JP2009542951A - Stirling engine assembly - Google Patents

Abstract

A Stirling engine assembly comprising a pair of Stirling engines (1) each having a head (3). Both engines are mounted such that their own heads are adjacent to each other and that one vibration substantially cancels the other vibration. A heat source assembly (7) surrounds the head and has a segmented structure adapted to be removably assembled about the engine.
[Selection] Figure 5

Description

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

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

  The concept of having a balanced pair of Stirling engines is known in a few applications of the prior art. In particular, this concept has been disclosed by NASA to provide a power source in a spacecraft designed for a far-reaching space trip using radioisotopes as a power source. For example, Lanny G. Thimeme and Jeffrey G. "NASA GRC Stirling Technology Development (NASA / TM-2003-212454)" by Schreiber, and Jeffrey G. Schreiber and Lanny G. See “Overview of NASA GRC Stirling Technology Development (NASA / TM-2004-2121969)” by Thiemé.

  In addition, a balanced pair of Stirling engines is also available from Sunpower. By Inc, for example, "Development of a High Frequency Engine-Powered 3kW (e) Generator Set": in (Proceedings of the 24 the Intersociety Energy Conversion Engineering Conference.Volume 5.New York Institute of Electrical and Electronics Engineers 1989), Proposed. This discloses a 3 kW assembly with a gas fired sodium heat pipe. Details of the heat source housing are not provided. However, since these two engines are separated from each other, they can be removed axially from the heater if needed for maintenance.

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

  The present invention addresses problems that are not recognized in the prior art.

  If the Stirling engines are connected with their heads adjacent to each other, the resulting assembly is effectively constricted towards the middle. The heater is positioned in this constricted portion. In certain applications, space constraints can make it difficult to move the two engines apart and access the heater assembly. In some cases, if the two engines are connected together, the heater assembly may not be accessible for maintenance unless some components of the system are partially destroyed. In the case of a domestic cogeneration assembly, it is desirable to be able to seal the engine assembly until it reaches the end of its life.

  In accordance with the present invention, a pair of Stirling engines, each having a head, mounted so that the heads are adjacent to each other and one vibration substantially cancels the other vibration. Stirling comprising: a pair of Stirling engines and a heat source assembly surrounding the head, the heat source assembly having a segmented structure adapted to be removably assembled about the engine An engine assembly is provided.

  Accordingly, the present invention provides for the first time a Stirling engine assembly comprising a pair of Stirling engines, wherein access to the heat source assembly for maintenance purposes is provided without the need to interfere with the engine.

  The heat source assembly may be any suitable heat source, many well known in the prior art. However, the heat source assembly is preferably a burner. More preferably, the heat source assembly is a gas combustion burner.

  The burner should be free of contaminants that could impair the metallurgical properties of the engine components (such as sulfur in some biofuels that corrode stainless steel) or block passages in the burner assembly. In can be supplied by gaseous fuel or any fuel that can be put in a gaseous state.

  A single heat source assembly may be adapted to provide heat to both engines. This makes the heater design easier. However, the heat source assembly may include a separate heat source for each engine. This provides a more flexible system and allows the two engines to be controlled independently. Also, if the thermal assembly is a burner, having a separate heat source for each burner makes it easier to design a single exhaust gas collector for the two engines.

  The or each burner preferably has an exhaust gas outlet having an involute structure in order to direct the exhaust gas flow substantially tangentially from the or each burner.

  There are many ways that two engines can be installed. Both engines can share a common housing. In this case, the part of the gas space in the housing is common to both engines. Both engines may be two engines mounted directly on each other, each engine having its own internal gas space, or two independent mounted on a common support. It may be an engine.

  An example of a Stirling engine assembly according to the present invention will now be described with reference to the accompanying drawings.

FIG. 3 is a schematic view of a first assembly. Figure 2 is a more detailed view of the burner and exhaust assembly of the first assembly. FIG. 2 is a schematic view similar to FIG. 1 of a second assembly. Figure 2 is a more detailed view of the burner and exhaust assembly of the second assembly. It is an exploded view of a combustion exhaust gas collector. FIG. 6 is a cross-sectional view of the collector manifold as seen from line XX in FIG. 5a.

