A variable pitch internal meshing conical twin-screw compressor rotor and its design method

Abstract

A variable pitch internal meshing conical twin screw compressor rotor and its design method. The profile of the outer rotor is an outer equidistant line structure of a short amplitude epicycloid; the inner rotor has one less tooth than the outer rotor, and the center of the pitch circle of the inner rotor is eccentrically arranged with the center of the pitch circle of the outer rotor. Rotate the profile of the outer rotor around its geometric center, while rotating, increase the equidistant distance d and move in a variable pitch motion form in the cross-sectional direction perpendicular to the outer rotor. The equidistant distance d and the pitch L have a linearly increasing relationship with the rotation angle; the surface scanned after the profile of the outer rotor rotates a certain angle is the three-dimensional inner surface structure of the outer rotor. The profile of the inner rotor always maintains a meshing relationship with the profile of the outer rotor and scans out the three-dimensional structure of the inner rotor after moving together with the outer rotor. The present invention improves the space utilization rate of the compressor, increases the single-stage compression ratio, reduces the energy consumption level, and avoids the generation of leakage channels.

Description

Technical Field

[0001] The present invention belongs to the field of compressors, and relates to a variable pitch internal meshing conical twin screw compressor rotor and a design method thereof. Background Art

[0002] Twin screw compressors are a type of positive displacement rotary compressor used to obtain medium and low pressure gases and have a wide range of applications in modern industry. They inherit many advantages of rotary machinery such as long service life, reliable operation, low vibration, low noise, stable operation, and no surging phenomenon. At the same time, they have characteristics such as no vulnerable parts like air valves, forced suction and exhaust, and simple processing, and are the core components in systems such as air supply, refrigeration, and waste heat recovery. Currently, for the convenience of processing, the common meshing relationship of twin screw compressor rotors is external meshing, which results in a large center distance and a long leakage line length between the rotors, thereby reducing the space utilization rate and increasing the leakage intensity, and ultimately making it impossible to miniaturize the current screw rotors. Compared with external meshing twin screw compressors, internal meshing twin screw compressors can effectively reduce the rotor center distance and avoid the leakage channels between the casing and the rotors, thus having the characteristics of high space utilization rate and low leakage intensity, and being an ideal solution for miniaturizing twin screw rotors. However, currently, the conventional equal pitch and equal diameter internal meshing twin screw rotors cannot achieve the internal compression process, greatly increasing the energy consumption level of the rotors. With the development of processing technology, it has become possible to process special-shaped screw rotors efficiently and with high precision. Summary of the Invention

[0003] The purpose of the present invention is to address the problems in the prior art such as low space utilization rate of twin screw compressor rotors, the existence of leakage channels, and high energy consumption, and to provide a variable pitch internal meshing conical twin screw compressor rotor and a design method thereof, which improve the rotor meshing accuracy and working efficiency of the twin screw compressor and reduce the energy consumption level of the compressor.

[0004] To achieve the above purpose, the present invention has the following technical solutions:

[0005] A variable pitch internal meshing conical twin-screw compressor rotor includes an outer rotor and an inner rotor. The profile of the outer rotor is an outer equidistant line structure of a short-drawn epicycloid. The short-drawn epicycloid is the locus of a point P that is inside a rolling circle with a radius of r and is fixedly connected to the rolling circle when the rolling circle with a radius of r rolls without slipping inside a base circle with a radius of R. The distance between point P and the center O3 of the rolling circle is e, and the ratio of R to r determines the number of teeth of the outer rotor. The profile of the outer rotor is an outer equidistant line with an equidistant distance of d drawn outward along the outer normal direction of each point of the short-drawn epicycloid. The inner rotor has one less tooth than the outer rotor, and the center of the pitch circle of the inner rotor is eccentrically arranged with respect to the center of the pitch circle of the outer rotor, with an eccentricity of e. The profiles of the inner and outer rotors can achieve a correct meshing relationship. Rotate the profile of the outer rotor around its geometric center, and while rotating, increase the equidistant distance d and move in a variable pitch motion form in the cross-sectional direction perpendicular to the outer rotor. The equidistant distance d and the pitch L have a linearly increasing relationship with the rotation angle. The surface scanned after the profile of the outer rotor rotates a certain angle is the three-dimensional inner surface structure of the outer rotor, and the profile of the inner rotor always maintains a meshing relationship with the profile of the outer rotor and scans out the three-dimensional structure of the inner rotor after moving together with the outer rotor.

