A convex rotor profile with inner straight conjugation and larger form factor

Abstract

The present invention discloses a convex rotor profile with inner straight conjugation and a larger shape coefficient, comprising half-lobe profiles of 4, 6, and 8 pitch circles circumferentially symmetrically adjacent to each other under 2, 3, and 4 lobes, wherein the half-lobe profile is composed of four parts, namely, a peak transition connecting arc, a peak conjugated profile, a valley conjugated straight line segment, and a valley transition connecting arc, which are smoothly connected end to end, and the corresponding endpoints and connection points are, in sequence, a peak point located on the peak symmetry axis, a peak starting point, a midpoint, a valley starting point, and a valley point located on the valley symmetry axis. The convex rotor profile with inner straight conjugation and a larger shape coefficient of the present invention has, firstly, a larger shape coefficient and volume utilization coefficient and a smaller conjugate leakage rate among similar convex rotors; and secondly, a profile structure that is easier to process among similar convex rotors.

Description

Technical Field

[0001] The invention belongs to the technical field of rotor pumps, and in particular relates to a convex rotor profile structure with inner direct conjugation and a larger shape coefficient. Background Art

[0002] The convex rotor pump is a type of positive displacement pump that uses the inlet vacuum suction generated during the rotation of two convex rotors (referred to as rotors) to transport the fluid medium to the outlet. It was first used in Roots vacuum pumps and is extremely widely used. It has also been gradually used in aerospace and marine equipment, which naturally puts forward higher requirements for the lightweight degree of the pump. Among them, the non-contact rotor pair formed by two identical convex rotors is the core component of the pump, and the number of rotor blades is usually 2 to 4.

[0003] The volumetric efficiency of the pump ≈ volumetric utilization coefficient × (100% - internal leakage rate), which determines the lightweight degree of the pump. The higher the volumetric efficiency, the better the lightweight degree. Among them, the volumetric utilization coefficient = "part of the blade slot volume used to extrude the medium in the volume of the rotor top cylinder / volume of the rotor top cylinder" ∝ "1-1 / square of the rotor shape coefficient", and the internal leakage rate ≈ radial leakage rate + axial leakage rate + conjugate leakage rate. Therefore, in the design of the rotor profile, it is always hoped to obtain higher volumetric efficiency by adopting the maximized shape coefficient and minimized internal leakage rate.

[0004] For common easy-to-process rotors with ordinary contour structures, the shape coefficient and conjugate leakage rate are directly determined by the shape of the conjugate segment in the rotor contour, while the radial leakage rate and axial leakage rate are little affected by the shape of the conjugate segment and can be ignored. Among them, the conjugate segment consists of two parts: the peak conjugate profile outside the pitch circle and the valley conjugate profile inside the pitch circle. Although the shape coefficient of ordinary rotors can be further improved after applying the high-profile technology of CN109630407B, the contour structure is relatively complex and relatively difficult to process. Summary of the invention

[0005] Regarding the contour structure of common easy-to-process rotors, the present invention aims at achieving the larger shape coefficient, smaller internal leakage rate (mainly reflected in smaller conjugate leakage rate) and easier processing expected in the background technology, and provides a special construction condition in which the chord height line of the half-blade node arc is the valley conjugate contour, which directly calculates the maximum shape coefficient that the rotor can obtain and determines the geometric shape of the peak conjugate contour.

[0006] To achieve the above purpose, the technical solution of the present invention is as follows:

[0007] A convex rotor profile with an inner straight conjugate and a larger shape coefficient includes a half-lobe profile, characterized in that the half-lobe profile is composed of four parts, namely a peak transition connecting arc, a peak conjugate profile, a valley conjugate straight line segment, and a valley transition connecting arc, which are smoothly connected end to end, and the corresponding endpoints and connection points are, in sequence, a peak point located on the peak symmetry axis, a peak starting point, a midpoint, a valley starting point, and a valley point located on the valley symmetry axis.

[0008] The half-leaf profile is a half-leaf profile with 4 adjacent pitch circles symmetrically in the circumferential direction under 2 leaves, a half-leaf profile with 6 adjacent pitch circles symmetrically in the circumferential direction under 3 leaves, and a half-leaf profile with 8 adjacent pitch circles symmetrically in the circumferential direction under 4 leaves.

[0009] Furthermore, the half-leaf contour is formed by the peak symmetry axis and the valley symmetry axis, the intersection of the peak symmetry axis and the valley symmetry axis is the rotor center, the angle between the peak symmetry axis and the valley symmetry axis is the half-leaf contour center angle, and the half-leaf contour center angle is uniquely determined by the number of rotor blades.

