KR20090028784A - A stirling engine assembly - Google Patents

Abstract

A Stirling engine assembly comprising a pair of Stirling engines (1) each having a head (3). The engines are mounted with their heads adjacent to one another and such that the vibrations of one substantially counteract the vibrations of the other. A heat source assembly (7) surrounds the heads, wherein the heat source assembly has a segmented configuration arranged to be removably assembled around the engines.

Description

Stirling engine assembly

The present invention relates to a stirling engine assembly comprising a pair of stirling engines.

The present invention is specifically designed for domestic combined heat and power systems with a Stirling engine system having a total electrical output of less than 2.5 kW. The invention is designed for a linear free piston Stirling engine. However, as will be appreciated by those skilled in the art, the present invention can be applied to a wide variety of stirling engines and can be used for a wide range of applications.

The concept of having one balanced pair of stirling engines is known in a few applications in the art. In particular, the concept has been disclosed by NASA to provide a power source in a spacecraft designed for distant space travel using a radioisotope as the power source. For example, "NASA GRC Stirling Technology Development Overview" by Lanny G. Thieme and Jeffrey G. Schreiber (NASA / TM 2003-212454) and "Overview of NASA GRC Stirling Technology Development" by Jeffrey G. Schreiber and Lanny G. Thieme. See (NASA-TM-2004-2121969).

In addition, one balanced pair of sterling engine is described, for example, in "Development of a High Frequency Engine-Powered 3 kW (e) Generator Set" (Proceedings of the 24 the Intersociety Energy Conversion Engineering Conference.Volume 5. New York: Institute of Electrical and Electronics Engineers (1989), proposed by Sunpower. This discloses a 3 kW assembly with a gas-fired sodium heat pipe.

No detailed description of the housing of the heat source is provided. However, if the two engines are separated from each other, they can be moved axially from the heater if necessary for maintenance.

The second Sunpower announcement was "A 5kW Electric Free-Piston Stirling Engine" by Neil W.Lane and William T.Beale, introduced at the 7th International Conference on Stirling Cycle Machines in Tokyo, Japan, November 5-8, 1995. . This discloses a 5 kW assembly suitable for a portable saw mill. It does not contain any information about the structural relationship between the burner and the engine.

The present invention addresses a problem not recognized in the prior art.

When the Stirling engines are connected to the heads adjacent to each other, the resulting assembly efficiently contracts towards the center. The heater is disposed at this retracted position. In certain applications, space limitations make it difficult to move the two engines separately to use the heater assembly. In some cases, where two engines are connected together, it is not possible to use a heater assembly for maintenance without partially damaging some elements of the system. In the case of a combined domestic heat and power system, it is desirable to seal the engine assembly for life.

According to the present invention, there is provided a Stirling engine assembly comprising a pair of Stirling engines each having a head, the engine being mounted with heads adjacent to each other and with one vibration generally counteracting the other vibration. The heat source assembly surrounds the head and the heat source has a segmented configuration arranged to be detachably assembled around the engine.

Thus, for the first time, the present invention provides a stirling engine assembly comprising a pair of stirling engines provided that access to the heat source assembly for maintenance purposes is provided without disturbing the engine.

The heat source assembly can be any suitable heat source, which is known. Preferably, however, the heat source assembly is a burner. More specifically, the heat source assembly is a burner using gas.

As long as it blocks the passage in the burner assembly or is free of contaminants that may contain metallurgy of the engine components (eg sulfur in some biofuels that corrode stainless steel), the burner is a gaseous fuel or It can be supplied by any fuel that can be in gaseous state.

There is a single heat source assembly arranged to provide heat to all of the engines. This results in a simpler heater design. However, the heat source assembly may include a separate heat source for each engine. This provides a more flexible system and allows for independent control of the two engines. Also, if the thermal assembly is a burner, having separate heat sources for each burner makes it easier to design a single exhaust gas collector for two engines.

Preferably each burner has a discharge gas outlet having a spiral configuration to direct the exhaust gas flow away from each burner in a generally tangential direction.

There are a number of ways in which two engines can be mounted. The two engines may share a common housing. In this case, part of the gas space in the housing is common to both engines. These may be two engines each having its own independent internal gas space mounted directly on each other, or may be two independent engines mounted on a common support.

