KR100964910B1 - A stirling engine assembly - Google Patents

Abstract

The present invention relates to a Stirling engine assembly for a DCHP system. The Stirling engine 1 is suspended from the mounting frame 5 by a plurality of tension springs 6. The annular vibration absorbing object 2 is suspended from the engine by a plurality of elastic members surrounding the Stirling engine and arranged asymmetrically around the main axis. The asymmetrical arrangement is provided by different rigid elastic members or by placing the elastic members at irregular intervals. The absorber 2 can have its own mass reduced in the vicinity of the elastic members.

Stirling Engine, DCHP, Dustproof, Suspension

Description

Stirling engine assembly {A STIRLING ENGINE ASSEMBLY}             

FIELD OF THE INVENTION The present invention relates to Stirling engine assemblies, and more particularly to Stirling engine assemblies suitable for use in domestic combined heat and power (DCHP) devices.

Such a device is intended to be used in a home environment instead of a conventional boiler. In this situation, it is very important that noise and vibration be kept at a very low level that is acceptable to the consumer.

A common method is to support the engine by mounting the engine on springs that block vibrations generated during normal engine operation. One example of a Stirling engine including such a configuration is US Pat. No. 4,400,941. In order to maximize the degree of blocking, a stiffness mounting system is required. However, implementing such a system with compression springs can lead to instability.

The Stirling engine assembly according to the present invention comprises a Stirling engine and a mounting frame on which the engine is mounted such that the axis on which the reciprocating portions of the engine are reciprocated is perpendicular to operation, the engine being mounted to the mounting frame by a plurality of tension springs. Hang

By tying the Stirling engine to the spring rather than on it, the springs used can be made of low rigidity, high deflection springs. Thus, the conflict between the need for stable support and the need for a low rigid mounting system in the prior art has been eliminated.

The springs on which the engine is suspended are particularly suitable for preventing the transmission of low frequency vibrations. In order to improve damping over a wide range of frequencies, rubber pads are preferably connected in series with each spring. Rubber pads can be installed between the spring and the engine, between the spring and the mounting frame, or both. Such rubber pads are particularly useful for damping high frequency vibrations.

The mounting frame is preferably connected to the lower half of the engine. This allows the use of springs longer than required when the mounting frame is connected to the upper half of the engine.

In order to provide additional radial stability to the Stirling engine in the surrounding suspension arrangement and also to provide a suitable seal against the combustion zone, the housing for the burners located around and above the upper dome of the engine has its inner bottom. A flexible annular guide may be included between the engine and the engine. This guide may be an 'O' ring, for example, of a material suitable for use in such a vibrating high temperature environment. This will allow some lateral movement so that engine vibration will not cause damage, prevent unwanted transmission of force while maintaining engine stability. Other sealing devices that can withstand high temperature and high vibration environments can also be used.

The springs have a free length of 100-150 mm and the total stiffness is between 0.6 and 0.9 kg / mm. When the engine is suspended, the length of the springs is equal to ± 20% of the engine body length.

The above-mentioned device is a suspension device which is particularly advantageous for Stirling engines. However, it is possible to further improve the design by providing a vibration absorber which minimizes vibration of the engine and thus relieves the burden of the suspension device. Therefore, the vibration absorbing mass is preferably configured to be suspended by the at least one elastic member and to provide a reverse phase force to the engine. The vibration absorbing object may be suspended just below the engine, or may be an annular object suspended around the engine. The latter configuration is advantageous for providing a Stirling engine with a smaller total height.

In the case of symmetric annular vibration absorbing objects, the pitching frequency tends to coincide with the vertical frequency due to the combination of the inertia around the horizontal axes of the object and the rotational rigidity around the same axes of the spring system.

The degree of pitching is related to the lack of radial stiffness symmetry, the possible offset from the spring stiffness center of the vibration absorbing object, and the proximity of the excitation frequency to the vertical tuning and pitching frequencies. Therefore, the elastic members are preferably arranged asymmetrically about the main axis center of the annular member. This can be done, for example, by providing elastic members with different stiffness. The different rigid elastic members are preferably arranged symmetrically on both sides of the first axis perpendicular to the main axis, and more preferably also symmetrically on both sides of the main axis and the second axis perpendicular to the first axis.