[0006] As a preferred embodiment of the variable pitch internal meshing conical twin-screw compressor rotor of the present invention, the profile shapes of the inner and outer rotors are adjusted by controlling the number of teeth Z2 of the outer rotor, the radius r of the rolling circle, and the eccentricity e.

[0007] As a preferred embodiment of the variable pitch internal meshing conical twin-screw compressor rotor of the present invention, the pitch circle radii of the inner and outer rotors are r p1 and r p2 , and the relationship between the pitch circle radii of the inner and outer rotors and the center distance is:

[0008]

[0009] Z1 is the number of teeth of the rotor with the inner rotor profile, and Z2 is the number of teeth of the rotor with the outer rotor profile, where Z2 = Z1 + 1.

[0010] As a preferred embodiment of the variable pitch internal meshing conical twin-screw compressor rotor of the present invention, the parametric equation of the short-drawn epicycloid is:

[0011]

[0012] where Z2 = R / r.

[0013] As a preferred embodiment of the variable pitch internal meshing conical twin-screw compressor rotor of the present invention, the parametric equation of the profile of the outer rotor is:

[0014]

[0015] Wherein, x' and y' are obtained by differentiating the parametric equations of the curtate hypocycloid, and the equations are as follows:

[0016]

[0017] As a preferred embodiment of the rotor of the variable pitch internally meshing conical twin screw compressor of the present invention, the conjugate curve of the profile of the outer rotor is:

[0018]

[0019] Inner rotor rotation angle And outer rotor rotation angle Satisfy:

[0020]

[0021] When the inner and outer rotors are meshed, the points on the inner rotor and the points on the outer rotor satisfy the following meshing angle equation:

[0022]

[0023] The parametric equation of the profile curve A1B1 of the inner rotor is:

[0024]

[0025] Where the value range of θ is:

[0026]

[0027] The generated profile is 1 / Z1 of the actual cross-sectional curve, and the complete inner rotor profile A1B1C1D1 is formed by rotational replication.

[0028] As a preferred embodiment of the rotor of the variable pitch internally meshing conical twin screw compressor of the present invention, the profile of the outer rotor is formed by scanning a helical line that is equally spaced and enlarged outward from the outer rotating edge of the outer rotor and simultaneously has a variable lead that linearly increases from L1 to L2 along the lead, and the profile of the inner rotor is formed by scanning a helical line that is equally spaced and enlarged outward from the inner rotating edge of the inner rotor and simultaneously has a variable lead that linearly increases from H1 to H2 along the lead. The inner and outer rotors in each cross-section comply with the meshing law; the inner and outer rotors rotate at angular velocities ω1 and ω2 respectively around their own axes, and can complete interference-free meshing operation.

[0029] The leads L1, L2 and H1, H2 of the guiding helical lines of the inner and outer rotors satisfy the following conditions:

[0030] Z1L1 = Z2H1

[0031] Z1L2 = Z2H2

[0032] The helix angles γ1 and γ2 of the inner and outer rotors satisfy the following conditions:

[0033]

[0034] Z1 is the number of rotor teeth of the inner rotor profile, and Z2 is the number of rotor teeth of the outer rotor profile, where Z2 = Z1 + 1.

[0035] The present invention also provides a twin-screw compressor that employs the variable pitch internally meshing conical twin-screw compressor rotor described above.