An example of a stirling engine assembly according to the invention is described with reference to the following attached drawings:

1 is a schematic view of a first assembly;

2 is a more detailed view of the burner and exhaust assembly of the first assembly;

3 is a schematic view of a second assembly similar to FIG. 1;

4 is a more detailed view of the burner and exhaust assembly of the second assembly;

5A is an enlarged view of a flue gas collector; And

FIG. 5B is a cross-sectional view through the X-X line in FIG. 5A showing the collector manifold. FIG.

1 shows a first linear free piston sterling engine 1 and a second linear free piston sterling engine 2. Each engine has a head 3, a cooling section 4 cooled by a coolant circuit (not shown) and an alternating current region 5 in which electrical power is generated at one or more electrical outputs V. All of these aspects of a stirling engine are known.

The engines 1, 2 are arranged in an axially aligned configuration. The engines may share the same housing as shown in FIG. 1. In this case, the engine still consists mainly of the conventional design, but is exposed at the hot end to the head of an adjacent engine that is open, rather than having the engine head having a closed dome. Alternatively, two independent engines can be mounted close together adjacent to each other. They are directly connected to each other or firmly or elastically connected to the common housing so that the force generated by one engine is transmitted to the other engine. The entire engine assembly is mounted on an elastic mount (not shown) to absorb small vibrations that still occur despite a stable arrangement.

Two engine heads 3 are provided with a plurality of longitudinally extending pins 6 common to both heads. Alternatively they may be annular fins or fins resembling individual fins.

As shown in FIG. 1, a single burner 7 surrounds the common head 3 to provide heat to the common head 3. However, each head 3 is provided with its annular exhaust gas collector 8. The burner and exhaust gas collector arrangements are described in more detail below with reference to FIG. 2.

The exhaust gas collector 8 is through the heat exchanger assembly 10. This produces a heat output T for use in domestic household hot water and space heating. The heat exchanger is divided into a first chamber 11, a second chamber 12 and a third chamber 13. There is an auxiliary burner 14 in the first chamber 11. It can operate independently of the engine burner 7 with its gas / air supply. The engine burner 7 and the auxiliary burner 14 are controlled by the controller C. The auxiliary burner 14 allows the system to meet a greater heat demand than is possible with the engine burner 7 alone. The auxiliary burner 14 fires in an outer radial direction onto the first heat exchanger coil 15 which provides a helical path for circulation of the receiver liquid through the heat exchanger 10. Exhaust gas from the auxiliary burner is supplied to the third chamber 13 along a duct 17 extending around the center baffle 16 and extending in the central direction. Exhaust gas from the exhaust gas collector 8 is supplied to the center of the second chamber 12, which gases are externally radially to the second heat exchanger coil 18, which is a continuation of the spiral passage of the first coil 15. Flow. These gases pass around the lower baffle 19 into a third chamber 13 that combines with gas from the first chamber 11 before passing through the third heat exchanger coil 20 (continuous of the previous coil). Exit through the exhaust outlet. In this regard, the gas is cooled to the point where the temperature of the gas drops below the dew point of the mixture so that condensation occurs while maximizing the efficiency of the heat recovery process. Condensation flows out through the condensation drain 22 through a suitable trap arrangement known in the art.

The burner assembly is described in more detail with reference to FIG. 2.

The burner 7 comprises a combustion gas inlet 30 which is in contact with an annular recuperator channel 31, thereby causing the incoming gas to whirl around the channel. The burners may be supplied to separate gas and air supplies, or may be supplied as a premixture of gas and air. Channel 31 has an annular baffle 32 through which incoming gas must flow to reach the burner. This allows to absorb heat from the exhaust gas flowing out in the process. In the recuperator channel 31 there is a first mixture dispersion plate 33 and a second mixture dispersion plate 34 which ensure the dispersion of the mixture entering the burner mesh 35.

Burner mesh 35 has an annular configuration that can be made of any known material, such as a knitted / woven metal mesh, ceramic foam, ceramic plaque, or any other suitable material. The mesh 35 is divided into two semicircular portions for ease of maintenance and assembly as described below.

If the burned gas gives heat to the engine head 3, it enters the exhaust gas collector 8, which is shown in more detail in FIGS. 5A and 5B. Each collector includes an inner portion 40 and an outer manifold 41. The inner portion 40 is ceramic and has a plurality of circumferentially spaced inlets 42 which are led by a spiral radius channel (not shown) that extends to a plurality of outlets 43 that exit the manifold 41. This ensures that once the gas enters the manifold 41, the gas continues to flow smoothly around the circumference of the manifold and out of the tangential outlet 44 which is fed to the heat exchanger head.

