Alpha Stirling Engine

Abstract

An alpha type Stirling engine (1) comprises an expansion cylinder (2) and a compression cylinder (3), a regenerator (4), a cooler (5), and a heater (6). Each one of the expansion cylinder (2) and the compression cylinder (3) has a movable piston (10, 11) connected to a respective linear electric generator/motor (8, 9), wherein the Stirling engine (1) further comprises a control unit (20) which is operatively connected to the linear electric generators/motors (8, 9) and which is configured to control the linear electric generators/motors (8, 9) individually so as to enable a different stroke length and/or motion profile of the piston (10) in the expansion cylinder (2) compared to the piston (11) in the compression cylinder (3).

Claims

1. An alpha type Stirling engine comprising: an expansion cylinder; a compression cylinder; a regenerator, a cooler, and a heater; wherein each one of the expansion cylinder and the compression cylinder has a movable piston connected to a respective linear electric generator/motor; and, a control unit operatively connected to the linear electric generators/motors and configured to control the linear electric generators/motors individually so as to enable a different stroke length and/or motion profile of the piston in the expansion cylinder compared to the piston in the compression cylinder.

2. The Stirling engine according to claim 1, wherein the control unit configured to control the linear electric generator/motors such that the stroke lengths and/or motion profiles are variable for both the expansion cylinder piston and the compression cylinder piston.

3. The Stirling engine according to claim 1, wherein the cylinders are arranged in line with the cylinder heads facing each other.

4. The Stirling engine according to claim 1, wherein the expansion and compression cylinders are configured in a V-arrangement.

5. The Stirling engine according to claim 1, wherein the expansion cylinder and the compression cylinder are arranged in parallel with each other and with the cylinder heads facing in the same direction.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The above, as well as additional objects, features and advantages of the present invention, will be better understood through the following illustrative and non-limiting detailed description of exemplary embodiments of the present invention, wherein:

[0024] FIG. 1 is a schematic drawing of a Stirling engine according to the present disclosure and

[0025] FIG. 2 is a schematic drawing of an alternative setup according to the present disclosure.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION

[0026] The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. The invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided for thoroughness and completeness. Like reference character refer to like elements throughout the description.

[0027] With reference to FIG. 1, an alpha type Stirling engine 1 comprises an expansion cylinder 2 and a compression cylinder 3, a regenerator 4, a cooler 5, and a heater 6. From a fluid path perspective, the expansion cylinder 2 and the heater 6 are provided on one side of the regenerator 4. The compression cylinder 3 and the cooler 5 are provided on the other side of the regenerator 4. Both the expansion cylinder 2 and the compression cylinder 3 has a piston 10, 11 which is movable within the respective cylinder 2, 3 and which is connected to a respective linear electric generator/motor 8, 9 controlled such that the stroke length and/or the motion profile is variable.

[0028] Further, in the linear electric generator/motor 8, 9, a magnet 12 moves in relation to an electromagnetic coil 13. This changes the magnetic flux passing through the coil, and thus induces the flow of an electric current, which can be used to do work. The linear electric generator/motor 8, 9, or sometimes called a linear alternator, thus converts the reciprocating motion to electric power. For some stages in the Stirling engine 1, the linear electric generator/motor instead drives the reciprocating motion with the use of electric power.

[0029] A control unit 20 is provided and operatively connected to the linear electric generators/motors 8, 9. The control unit 20 is configured to control the linear electric generators/motors 8, 9 individually so as to enable a different stroke length and/or motion profile of the piston 10 in the expansion cylinder compared to the piston 11 in the compression cylinder 3. Hereby a flexible control is achievable as explained previously in this disclosure.

[0030] Turning to FIG. 2, the cylinders 2, 3 are arranged in line with the cylinder heads 7 facing each other (this is contrast to FIG. 1 in which the cylinders 2, 3 are arranged in parallel with each other and with the cylinder heads 7 facing in the same direction).

[0031] Preferably, the piston movement of the expansion cylinder 2 and the compression cylinder 3 are arranged to be controlled individually. One advantage is that the cylinders or rather the pistons to some extent will balance each other throughout the strokes.

[0032] Although not illustrated in FIG. 2 it should be understood that the linear electric generators/motors 8, 9 may suitably be controlled by a control unit in a corresponding manner as explained in connection with the control unit 20 in FIG. 1.

[0033] It is to be understood that the present invention is not limited to the embodiments described above and illustrated in the drawings; rather, the skilled person will recognize that many changes and modifications may be made within the scope of the appended claims. For example, a spring could be arranged at the end of the reciprocating members of the piston in order to provide balancing motion or aid in piston movement at stroke end points.