CN111159792A - Volute profile generation method of centrifugal fan - Google Patents
Volute profile generation method of centrifugal fan Download PDFInfo
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Abstract
The invention discloses a volute profile generation method of a centrifugal fan, which comprises the following steps: 1) obtaining a basic molded line: establishing a coordinate system, taking a point in the positive direction of the X axis as a starting point of the basic molded line, and obtaining the basic molded line through a spiral line equation; also comprises the following steps: 2) generating a first initial profile: rotating the X axis counterclockwise by a certain angle to obtain a third intersection point close to the tail end of the basic molded line, thus obtaining a first straight line segment tangent with the basic molded line, taking a first exit point on the first straight line segment as a starting point to obtain a second straight line segment, then taking a second exit point on the second straight line segment as a starting point to make a third straight line segment parallel to the first straight line segment, and obtaining a fourth intersection point of the third straight line segment and the basic molded line; 3) generating a second initial profile: enabling a fourth intersection point on the third straight-line segment to shift a certain angle clockwise along the first initial profile to obtain a fifth intersection point, and generating a second initial profile; 4) and correcting the second initial profile to obtain a third initial profile.
Description
Technical Field
The invention relates to a power device, in particular to a volute profile generation method of a centrifugal fan.
Background
The centrifugal fan volute has two functions, one is used for collecting fluid flowing out of the impeller, and the other is used for converting kinetic energy of high-speed fluid flowing out of the impeller into required potential energy. The volute profile is a boundary for restraining the movement of fluid in the volute, and the volute profile also determines the position of the volute tongue and the size of the volute tongue gap, so that the diffusion performance of the volute is greatly influenced.
The volute tongue is used as a key part for influencing the noise and the backflow of the whole fan system, and only one recommended clearance value in a general design method is as follows: for household appliances, the size of a commonly used volute base circle D2 is 50-500 mm, the circumferential clearance value t between the top end of a volute tongue and the outer circle of an impeller is (0.05-0.1) D2, and the arc radius r between the top end of the volute tongue and (0.03-0.05) D2. For small fan systems, the clearance value is often only the minimum value of the recommended range, and a larger volute tongue clearance is necessary to further reduce noise.
At present, there are two methods for increasing the volute tongue clearance, the first is to dynamically adjust the volute tongue clearance: the volute tongue disclosed in the applicant's chinese patent application No. 201711451180.5 comprises a support frame and a flexible volute tongue wall disposed on the support frame to form an outer contour of the volute tongue, wherein the support frame comprises an upper support body disposed at a root of the volute tongue, a lower support body, and a variable R cylinder disposed at a head of the volute tongue, and further comprises a driving mechanism for driving the variable R cylinder to rotate, and the variable R cylinder is driven to rotate to realize variable R adjustment of the volute tongue, so as to change a gap between the volute tongue and an impeller, thereby improving fan performance or reducing noise, and enabling the volute tongue to better adapt to various actual working conditions. The dynamic adjusting mode has complex mechanism and higher cost.
The second is to adopt a step volute tongue: the utility model discloses a slope ladder volute tongue fan spiral case that chinese patent application number is 201510782850.6 discloses, includes spiral case front bezel, spiral case back plate and presss from both sides and locates the rampart between spiral case front bezel, the spiral case back plate leaves the air outlet of fan on the rampart, and air outlet department is equipped with the volute tongue, and the volute tongue is slope ladder volute tongue, is equipped with first inclined plane volute tongue and second inclined plane volute tongue on the body of slope ladder volute tongue, through first inclined plane volute tongue and second inclined plane volute tongue form heterogeneous buffer zone on the slope ladder volute tongue for the impact of buffering air current to slope ladder volute tongue can make this fan effectively reduce the noise. However, when the stepped volute tongue is in large flow, two kinds of noises are generated by the collision of the two volute tongues, the sound quality is poor, and meanwhile, the stepped volute tongue is not easy to process and needs to be separately processed and assembled by plastic parts.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a volute profile generation method of a centrifugal fan, which is simple and easy to process and has low noise in large flow, aiming at the defects of the prior art.
