A rotor profile for Roots blower and its design method

Abstract

The present invention provides a rotor profile for a Roots blower and a design method thereof, belonging to the technical field of rotor profiles. The present invention comprises a rotor body composed of sequentially connected blade peaks and blade valleys. The profile from the lowest point of any blade valley to the highest point of its adjacent blade peak is composed of a smoothly connected pin tooth arc segment AB, a straight line segment BC, a curved segment CD, a transition tangent segment DE, an arc segment EF, a chamfered segment FG, and a tooth tip seal segment GH. The transition tangent segment DE is the transition tangent between the curved segment CD and the arc segment EF. This invention achieves a high area utilization coefficient, a large unit volume, high volumetric efficiency, and high overall blower operating efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of rotor profiles, and in particular to a rotor profile for a Roots blower and a design method thereof. Background Art

[0002] The Roots blower is a twin-rotor positive displacement rotary blower, originally invented by the American Roots brothers in 1854, inspired by repairing a figure-8 impeller water pump. It is used for air conveyance. It utilizes a pair of intermeshing rotors rotating in opposite directions. The impellers maintain a gap between the casing and the side panels, while a synchronous gear drive maintains a certain gap between the two impellers. As the impellers rotate, the space between the impellers and the casing creates a gap between the impellers and the casing, completing the intake and exhaust process from the inlet to the outlet, thus conveying gas. Due to its simple structure, minimal maintenance, and forced air delivery, the gap between the rotors and the casing eliminates the need for lubrication, resulting in oil-free conveying. It is widely used in various industries, such as petrochemicals, cement, steel, food, sewage treatment, tap water, and other fields for conveying materials or gases. Depending on the gas inlet and pressure, the Roots blower can be used to extract air, either with negative pressure or vacuum at the inlet. In this case, it is conventionally called a Roots vacuum pump, but the basic structure and principles remain the same. The most important component of a Roots blower is the impeller rotor. Over the course of its development, it initially had two blades, later developing three and even four blades. Currently, the three-blade design is the most widely used, while the four-blade design lacks significant advantages and is only partially used in mechanical superchargers. The rotor's profile determines the operating efficiency and noise level of the Roots blower, as well as the rotor's machining process, the selection of production machine tools, and its production efficiency. Therefore, the design of the rotor's profile is crucial to Roots blower design.

[0003] The existing profile structures are usually pin-tooth arc, involute and cycloid. These profiles have different focuses and disadvantages. For example, the cycloid impeller has the advantages of smooth engagement and low noise, but the processing area is large and the production efficiency is low, the area utilization coefficient is small and the volumetric efficiency is low. The involute impeller has a larger area utilization coefficient, but the reduction of the impeller head leads to an increase in the width of the opening during exhaust, a larger backflow impact and higher noise. The pin-tooth arc impeller is in the middle position compared with the first two, but the processing technology and production efficiency are still not optimized enough. Summary of the Invention

[0004] In view of this, in order to solve the above-mentioned deficiencies in the prior art, on the one hand, the present invention provides a rotor profile for a Roots blower, wherein the profile from the lowest point of any blade valley to the highest point of its adjacent blade peak is composed of a pin tooth arc segment AB, a straight line segment BC, a curve segment CD, a transition tangent segment DE, an arc segment EF, a chamfered line segment FG and a tooth top sealing line segment GH that are smoothly connected in sequence. The area utilization coefficient is high, the unit volume is large, the volumetric efficiency is high, and the overall operating efficiency of the blower is high.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A rotor profile for a Roots blower, comprising a rotor body composed of sequentially connected blade peaks and blade valleys, wherein the profile from the lowest point of any blade valley to the highest point of its adjacent blade peak is composed of a pin tooth arc segment AB, a straight line segment BC, a curved segment CD, a transition tangent segment DE, an arc segment EF, a chamfered line segment FG, and a tooth tip sealing line segment GH, which are smoothly connected in sequence;

[0007] The transition tangent segment DE is a transition tangent between the curve segment CD and the arc segment EF.

[0008] Preferably, the rotor body is a three-blade rotor.