Alternatively, an asymmetrical arrangement can be provided by grouping the elastic members close to the first axis perpendicular to the main axis. In this arrangement, the elastic members are preferably arranged symmetrically on both sides of the first axis.

In any case, the mass of the vibration absorbing object can be reduced compared to the rest of the vibration absorbing object in the vicinity of the horizontal axis of the maximum rotational rigidity.

The asymmetric annular vibration absorbing object includes a Stirling engine and a mounting frame on which the engine is mounted such that an axis in which the reciprocating portions of the engine are reciprocated is perpendicular to operation, wherein the annular vibration absorbing object surrounds the Stirling engine and includes a plurality of annular vibration absorbing objects. The resilient members are suspended from the engine to provide reverse force to the engine, which forms a standalone form of the invention, broadly defined as a Stirling engine assembly asymmetrically disposed about the major axis of the annular member.

This configuration can be used when the engine is suspended from the springs or from other elastic mounts in accordance with the first aspect of the invention.

One embodiment of a Stirling engine assembly according to the present invention will be described in detail below with reference to the accompanying drawings.

1 is a schematic cross-sectional view of a Stirling engine assembly.

2A is a front elevational view of a portion of a mounting assembly including two springs.

FIG. 2B is a side elevation view of the configuration shown in FIG. 2A.

3 is a schematic cross-sectional view of an assembly different from the assembly shown in FIG. 1.

4 is a schematic diagram showing the mechanical principle of a suspension device.

5A is a diagram illustrating various vibration modes of an annular vibration absorbing object.             

5B is a view showing axes of a vibration absorbing object.

6 is a schematic view showing a first spring device.

7 is a schematic view showing a second spring device.

8 is a perspective view of an annular object suitable for use with the apparatus of FIG. 7.

The Stirling engine assembly includes the Stirling engine 1 which is well known in the art. The Stirling engine has a displacement and power pistons, all of which are configured to reciprocate in the vertical direction. This vertical reciprocation produces a net vertical vibration of the Stirling engine 1 itself.

In order to reduce this vibration, the vibration absorbing object 2 is supported by a plurality of compression springs 3 both above and below the vibration absorbing object 2, which are firmly attached to the bottom of the Stirling engine 1. It is housed in a fixed housing 4. The object 2 and the springs 3 vibrate as close as possible anti-phase to the Stirling engine 1 when the Stirling engine 1 is operating at the normal operating frequency. It is adjusted to. As a result, the total vibration of the Stirling engine 1 and the housing 4 is greatly reduced.

The device comprises eight compression springs 3 above the 10.5 kg (± 10%) vibration-blocking object 2 and eight compression springs below. The springs, for example, have a free length of 67 mm and a stiffness of 66.25 N / mm (± 10%). The absorber is adjusted to absorb vibrations of the frequency from 48 Hz to 52 Hz (lowest vibration at 50.25 Hz).             

The stirling engine 1 and housing 4 assembly described above is mounted to a mounting frame 5 surrounding the head of the engine as shown in FIG. 1. The engine 1 and the housing 4 are suspended from the mounting frame by a number of mounting assemblies arranged at regular intervals around the Stirling engine, one of which is shown in FIGS. 2a and 2b. Each mounting assembly comprises a pair of tension springs 6 with an upper end with a ring 7 for attachment to the mounting frame 5. The second ring 8 attaches the lower end of each spring to the frame 9.

The thickness of the spring wire is chosen to be sufficient to support the weight of the engine 1 and the absorbent body 2, which may be between 40 and 80 kg but is typically 60 kg. In this embodiment, the wire diameter is typically 2.4 mm.