The technical scheme adopted by the invention for solving the technical problems is as follows: a volute profile generation method of a centrifugal fan comprises the following steps:
1) obtaining a basic molded line: establishing a coordinate system, determining an X axis and a Y axis, taking an original point of the coordinate system as a circle center to obtain a base circle with the radius of D2, taking a point in the positive direction of the X axis as a starting point of a basic molded line, and obtaining a basic molded line through a spiral line equation, wherein a first intersection point is arranged between the X axis and the basic molded line and close to the tail end, the X coordinate of the first intersection point is larger than the starting point, and the tail end of the basic molded line is positioned in a first quadrant of the coordinate system; the Y axis and the basic molded line have a second intersection point, and the second intersection point is located in the positive direction of the Y axis and is the highest point of the basic molded line; the method is characterized in that: also comprises the following steps:
2) generating a first initial profile: rotating counterclockwise for a certain angle from the X axis to obtain a third intersection point close to the tail end with the basic molded line, and thereby obtaining a first straight line segment tangent to the base profile, said first straight line segment and the base profile being tangent to a third intersection point, the inclination angle of the first straight line segment is theta 1, the end point of the first straight line segment far away from the third intersection point is a first outlet point of the volute, taking the first outlet point as a starting point, making a second straight line segment which is parallel to the X axis and extends for a certain distance towards the Y axis, taking the end point of the second straight line segment far away from the first outlet point as a second outlet point of the volute, then, taking the second exit point as a starting point to make a third straight line segment parallel to the first straight line segment to obtain a fourth intersection point of the third straight line segment and the basic molded line, the first initial molded line generated by the method is composed of a part between the fourth intersection point and the third intersection point of the basic molded line, a first straight line segment, a second straight line segment and a third straight line segment; at the moment, the gap between the fourth intersection point and the base circle is t, and t is more than or equal to tmin，tminSetting a minimum clearance value for a standard method;
3) generating a second initial profile: if t and tminDifference of (2)More than 1% of D2, enabling a fourth intersection point on the third straight line section to shift a certain angle clockwise along the first initial molded line to obtain a fifth intersection point, and enabling the generated second initial molded line to be composed of a part between the fifth intersection point and the third intersection point of the basic molded line, the first straight line section, the second straight line section and the third straight line section; the gap between the fifth intersection point and the base circle is t ', and t' ≧ tmin；
4) Generating a third initial profile: taking a sixth intersection point on the fourth straight line segment as a first correction point, wherein the X coordinate of the sixth intersection point is smaller than the fifth intersection point, and the Y coordinate of the sixth intersection point is larger than the fifth intersection point; and taking a point on the part of the second initial profile, which is positioned in the second quadrant of the coordinate system, as a second correction point, connecting the first correction point and the second correction point through a spline curve to replace the part between a fifth intersection point of the second initial profile and the second correction point, so as to generate a third initial profile, and rounding at a sixth intersection point to form a volute tongue of the volute.
According to an aspect of the present invention, in step 4), a third initial profile is generated by an offset dotting method, and the spline curve is a first spline curve, including the following steps:
4.1) shifting the parts of the second initial molded line in the first quadrant and the second quadrant of the coordinate system outwards in parallel in a direction away from the center of the circle by one or at least two equal intervals, wherein the outermost side is a first shifting line, the innermost side is an nth shifting line, n is the number of the shifting lines, and the middle shifting lines from the first shifting line to the nth shifting line are respectively the ln-1 shifting lines of the second shifting line … …;
4.2) taking an intersection point of a fourth straight line segment and the first offset line to obtain a sixth intersection point, connecting the sixth intersection point with the circle center to obtain a fifth straight line segment, and connecting the second outlet point with the sixth intersection point to obtain a sixth straight line segment;
4.3) taking the offset uniform dividing line from the sixth intersection point to the second correction point at an equal angle relative to the circle center, wherein the number of the offset uniform dividing lines is the number of the offset lines plus 1, the first offset uniform dividing line is superposed with the fifth straight line segment, the n +1 th offset uniform dividing line is a connecting line of the second correction point and the circle center, and the middle offset uniform dividing line from the first offset uniform dividing line to the n +1 th offset uniform dividing line is the second offset uniform dividing line … …, the ln' offset uniform dividing line respectively; and sequentially taking the intersection point … … of the second deviation average wire and the second deviation wire, the intersection point of the nth deviation average wire and the nth deviation wire, and connecting the sixth intersection point, the n-1 intersection points of the deviation average wires, the n-1 intersection points of the corresponding deviation wires and the second correction point by using the first spline curve, thereby generating a third initial molded wire.
