Axial thrust self-balancing structure and axial thrust self-balancing method

Abstract

The invention discloses an axial thrust self-balancing structure and an axial thrust self-balancing method, and relates to the technical field of air Brayton expander power generation, the axial thrust self-balancing structure comprises a machine shell and a rotating shaft rotationally connected with the machine shell, the rotating shaft is provided with an annular balancing cavity, and the axis of the balancing cavity is coaxial with the axis of the rotating shaft; two sides of the balance cavity are respectively a compression side and an expansion side; the balance cavity is internally provided with N heat insulation plates, the N heat insulation plates are arranged in the axis direction of the rotating shaft and divide the balance cavity into N + 1 cavities, and N is larger than or equal to 2; the sides, away from the rotating shaft, of all the heat insulation plates are fixedly connected with the machine shell. The sides, close to the rotating shaft, of all the heat insulation plates stretch into the balance cavity and are in clearance fit with the balance A plurality of through holes are formed in all the heat insulation plates, and the through holes in the adjacent heat insulation plates are staggered. Through the structural design of the balancing chamber, the pressure field of the chamber is uniformly distributed, so that the self-balancing of axial thrust is realized, and the radial flow type expansion compressor coaxial device can safely, stably and efficiently operate under multiple working conditions.

Description

Technical Field

[0001] The invention relates to the technical field of air Brayton expander power generation, in particular to an axial thrust self-balancing structure and an axial thrust self-balancing method. Background Art

[0002] In the air Brayton cycle power generation device, the unit will first pressurize and heat the air, and then expand it to do work. The compressor and expander are coaxial, and the two ends of the coaxial rotating shaft 1 of the two are respectively the compression side 12 and the expansion side 11; in the technical requirements for the operation of the unit, it is necessary to reduce the interference between the compression side 12 and the expansion side 11 as much as possible, that is, to reduce the leakage of the fluid on the compression side 12 to the expansion side 11 as much as possible, and to avoid heat exchange between the compression side 12 and the expansion side 11 as much as possible. Therefore, under the premise of simple structure, a feasible solution is to open a balancing groove 13 on the rotating shaft 1. On the one hand, the balancing groove 13 cooperates with the stator component and the steam seal component 5 to form a structure similar to a labyrinth seal, thereby improving the sealing reliability. On the other hand, the degree of heat conduction is reduced by the balancing groove 13, thereby achieving a heat insulation effect. Since there are impellers 2 on both sides of the rotating shaft 1, the pressure on the compression side 12 and the expansion side 11 is not much different, and the pressure on the compression side 12 is slightly greater than that on the expansion side 11. However, after the balancing groove 13 is opened, the two sides of the balancing groove 13 are respectively affected by the fluid pressure on the compression side 12 and the fluid pressure on the expansion side 11, and the areas on both sides of the balancing groove 13 are basically the same, and there is no other structure, which makes the forces on both sides of the balancing groove 13 inconsistent, that is, the force acting on the inner wall of the side close to the compression side 12 is much greater than the force acting on the inner wall of the side close to the expansion side 11, thereby bringing about an axial thrust, which is difficult to balance (such as Figure 1 As shown). Usually, considering the simple structure of the unit, the air bearing design with smaller thrust load will be adopted. However, the thrust that the current air bearing can withstand is 1000N. If the axial thrust balance effect of the unit is poor, that is, the coaxial axial thrust is greater than 1000N, it will directly lead to the failure of the air film support, and then cause the device to shut down, resulting in safety accidents and significant economic losses.

[0003] In the air Brayton cycle power generation device, since the axial thrust of the rotating shaft will exceed the load that the air bearing can bear, there are two main ways to solve the problem of the difficulty in balancing the axial thrust, that is, using a bearing with a large load-bearing capacity to bear the axial thrust or introducing an air source in the middle to balance the thrust. Choose an oil bearing or an electromagnetic bearing with a large load-bearing capacity to balance the thrust, but this method makes the structure more complicated and also increases the cost of the unit; the air source is introduced by introducing an external high-pressure air source into the corresponding side chamber of the rotor to increase the average pressure of the chamber gas, but this method requires the addition of an air bleed pipeline, a regulating valve and a control module, and the structural design is complicated, which increases the cost of the unit.