  FIG. 1 shows a first linear free piston Stirling engine 1 and a second linear free piston Stirling engine 2. Each engine has a head 3, a cooled region 4 cooled by a refrigerant circuit (not shown), and an alternator region 5 in which electric power is generated as one or more electric outputs V. All of these aspects of Stirling engines are well known in the art.

  The engines 1 and 2 are arranged in a structure aligned in the axial direction. Both engines may share the same housing as shown in FIG. In this case, the engine remains largely conventional, but the engine head does not have a closed dome, and the engine head is hot against the adjacent engine head, which is also open. It is exposed at the edge. Alternatively, two independent engines may be mounted as close as possible to each other. They must be connected directly to each other or to a common housing, firmly or elastically, so that the force generated by one is transmitted to the other. The entire engine assembly is mounted on a resilient mounting member (not shown) to absorb small vibrations that still occur despite the balanced arrangement.

  The heads 3 of the two engines are provided with a plurality of longitudinally extending fins 6 that are common to both heads. These could alternatively be annular fins or separate pin-like fins.

  As shown in FIG. 1, a single burner 7 surrounds both common heads 3 and provides heat to both. However, each head 3 is provided with an annular combustion exhaust gas collector 8 of each head 3 itself. The arrangement of the burner and the flue gas collector will be described in more detail below with reference to FIG.

  The flue gas collector 8 continues to the heat exchanger assembly 10. This heat exchanger assembly 10 generates a thermal output T that is used to heat domestic water and space. This heat exchanger is divided into a first chamber 11, a second chamber 12, and a third chamber 13. Within the first chamber 11 is a supplementary burner 14. The supplementary burner 14 has its own gas / air supply and can be operated independently of the engine burner 7. The engine burner 7 and the supplementary burner 14 are controlled by the control device C. This supplementary burner 14 allows the system to meet a greater heat demand than is possible with the engine burner 7 alone. The supplementary burner 14 burns radially outward toward a first heat exchanger coil 15 that provides a helical passage for the heat receiving liquid to circulate through the heat exchanger 10. The exhaust gas from the supplementary burner then passes around a horizontal baffle 16 and is supplied to the third chamber 13 along a duct 17 extending centrally. The exhaust gas from the combustion exhaust gas collector 8 is supplied to the central portion of the second chamber 12, where the diameter is directed toward the second heat exchanger coil 18, which is an extension of the spiral passage of the first coil 15. Flows outward in the direction. These gases pass around the lower baffle 19 and flow to the third chamber 13 where they combine with the gas from the first chamber 11 and then the third heat exchanger. Passes through the coil 20 (extension of the previous coil) and exits through the flue gas outlet 21. At this point, these gases have been cooled to a point where the temperature of these gases is below the dew point of the mixture, causing condensation and maximizing the efficiency of the heat recovery process. The condensate flows out through condensate drain 22 via a suitable trap device well known in the art.

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

  The burner 7 is provided with a combustion gas inlet 30 tangentially leading to the annular recuperation channel 31, whereby the incoming gas swirls around this channel. The burner may be supplied with a gas supply and an air supply separately, or may be supplied with a mixture of gas and air in advance. The channel 31 has an annular baffle 32 and the incoming gas must flow around the annular baffle 32 in order to reach the burner. This allows the channel 31 to absorb heat from the exiting exhaust gas in this process. Within the recuperation channel 31 are a first mixture distribution plate 33 and a second mixture distribution plate 34 that distribute the incoming mixture to the burner mesh 35 reliably and evenly.

  The burner mesh 35 has an annular structure, which may be formed of any known material, such as, for example, a knitted / woven wire mesh, ceramic foam, ceramic plaque or any other suitable material. . The mesh 35 is divided into two semicircular portions to facilitate assembly and maintenance as described below.

  The burned gas, once passing heat to the engine head 3, enters the flue gas collector 8, 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 made of ceramic and has a plurality of circumferentially spaced inlets 42 that are widened involute-like radial channels (not shown). To a plurality of outlets 43 that discharge into the manifold 41. This ensures that once the gas enters the manifold 41, it continues to flow smoothly around the circumference of the manifold and exits the tangential outlet 44 and is supplied to the heat exchanger head.