The collector interior 40 is of ceramic material consisting of two semi-annular half segments along the helical line of the inner channel. Gaskets (eg, ceramic fiber mats or nickel loaded graphite) 45 are provided between the halves to protect the halves and hinder any gas flow.

Manifold 41 is assembled from a pair of semi-annular segments. The manifold has a position flange 46 on the inner surface. These force the segments of the inner portion 40 together on the assembly to form an annular flow passage 47 at the radially outermost portion of the manifold 41. As is apparent from FIG. 5A, the split between the two halves of the manifold 41 is separated from the split of the inner portion by 90 ° to prevent through-flow and to minimize the risk of leakage. Is off-set. The two parts of the manifold 41 have overlapping ends fitted closely together with the joint sealed by the gasket.

Although the engine assembly is designed to minimize residual vibration levels, the combined assembly still vibrates to a certain extent, especially during momentary operations such as start or grid connection / disconnection, and in a fixed seal such as a ceramic scrubber. Can cause difficulties. Therefore, a flexible seal is provided between the burner assembly and the engines (1, 2). As shown in FIG. 2, this interface is sealed by an upper annular flexible seal 50 and a lower annular flexible seal 51. The upper coolant circuit 52 is provided directly below the upper annular flexible seal 50 and the lower coolant circuit 53 provides the lower flexible seal 51 to protect these seals from the heat of the burners and to maximize the operating efficiency of the engine. Is provided immediately above. This coolant circuit can be in parallel or in series with the coolant circuit which circulates the fluid to the cooling section 4 of the engine 1, 2.

The assembly of the burner arrangement described above is described.

Ideally, the initial assembly of the burners around the engine pairs 1, 2 is performed horizontally before the module is mounted in place in the application. However, it is possible to carry out assembly with the engine pairs 1, 2 mounted at the upper end in the application. Any burner removal for the maintenance operation will be performed on the vertical assembly.

The burner assembly is mounted between the upper burner support plate and the lower burner support plate, each of which has a two-part configuration (inner 60, to allow the outer part 69 74 to be installed if the engine is in situ). 61) and exteriors 69 and 74).

Initially, the upper and lower inner burner support plates 60, 61 are soldered to the engine during manufacture. The upper insulation block 62 and the lower insulation block 63 are fitted around the engine adjacent to the respective internal burner supports. These again consist of a two-part semi-cyclic configuration. The joining surfaces of the two parts may have interlocking corrugations, for example, fitted with a ceramic fiber mat or alternatively used to prevent any direct spinning path through the joint.

The inner portion 40 of the exhaust gas collector (shown in FIG. 5A) is put in place. The manifold 41 is fitted on these as described above. The semi-annular insulating support block 68 is arranged on each side of the two exhaust gas collectors 8.

The upper outer burner support plate 69 is welded in place to the upper inner burner support plate 60. Upper annular flexible seal 50 and upper coolant channel 52 with soldered sealing support ring 69A (all of which may be single annular pieces if large enough to be provided on engine 2) below the engine Is pushed up. The top of the upper annular flexible seal 50 is provided on the outermost edge of the upper outer burner support plate 69.

The burner body, which consists of two semi-annular segments, each comprising a distribution plate 33, 34 and a burner mesh 35, ensures that the burner body is fitted around the tangential gas collector outlet 44, Assembled around the previous devices. Joints between the various segments tightly fit the interlocking joints with gaskets to prevent leakage. The coolant channel 52 is fixed in relation to the burner body using bolts 70 fixed from the recuperator channel 31. The clamping ring 71 is fitted around the upper annular flexible seal 50 to secure the seal in place.

Lower coolant channel 53 with soldered sealing support ring 72 is pressed from below and clamped in place from within recuperator channel 31 using bolt 73. The lower outer burner support plate 74 is welded onto the lower inner burner support plate 61.

The baffle 32 having a two piece configuration is fitted around the upper mixture dispersion plate 33 and fixed in place by bolts 75. The burner inlet plate 76 having a two piece structure is fitted around the outer positioning lip 77 of the burner body which treats it to fit around the exhaust gas outlet 44. The joint between the two halves has a gasket that is stable to the opening while the exhaust gas outlet 44 has a gas-tight seal to prevent leakage of the combustible mixture. Clamping ring 78 is formed around burner inlet plate 76 as shown.