[0004] Therefore, a new solution is needed to solve the above technical problems. Summary of the invention

[0005] The purpose of the present invention is to provide an axial thrust self-balancing structure and an axial thrust self-balancing method to address the above-mentioned problems. By designing a balancing chamber structure, the chamber pressure field is evenly distributed, thereby achieving self-balancing of the axial thrust, so that the coaxial device of the radial expansion compressor can operate safely, stably and efficiently under multiple working conditions.

[0006] The technical solution adopted by the present invention is as follows: an axial thrust self-balancing structure, applied to a radial coaxially arranged expander-compressor, comprising a casing and a rotating shaft rotatably connected to the casing, wherein an annular balancing chamber is provided on the rotating shaft, and the axis of the balancing chamber is coaxial with the axis of the rotating shaft; the two sides of the balancing chamber are respectively a compression side and an expansion side; N heat insulation boards are provided in the balancing chamber, and the N heat insulation boards are arranged along the axial direction of the rotating shaft and divide the balancing chamber into N+1 chambers, N≥2; the side of all the heat insulation boards away from the rotating shaft is fixedly connected to the casing, and the side close to the rotating shaft extends into the balancing chamber and is gap-matched with the balancing chamber; a plurality of through holes are provided on all the heat insulation boards, and the through holes on adjacent heat insulation boards are staggered.

[0007] Furthermore, N=2.

[0008] Furthermore, both the compression side and the expansion side have impellers.

[0009] Furthermore, the outer diameter and the root diameter of the impeller on the compression side and the impeller on the expansion side are the same.

[0010] Furthermore, steam seals are provided between the side of the balance chamber close to the compression side and the casing, and between the side of the balance chamber close to the expansion side and the casing.

[0011] Furthermore, the steam seal member includes a steam seal body and steam seal teeth, the steam seal teeth are fixed on the steam seal body, and the steam seal body is fixed on the casing.

[0012] Furthermore, an annular protrusion matching with the steam seal teeth is provided on one side of the balance chamber close to the compression side and one side of the balance chamber close to the expansion side.

[0013] Furthermore, the heat insulation board is fixed on the steam seal body.

[0014] Furthermore, the steam seal body is detachably fixedly connected to the casing.

[0015] An axial thrust self-balancing method is disclosed, wherein a plurality of heat insulation plates with through holes are installed on a casing, the heat insulation plates are arranged in a staggered manner with the through holes, and the heat insulation plates extend into a balancing groove to divide the balancing groove into a plurality of chambers, and through the staggered through holes, high-pressure fluid leaking into the balancing groove from a compression side and low-pressure airflow leaking into the balancing groove from an expansion side are fully mixed in each chamber, so that the pressure in all chambers tends to be consistent, and the pressure difference on both sides of the balancing groove is reduced, thereby reducing the axial thrust.

[0016] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0017] 1. The present invention installs a plurality of heat insulation boards with through holes on the casing, the heat insulation boards are arranged in a staggered manner, and the heat insulation boards extend into the balancing tank to divide the balancing tank into a plurality of chambers. Through the staggered through holes, the high-pressure fluid leaking into the balancing tank from the compression side and the low-pressure airflow leaking into the balancing tank from the expansion side are rectified, and through the gap formed by the heat insulation board and the gap at the bottom of the balancing chamber, the two fluids are fully mixed in each chamber in the balancing tank, so that the pressure field in the balancing tank is evenly distributed, thereby reducing the pressure difference on both sides of the balancing tank, achieving the purpose of reducing the axial thrust, and ensuring the stable and efficient operation of the entire unit under the operating conditions;

[0018] 2. The present invention provides a heat insulation board, and the heat insulation board divides the balance tank into a plurality of chambers. The heat insulation board, the plurality of chambers, and the heat insulation board are arranged in a staggered manner to effectively block the radiation heat exchange, thereby reducing the thermal influence between the compression side and the expansion side;

[0019] 3. The present invention does not require an external air source, can achieve self-balancing of the axial thrust under multiple operating conditions, reduce the axial thrust so that the axial thrust can be balanced by using an air bearing, and further achieve the simple and compact structure required by the unit, and can be applied and promoted on a large scale. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention will now be described by way of example with reference to the accompanying drawings, in which:

[0021] Figure 1 This is a schematic diagram of the currently adopted solution;