[0010] Furthermore, the intersection of the peak symmetry axis and the pitch circle is the peak node, and the intersection of the valley symmetry axis and the pitch circle is the valley node; the midpoint of the pitch circle arc between the peak node and the valley node is the midpoint.

[0011] Furthermore, any point on the pitch circle arc between the peak node and the midpoint is an instantaneous node; the pitch circle tangent at the instantaneous node is the instantaneous tangent line, the vertical line segment from the instantaneous node to the valley conjugate straight line segment is the instantaneous vertical line, and the endpoint of the non-instantaneous node on the instantaneous vertical line is the instantaneous vertical foot; the mirror symmetry line of the non-instantaneous vertical line on the instantaneous vertical line about the instantaneous tangent line is the instantaneous radial line, and the endpoint of the non-instantaneous node on the instantaneous radial line is the instantaneous contour point.

[0012] The valley conjugate straight line segment is a chord height line of the nodal arc between the peak node and the valley node, and the two end points of the chord height line are the mid-node and the valley starting point respectively.

[0013] The peak conjugate contour is a trajectory line of instantaneous contour points when the instantaneous node continuously moves from the mid-node to the peak node, and the two end points of the trajectory line of instantaneous contour points are the mid-node and the peak starting point respectively.

[0014] Furthermore, the peak transition connection arc has the peak node as the center, and the radius of the peak transition connection arc is determined by the shape coefficient and the pitch circle radius. Specifically, the radius of the peak transition connection arc satisfies the numerical value:

[0015] Peak transition connection arc radius = (shape coefficient - 1) × pitch circle radius.

[0016] Furthermore, the valley transition connection arc has the valley node as the center, and the radius of the valley transition connection arc is determined by the shape coefficient and the pitch circle radius. Specifically, the radius of the valley transition connection arc satisfies the numerical value:

[0017] The radius of the valley transition connection arc = (shape coefficient - 1) × the pitch circle radius.

[0018] The shape coefficient = 1 + length between the peak node and the starting point of the valley / pitch circle radius, that is, 1.7071, 1.5, and 1.3827 for 2-leaf, 3-leaf, and 4-leaf rotors, which are larger than the existing largest shape coefficients of 1.6699, 1.4770, and 1.3680 for arc rotors, so a larger shape coefficient is obtained; common involute and arc rotors belong to convex-convex and partially convex-convex conjugate modes, while the rotor of the present invention belongs to a convex-flat conjugate mode, so a smaller conjugate leakage rate can be obtained; the two inter-leaf transition connecting arcs symmetrical about the valley symmetry axis in the valley can be made into standard arcs that can be processed simultaneously at one time by fine-tuning the pitch circle radius, and the inner side of the pitch circle is a straight conjugate contour, so it is easier to process.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The convex rotor profile with inner direct conjugation and larger shape coefficient of the present invention has a larger shape coefficient and volume utilization coefficient and a smaller conjugate leakage rate among similar convex rotors; and has a profile structure that is easier to process among similar convex rotors. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Other features, objectives and advantages of the present invention will become more apparent from a reading of the detailed description of non-limiting embodiments made with reference to the following accompanying drawings.

[0022] Figure 1 Schematic diagram of the half-lobe profile structure of a convex rotor with an inner straight conjugate segment.

[0023] In the figure: O, rotor center, 0, peak point, 1, peak starting point, 2, mid-node, 3, valley starting point, 4, valley point, 5, peak node, 6, valley node, 7, instantaneous node, 8, instantaneous vertical foot, 9, instantaneous contour point, O50, peak symmetry axis, O46, valley symmetry axis, 01, peak transition connecting arc, 12, peak conjugate contour, 23, valley conjugate straight line segment, 34, valley transition connecting arc; ρ, length of instantaneous radial line, θ, center angle of the nodal arc between the instantaneous node and the mid-node, 77', instantaneous tangent line, α, angle between the instantaneous radial line and the peak symmetry axis, r, nodal circle radius, ε, shape coefficient, Central angle of half leaf outline. DETAILED DESCRIPTION

[0024] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further explained below in conjunction with specific implementation methods.