Preferably, the included angle between the connecting line of the second correction point and the circle center and the Y axis is 3-20 degrees, and the distance between adjacent offset lines is 0.4-1 mm.
According to another aspect of the present invention, in step 4), a third initial profile is generated by a rotational dotting method, and the spline curve is a second spline curve, including the steps of:
4.1) rotating the part between the second correction point and the starting point of the basic molded line once or at least twice at equal angles in the direction away from the circle center by taking the second correction point as a rotation center, wherein the rotation angle is the largest and the m-th rotation line, the m is the number of the rotation lines, and the middle rotation lines from the first rotation line to the m are respectively the m-1 rotation lines of the second rotation line … …;
4.2) taking the intersection point of the fourth straight line segment and the first rotating line as a sixth intersection point, connecting the sixth intersection point with the circle center to obtain a fifth straight line segment, and connecting the second outlet point with the sixth intersection point to obtain a sixth straight line segment;
4.3) taking rotation uniform distribution lines from the sixth intersection point to the second correction point at equal angles relative to the circle center, wherein the number of the rotation uniform distribution lines is the number of the rotation lines plus 1, the first rotation uniform distribution line is superposed with the fifth straight line segment, the m + 1-th rotation uniform distribution line is a connecting line of the second correction point and the circle center, and the middle rotation uniform distribution line from the first rotation uniform distribution line to the m-th rotation uniform distribution line is respectively the Nm' th rotation uniform distribution line of the second rotation uniform distribution line … …; and sequentially taking the intersection point … … of the second rotation average line and the second rotation line, the intersection point of the mth rotation average line and the mth rotation line, and connecting the sixth intersection point by using a second spline curve, wherein the rotation average lines are connected with n-1 intersection points of the corresponding rotation line and the second correction point, so that a third initial profile is generated.
Preferably, the angle delta between the connecting line of the second correction point and the center of the circle and the Y axis is 0-30 degrees, and the angle range of each rotation is 0.5-2 degrees.
Preferably, the coordinates of the second intersection point are: x is 0, Y is h, the height of the volute is h1, h1-h is more than or equal to 20mm, and the Y coordinate of the first outlet point is h 1.
Preferably, the value range of theta 1 is 0-30 degrees.
Preferably, the length of the second straight line section is 1.3-2.0 times of the length between the starting point of the basic molded line and the first intersection point.
Compared with the prior art, the invention has the advantages that: the tail end of the spiral basic molded line is prolonged, the outlet of the spiral basic molded line is inclined towards the volute tongue, the parts positioned in the first quadrant and the second quadrant are corrected by spline curves, the volute tongue clearance is increased, the noise is reduced, meanwhile, the generating method can reduce the processing difficulty, the spiral basic molded line can be made by using a sheet metal part, and the spiral tongue area does not need to be separately processed by using a casting part or a plastic part for assembly.
Drawings
Fig. 1 is a schematic profile view generated in step 1) of a volute profile generation method according to an embodiment of the present invention;
fig. 2 is a schematic profile view generated in step 2) of the volute profile generation method according to the embodiment of the present invention;
fig. 3 is a schematic view of a volute obtained after profile stretching generated in step 2) of the volute profile generation method according to the embodiment of the present invention;
FIG. 4 is a schematic diagram comparing the profile rounding generated in step 2) of the volute profile generating method according to the embodiment of the present invention with the prior art;
fig. 5 is a schematic diagram of a second initial profile generated by the volute profile generating method according to the embodiment of the invention;
fig. 6 is a first mode modification schematic diagram of a first initial profile generated by the volute profile generation method according to the embodiment of the invention;
FIG. 7 is an enlarged view of a portion I of FIG. 6;
fig. 8 is a schematic diagram of a second modification manner of the first initial profile generated by the volute profile generation method according to the embodiment of the invention;
fig. 9 is an enlarged view of a portion ii of fig. 8.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar functions.