[0022] Figure 2 It is a structural schematic diagram of the present invention;

[0023] Figure 3 It is a mechanical analysis diagram of the present invention;

[0024] Markings in the figure: 1-rotating shaft; 11-expansion side; 12-compression side; 13-balance groove; 14-chamber; 2-impeller; 3-heat insulation board; 31-through hole; 4-annular protrusion; 5-steam seal; 6-casing. DETAILED DESCRIPTION

[0025] In the description of this specification, it should be noted that if the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc. appear, the orientation or position relationship indicated is based on the orientation or position relationship shown in the drawings, or is the orientation or position relationship in which the product of this specification is usually placed when used. It is only for the convenience of describing this specification and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this specification.

[0026] In addition, if the terms "horizontal" or "vertical" appear in the description of this specification, it does not mean that the components are required to be absolutely horizontal or suspended, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0027] In the description of this specification, it should also be noted that, unless otherwise clearly stipulated and limited, the terms "set", "installed", "connected" and "connected" should be understood in a broad sense. For example, the connection can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be a connection between the internal parts of two elements.

[0028] Example 1

[0029] like Figure 2-Figure 3 As shown, an axial thrust self-balancing structure is applied to a radial coaxially arranged expander-compressor, comprising a casing 6 and a rotating shaft 1 rotatably connected to the casing 6, wherein the rotating shaft 1 is provided with an annular balancing chamber, the axis of which is coaxial with the axis of the rotating shaft 1; the two sides of the balancing chamber are respectively a compression side 12 and an expansion side 11; the balancing chamber is provided with N heat insulation boards 3, which are arranged along the axial direction of the rotating shaft 1 and divide the balancing chamber into N+1 chambers 14, where N≥2; the side of all the heat insulation boards 3 away from the rotating shaft 1 is fixedly connected to the casing 6, and the side close to the rotating shaft 1 extends into the balancing chamber and is gap-matched with the balancing chamber; a plurality of through holes 31 are provided on all the heat insulation boards 3, and the through holes 31 on adjacent heat insulation boards 3 are staggered.

[0030] In this embodiment, the gap size between the insulation board 3 and the bottom gap of the balance chamber is preferably 0.8mm-1.2mm; on the one hand, this size design can avoid the impact of the insulation board 3 when the shaft 1 vibrates, affecting the normal operation of the unit, that is, the gap size cannot be too small; on the other hand, it ensures the isolation of the chamber 14 and achieves the maximum effect of reducing gas leakage and blocking heat radiation as much as possible, that is, the gap size cannot be too large.

[0031] In this embodiment, the preferred number of heat insulation boards 3 is two, and of course it can be more than two; the two heat insulation boards 3 divide the balancing tank 13 into three chambers 14; through holes 31 are provided on the heat insulation boards 3, and the adjacent heat insulation boards 3 are arranged in a staggered manner with the through holes 31, so that all the through holes 31 cooperate to achieve a rectifying effect, that is, through the staggered through holes 31, the high-pressure fluid leaking from the compression side 12 into the balancing tank 13 and the low-pressure airflow leaking from the expansion side 11 into the balancing tank 13 are rectified, and the heat insulation board 3 and the cavity bottom gap of the balancing cavity are matched to form a rectifier. The gap between the two fluids is closed, so that the two fluids are fully mixed in each chamber 14 in the balancing tank 13, and the pressure field in the balancing tank 13 is evenly distributed, thereby reducing the pressure difference on both sides of the balancing tank 13, and achieving the purpose of reducing the axial thrust; through CFD finite element simulation software, simulation is performed, and the maximum value of the axial thrust is within 1000N of the air bearing by adopting the balancing structure, which meets the use conditions of the air bearing, that is, the axial thrust is reduced by the self-balancing structure, so that the unit can use the air bearing to balance the axial thrust, thereby achieving the purpose of simple and compact unit structure.

[0032] In this embodiment, adjacent insulation boards 3 are arranged with through holes 31 staggered, that is, the insulation boards 3 are projected on a surface and can completely close both sides of the surface, thereby achieving the effect of isolating heat radiation; during the operation of the unit, the temperature of the expansion side 11 is high, and the heat radiation of the expansion side 11 to the surrounding environment cannot be ignored, especially the temperature impact on the compression side 12 cannot be ignored (the temperature of the compression side 12 is affected, and the fluid pressure of the compression side 12 will be affected); thanks to the use and arrangement of the insulation board 3, the heat radiation received by the compression side 12 can be reduced to a minimum.