[0009] Preferably, the center distance between the two mutually meshing rotor bodies is the distance between the centers of their respective pitch circles, the centers of the two pitch circles are O1 and O2 respectively, the center distance O1O2=2a, and the diameter of the pitch circle DW=2a*2*Z / (2*Z)=2a, wherein DW is the diameter of the pitch circle, 2a is the center distance, and Z is the number of rotor teeth.

[0010] Preferably, the leaf valley radius is: r1 = 0.5a + e, and the leaf peak radius is: r2 = 0.5ae, wherein e = (0-0.02)a, and a is half of the center distance.

[0011] Preferably, the chamfer angle between the chamfered line segment FG and the line O1O2 connecting the centers of the two pitch circles is between 10° and 45°.

[0012] Preferably, the width of the tooth top sealing line segment GH is (0.02-0.05)a / 2.

[0013] On the other hand, the present invention provides a method for designing a rotor profile for a Roots blower, comprising the following steps:

[0014] Pin tooth arc segment AB: The center of the blade valley I is on the pitch circle of the rotor body, and the centers of the two pitch circles of the two meshing rotor bodies are O1 and O2 respectively. 2， ∠IO1O2 is 60°, and an arc is drawn with the radius r1 of the leaf valley. Point A intersects the line IO1, and point B is determined by the line segment BC.

[0015] Line segment BC: Draw a straight line through the center O1 and extend it to the pitch circle, intersecting the pitch circle at point C. The angle between the straight line and the line connecting the centers of the two pitch circles O1O2 is 30°, and the intersection of the straight line and the leaf valley arc is B;

[0016] Curve segment CD: is the conjugate curve of another three-blade rotor meshing with the three-blade rotor relative to line segment BC, and is drawn by coordinate transposition to form the envelope curve CD;

[0017] Arc segment EF: Draw an arc with the node P on the pitch circle as the center and r2 as the radius. D is the tangent of the arc, and the tangent point is E. Point F is determined by the chamfer segment FG and the tooth top sealing segment GH.

[0018] Tooth top sealing line segment GH: draw an arc with O1 as the center and R as the radius. Point H is the intersection of the arc and the line connecting the centers of the two pitch circles O1O2. Point G is obtained according to the value of the tooth top sealing line width, where R is the distance from the center of the pitch circle to the highest point of the blade peak;

[0019] Chamfer line segment FG: The chamfer starts from point G, and the chamfer line intersects with the leaf peak radius arc at point F.

[0020] The rotor profile for a Roots blower provided by the present invention has a profile from the lowest point of any blade valley to the highest point of its adjacent blade peak composed of a pin tooth arc segment AB, a straight line segment BC, a curved segment CD, a transition tangent segment DE, an arc segment EF, a chamfered line segment FG, and a tooth tip sealing line segment GH that are smoothly connected in sequence. This shape of the rotor profile has the following beneficial effects:

[0021] 1) The area utilization coefficient should be high, the unit volume should be large, the volume efficiency should be high, and the overall operation efficiency of the fan should be high;

[0022] 2) The rotor has a symmetrical geometric shape and a high allowable linear speed. The speed can be increased to increase the flow rate. The operation is stable, the discharge opening width has a small sudden change, the impact is small, and the backflow pulse noise is low;

[0023] 3) Good sealing performance, continuous engagement without interruption, less leakage and high volumetric efficiency;

[0024] 4) The simple structure is conducive to production and manufacturing, with high processing precision and improved production efficiency;

[0025] 5) It has sufficient strength to achieve a large pressure difference while meeting the maximum area utilization coefficient, thereby improving the fan capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the rotor profile structure;

[0027] In the figure, O1 and O2 are the centers of the two pitch circles, DW is the diameter of the pitch circle, R is the distance between the center of the pitch circle and the highest point of the leaf peak, r1 is the leaf valley radius, and r2 is the leaf peak radius. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0029] The present invention is Figure 1 The three-blade rotor shown here illustrates the contour formation. The two rotors have identical contours, with the three impellers evenly spaced, each symmetrical about the central axis. For ease of description, we'll use the AH segment of one rotor, a 1 / 6 portion. Once this 1 / 6 portion is understood, the entire rotor end profile can be obtained using a mirrored array. The AH segment is comprised of seven basic lines, including arcs, straight lines, and envelopes.