In the description of the present invention, it is to be understood that the terms "central," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," and the like are used in the orientations and positional relationships indicated in the drawings for convenience in describing the present invention and to simplify the description, but are not intended to indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and that the directional terms are used for purposes of illustration and are not to be construed as limiting, for example, because the disclosed embodiments of the present invention may be oriented in different directions, "lower" is not necessarily limited to a direction opposite to or coincident with the direction of gravity. Furthermore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature.
The volute profile of the centrifugal fan is generally a spiral line, and the spiral line equation is R2 EXP (M θ) through calculation of fluid mechanics, where R2 is the outer radius of the impeller, and M is a parameter related to fluid properties. After R2 and M are determined, the basic molded line (spiral line) of the volute can be obtained. Or other existing means may be used to obtain the base profile.
However, on the basis of the basic molded line, how to select the position of the volute tongue has great difficulty in practice. And the volute tongue plays an important role in noise and backflow of the whole machine. Hereinafter, counterclockwise means a rotational direction from the positive X-axis direction to the positive Y-axis direction, and clockwise means a rotational direction from the positive Y-axis direction to the positive X-axis direction.
The volute profile is typically characterized in that as the angle increases, points on the curve are spaced from the center point at greater distances, and the clearance at the volute tongue is greater within a specified range, and the noise is lower. The method of the present invention is designed based on the above-described principle.
Example one
The volute profile generation method of the centrifugal fan comprises the following steps:
1) obtaining a basic molded line L: as shown in fig. 1, establishing a coordinate system, determining an X axis and a Y axis perpendicular thereto, and taking an origin of the coordinate system as a center O to obtain a base circle Q with a radius D2, as shown by a dotted line in fig. 1, where the base circle Q represents an outer circle of an impeller of a centrifugal fan; taking one point in the positive direction of the X axis as a starting point F of the basic molded line L, obtaining the basic molded line L through the spiral line equation R, D2 EXP (m theta), wherein theta is the angle of the one point on the spiral line relative to the positive direction of the X axis, a first intersection point G is formed between the X axis and the basic molded line L close to the tail end, and the X coordinate of the first intersection point G is larger than the starting point F; the X axis and the Y axis divide the plane into a first quadrant, a second quadrant, a third quadrant and a fourth quadrant, the quadrants are defined as a general coordinate system, wherein the tail end of the basic molded line L is positioned in the first quadrant; the Y axis and the basic molded line L are provided with a second intersection point H, the second intersection point H is located in the positive direction of the Y axis and is the highest point of the basic molded line L, the coordinate of the second intersection point H is (X is 0, Y is H), the height of the reserved volute is H1, H1-H is larger than or equal to 20mm, the reserved volute serves as a reserved machining space, and the total height of the whole volute molded line is correspondingly determined after the height of H1 is determined. That is, the maximum value of h1 is limited by the height of the whole machine, the minimum value is generally 20mm larger than h, and the Y coordinate of the first exit point B is h 1.
