Variable backlash twin-screw compressor rotor design method, rotor and compressor

Abstract

A design method for the rotors of a variable backlash twin-screw compressor, the rotors, and the compressor. In the method, the radial cross-section of the rotor gradually shrinks from the suction end to the discharge end, that is, the clearance between the teeth of the male and female rotors gradually increases; determine the change curve of the clearance between the teeth in the length direction of the rotor; convert the change curve of the clearance between the teeth into a scaling factor; apply the scaling factor to the design of the helical surface of a traditional cylindrical rotor to obtain the helical surface equation. The present invention can prevent the male and female rotors from being locked due to force deformation, thermal expansion, etc., and at the same time is beneficial to reducing the inter-tooth leakage and improving the compressor efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of screw compressors, and particularly relates to a design method for a rotor of a variable tooth clearance twin screw compressor, a rotor and a compressor. Background Art

[0002] A twin screw compressor is a positive displacement rotary compressor used to obtain high-pressure gas and has wide applications in fields such as mines, power, metallurgy, construction, machinery, and refrigeration. It inherits the advantages of long service life, low noise, small vibration, stable operation, and no surging of rotary machinery, and at the same time has the characteristics of simple structure and no vulnerable parts such as inlet and exhaust valves. Therefore, it is a core component in systems such as high-pressure gas transmission, refrigeration, and waste heat recovery.

[0003] The rotor is the core component of a screw compressor used to achieve the gas compression process. In traditional twin screw compressors, the rotor usually has a cylindrical shape, that is, the radial cross-section remains consistent. However, some problems may occur during operation with this design. One of them is the phenomenon of locking of the male and female rotors caused by rotor force deformation and thermal expansion. The common solution to this is to increase the tooth clearance between the rotors. However, the deformation and thermal expansion amounts from the suction end to the discharge end of the rotor during operation are uneven. Usually, the pressure and temperature gradually increase from the suction end to the discharge end, and the rotor deformation and expansion amounts also gradually increase. Therefore, increasing the tooth clearance in the same proportion in the rotor length direction will result in an increase in tooth tip leakage on the side close to the low pressure.

[0004] The above information disclosed in the background art section is only used to enhance the understanding of the background of the present invention, and thus may include information that does not constitute the prior art known to those of ordinary skill in the art. Summary of the Invention

[0005] Aiming at the problems existing in the prior art, the present invention provides a design method for a rotor of a variable tooth clearance twin screw compressor, a rotor and a compressor, which can prevent the male and female rotors from locking after thermal expansion and is beneficial to reducing tooth tip leakage.

[0006] The object of the present invention is achieved through the following technical solutions. The design method for a rotor of a variable tooth clearance twin screw compressor includes the following steps.

[0007] The rotor of the variable tooth clearance twin screw compressor to be designed includes a suction end and an opposite discharge end, and the radial cross-section of the rotor gradually decreases from the suction end to the discharge end.

[0008] Based on the force deformation and thermal expansion of the rotor, determine the change curve of the tooth clearance in the rotor length direction.

[0009] Convert the change curve into a scaling factor. The curve formed by the scaling factors of each cross-section is a scaling line. The calculation expression of the scaling factor is as follows:

[0010]

[0011] Wherein, R is the radius of the rotor tooth tip circle, D(τ) represents the thermal expansion amount when the spiral angle is τ, and τ is the spiral angle starting from the suction end face;

[0012] Based on the scaling factor, the spiral surface equation is obtained, and the expression is as follows:

[0013]

[0014] Wherein, x and y are the rotor profile equations, p is the spiral characteristic number, and a twin-screw compressor rotor with a variable tooth clearance whose radial section gradually shrinks from the suction end to the discharge end is generated based on the spiral surface equation.

[0015] In the method described above, the variation curve is simplified to an inclined straight line, and its expression is as follows,

[0016]

[0017] Wherein, τ is the spiral angle starting from the suction end face, δ min is the minimum tooth clearance, δ max is the maximum tooth clearance, and τ z is the twist angle.

[0018] In the method described above, the variation curve of the tooth clearance in the rotor length direction is:

[0019]

[0020] Wherein, τ is the spiral angle starting from the suction end face, T(τ) represents the temperature when the spiral angle is τ, T s is the suction temperature, V0 is the maximum tooth clearance volume, V i (τ) represents the tooth clearance volume when the spiral angle is τ, k is the isentropic index, α is the thermal expansion coefficient, and R is the radius of the rotor tooth tip circle.

