CN112746969A

CN112746969A - Low-leakage Roots rotor profile with larger form factor

Info

Publication number: CN112746969A
Application number: CN202110097509.2A
Authority: CN
Inventors: 李玉龙; 孙军慈; 范钧; 赵岩
Original assignee: Suqian College
Current assignee: Suqian College
Priority date: 2021-01-25
Filing date: 2021-01-25
Publication date: 2021-05-04

Abstract

The invention discloses a low-leakage Roots rotor profile with a larger shape coefficient, which consists of half impeller profiles which are circumferentially symmetrically adjoined by 2 times of blade number, wherein the half impeller profiles sequentially consist of four parts, namely a peak concentric circular arc outside a pitch circle, a peak conjugate profile, a valley transition curve inside the pitch circle and a valley concentric circular arc, which are connected end to end, and corresponding end points and connecting points sequentially comprise a peak point, a middle node, a root point and a valley point which are positioned on a peak symmetry axis. The invention has larger shape coefficient and volume utilization coefficient; the radial leakage rate and the conjugate leakage rate are smaller, so that the device has higher volumetric efficiency and better lightweight effect.

Description

Low-leakage Roots rotor profile with larger form factor

Technical Field

The invention belongs to the technical field of roots pumps, and particularly relates to a low-leakage profile structure with a larger shape coefficient for a roots rotor.

Background

The roots pump is a vacuum displacement pump which utilizes inlet vacuum suction force generated by two identical roots rotors (simply called rotors) in a conjugate rotation process to convey gas media to an outlet, and the number of the rotor blades is usually 2-4. The volume efficiency of the pump is directly determined by a volume utilization coefficient x (100% -internal leakage rate), and the higher the volume efficiency is, the better the weight reduction degree is. The volume utilization coefficient is ═ the volume of partial blade grooves used for extruding the medium in the volume of the rotor top cylinder/the volume of the rotor top cylinder: ═ 1-1/square of the shape coefficient of the rotor, and the internal leakage rate ≈ the radial leakage rate + the axial leakage rate + the conjugate leakage rate. Therefore, in the construction of rotor profiles, it is always desirable to achieve higher volumetric efficiency by employing a larger form factor and a smaller internal leakage rate.

For a common rotor with a shape coefficient completely determined by a conjugate profile, the conjugate profiles with larger shape coefficients are circular arcs and involutes at present, and larger shape coefficients of 1.6699, 1.4770, 1.3680, 1.6177, 1.4638 and 1.3655 can be obtained under 2 leaves, 3 leaves and 4 leaves respectively. The conjugate profile consists of two parts, namely a peak conjugate profile outside a pitch circle and a valley conjugate profile inside the pitch circle.

Although the axial leakage rate is slightly influenced by the contour structure of the rotor, the radial leakage and the conjugate leakage can be effectively controlled through the contour improvement of the equal-gap seal and the multi-point seal of the conjugate area in the radial direction of the inner surface of the pump shell, so that the smaller radial leakage rate and the conjugate leakage rate are realized. The closed space caused by multipoint sealing of the conjugate zone can cause pressure impact of media in the closed space, but the influence of the pressure impact is relatively small for a Roots rotor pair which uses gas media and has non-contact gaps.

Disclosure of Invention

The invention provides a low-leakage rotor profile with larger form factor, radial equal gap and conjugate zone multi-point position sealing by aiming at the expected high volume efficiency in the background technology of a roots pump and the special geometrical relation that a valley conjugate profile is shrunk and gathered on a pitch circle (namely, the valley conjugate profile is not included).

In order to achieve the purpose, the technical solution of the invention is as follows:

a low leakage roots rotor profile with a larger form factor comprised of 2 times the number of lobes circumferentially symmetrically adjacent half-lobe profiles, wherein: the semi-impeller profile is formed by sequentially connecting four parts of a peak concentric circular arc outside a pitch circle, a peak conjugate profile, a valley transition curve inside the pitch circle and a valley concentric circular arc end to end, and corresponding end points and connecting points are sequentially a peak point, a middle node, a root point and a valley point on a peak symmetry axis.

The peak symmetry axis and the valley symmetry axis are boundary lines of a half impeller profile, the intersection point of the peak symmetry axis and the valley symmetry axis is the center of the rotor and the center of the concentric circular arc, the included angle between the two is a half impeller profile central angle uniquely determined by the number of blades, the intersection points of the two and a pitch circle are a peak node and a valley node respectively, the pitch circular arc between the two is a half impeller pitch circular arc, the center point is a middle node, the intersection point of a normal line of the peak conjugate profile at the vertex and the pitch circle is a top node, the pitch circular arc from the top node to the middle node is a conjugate pitch circular arc, the pitch circular arc central angle from the top node to the peak node is a multi-point sealing angle, any point on the conjugate pitch circular arc is an instant node, a normal line segment from the instant node to the peak conjugate profile is an instant radial line, and the point of the.

The peak conjugate profile is uniquely determined by its instant ray length and orientation.