  The collector inner side 40 is formed from a ceramic material consisting of two semi-annular half segments that are divided along the involute line of the inner channel. A gasket (eg, ceramic fiber mat or nickel-containing graphite) 45 is provided between the halves to provide a cushioning effect between the halves and to prevent any flow of gas.

  Manifold 41 is also assembled from a pair of semi-annular segments. This manifold has a positioning flange 46 on the inner surface of the manifold itself. When these flanges 46 are assembled, the segments of the inner portion 40 are pressed together so that the inner portion 40 forms an annular flow path 47 in the radially outermost portion of the manifold 41. Yes. As is apparent from FIG. 5a, the split between the two halves of the manifold 41 is offset by 90 ° from the inner split, preventing flow through and minimizing the risk of leakage. The two parts of the manifold 41 have overlapping ends that fit snugly together with a connection sealed by a gasket.

  Although engine assemblies are designed to minimize residual vibration levels, the combined assemblies still vibrate to some extent, especially during transient operations such as starting and grid connection / disconnection, thereby Difficulties can arise for fixed seals such as ceramic washers. Therefore, a flexible seal is provided between the burner assembly and the engines 1,2. As shown in FIG. 2, this boundary surface is sealed by an upper annular flexible seal 50 and a lower annular flexible seal 51. In order to protect these seals from the heat of the burner and to maximize engine operating efficiency, an upper refrigerant circuit 52 is provided directly below the upper annular flexible seal 50 and a lower refrigerant circuit 53 is provided at the lower It is provided immediately above the flexible seal 51. This refrigerant circuit may be in series or in parallel with the refrigerant circuit that circulates fluid in the low temperature portion 4 of the engines 1 and 2.

  The assembly of the above-described burner device will be described below.

  Ideally, a burner is first assembled horizontally around the engine pair 1, 2 and then this module is mounted in place in the equipment. However, it is also possible to assemble with the upper ends of the engine pairs 1 and 2 attached in the equipment. The removal of the burner for maintenance work is also arbitrarily performed with respect to such a vertical assembly.

  The burner assembly is mounted between upper and lower burner support plates, each of which can have a two-part structure (inner side 60, 61 and outer side 69, 74), and the outer side when the engine is in place. Portions 69 and 74 can be installed.

  First, the upper and lower inner burner support plates 60, 61 are brazed to the engine during manufacture. The upper insulation block 62 and the lower insulation block 63 are then fitted around the engine adjacent to the respective inner burner support. These are also two-part semi-annular structures. The joining surfaces of these two parts are, for example, sandwiched together with ceramic fiber mats or alternatively have corrugated corrugations, which also serve to prevent the radiation path from passing straight through the connection. To do.

  The inner part 40 of the flue gas collector (shown in FIG. 5a) is then placed in place. The manifold 41 is externally fitted to the inner part 40 as described above. A semi-annular thermal support block 68 is then positioned on each side of the two flue gas collectors 8.

  The upper outer burner support plate 69 is welded to the upper inner burner support plate 60 in place. Upper refrigerant channel 52 having an upper annular flexible seal 50 and a brazed shield support ring 69A (both upper annular flexible seal 50 and upper refrigerant channel 52 are sufficient to fit over engine 2). Because of its size, it may be a single annular piece) pushed up from below the engine. The upper portion of the upper annular flexible seal 50 is fitted on the outermost edge of the upper outer burner support plate 69.

  The burner body, including the distribution plates 33, 34 and the burner mesh 35 (each of which is formed from two semicircular segments) then fits around the gas collector outlet 44 in a tangential direction. As such, it is assembled around the previous components. Connections between the various segments are tightly fitting and engaging connections, and gaskets are fitted to these engaging connections to prevent leakage. The refrigerant channel 52 is fixed to the burner body using a bolt 70 that is fixed through the recuperation channel 31. A clamping ring 71 is fitted around the upper annular flexible seal 50 to secure the seal in place.

  Next, the lower refrigerant channel 53 having the brazed seal support ring 72 is pushed from below and is bolted in place using bolts 73 from within the recuperation channel 31. Next, the lower outer burner support plate 74 is welded onto the lower inner burner support plate 61.

