classifications

• H02K2201/18

  Machines moving with multiple degrees of freedom · CPC title

• F01K7/00

  Steam engine plants characterised by the use of specific types of engine (F01K3/02 takes precedence); Plants or engines characterised by their use of special steam systems, cycles or processes (reciprocating-piston engines using uniflow principle F01B17/04); Control means specially adapted for such systems, cycles or processes; Use of withdrawn or exhaust steam for feed-water heating · CPC title

• F01K25/08

  using special vapours · CPC title

• H02K21/222

  Flywheel magnetos · CPC title

• H02K7/1884

  structurally associated with free piston engines · CPC title