2) Generating a first initial profile L1: referring to fig. 2, a third intersection point a close to the end of the basic molded line L is obtained by rotating the X-axis counterclockwise by an angle θ 1, and a first straight line AB (the inclination angle is θ 1) tangent to the basic molded line L is obtained, the value range of θ 1 is preferably 0 to 30 degrees, more preferably 12 to 18 degrees, the first straight line AB and the basic molded line are tangent to the third intersection point a, and the other end point B of the first straight line AB is a first exit point of the volute. After the base profile L is determined, the starting points F andthe length between the first intersection points G is fixed, a second straight line segment BC which is parallel to the X axis and extends towards the Y axis is made by taking the first outlet point B as a starting point, the point C is a second outlet point of the volute, the length of the second straight line segment BC is preferably 1.3-2.0 times, more preferably 1.35-1.55 times, the length between the starting point F and the first intersection point G, and the initial size which meets the requirement of an external environment is selected according to actual; then, taking the second outlet point C as a starting point to make a third straight line segment CD of a parallel line with the first straight line segment AB to obtain a fourth intersection point D with the basic line L; detecting the gap t between the fourth intersection point D and the base circle Q, if t is more than or equal to tmin(the minimum clearance value is set by the standard method, and is generally 0.035D2), a first original profile L1 is basically determined, and the first original profile L1 is formed by the basic profile L, the first straight line segment AB, the second straight line segment BC and the third straight line segment CD.
At this time, if the length B is perpendicular to the first initial profile L1, i.e. perpendicular to the paper surface of fig. 2, the annular wall 1 of the volute is obtained after the whole length B is stretched, and the arrow in fig. 3 is the stretching direction; thereafter, a volute tongue is formed by rounding at each fourth intersection point D, an optimized profile L4 shown in fig. 4 is obtained, referring to fig. 4, the optimized profile L4 is compared with the prior art volute profile, wherein the straight line segment B1C1 is the outlet of the prior art volute, D1 is the position of the prior art volute tongue, and the straight line segment AB1 of the prior art is perpendicular to the X axis, so that compared with the prior art profile (the way that the second intersection point G is directly and vertically upward as the outlet), the optimized profile L4 is inclined to generate the outlet and the volute tongue, so that the position of the volute tongue is shifted to the Y axis as a whole, the volute tongue gap t is increased, and noise is reduced.
The optimized profile L4 has the tip arc radius r of the volute tongue being (0.03-0.05) D2, the stretching length B being 1-1.4B, and B being the length of the impeller.
3) Generating a second initial profile L2: if the gap t is large, it is larger than tminAbove this value of 1% D2, in order to increase the static pressure and reduce the flow rate, the fourth intersection D of the third straight line segment CD may be shifted clockwise by a certain angle along the first initial profile L1 to form a fifth intersection D ', and the fourth straight line segment CD ' may be formed between the second exit point C and the fifth intersection D ', thereby forming a second initial profile L2, which is formed from the baseThe molded line L, the first straight line segment AB, the second straight line segment BC and the fourth straight line segment CD'. Referring to FIG. 5, the central angle between the fourth intersection D and the fifth intersection D 'is less than 30 degrees, and the gap t' between the fifth intersection D 'and the base circle Q also satisfies the above requirement, t' ≧ tminAt this time, the outlet of the volute is in a gradually enlarged shape, and the function of reducing the flow speed and increasing the static pressure is achieved.
4) Generating a third initial profile L3: in a small space, the static pressure needs to be increased, the flow rate needs to be reduced, so that the angle between the third straight line section CD and the fourth straight line section CD' needs to be enlarged, and the volute tongue clearance is inevitably reduced after the angle is enlarged, thereby the noise is increased. The method is suitable for the method which can also increase the volute tongue clearance after the angle of the fourth straight line segment CD' is fixed. The method is also suitable for other occasions and is limited by the structure or diffusion requirement, and when the CD angle of the third straight line section is large and cannot be changed, the volute tongue clearance can be increased and the noise can be reduced.
The inclination angle of the first straight line segment AB and the length range of the second straight line segment BC are made small by the installation environment or other constraints. Even if the maximum value is used, the volute tongue clearance t is still small, or the noise at the volute tongue is still large. The following steps are implemented using offset dotting, see fig. 6 and 7:
4.1) the parts of the second initial profile L2, which are located in the first quadrant and the second quadrant of the coordinate system, are shifted outwards in parallel in the direction away from the center O, and the gap between two adjacent shifted lines is not too large, and the value is between 0.4 and 1 mm. And at least two offset lines are outwards offset by one or equal intervals according to requirements and practical conditions, wherein the outermost line (the line farthest from the second base profile L) is a first offset line L1, the innermost line (the line closest to the second initial profile L2) is an n-th offset line ln, n is the number of offset lines, and the middle lines from the first offset line L1 to the n-th offset line ln are respectively an ln-1-th offset line ln-1 of the second offset line L2 … …. In the present embodiment, there are five offset lines, i.e., a first offset line l1, a second offset line l2, a third offset line l3, a fourth offset line l4, and a fifth offset line l 5.