The length and the azimuth of the transient line are uniquely determined by the symmetrical relation of a direct line segment from the transient node to the middle node and a tangent line of a pitch circle at the transient node, and a multi-point sealing angle and a half-top sealing angle are determined.

The half top sealing angle is a central angle of a half lobe peak concentric circular arc.

The shape coefficient-1 is the length from the peak point to the peak node/pitch circle radius, i.e. 1.7654, 1.5176 and 1.3902 under 2 leaves, 3 leaves and 4 leaves, which is larger than the maximum shape coefficient of the conventional ordinary rotors of 1.6699, 1.4770 and 1.3680, so that the shape coefficient is larger.

The valley transition curve is a rotation avoidance trajectory line generated on the rotor by the vertex on the paired rotor, and the conjugate rotation angle of the rotor pair is also a multi-point sealing angle.

Thus, when the rotation angle of the rotor pair is in the interval of [0, half top sealing angle), 5 sealing points are arranged, and when the rotation angle of the rotor pair is equal to the half top sealing angle, 4 sealing points are arranged; there will be 3 sealing points in the interval (half top sealing angle, multi-point sealing angle), there will be 2 sealing points when the rotor pair rotation angle is the multi-point sealing angle; compared with a common rotor which only has 1 sealing point position in the whole process, the invention obtains smaller conjugate leakage rate for the rotor with 1 sealing point position in the interval (multi-point sealing angle, half-lobe central angle/2), and the invention realizes smaller radial leakage rate by adding the radial equal gap sealing of 2 multiplied by half-top sealing angle of the lobe.

Compared with the prior art, the invention has the following beneficial effects:

the invention has a low-leakage Roots rotor profile with a larger form factor, and a larger form factor and volume utilization factor; and the second one has smaller radial leakage rate and conjugate leakage rate, so that the second one has higher volumetric efficiency and better lightweight effect.

Drawings

Other features, objects and advantages of the present invention will become more apparent upon reading of the following detailed description of non-limiting embodiments thereof, with reference to the accompanying drawings.

FIG. 1 is a schematic view of a half-lobe profile configuration for a Roots rotor having a larger form factor and low leakage effect.

Fig. 2 is a schematic diagram of the generation of a valley transition curve.

FIG. 3 is a diagram illustrating the number of seal dot bits in different intervals.

Wherein: o, rotor center, 0, peak point, 1, vertex, 2, middle node, 3, root point, 4, valley point, 5, peak node, 6, valley node, 7, transient node, 77', pitch tangent, 8, transient profile point, 9, top node, O50, peak symmetry axis, O46, valley symmetry axis, 01, peak concentric arc, 12, peak conjugate contour, 23, valley transition curve, 34, valley concentric arc, 72, direct line segment, 78, transient line, r, pitch radius, epsilon, shape coefficient, phi, half impeller profile center angle, sigma, half top seal angle, beta, rotor pair rotation angle, beta^*A multi-point sealing angle, O', a mating rotor center.

Detailed Description

In order to make the technical means, the creation characteristics, the achievement purposes and the effects of the invention easy to understand, the invention is further described with the specific embodiments.

As shown in fig. 1 to 3, a low-leakage roots rotor profile with a larger form factor is composed of half-blade profiles which are circumferentially symmetrically adjoined by 2 times the number of blades and are sequentially composed of four parts, namely a peak concentric circular arc 01 outside the pitch circle, a peak conjugate profile 12, a valley transition curve 23 inside the pitch circle and a valley concentric circular arc 34, which are connected end to end, and corresponding end points and connecting points are sequentially a peak point 0, a peak point 1, a middle node 2, a root point 3 and a valley point 4 on a valley symmetry axis O46 on a peak symmetry axis O50. Wherein, the peak symmetry axis and the valley symmetry axis are boundary lines of a half impeller profile, the intersection point of the peak symmetry axis and the valley symmetry axis is the center of the rotor center O and the center of the peak concentric circular arc 01 and the valley concentric circular arc 34, the included angle of the peak symmetry axis and the valley concentric circular arc is the half impeller profile central angle phi uniquely determined by the number of blades, the intersection points of the peak symmetry axis and the valley concentric circular arc are a peak node 5 and a valley node 6 respectively, and a pitch circular arc between the peak symmetry axis and the valley symmetry axis is a half impeller profile circular; the middle point of the half-leaf pitch arc is a middle node 2, the intersection point of the normal of the peak conjugate profile at the vertex 1 and the pitch circle is a top node 9, the pitch arc from the top node 9 to the middle node 2 is a conjugate pitch arc, and the central angle of the pitch arc from the top node 9 to the peak node 5 is a multi-point sealing angle beta^*Any point on the conjugate nodal arc is an instant node 7, a normal line segment from the instant node 7 to the peak conjugate profile 12 is an instant radial line 78, a point of the instant radial line 78 on the peak conjugate profile 12 is an instant profile point 8, 77' is a pitch circle tangent line at the instant node 7, r is a pitch circle radius, epsilon is a shape coefficient, N is the number of rotor blades, and lambda is a volume utilization coefficient.