[0025] like Figure 1As shown, a convex rotor profile with inner straight conjugation and larger shape coefficient, wherein the half-lobe profile is composed of four parts, namely, peak transition connection arc 01, peak conjugated profile 12, valley conjugated straight line segment 23, and valley transition connection arc 34, which are smoothly connected end to end, and the corresponding endpoints and connection points are, in order, peak point 0 located on the lobe symmetry axis, peak starting point 1, midpoint 2, valley starting point 3, and valley point 4 located on the valley symmetry axis. Among them, the half-lobe profile is formed by the peak symmetry axis and the valley symmetry axis, the intersection of the peak symmetry axis and the valley symmetry axis is the rotor center O, and the angle between the peak symmetry axis and the valley symmetry axis is the center angle of the half-lobe profile uniquely determined by the number of rotor blades. The intersection of the peak symmetry axis and the pitch circle is the peak node 5, the intersection of the valley symmetry axis and the pitch circle is the valley node 6, the valley conjugate straight line segment is the chord height line 23 of the pitch circle arc between the peak node and the valley node, the midpoint of the pitch circle arc between the peak node and the valley node is the midpoint 2, and any point on the pitch circle arc between the peak node and the midpoint is the instantaneous node 7; the pitch circle tangent at the instantaneous node is the instantaneous tangent line 77', the vertical line segment from the instantaneous node to the valley conjugate straight line segment is the instantaneous vertical line 78, and point 8 is the corresponding instantaneous vertical foot; the mirror symmetry line of the instantaneous vertical line about the instantaneous tangent line is the instantaneous radial line 79; point 9 is the corresponding instantaneous contour point; ρ is the length of the instantaneous radial line, θ is the center angle of the pitch circle arc between the instantaneous node and the midpoint, r is the pitch circle radius, ε is the shape coefficient, N is the number of rotor blades, and λ is the volume utilization coefficient;

[0026] Under the premise of given pitch circle radius r and leaf number N, peak symmetry axis O50, peak node 5, mid node 2, valley node 6, half leaf contour center angle The chord height line 23 and the valley symmetry axis O46 are both uniquely determined;

[0027] First, the instantaneous radial line 79 and the instantaneous vertical line 78 are symmetrical about the instantaneous tangent line 77':

[0028]

[0029] A peak conjugate profile 12 is uniquely constructed.

[0030] Secondly, from ε = 1 + the length between the peak node and the starting point of the valley / the radius of the pitch circle r, we can get:

[0031]

[0032] And taking the peak node 5 and the valley node 6 as the circle center and r×(2-ε) as the radius, a peak transition connection arc 01 and a valley transition connection arc 34 are constructed respectively;

[0033] Then, by further deduction of the volume utilization coefficient calculation, we get:

[0034]

[0035] The upper limit shape coefficient ε' and volume utilization coefficient λ' of the involute rotor

[0036]

[0037] In comparison, the shape coefficient ε of the rotor of the present invention is increased by 5.53% under 2 blades, 2.47% under 3 blades and 1.26% under 4 blades, and the volume utilization coefficient λ is increased by 4.43% under 2 blades, 3.46% under 3 blades and 2.52% under 4 blades.

[0038] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention.

Claims

1. A convex rotor with inner direct conjugation and larger form factor, comprising a convex rotor profile, the convex rotor profile comprising a half-lobe profile, characterized in that The half-leaf profile is composed of four parts, namely, a peak transition connecting arc, a peak conjugate profile, a valley conjugate straight line segment, and a valley transition connecting arc, which are smoothly connected end to end, and the corresponding endpoints and connection points are, in order, a peak point located on the peak symmetry axis, a peak starting point, a midpoint, a valley starting point, and a valley point located on the valley symmetry axis; The peak transition connection arc has the peak node as its center, and the radius of the peak transition connection arc is determined by the shape coefficient and the pitch circle radius; The peak conjugate contour is a trajectory line of instantaneous contour points when the instantaneous node continuously moves from the mid-node to the peak node, and the two end points of the trajectory line of instantaneous contour points are the mid-node and the peak starting point respectively; The valley conjugate straight line segment is a chord height line of the nodal arc between the peak node and the valley node, and the two end points of the chord height line are the mid-node and the valley starting point respectively; The valley transition connection arc has the valley node as its center, and the radius of the valley transition connection arc is determined by the shape coefficient and the pitch circle radius.

2. A convex rotor with inner direct conjugation and larger form factor as claimed in claim 1, characterized in that: The half-leaf profile is a half-leaf profile with 4 adjacent pitch circles symmetrically in the circumferential direction under 2 leaves, a half-leaf profile with 6 adjacent pitch circles symmetrically in the circumferential direction under 3 leaves, and a half-leaf profile with 8 adjacent pitch circles symmetrically in the circumferential direction under 4 leaves.

3. A convex rotor with built-in conjugation and larger form factor as claimed in claim 1, characterized in that: The radius of the peak transition connection arc satisfies the following numerical value: Peak transition connection arc radius = (shape coefficient - 1) × pitch circle radius.

4. A convex rotor with inner direct conjugation and larger form factor as claimed in claim 1, characterized in that: The radius of the valley transition arc satisfies the following numerical value: The radius of the valley transition connection arc = (shape coefficient - 1) × the pitch circle radius.

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