The lower annular flexible seal 51 is then pressed from below around the lip of the seal support ring 72 and the outer edge of the outer lower burner support plate 74. The clamping ring 79 is formed around the lower seal in the same way as the clamping ring 71.

In the procedure described above, the cooling channels 52, 53 are a piece of annular components. However, it may be simpler to split all annular components allowing the entire burner assembly to be divided into semi-annular segments. The two cooling channel segments can be placed in position around the heater head and tightly seal all joints with ceramic matting or gaskets where appropriate.

Other components such as flame probes, igniters and thermocouples are not shown here, but may be installed in a conventional manner, if desired.

A second example of the invention is shown in FIGS. 3 and 4.

Most of the components are the same as those shown in the first example and are denoted by the same reference numerals.

The difference is that there are two burner meshes 35a and 35b, each having a supply of combustible gas 80. There is a single exhaust gas collector 81 between the two meshes 35a and 35b which provides only a single inlet to the second chamber 12 of the heat exchanger 10 rather than the two inlets of the previous example.

If each of the two burners has its own gas / air stream, each stream can be controlled by the controller C for the individual burners. For example, from a multi-port splitter as described in WO 2004/085893. The splitter valve can also be used to feed the auxiliary burner 14. This provides a system with two Stirling engines that are fully independently controllable. Alternatively, instead of a multi-port splitter valve, two consecutive two-port splitter valves, one for separating the flow between the auxiliary burner and the engine and at the engine branch to control the split between the engine burner Another one of can be used.

In contrast, the two engines in the first embodiment are controlled via solenoid butterfly valves activated at the outlet 44.

The circulation of water through the coolant circuits 52, 53 is also controlled to control the temperature of the cooling section of the engine in the same way that the temperature at the hot end is controlled by controlling the burners mentioned above.

The axial position of the burners in relation to the engine head can be adjusted during assembly to balance the heat provided to each stirling engine head to balance the operation of each engine so that they operate in substantially opposite directions, and balance Off-vibration is minimized. The axial position can also be changed during regular service so that changes in balance in time are compensated for.

The engine can be balanced during operation if the temperatures of the two heads can be controlled independently (as set above). In addition to controlling the axial positioning mentioned above, such control may be required if there is a wide range of characteristics on the engine such that a slight difference in firing rate may be required. Alternatively, it may be necessary for the temperatures of the two engine heads to rise together, but a change in manufacturing permit between the engines, or gravity-induced in operation between the upper and lower engines. Even if the tea is heated at the same rate, it can bring a change in thermal temperature. Independent control can prevent this change.

Although the design described above uses engine pairs in a vertical orientation, it is possible to use any of the configurations described above in a horizontal configuration.

Included in the context of the present invention.

Claims (15)

A pair of stirling engines each having a head, and A heat source assembly surrounding the head, the engine mounted with engine heads adjacent to each other and mounted such that vibrations of one of the engines substantially cancel vibrations of the other engine, the heat source assembly being around the engine A stirling engine assembly having a segmented configuration arranged to be detachably assembled to a. The method of claim 1, The stir engine assembly sharing a common housing. The method of claim 1, The pair of engines each having its own independent internal gas space. The method of claim 3, wherein And a pair of engines mounted to each other. The method of claim 3, wherein The stirling engine assembly of which the pair of engines is mounted to a common support. The method according to any one of claims 1 to 5, wherein The heat source is a burner stirling engine assembly. The method of claim 6, The stir engine assembly sharing a common burner element. The method of claim 7, wherein Each of said engines is coupled to a self-owning exhaust gas outlet. The method of claim 8, A stir engine assembly each having a self-owned valve. The method of claim 6, Each of said engines is coupled to a self-owning burner. The method of claim 10, The burner shares a common exhaust outlet. The method according to claim 8 or 11, wherein Each of said exhaust gas outlet or said exhaust gas outlet has a helical configuration for directing exhaust gas flow away from said burner or each of said burners in a generally tangential direction. The method according to any one of claims 1 to 12, A stir engine assembly further comprising an auxiliary burner for causing the assembly to generate additional heat. The method of claim 11, wherein The engine and auxiliary burners having a maximum heat output of less than 50 kW. The method according to any one of claims 1 to 14, Said engine having a maximum coupled electrical output of less than 2,5 kW.

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