[0021] A twin-screw compressor rotor with a variable tooth clearance is generated by the design method of the twin-screw compressor rotor with a variable tooth clearance.

[0022] A twin-screw compressor rotor with a variable tooth clearance, characterized in that

[0023] The twin-screw compressor rotor with a variable tooth clearance includes a suction end and an opposite discharge end, and the radial section of the rotor gradually shrinks from the suction end to the discharge end;

[0024] The twin-screw compressor rotor is expressed by the spiral surface equation as follows:

[0025]

[0026] In the formula, x and y are the equations of the rotor profile, p is the spiral characteristic number, and τ is the spiral angle with the suction end face as the starting position;

[0027] Scaling factor:

[0028]

[0029] In the formula, R is the radius of the rotor tip circle, and D(τ) represents the thermal expansion amount when the spiral angle is τ.

[0030] In the rotor of the tooth clearance twin-screw compressor described above, the variable tooth clearance twin-screw compressor rotor has a left-handed spiral surface.

[0031] A compressor includes,

[0032] A housing, which includes a working chamber,

[0033] The variable tooth clearance twin-screw compressor rotor described above is adaptively accommodated in the working chamber.

[0034] In the compressor described above, the housing further includes axial suction and discharge orifices corresponding to the suction and discharge ends of the rotor.

[0035] In the compressor described above, the housing further includes a radial suction orifice.

[0036] Compared with the prior art, the present invention has the following advantages: By adjusting the design of the radial cross-section of the rotor, it gradually shrinks from the suction end to the discharge end, that is, the tooth clearance between the male and female rotors gradually increases. Through this design, the rotor can still maintain an appropriate clearance after force deformation and thermal expansion, avoiding the occurrence of jamming.

[0037] Furthermore, the traditional method to solve the jamming phenomenon is to increase the radial clearance of the rotor. However, the thermal expansion of the rotor from the suction end to the discharge end during operation is uneven. Usually, the pressure and temperature gradually increase from the suction end to the discharge end, and the deformation and expansion amounts of the rotor will also gradually increase. Therefore, increasing the tooth clearance in the same proportion in the rotor length direction will cause an increase in tooth tip leakage on the side close to the low pressure. The tooth clearance of the rotor of the present invention gradually increases from the suction end to the discharge end, which is closer to the force deformation and thermal expansion amount during operation. It is beneficial to reduce tooth tip leakage and improve the efficiency of the compressor. Description of the Drawings

[0038] Upon reading the detailed description of the preferred specific embodiments below, various other advantages and benefits of the present invention will become clear to those of ordinary skill in the art. The accompanying drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present invention. Obviously, the drawings described below are only some embodiments of the present invention, and those of ordinary skill in the art can obtain other drawings based on these drawings without creative efforts. Moreover, throughout the drawings, the same reference numerals are used to represent the same components.

[0039] In the drawings:

[0040] Figure 1 is a schematic diagram of the rotor structure of the variable tooth clearance twin-screw compressor according to Embodiment 1 of the present invention;

[0041] Figure 2 is a schematic diagram of the tooth clearance between the teeth of the rotor of the variable tooth clearance twin-screw compressor of the present invention;

[0042] Figure 3 is a schematic diagram of the rotor structure of the variable tooth clearance twin-screw compressor according to Embodiment 2 of the present invention.

[0043] The present invention will be further explained below with reference to the drawings and embodiments. Specific Embodiments

[0044] The following will refer to the attached Figures 1 to 3 The specific embodiments of the present invention will be described in more detail. Although the specific embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present invention can be understood more thoroughly and the scope of the present invention can be completely conveyed to those skilled in the art.

[0045] It should be noted that certain terms are used in the specification and claims to refer to specific components. Those skilled in the art should understand that technicians may use different terms to refer to the same component. The specification and claims do not use the difference in terms as a way to distinguish components, but use the difference in functions of components as the criterion for distinction. As mentioned throughout the specification and claims, "comprising" or "including" is an open-ended term and should be interpreted as "including but not limited to". The following description of the specification is for the purpose of implementing the preferred embodiments of the present invention, but the description is for the general purpose of the specification and is not intended to limit the scope of the present invention. The protection scope of the present invention shall be determined by the scope defined by the appended claims.

[0046] For the convenience of understanding the embodiments of the present invention, the following will further explain with specific embodiments as examples in conjunction with the drawings, and each drawing does not constitute a limitation to the embodiments of the present invention.

[0047] For better understanding, in one embodiment, as Figures 1 to 3 shown, the method for designing the rotor of a variable tooth clearance twin-screw compressor includes the following steps.