[0036] The present invention also provides a design method for a variable pitch internally meshing conical twin-screw compressor rotor, including the following steps:

[0037] - Optimize the rotor center distance e, the rolling circle radius r, the number of outer rotor teeth Z2, the initial lead L1, and the final lead L2 of the outer rotor guiding helix according to the volume size and the pumping rate;

[0038] - Optimize the outer rotor helix angle γ2 according to the gas tightness requirement and the stress performance requirement;

[0039] - Solve the rotor profile using the optimized parameters to determine the three-dimensional contour surfaces of the outer rotor and the inner rotor.

[0040] Compared with the prior art, the present invention has the following beneficial effects: The variable pitch internally meshing conical twin-screw compressor rotor enables the screw compressor to realize the gas pressurization and transportation process, improves the space utilization rate, increases the single-stage compression ratio, reduces the energy consumption level of the compressor, avoids the generation of leakage channels between the rotor and the casing, is conducive to improving the volumetric efficiency, adiabatic efficiency, stress performance, etc. of the twin-screw compressor, and makes it possible to miniaturize the twin-screw compressor. Compared with other conventional pump types, it has the advantages of fewer wearing parts, compact structure, high pumping rate, no surging, low vibration and noise.

[0041] Furthermore, the outer rotor profile of the present invention adopts the outer equidistant curve of the curtate hypocycloid, which increases with the change of the axial length. The inner rotor profile on each cross-section is derived from the outer rotor profile on the corresponding cross-section, and the inner and outer rotors can achieve a non-interfering meshing relationship. The twin-screw rotor profile of the present invention is an internal meshing relationship, making the two rotors more compact, and a closed working volume cavity can be realized without using a casing, avoiding the leakage area between the tooth tip of the external meshing twin-screw rotor and the casing, which is conducive to improving the thermal performance of the rotor. And the twin-screw compressor rotor profile of the present invention has a variable pitch and adopts a conical form, which can further improve the space utilization rate and provide a larger single-stage compression ratio. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 Schematic structural diagram of the variable pitch internally meshing conical twin-screw compressor rotor profile of the present invention;

[0043] Figure 2 Schematic diagram of the change process of the meshing relationship of the rotor profile of the present invention;

[0044] Figure 3 Schematic diagram of the assembly structure of the inner and outer rotors of the present invention;

[0045] Figure 4 Schematic diagram of the cross-section change of the inner and outer rotors in the embodiment of the present invention;

[0046] Figure 5 Schematic diagram of the working process of the inner and outer rotors of the present invention;

[0047] Figure 6 Schematic diagrams of the inner and outer rotor profiles under different parameters when the equal distance d of the present invention is equal to 3:

[0048] (a) r = 3, e = 2, Z2 = 3; (b) r = 3, e = 2.4, Z2 = 3; (c) r = 3, e = 2.8, Z2 = 3;

[0049] (d) r = 3, e = 2, Z2 = 4; (e) r = 3, e = 2.4, Z2 = 4; (f) r = 3, e = 2.8, Z2 = 4. Detailed implementation manners

[0050] The present invention will be further described in detail below with reference to the accompanying drawings.