[0030] like Figure 1 As shown, the rotor profile for a Roots blower provided by the present invention includes a rotor body composed of blade peaks and blade valleys connected in sequence, and the profile from the lowest point of any blade valley to the highest point of its adjacent blade peak is composed of a pin tooth arc segment AB, a straight line segment BC, a curved segment CD, a transition tangent segment DE, an arc segment EF, a chamfered line segment FG, and a tooth top sealing line segment GH connected in sequence and smoothly;

[0031] The transition tangent segment DE is a transition tangent between the curve segment CD and the arc segment EF.

[0032] In the present invention, the rotor body is a three-lobed rotor.

[0033] In the present invention, the rotor profile is taken as follows:

[0034] In the present invention, the center distance between the two mutually meshing rotor bodies is the distance between the centers of their respective pitch circles. The centers of the two pitch circles are O1 and O2 respectively, the center distance O1O2=2a, and the diameter of the pitch circle DW=2a*2*Z / (2*Z)=2a, wherein DW is the diameter of the pitch circle, 2a is the center distance, and Z is the number of rotor teeth.

[0035] In the present invention, the blade valley radius is: r1=0.5a+e, and the blade peak radius is: r2=0.5ae, wherein e=(0-0.02)a, and a is half of the center distance (radius of the pitch circle).

[0036] In the present invention, the chamfer angle between the chamfered line segment FG and the line O1O2 connecting the centers of the two pitch circles is between 10° and 45°.

[0037] In the present invention, the width of the tooth top sealing line segment GH is (0.02-0.05)a / 2.

[0038] In the present invention, the pitch ratio: R / a=1.5.

[0039] In the rotor profile for Roots blower provided by the present invention,

[0040] Pin tooth arc segment AB, simple rule;

[0041] The straight line segment BC is simple and regular, making it easy to process;

[0042] Curved segment CD forms an engagement with BC on the other rotor during the entire rotation process, maintaining the sealing characteristics;

[0043] Arc segment EF is simple and regular, and easy to process. At the same time, because the meshing characteristic of the pin tooth arc is that the entire arc surface meshes at the same time, and the rotor sealing is achieved by point D at this moment, it is not necessary to fine-machine the entire arc surface. This surface can be lower than the tooth top arc and only rough-machined, reducing the area of ​​fine-machining and improving production efficiency without affecting operating efficiency.

[0044] The tooth top sealing line segment GH is used to form a seal with the casing and cylinder body, forming a small-area sealing line, rather than the entire pin tooth arc tooth top seal. The advantage is that when the Roots blower encounters a short-term overload deformation and bending or high-temperature expansion during operation, the rotor and cylinder body will contact and rub. Since it is not a large-scale collision, it will not cause major losses. Once the overload and overtemperature disappear, the rotor returns to its position and continues to operate.

[0045] On the other hand, the present invention provides a method for designing a rotor profile for a Roots blower, comprising the following steps:

[0046] Pin tooth arc segment AB: The center of the blade valley I is on the pitch circle of the rotor body, and the centers of the two pitch circles of the two meshing rotor bodies are O1 and O2 respectively. 2， ∠IO1O2 is 60°, and an arc is drawn with the radius r1 of the leaf valley. Point A intersects the line IO1, and point B is determined by the line segment BC.

[0047] Line segment BC: Draw a straight line through the center O1 and extend it to the pitch circle, intersecting the pitch circle at point C. The angle between the straight line and the line connecting the centers of the two pitch circles O1O2 is 30°, and the intersection of the straight line and the leaf valley arc is B;

[0048] Curve segment CD: is the conjugate curve of another three-blade rotor meshing with the three-blade rotor relative to line segment BC, and is drawn by coordinate transposition to form the envelope curve CD;

[0049] Arc segment EF: Draw an arc with the node P on the pitch circle as the center and r2 as the radius. D is the tangent of the arc, and the tangent point is E. Point F is determined by the chamfer segment FG and the tooth top sealing segment GH.

[0050] Tooth top sealing line segment GH: draw an arc with O1 as the center and R as the radius. Point H is the intersection of the arc and the line connecting the centers of the two pitch circles O1O2. Point G is obtained according to the value of the tooth top sealing line width, where R is the distance from the center of the pitch circle to the highest point of the blade peak;

[0051] Chamfer line segment FG: The chamfer starts from point G, and the chamfer line intersects with the leaf peak radius arc at point F.