In order to provide optimum suspension damping to reduce low frequency vibration, the springs should be as long as possible and the mounting points need to be as far away as possible from the designable range. In this embodiment, the upper mounting frame 5 is located directly below the engine burner housing and the lower engine mounting ring 12 is located on the lower engine flange. The extended length of the spring is then approximately equal to the length of the engine body (typically 190 mm) except the cooler 13, heat transfer head 14 and rear end dome 15 (as shown in FIG. 1). same. In addition, care must be taken to ensure that the natural frequency of the spring (surge frequency) does not match the operating frequency of the engine or its harmonics, as this will result in unacceptable resonances.

In the configuration of this embodiment in which six to twelve (typically eight) springs are arranged in pairs and arranged at regular intervals around the engine, the free lengths of the springs range from 100 to 150 mm (typically 127 mm). It is preferable. Total spring stiffness is between 0.6 and 0.9 kg / mm (typically 0.75 kg / mm), and the stiffness (spring rate) of each spring in this embodiment is typically 0.09 kg / mm.

In each frame 9 a rubber element 10 is placed. This rubber element 10 supports the mounting bolt 11, by means of which the mounting assembly is attached to the mounting ring 12 on the Stirling engine 1. Thus, all vibrations of the Stirling engine 1 are transmitted via the bolt 11 to the rubber element 1 and to the frame 9 and then through the spring 6 to the mounting frame 5.

Alternatively, or in addition to the rubber element 10 at the bottom of each spring, a rubber element may be provided at the top of each spring.

The stiffness per rubber element 10 based on four sets of springs is for example 110 N / mm. Since the rubber elements are designed to remove high frequencies, the stiffness exemplified above is adequate, and the strain is maintained at an appropriate level, bearing in mind that the rubber's performance degrades at elevated temperatures.

Since the high frequency vibration is attenuated by the rubber element 10 and at the same time the low frequency vibration is attenuated by the spring 6, the vibration experienced by the mounting frame 5 is negligible and acceptable for the DCHP device. Are within the limits.

An assembly other than that shown in FIG. 1 is shown in FIG. 3. In this configuration, the housing 4 'is mounted so as to surround the Stirling engine 1 rather than hanging directly under the Stirling engine 1 as in FIG. In this embodiment, the absorbent body 2 'is annular and surrounds the Stirling engine. In this embodiment, the diameter of the mounting ring 12 needs to be considerably larger than that of FIG. However, the total height of the device is reduced, so the present design is useful when the up and down space is limited. For other parts, the apparatus is the same as that shown in FIG. 1 and the same reference numerals have been used to designate the same parts.

The mechanical principle of the assembly is shown in FIG. 4. Symbols in the drawings have the following meanings.

m1-main engine mass

m2-mass of absorber (2)

k1-tension spring (6) rigidity x number of tension springs

c1-damping value associated with the tension spring device

k2-compressive stiffness of the rubber element 10 × number of rubber elements

c2-damping value associated with the compressed rubber element

k3-compression springs (3) rigid × number of compression springs (typically 16)

c3-damping value associated with the movement of the air around the absorber and the compression spring

Modifications of the annular absorber of FIG. 3 will be described with reference to FIGS. 5 to 8.

5A and 5B define an axis system for the annular object. The X, Y and Z axes are orthogonal to each other, the X and Y axes are horizontal axes in the plane of the annular object and intersect at the center of the annular object, and the Z axis is a vertical axis extending from the center of the annular object 2 '. The natural excitation frequency causes vertical reciprocation in the direction of the arrow 20. However, the pitching frequency tends to coincide with the vertical frequency, causing pitching around the X and Y axes as indicated by arrows 21 and 22, respectively. The annular absorber also rotates about the Z axis as indicated by arrow 23. In order to reduce the pitching around the X and Y axes, an asymmetrical arrangement of the springs or absorber inertia is proposed.

The first example is shown in FIG. This configuration is generally suitable when the rotational inertia around the X and Y axes of the absorber is the same. In this example, the absorber 2 'has a uniform cross section and a uniform mass. As shown in FIG. 6, four of the springs are arranged so that the stiffness is K and the other four are 0.5K, thereby changing the stiffness around the absorber but changing the stiffness across the absorber. It should be noted that the stiffness of the spring is symmetrical on both sides of the X and Y axes. The spring stiffness pattern is repeated above and below the absorbent body. In the second configuration, both the spring stiffness and the absorber rotational inertia are asymmetric.