[0048] The rotor of the variable tooth clearance twin-screw compressor to be designed includes a suction end and an opposite discharge end, and the radial cross-section of the rotor gradually decreases from the suction end to the discharge end.

[0049] Determine the variation curve of the tooth clearance in the rotor length direction based on the rotor force deformation and thermal expansion.

[0050] Convert the variation curve into a scaling factor, and the curve formed by the scaling factors of each cross-section is the scaling line. The calculation expression of the scaling factor is as follows:

[0051]

[0052] In the formula, R is the radius of the rotor tip circle, and D(τ) represents the thermal expansion amount when the helix angle is τ.

[0053] Based on the scaling factor, obtain the helicoid equation, and the expression is as follows:

[0054]

[0055] In the formula, x and y are the rotor profile equations, p is the helix characteristic number. Generate a rotor of a variable tooth clearance twin-screw compressor with a radial cross-section gradually decreasing from the suction end to the discharge end based on the helicoid equation.

[0056] In the preferred embodiment of the method, the variation curve is simplified to an inclined straight line, and its expression is as follows.

[0057]

[0058] In the formula, τ is the helix angle starting from the suction end face, δ min is the minimum tooth clearance, δ max is the maximum tooth clearance, and τ z is the twist angle.

[0059] In the preferred embodiment of the method, the variation curve of the tooth clearance in the rotor length direction is:

[0060]

[0061] In the formula, τ is the helix angle starting from the suction end face, T(τ) represents the temperature when the helix angle is τ, T s is the suction temperature, V0 is the maximum tooth clearance volume, V i (τ) represents the tooth clearance volume when the helix angle is τ, k is the isentropic exponent, α is the thermal expansion coefficient, and R is the radius of the rotor tip circle.

[0062] In one embodiment, the method includes determining the variation curve of the inter-tooth clearance in the rotor length direction; converting the inter-tooth clearance variation curve into a scaling factor; and applying the scaling factor to the design of the cylindrical rotor helical surface to obtain the helical surface equation. The present invention can prevent the male and female rotors from being locked due to force deformation, thermal expansion, etc., and at the same time is beneficial to reducing the inter-tooth leakage and improving the compressor efficiency.

[0063] Embodiment 1

[0064] See Figure 1 , the present invention provides a variable tooth clearance twin-screw compressor rotor. The rotor is integrally in a conical structure with one end large and the other end small. The radial cross-section of the rotor gradually shrinks from the suction end to the discharge end, and the inter-tooth clearance of the rotor gradually increases from the suction end to the discharge end. The design method steps are as follows:

[0065] Step 1: Determine the variation curve of the inter-tooth clearance in the rotor length direction according to factors such as rotor force deformation and thermal expansion. Since when the compressor is working, the pressure and temperature gradually increase from the suction end to the discharge end, the deformation amount and expansion amount of the rotor will also gradually increase. Therefore, the design of the inter-tooth clearance should also gradually increase from the suction end to the discharge end. To simplify the design process and facilitate machining, the variation curve of the inter-tooth clearance in the rotor length direction can be simplified to an inclined straight line. The curve expression is as follows (using the helix angle τ instead of the change in the rotor length direction):

[0066]

[0067] In the formula, τ is the helix angle (starting from the suction end face), δ min is the minimum (suction end) inter-tooth clearance, δ max is the maximum (discharge end) inter-tooth clearance, and τ z is the twist angle.

[0068] Step 2: Convert the inter-tooth clearance variation curve into a scaling factor. The curve formed by connecting the scaling factors of each cross-section is the scaling line, as Figure 1 shown. The calculation expression of the scaling factor is as follows:

[0069]

[0070] In the formula, R is the radius of the rotor tooth tip circle.

[0071] Step 3: Apply the scaling factor to the design of the traditional cylindrical rotor helical surface, and the helical surface equation (taking the right-handed helical surface as an example) can be obtained. The expression is as follows:

[0072]

[0073] Wherein, x and y are the rotor profile equations, and p is the spiral characteristic number.

[0074] See Figure 2 , when the male and female rotors designed by the above method mesh with each other, the clearance between the rotor teeth gradually increases from the suction end to the discharge end. Through this design, when the compressor is working, the rotor can still maintain an appropriate clearance after being deformed by force and thermally expanded, avoiding the occurrence of jamming.