[0051] As Figure 1 shown, the outer rotor profile of the present invention is designed as an outer equidistant line structure (curve A2B2C2D2) of a short-drawn epicycloid. This short-drawn epicycloid is the locus of a point P that is inside the rolling circle and fixedly connected to the rolling circle when a rolling circle with a radius of r rolls without slipping inside a base circle with a radius of R. The distance between point P and the center O3 of the rolling circle is e, and the ratio of R to r determines the number of teeth of the outer rotor ( Figure 1 in which R / r = Z2 = 3). The outer equidistant line with an equidistant distance of d is made along the outer normal direction of each point of the short-drawn epicycloid to obtain the outer rotor profile. The inner rotor has one less tooth than the outer rotor, and the center of the inner rotor pitch circle and the center of the outer rotor pitch circle are eccentrically arranged (eccentric distance is e). Based on these geometries, the inner rotor profile (curve A1B1C1D1) is derived from the outer rotor profile according to the meshing relationship. As Figure 2 shown, the inner and outer rotor profiles can achieve a correct meshing relationship. As Figure 3, the outer rotor profile is rotated around its geometric center. While rotating, the equal-distance d is increased and it moves in the direction perpendicular to the cross-section of the outer rotor in the form of a variable pitch motion. The equal-distance d and the pitch L have a linearly increasing relationship with the rotation angle. The surface scanned after the outer rotor profile rotates a certain angle is the three-dimensional inner surface structure of the outer rotor. The inner rotor profile always maintains a meshing relationship with the outer rotor profile and scans out the three-dimensional structure of the inner rotor as it moves together with the outer rotor. As Figure 4 shown, taking the eccentricity e as 2.4 mm, the rolling radius r as 3 mm, and the number of teeth Z2 of the outer rotor as 3 as an example, as the equal-distance d increases (from 3 mm to 15 mm), the profiles of the inner and outer rotors change. As Figure 5 shown, the combined rotation of the inner and outer rotors can achieve a periodic change in the volume of the internal cavity, realizing the forced transportation effect of gas. As Figure 6 shown, the profiles of the inner and outer rotors can achieve flexible shape adjustment.

[0052] Figure 1 shown, the number of teeth Z1 of the inner rotor profile is 2, the number of teeth Z2 of the outer rotor is 3, and the center distance between the inner and outer rotors is e. The pitch circle radii of the inner and outer rotors are r p1 and r p2 , respectively. The base circle radius of the outer equal-distance line profile of the outer rotor short-drawn epicycloid is R, the rolling radius is r, and the equal-distance is d. The inner rotor profile can be obtained from the meshing relationship by the inner rotor profile equation. The variable parameters of the inner and outer rotor profiles are: the number of teeth Z2 of the outer rotor, the rolling radius r, and the eccentricity e.

[0053] Figure 2 shown, the inner and outer rotor profiles can complete non-interfering meshing. Figures 3 - 5 shown, the outer rotor is formed by scanning a helix with a variable lead that rotates and expands outward equally from the outer rotor profile, and at the same time the lead linearly increases from L1 to L2. The inner rotor is formed by scanning a helix with a variable lead that rotates and expands from the inner rotor profile, and at the same time the lead linearly increases from H1 to H2. On each cross-section, the inner and outer rotors follow the meshing law. The inner and outer rotors rotate at angular velocities ω1 and ω2 respectively around their own axes, and can complete non-interfering meshing operation, realizing the operation of the basic volume chamber from the suction end face to the exhaust end face. Figure 6 shown, the rotor profile can be controlled by the number of teeth Z2 of the outer rotor, the rolling radius r, and the eccentricity e respectively to control the shape of the profile.

[0054] The relationship between the pitch circle radii and the center distance of the inner and outer rotors is:

[0055]

[0056] where Z2 = Z1 + 1.

[0057] The parametric equation of the short-drawn epicycloid is:

[0058]

[0059] where Z2 = R / r.

[0060] Deriving the above equation gives:

[0061]

[0062] The parametric equations of the outer equidistant curve A2B2C2D2 of the outer rotor short amplitude epicycloid are:

[0063]

[0064] The conjugate curve of the outer rotor profile is:

[0065]

[0066] Inner rotor rotation angle and outer rotor rotation angle satisfy:

[0067]

[0068] When the inner and outer rotors are meshing, the points on the inner rotor and the points on the outer rotor should satisfy the meshing angle equation

[0069]

[0070] The parametric equations of the inner rotor profile curve A1B1 are:

[0071]

[0072] where the value range of θ is:

[0073]

[0074] The generated profile is 1 / Z1 of the actual cross-section curve, and the complete inner rotor profile A1B1C1D1 is formed by rotational replication.