The second configuration is shown in Fig. 7, which is particularly suitable when the rotational inertia of the absorber ring is different at the center of the X axis and at the center of the Y axis. In this example, eight springs of the same rigidity K 'are provided, but are grouped by the maximum axis of inertia X that meets the need to maintain sufficient stability in operation. In this example, an annular object 2 "is provided on both sides that essentially includes a pair of cutouts 25, and eight springs are configured to attach to the mounting points 26 above and below each cutout. do.

Claims (22)

A Stirling engine, and a mounting frame on which the engine is mounted such that the axis on which the reciprocating portions of the engine reciprocate are perpendicular in operation, wherein the engine is suspended on the mounting frame by a plurality of tension springs. The Stirling engine assembly of claim 1, wherein a rubber pad is connected in series with each spring. The Stirling engine assembly according to claim 1 or 2, wherein the free length of the springs is between 100 and 150 mm. A Stirling engine assembly according to claim 1 or 2, wherein the length of the springs is equal to ± 20% of the length of the engine body when the Stirling engine is suspended on the springs. The Stirling engine assembly according to claim 1 or 2, wherein the total stiffness of the springs is 0.6-0.9 kg / mm. The Stirling engine assembly according to claim 1 or 2, wherein the mounting frame is connected to the lower half of the engine. The Stirling engine assembly of claim 1, wherein the vibration absorbing object is suspended from the engine by at least one elastic member and is configured to provide an anti-phase force to the engine. 8. The Stirling engine assembly of claim 7 wherein the vibration absorbing object is annular and surrounds the Stirling engine. The Stirling engine assembly of claim 8, wherein the elastic members are disposed asymmetrically about the major axis of the annular member. 10. The Stirling engine assembly of claim 9, wherein the asymmetrical arrangement is provided by different rigid elastic members. The Stirling engine assembly of claim 10, wherein the resilient members are symmetrically disposed on either side of the first axis perpendicular to the main axis. 12. The Stirling engine assembly of claim 11, wherein the resilient members are also symmetrically disposed on both sides of the main axis and the second axis perpendicular to the first axis. 10. The Stirling engine assembly of claim 9, wherein the asymmetrical arrangement is provided by bunching elastic members close to a first axis perpendicular to the main axis. The Stirling engine assembly of claim 13, wherein the elastic members are symmetrically disposed on both sides of the first axis. The Stirling engine assembly according to claim 9, wherein the mass of the vibration absorbing object is reduced in comparison to the rest of the vibration absorbing object in the vicinity of the elastic members. A stirling engine and a mounting frame on which the engine is mounted such that the axis on which the reciprocating portions of the engine reciprocate are perpendicular to operation, wherein an annular vibration absorbing object surrounds the Stirling engine and is suspended from the engine by a plurality of elastic members Providing a reverse force to the engine, the elastic members being asymmetrically disposed about the major axis of the annular member. 17. The Stirling engine assembly of claim 16, wherein the asymmetrical arrangement is provided by different rigid elastic members. 18. The Stirling engine assembly of claim 17, wherein the resilient members are symmetrically disposed on either side of the first axis perpendicular to the main axis. 19. The Stirling engine assembly of claim 18, wherein the resilient members are also symmetrically disposed on both sides of the main axis and the second axis perpendicular to the first axis. 17. The Stirling engine assembly of claim 16, wherein the asymmetrical arrangement is provided by bunching elastic members close to a first axis perpendicular to the main axis. The Stirling engine assembly of claim 20, wherein the elastic members are symmetrically disposed on both sides of the first axis. 22. The Stirling engine assembly according to any one of claims 16 to 21, wherein the mass of the vibration absorbing object is reduced in comparison to the rest of the vibration absorbing object in the vicinity of the elastic members.

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