[0033] Preferably, the diameter of the through holes 31 is 10-16 mm, and the axis of the heat insulation board 3 is taken as the center of the circumferential array, and the through holes 31 are evenly distributed in the radial direction.

[0034] Example 2

[0035] Based on Example 1, a specific implementation method that can be implemented is further proposed.

[0036] A feasible implementation manner is that both the compression side 12 and the expansion side 11 have an impeller 2; in this embodiment, the impeller 2 on the compression side 12 has the same size as the impeller 2 on the expansion side 11, that is, the impellers 2 on both sides have the same outer diameter R2 and the same root diameter Rh, so that the area of ​​action of the fluid on both sides is the same.

[0037] A feasible implementation manner is that steam seals 5 are provided between the side of the balancing chamber close to the compression side 12 and the casing 6, and between the side of the balancing chamber close to the expansion side 11 and the casing 6. By providing the steam seals 5, the balancing groove 13 is sealed, thereby reducing the leakage of the fluid on the compression side 12 to the expansion side 11 through the balancing chamber.

[0038] More importantly, although the steam seal 5 seals the compression side 12 and the expansion side 11 on both sides of the rotating shaft 1; however, in the present solution, the steam seal 5 is arranged on the side of the balancing groove 13 and close to the top of the balancing groove 13, and its purpose is to cooperate with the casing 6 to seal the balancing groove 13 and reduce the fluid at the compression side 12 and the expansion side 11 from entering the balancing groove 13 as much as possible; compared with the prior art, in theory, the fluid pressure at the compression side 12 and the expansion side 11 will not directly act on the inner side wall of the balancing groove 13, and even if it does, it will only act on the notch position of the balancing groove 13 (the assembly position of the steam seal 5 to the The inner wall portion between the notches of the balancing groove 13), according to the pressure formula, can be determined that the effective area is greatly reduced, so the generated axial thrust is also reduced; in fact, the steam seal 5 cannot be completely sealed, so there is fluid leakage from the compression side 12 and the expansion side 11 from the steam seal 5 to the balancing groove 13, and the balancing groove 13 benefits from the design of the heat insulation plate 3 with the through hole 31, which can effectively neutralize the pressure difference on both sides of the balancing groove 13, and the axial thrust will not be too high; on the other hand, arranging the steam seal 5 at this position can also improve the air pressure stability in the balancing groove 13.

[0039] A feasible implementation method is that an annular protrusion 4 matching the steam seal teeth is provided on one side of the balance chamber close to the compression side 12 and one side of the balance chamber close to the expansion side 11 to increase the flow resistance of leakage, reduce gas leakage, enhance the steam seal sealing effect, and maintain the pressure inside and outside the chamber 14 stable.

[0040] Furthermore, the heat insulation board 3 is fixed on the steam seal body, which is convenient for modifying the existing unit on the one hand, and is easier to replace than directly connecting to the casing 6 on the other hand.

[0041] Furthermore, the steam seal body and the casing 6 are detachably fixedly connected, for example, by bolting or the like.

[0042] Example 3

[0043] A method for self-balancing axial thrust is disclosed. A plurality of heat insulation plates 3 with through holes 31 are installed on a casing 6. The heat insulation plates 3 are arranged in a staggered manner with the through holes 31, and the heat insulation plates 3 extend into a balancing groove 13 to divide the balancing groove 13 into a plurality of chambers 14. Through the staggered through holes 31, high-pressure fluid leaking into the balancing groove 13 from a compression side 12 and low-pressure airflow leaking into the balancing groove 13 from an expansion side 11 are fully mixed in each chamber 14, so that the pressure in all chambers 14 tends to be consistent, and the pressure difference on both sides of the balancing groove 13 is reduced, thereby reducing the axial thrust.

[0044] Specifically, using the axial thrust self-balancing structure described in any one of Examples 1-2, the force analysis is as follows.