[0075] The lead L1, L2 of the lead helical lines of the inner and outer rotors and H1, H2 satisfy the following conditions:

[0076] Z1L1 = Z2H1

[0077] Z1L2 = Z2H2

[0078] The helix angles γ1 and γ2 of the inner and outer rotors satisfy the following conditions:

[0079]

[0080] The independent variables in the above solution process are: the independent variables of the profile curve (the number of teeth of the outer rotor Z2, the radius of the rolling circle r, and the eccentricity e), and the independent variables of the guiding curve (the initial lead L1, the final lead L2, and the rotation angle γ2 of the guiding helix of the outer rotor). By changing the number of teeth of the outer rotor Z2, the radius of the rolling circle r, and the eccentricity e, an Figure 6 internal meshing twin-screw rotor profile curve is obtained. It can be seen that the internal meshing twin-screw rotor profile curve of the present invention makes the two rotors more compact, and a closed working volume cavity can be realized without using a housing, avoiding the leakage area between the tooth tip of the external meshing twin-screw rotor and the housing, which is beneficial to improving the thermal performance of the rotor. Moreover, the present invention has a variable pitch and adopts a conical form, which can further improve the space utilization rate and provide a larger single-stage compression ratio.

[0081] Embodiment

[0082] The outer rotor profile curve of the variable pitch internal meshing conical twin-screw rotor designed in the present invention is A2B2C2D2, and the inner rotor profile curve is the conjugate curve A1B1C1D1 of the outer rotor profile curve. The inner and outer rotors designed in the present invention are formed by magnifying the variable rotation side of the rotor profile curve and scanning along the guiding helix. Its independent parameters include the number of teeth of the outer rotor Z2, the radius of the rolling circle r, the eccentricity e, the initial lead L1, the final lead L2, and the rotation angle γ2 of the guiding helix of the outer rotor. The design process is as follows:

[0083] 1. Optimize the center distance e of the rotor, the radius of the rolling circle r, the number of teeth of the outer rotor Z2, the initial lead L1, and the final lead L2 of the guiding helix of the outer rotor according to the volume size and pumping rate, as Figure 1 shown. Take the center distance e of the inner and outer rotor profile curves as 2.4 mm, the number of teeth of the outer rotor Z2 as 3, the radius of the rolling circle r of the outer rotor profile curve as 3 mm, the initial lead L1 of the guiding helix of the outer rotor as 10 mm, the final lead L2 as 80 mm, the initial equidistant distance d1 as 3 mm, and the final equidistant distance d2 as 15 mm.

[0084] 2. Optimize the rotation angle γ2 of the outer rotor helix as 2π (720°) according to the requirements of gas tightness, mechanical properties, etc.

[0085] 3. Solve the rotor profile curve using the above optimized parameters:

[0086] Determine the three-dimensional contour surface of the outer rotor using the following formula:

[0087]

[0088] Determine the three-dimensional contour surface of the inner rotor using the following formula:

[0089]

[0090] The above are only the preferred embodiments of the present invention and are not intended to limit the technical solutions of the present invention. Those skilled in the art should understand that, without departing from the spirit and principles of the present invention, several simple modifications and substitutions can be made to the technical solutions, and these modifications and substitutions also fall within the protection scope covered by the claims.

Claims

1. A variable pitch internal meshing conical twin screw compressor rotor, characterized in that: It includes an outer rotor and an inner rotor. The profile curve of the outer rotor is an outer equidistant curve structure of a short-diameter epicycloid. The short-diameter epicycloid is the locus of a point P that is inside the rolling circle and fixedly connected to the rolling circle when a rolling circle with a radius of r rolls without slipping inside a base circle with a radius of R. The distance between point P and the center O3 of the rolling circle is e. The ratio of R to r determines the number of teeth of the outer rotor. The profile curve of the outer rotor is an outer equidistant curve with an equidistant distance of d made by moving the short-diameter epicycloid outward along the outer normal direction of each point. The inner rotor has one less tooth than the outer rotor, and the center of the pitch circle of the inner rotor is eccentrically arranged with the center of the pitch circle of the outer rotor, and the eccentricity is e. The profile curves of the inner and outer rotors can achieve a correct meshing relationship. Rotate the profile curve of the outer rotor around its geometric center, and while rotating, increase the equidistant distance d and move in a form of variable pitch in the cross-sectional direction perpendicular to the outer rotor. The equidistant distance d and the pitch L have a linearly increasing relationship with the rotation angle. The surface scanned after the profile curve of the outer rotor rotates a certain angle is the three-dimensional inner surface structure of the outer rotor. The profile curve of the inner rotor always maintains a meshing relationship with the profile curve of the outer rotor and scans out the three-dimensional structure of the inner rotor after moving with the outer rotor. Adjust the profile curve shapes of the inner and outer rotors by controlling the number of teeth Z2 of the outer rotor, the radius r of the rolling circle, and the eccentricity e.