[0075] Embodiment 2

[0076] See Figure 3 , since the temperature of the compression chamber is relatively high when the compressor is working, and rotor jamming is generally caused by thermal expansion, the clearance change curve in Step 1 of the above embodiment can be calculated according to the principles of adiabatic compression and thermal expansion. The calculation expression is as follows:

[0077]

[0078] Wherein, T(τ) represents the temperature at a spiral angle of τ, T s is the suction temperature, V0 is the maximum tooth clearance volume, V i (τ) represents the tooth clearance volume at a spiral angle of τ, k is the isentropic index, D(τ) represents the thermal expansion amount at a spiral angle of τ, α is the thermal expansion coefficient, and R is the radius of the rotor tip circle.

[0079] Taking the thermal expansion amount curve as the clearance change curve in Step 1 of the above embodiment, the subsequent design steps are the same as above. The reduction trend of the radial cross-section of the rotor designed in this way is adapted to the thermal expansion trend during rotor operation, that is, the reduction amount of each cross-section is complementary to the thermal expansion amount during operation.

[0080] The present invention adjusts the design of the rotor radial cross-section so that it gradually shrinks from the suction end to the discharge end, that is, the clearance between the teeth of the male and female rotors gradually increases. Through this design, the rotor can still maintain an appropriate clearance after being deformed by force and thermally expanded, avoiding the occurrence of jamming.

[0081] A variable-clearance twin-screw compressor rotor is generated by the variable-clearance twin-screw compressor rotor design method. Further, the variable-clearance twin-screw compressor rotor has a left-handed helical surface.

[0082] In one embodiment, the maximum clearance between the variable-clearance twin-screw compressor rotors is 10 microns.

[0083] A compressor includes,

[0084] a housing, which includes a working chamber,

[0085] the variable-clearance twin-screw compressor rotor as described above, which is adaptively accommodated in the working chamber.

[0086] The body further includes axial suction and exhaust orifices corresponding to the suction and exhaust ends of the rotor.

[0087] Furthermore, the body further includes a radial suction orifice.

[0088] Although the embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the above specific embodiments and application fields. The above specific embodiments are merely illustrative and guiding, rather than restrictive. Those of ordinary skill in the art can also make many forms under the inspiration of this specification and without departing from the scope protected by the claims of the present invention, and these all fall within the scope of protection of the present invention.

Claims

1. A design method for the rotor of a variable backlash twin-screw compressor, characterized in that, It includes the following steps: The variable clearance twin-screw compressor rotor to be designed includes a suction end and an opposite discharge end, and the radial cross-section of the rotor gradually shrinks from the suction end to the discharge end; Determine the variation curve of the tooth clearance in the rotor length direction based on the force deformation and thermal expansion of the rotor; Convert the variation curve into a scaling factor, and the curve formed by the scaling factors of each cross-section is the scaling line. The calculation expression of the scaling factor is as follows: ， Wherein, is the radius of the rotor tooth tip circle, represents the thermal expansion amount when the spiral angle is , is the spiral angle starting from the suction end face; Obtain the helicoid equation based on the scaling factor, and the expression is as follows: ， In the formula, is the rotor profile equation, is the spiral characteristic number, and a twin-screw compressor rotor with a variable tooth clearance in which the radial cross-section gradually decreases from the suction end to the discharge end is generated based on the spiral surface equation.

2. The method according to claim 1, wherein The variation curve is simplified to an inclined straight line, and its expression is as follows: ， In the formula, is the spiral angle starting from the suction end face, is the minimum tooth space clearance, is the maximum tooth space clearance, is the twist angle.

3. The method according to claim 1, wherein The variation curve of the tooth clearance in the rotor length direction is: ， Wherein, is the helix angle starting from the suction end face, represents the temperature when the helix angle is , is the suction temperature, is the maximum inter-tooth volume, represents the inter-tooth volume when the helix angle is , is the isentropic exponent, is the coefficient of thermal expansion, is the radius of the rotor tooth tip circle.

4. A variable backlash twin-screw compressor rotor, characterized in that, It is generated by the variable clearance twin-screw compressor rotor design method according to any one of claims 1-3.

5. The rotor of the backlash twin-screw compressor according to claim 4, characterized in that, The variable clearance twin-screw compressor rotor has a left-handed helicoid.

6. A compressor, characterized in that, It includes: A housing, which includes a working chamber; The variable clearance twin-screw compressor rotor according to claim 4 or 5, which is adaptively accommodated in the working chamber.

7. The compressor according to claim 6, characterized in that, The housing further includes axial suction and discharge orifices corresponding to the suction and discharge ends of the rotor.

8. The compressor according to claim 6, wherein The housing further includes a radial suction orifice.

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