[0045] The compression side 12 and the impeller 2 at the compression side 12 are subjected to a rightward force Fcf, and the inner wall of the balancing groove 13 close to the compression side 12 is subjected to leftward forces Fcb1 and Fcb2; the expansion side 11 and the impeller 2 at the expansion side 11 are subjected to a leftward force Ftf, and the inner wall of the balancing groove 13 close to the expansion side 11 is subjected to leftward forces Ftb1 and Ftb2; the axial force is positive to the right, and the axial thrust F of the rotating shaft 1 is F=Ftb1+Ftb2–Ftf–(Fcb1+Fcb2-Fcf). Among them, under the axial thrust self-balancing structure, Fcf is slightly larger than Ftf, and can be regarded as equal; the action areas of the force Fcb1 and the force Ftb1 are both small, and the pressure difference formed by the two is small in value; the gas pressure in the balance groove 13 is evenly distributed, and the pressure acting on the two side walls of the balance groove 13 is basically the same. Because the force areas on both sides are the same, Fcb2≈Ftb2, so the axial thrust on the shaft 1 is relatively low, and after inspection, it does not exceed 700N. It can be seen that this method can effectively reduce the axial thrust.

[0046] The present invention is not limited to the above-mentioned specific embodiments, but extends to any new features or any new combination disclosed in this specification, as well as any new method or process steps or any new combination disclosed.

Claims

1. An axial thrust self-balancing structure, applied to a radial flow coaxially arranged expander-compressor, comprising a casing (6) and a rotating shaft (1) rotatably connected to the casing (6), wherein an annular balancing chamber is provided on the rotating shaft (1), and the axis of the balancing chamber is coaxial with the axis of the rotating shaft (1); the two sides of the balancing chamber are respectively a compression side (12) and an expansion side (11); the characteristics are: The balancing cavity is provided with N heat insulation plates (3), which are arranged along the axial direction of the rotating shaft (1) and divide the balancing cavity into N+1 chambers (14), where N≥2; the side of all the heat insulation plates (3) away from the rotating shaft (1) is fixedly connected to the housing (6), and the side close to the rotating shaft (1) extends into the balancing cavity and fits the gap of the balancing cavity; a plurality of through holes (31) are provided on all the heat insulation plates (3), and the through holes (31) on adjacent heat insulation plates (3) are staggered.

2. The axial thrust self-balancing structure according to claim 1, characterized in that: N＝2。 3. The axial thrust self-balancing structure according to claim 1, characterized in that: The compression side (12) and the expansion side (11) both have an impeller (2).

4. The axial thrust self-balancing structure according to claim 3 is characterized in that: The outer diameter and root diameter of the impeller (2) on the compression side (12) and the impeller (2) on the expansion side (11) are the same.

5. The axial thrust self-balancing structure according to claim 1, characterized in that: Steam seals (5) are provided between the side of the balance chamber close to the compression side (12) and the casing (6), and between the side of the balance chamber close to the expansion side (11) and the casing (6).

6. The axial thrust self-balancing structure according to claim 5, characterized in that: The steam seal member (5) comprises a steam seal body and steam seal teeth, wherein the steam seal teeth are fixed on the steam seal body, and the steam seal body is fixed on the casing (6).

7. The axial thrust self-balancing structure according to claim 6, characterized in that: An annular protrusion (4) matching with the steam seal teeth is provided on one side of the balance chamber close to the compression side (12) and one side of the balance chamber close to the expansion side (11).

8. The axial thrust self-balancing structure according to claim 6, characterized in that: The heat insulation board (3) is fixed on the steam seal body.

9. The axial thrust self-balancing structure according to claim 8, characterized in that: The steam seal body is detachably fixedly connected to the casing (6).

10. An axial thrust self-balancing method, characterized in that: A plurality of heat insulation plates (3) with through holes (31) are mounted on the casing (6). The heat insulation plates (3) are arranged in a staggered manner with the through holes (31). The heat insulation plates (3) extend into the balancing groove (13) to divide the balancing groove (13) into a plurality of chambers (14). Through the staggered through holes (31), the high-pressure fluid leaking from the compression side (12) into the balancing groove (13) and the low-pressure airflow leaking from the expansion side (11) into the balancing groove (13) are fully mixed in each chamber (14), so that the pressure in all the chambers (14) tends to be consistent, and the pressure difference on both sides of the balancing groove (13) is reduced, thereby reducing the axial thrust.

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