Under the premise that the pitch circle radius r and the number N of the rotor blades are given, a peak symmetry axis O50, a peak node 5, a middle node 2, a valley node 6, a half-impeller profile central angle phi and a valley symmetry axis O46 are uniquely determined:

in the first step, the shape coefficient-1, i.e., the length from the peak point to the peak node/the pitch circle radius, i.e., the length from the peak node to the middle node/the pitch circle radius, is symmetric about the pitch circle tangent 77', and the peak conjugate profile 12 is uniquely constructed by the structural relationship, i.e.,:

and secondly, deriving from the triangular geometrical relationship in the delta 1O9 and the calculation of the volume utilization coefficient:

maximum shape factor epsilon with involute rotor_jAnd its volume utilization coefficient lambda_jIs/are as follows

Compared with the prior art, the shape coefficient epsilon of the rotor is respectively improved by 9.13 percent under 2 leaves, 3.68 percent under 3 leaves and 1.81 percent under 4 leaves, and the volume utilization coefficient lambda is respectively improved by 8.06 percent under 2 leaves, 5.38 percent under 3 leaves and 3.72 percent under 4 leaves;

thirdly, constructing a peak concentric arc 01 (with the radius of r multiplied by epsilon) and a valley concentric arc 34 (with the radius of r multiplied by epsilon (2-epsilon)) by using the known r and the obtained epsilon and sigma;

a fourth step of determining beta from the obtained^*And a rotation avoidance trajectory line generated on the rotor by the vertex on the paired rotor, and constructing a valley transition curve 23.

There will be 5 sealing points in [0, σ ], (σ, β)^*) There are 3 sealing points in the sealing ring (beta)^*Phi/2) with 1 sealing point, compared with a common rotor with only 1 sealing point (0, phi/2), the multi-point sealing ratio of the invention is 2 beta^*/φ>50%, therefore, a smaller conjugate leakage rate is obtained, and the invention realizes a smaller radial leakage rate by adding the radial equal-gap sealing of the large central angle of 2 multiplied by sigma.

While there have been shown and described what are at present considered the fundamental principles and essential features of the invention and its advantages, it will be apparent to those skilled in the art that the invention is not limited to the details of the foregoing exemplary embodiments, but is capable of other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims

1. A low leakage roots rotor profile with a larger form factor comprised of 2 times the number of lobes circumferentially symmetrically adjacent half-lobe profiles, wherein: the semi-impeller profile is formed by sequentially connecting four parts of a peak concentric circular arc outside a pitch circle, a peak conjugate profile, a valley transition curve inside the pitch circle and a valley concentric circular arc end to end, and corresponding end points and connecting points are sequentially a peak point, a middle node, a root point and a valley point on a peak symmetry axis.

2. A low leakage roots rotor profile with a larger form factor as set forth in claim 1 wherein: the peak symmetry axis and the valley symmetry axis are boundary lines of the half impeller profile, and the intersection point of the peak symmetry axis and the valley symmetry axis is the center of the rotor and the center of the concentric circular arc.

3. A low leakage roots rotor profile with a larger form factor as set forth in claim 1 wherein: the included angle between the peak symmetry axis and the valley symmetry axis is a half-impeller profile circle center angle uniquely determined by the number of blades, the intersection points of the peak symmetry axis and the valley symmetry axis and a pitch circle are respectively a peak node and a valley node, a pitch arc between the peak symmetry axis and the valley symmetry axis is a half-blade pitch arc, and the middle point is a middle node.

4. A low leakage roots rotor profile with a larger form factor as set forth in claim 1 wherein: the intersection point of the normal line of the peak conjugate profile at the vertex and the pitch circle is a vertex node, the pitch arc from the vertex node to the middle node is a conjugate pitch arc, the pitch arc central angle from the vertex node to the peak node is a multi-point sealing angle, any point on the conjugate pitch arc is an instantaneous node, the normal line segment from the instantaneous node to the peak conjugate profile is an instantaneous line, and the point of the instantaneous line located on the peak conjugate profile is an instantaneous profile point.

5. A low leakage roots rotor profile with a larger form factor as set forth in claim 1 wherein: the peak conjugate profile is uniquely determined by its instant ray length and orientation.

6. A low leakage roots rotor profile with larger form factor as set forth in claim 4 wherein: the length and the azimuth of the transient line are uniquely determined by the symmetrical relation of a direct line segment from the transient node to the middle node and a tangent line of a pitch circle at the transient node, and a multi-point sealing angle and a half-top sealing angle are determined.

7. A low leakage roots rotor profile with a larger form factor as set forth in claim 6 wherein: the half top sealing angle is a central angle of a half lobe peak concentric circular arc.

8. A low leakage roots rotor profile with a larger form factor as set forth in claim 1 wherein: the shape factor-1-the length of the peak point to the peak node/pitch circle radius-the length of the peak node to the middle node/pitch circle radius.

9. A low leakage roots rotor profile with a larger form factor as set forth in claim 1 wherein: the valley transition curve is a rotation avoidance trajectory line generated on the rotor by the vertex on the paired rotor, and the conjugate rotation angle of the rotor pair is a multi-point sealing angle.