  The baffle plate 32 having a two-piece structure is fitted around the upper mixture distribution plate 33 and fixed in place by a bolt 75. The burner inlet plate 76, which also has a two-piece structure, is fitted around the burner body outer positioning lip 77, taking care that the burner body is fitted around the flue gas outlet 44. The connection between the two halves is fitted with a tight gasket to prevent opening, while the flue gas outlet 44 is hermetically sealed to prevent leakage of the combustible mixture. Is fitted. A clamping ring 78 is fitted around the burner inlet plate 76 as shown.

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

  In the procedure described above, the cooling channels 52, 53 are integral annular components. However, it may be easier to divide all of the annular components so that the entire burner assembly can be divided into semi-annular segments. These two cooling channel segments are placed in appropriate locations around the heater head, with all connections securely sealed with a ceramic mat or gasket, as appropriate.

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

  A second example of the present invention is shown in FIGS.

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

  The difference is that there are now two burner meshes 35a, 35b, each having its own supply of combustible gas 80. Between these two burner meshes 35a, 35b is a single flue gas collector 81, which is not the two inlets in the previous example, but the second of the heat exchanger 10. Only a single entrance to the chamber 12 is provided.

  Since each of the two burners has its own gas / air flow, each flow can be controlled by the controller C for the individual burner. For example, the multi-port splitter described in the above-mentioned International Publication No. 2004/085893. A splitter valve can also be used to supply supplemental burner 14. This provides a system with two Stirling engines that can be controlled completely independently. Alternatively, two consecutive two-port splitter valves can be used instead of a multi-port splitter valve, one splitter valve splitting the flow between both engines and the supplementary burner, and the next splitter valve in the engine branch Can control the diversion between engine burners.

  In contrast, the control of the two engines in the first example is effected via a solenoid driven butterfly valve in the outlet 44.

  The circulation of water through the refrigerant circuits 52, 53 is also controlled in the same way that the temperature at the hot end is controlled by controlling the burner as mentioned above to control the temperature in the cold part of the engine. .

  The axial position of the burner with respect to the engine head is adjusted in order to balance the operation of each engine so that each engine operates in true reverse phase and potential unbalanced vibration is minimized. It can be adjusted in between to balance the heat provided to each Stirling engine head. The axial position can also be changed during periodic inspections to compensate for changes in equilibrium over time.

  Since the temperatures of the two engine heads can be controlled independently (as described above), both engines can be balanced during operation. Such control is desirable in addition to controlling the axial positioning referred to above. This is because the engine characteristics can be extended so that differences in combustion rates can be required. Alternatively, it may be necessary for the temperature of the two engine heads to rise together, but due to variations in manufacturing tolerances between the two engines and the difference in gravity that occurs between the upper and lower engines during operation, Even when heated at the same speed, the head temperature may vary. Independent control can prevent this variation.

  Although the above design uses engine pairs in a vertical orientation, any of the above structures can be used in a horizontal structure.

Claims (15)

A pair of Stirling engines each having a head, the engine being mounted such that the heads are adjacent to each other and one vibration substantially cancels the other vibration Stirling engine,
A heat source assembly surrounding the head, the heat source assembly having a segmented structure adapted to be removably assembled about the engine;
Stirling engine assembly comprising.   The assembly of claim 1, wherein the two engines share a common housing.   The assembly of claim 1, wherein the two engines each have their own independent internal gas space.   The assembly of claim 3, wherein the two engines are attached to each other.   The assembly of claim 3, wherein the two engines are attached to a common support.   The assembly according to any one of claims 1 to 5, wherein the heat source is a burner.   The assembly of claim 6, wherein the engines share a common burner element.   The assembly of claim 7, wherein each engine is associated with its own exhaust outlet.   9. An assembly according to claim 8, wherein each exhaust outlet has its own valve.   The assembly of claim 6, wherein each engine is associated with its own burner.   The assembly of claim 10, wherein the burners share a common exhaust.   12. An assembly according to claim 8 or 11, wherein the or each exhaust gas outlet has an involute structure for directing the exhaust gas stream from the or each burner in a substantially tangential direction.   13. An assembly according to any one of the preceding claims, further comprising an auxiliary burner that allows the assembly to generate additional heat.   The assembly of claim 11, wherein the engine and auxiliary burner have a maximum heat output of less than 50 kW.   15. An assembly according to any one of the preceding claims, wherein both engines together have a maximum electrical output of less than 2.5 kW.

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