[0052] The outstanding advantage of the rotor profile provided by the present invention and the method involved is that it improves the area utilization coefficient. According to calculations, it can reach 0.53. Under the same diameter-to-pitch ratio of 1.5, it is 2% higher than the maximum area utilization coefficient of 0.5185 of the traditional involute profile, thereby improving the volumetric efficiency and thus the overall operating efficiency. The diameter-to-pitch ratio of 1.5 ensures that the rotor has sufficient strength to achieve a large pressure difference and improve the operating capacity of the fan. In addition, under the premise of ensuring sealing, only BC and CD are the finishing surfaces, which reduces the finishing area and improves production efficiency. At the same time, since only the CD segment in the machining surface is an irregular surface that requires high-precision machine tools, it is beneficial to the selection of machine tools, reduces the use of finishing machine tools, and reduces costs. The EF line segment designed to reduce the finishing surface also forms the GH tooth top sealing line, which reduces the failure rate and ensures the safe operation of the equipment.

[0053] The above embodiments are only used to illustrate the invention and are not used to limit the invention. As long as they are within the essential spirit of the invention, changes and modifications to the above embodiments will fall within the scope of the patent requirements of the present invention.

Claims

1. A Roots blower rotor, comprising a rotor body consisting of sequentially connected blade peaks and blade valleys, characterized in that: The rotor profile is as follows: The profile line from the lowest point of any blade valley to the highest point of its adjacent blade peak is composed of a pin tooth arc segment AB, a straight line segment BC, a curve segment CD, a transition tangent segment DE, an arc segment EF, a chamfered line segment FG and a tooth top sealing line segment GH that are smoothly connected in sequence; The transition tangent segment DE is a transition tangent between the curve segment CD and the arc segment EF; The rotor profile design method comprises the following steps: Pin tooth arc segment AB: The center of the blade valley I is on the pitch circle of the rotor body, and the centers of the two pitch circles of the two meshing rotor bodies are O1 and O2 respectively. 2， ∠IO1O2 is 60°, and an arc is drawn with the radius r1 of the leaf valley. Point A intersects the line IO1, and point B is determined by the line segment BC; Line segment BC: Draw a straight line through the center O1 and extend it to the pitch circle, intersecting the pitch circle at point C. The angle between the straight line and the line connecting the centers of the two pitch circles O1O2 is 30°, and the intersection of the straight line and the leaf valley arc is B; Curve segment CD: is the conjugate curve of the other rotor meshing with this rotor relative to line segment BC, and is drawn by coordinate transposition to form the envelope CD; Arc segment EF: Draw an arc with the node P on the pitch circle as the center and r2 as the radius. D is the tangent of the arc, and the tangent point is E. Point F is determined by the chamfer segment FG and the tooth top sealing segment GH. Tooth top sealing line segment GH: draw an arc with O1 as the center and R as the radius. Point H is the intersection of the arc and the line connecting the centers of the two pitch circles O1O2. Point G is obtained according to the value of the tooth top sealing line width, where R is the distance from the center of the pitch circle to the highest point of the blade peak; Chamfer line segment FG: The chamfer starts from point G, and the chamfer line intersects with the leaf peak radius arc at point F.

2. The rotor of a Roots blower according to claim 1, characterized in that: The rotor body is a three-blade rotor.

3. The rotor of a Roots blower according to claim 1, characterized in that: The center distance between the two mutually meshing rotor bodies is the distance between the centers of their respective pitch circles. The centers of the two pitch circles are O1 and O2 respectively, the center distance O1O2=2a, and the diameter of the pitch circle DW=2a*2*Z / (2*Z)=2a, where DW is the diameter of the pitch circle, 2a is the center distance, and Z is the number of rotor teeth.

4. The rotor of a Roots blower according to claim 3, characterized in that: Leaf valley radius: r1=0.5a+e, leaf peak radius: r2=0.5ae, where e=(0~0.02)a, a is half of the center distance.

5. The rotor of a Roots blower according to claim 1, characterized in that: The chamfer angle between the chamfered line segment FG and the line O1O2 connecting the centers of the two pitch circles is between 10° and 45°.

6. The rotor of a Roots blower according to claim 1, characterized in that: The width of the tooth top sealing line segment GH is (0.02-0.05)a / 2.

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