2. The variable pitch internal meshing conical twin-screw compressor rotor according to claim 1, wherein: The pitch circle radii of the inner and outer rotors are r p1 and r p2 , respectively. The relationship between the pitch circle radii of the inner and outer rotors and the center distance is as follows: Z1 is the number of teeth of the rotor of the inner rotor profile curve, and Z2 is the number of teeth of the rotor of the outer rotor profile curve, where Z2 = Z1 + 1.

3. The variable-pitch internal meshing conical twin-screw compressor rotor according to claim 2, wherein: The parametric equation of the short-diameter epicycloid is: where Z2 = R / r.

4. The variable-pitch internal meshing conical twin-screw compressor rotor according to claim 3, wherein: The parametric equation of the profile curve of the outer rotor is: In the formula, x′ and y′ are obtained by differentiating the parametric equation of the short-diameter epicycloid, and the equations are as follows:

5. The variable-pitch internal meshing conical twin-screw compressor rotor according to claim 4, wherein: The conjugate curve of the profile curve of the outer rotor is: Inner rotor rotation angle and outer rotor rotation angle satisfy: When the inner and outer rotors are meshing, the points on the inner rotor and the points on the outer rotor satisfy the following meshing angle equation: The parametric equation of the profile curve A1B1 of the inner rotor is: where the value range of θ is: The generated profile curve is 1 / Z1 of the actual cross-sectional curve, and the complete profile curve A1B1C1D1 of the inner rotor is formed by rotation and replication.

6. The variable pitch internal meshing conical twin-screw compressor rotor according to claim 1, wherein: The profile curve of the outer rotor is scanned and formed by an outer equidistant magnification from the rotating edge of the outer rotor and a spiral line with a variable lead that linearly increases from L1 to L2 along the lead. The profile curve of the inner rotor is scanned and formed by an outer equidistant magnification from the rotating edge of the inner rotor and a spiral line with a variable lead that linearly increases from H1 to H2 along the lead. On each cross-section, the inner and outer rotors all follow the meshing law. The inner and outer rotors rotate at angular velocities ω1 and ω2 respectively around their respective axes and can complete non-interfering meshing operation. The initial lead L1 and the final lead L2 of the guiding spiral line of the outer rotor and the initial lead H1 and the final lead H2 of the guiding spiral line of the inner rotor satisfy the following conditions: Z1L1 = Z2H1 Z1L2 = Z2H2 The helix angles γ1 and γ2 of the inner and outer rotors satisfy the following conditions: Z1 is the number of teeth of the rotor of the internal rotor profile, and Z2 is the number of teeth of the rotor of the external rotor profile, where Z2 = Z1 + 1.

7. A twin-screw compressor, characterized in that: Adopt the variable pitch internal meshing conical twin screw compressor rotor described in any one of claims 1-6.

8. A design method for a variable pitch internally meshing conical twin-screw compressor rotor according to any one of claims 1-6, characterized in that It includes the following steps: - Optimize the rotor center distance e, the rolling circle radius r, the number of teeth Z2 of the external rotor, the initial lead L1 and the final lead L2 of the external rotor guiding helix according to the volume size and the pumping rate; - Optimize the external rotor helix angle γ2 according to the requirements of gas tightness and force performance; - Use the optimized parameters to solve the rotor profile and determine the three-dimensional contour surfaces of the external rotor and the internal rotor.

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