4.2) the intersection point of the original fourth straight-line segment CD 'and the first offset line l1 is a sixth intersection point D' serving as a first correction point, the sixth intersection point D 'is connected with the circle center O to obtain a fifth straight-line segment OD', the second outlet point C is connected with the sixth intersection point D 'to obtain a sixth straight-line segment CD', the sixth straight-line segment CD 'is a part of the original fourth straight-line segment CD', the X coordinate of the sixth intersection point D 'is smaller than the fifth intersection point D', and the Y coordinate of the sixth intersection point D 'is larger than the fifth intersection point D'; and taking a seventh intersection point E as a second correction point on the part of the second initial molded line L2, which is positioned in the second quadrant, wherein an included angle between a connecting line of the seventh intersection point E and the circle center O relative to the Y axis is 3-20 degrees. The seventh intersection point E is in the second quadrant, whereby the intersection point of the newly created profile is in the second quadrant, which, if taken in the first quadrant, is liable to induce surge and increase noise.
4.3) from the sixth intersection point D' to the seventh intersection point E, and the equal angle is deviated relative to the circle center O to obtain the uniform dividing lines, and the quantity of the deviated uniform dividing lines is the quantity of the deviated lines plus 1. In the present embodiment, there are six offset average splitting lines, which are respectively a first offset average splitting line l1 ', a second offset average splitting line l 2', a third offset average splitting line l3 ', a fourth offset average splitting line l 4', a fifth offset average splitting line l5 'and a sixth offset average splitting line l 6', in the present embodiment. And sequentially taking an intersection point … … of a second deviation average line L2 ' and a second deviation average line L2, connecting a sixth intersection point D ', above all deviation average lines with n-1 intersection points and a seventh intersection point E of corresponding deviation lines by using a first uniform curve L ', performing fillet transition treatment between the interface of the first uniform curve L ' and the second initial molded line L and a sixth straight line segment CD ', wherein the minimum fillet is larger than the distance between two deviation lines and is generally selected to be ten times of the distance between the deviation lines, thereby generating a third initial molded line L3 which is composed of the first uniform curve L ', the EA section of the basic molded line L, the first straight line section AB, the second straight line segment BC and the sixth straight line segment CD '. The clearance of the volute tongue of the third initial molded line L3 is enlarged and can be expanded. In addition, if the distance between the two leftmost dots shown in fig. 6 is less than 0.5mm, no processing may be performed. And rounding at the sixth intersection point D' to form a volute tongue of the volute.
The volute tongue clearance can be increased by 0.01D-0.04D maximally by the offset dotting method, but the clearance is not increased to exceed 0.1D 2.
Example two
Referring to fig. 8 and 9, the present embodiment is different from the first embodiment in that a rotational dotting method is used instead of the offset dotting method to generate the third initial profile L3. The method comprises the following steps:
4.1) taking a point I at the part of the second initial molded line L2 in the second quadrant, taking the point I as a rotation center, rotating the curve segment IF once or twice at equal angles in the direction away from the circle center O, taking the rotation center I as a second correction point, wherein the angle delta between the connecting line of the second correction point I and the circle center O and the Y axis is 0-30 degrees, and the angle range of single rotation is 0.5-2 degrees; the first rotation line N1 at the largest rotation angle, the mth rotation line Nm at the smallest rotation angle, m being the number of rotation lines, and the middle rotation lines Nm from the first rotation line N1 to the mth rotation line Nm being the m-1 rotation lines Nm-1 of the second rotation line N2 … …, respectively. In the present embodiment, there are five rotation lines, which are the first rotation line N1, the second rotation line N2, the third rotation line N3, the fourth rotation line N4, and the fifth rotation line N5.
4.2) the intersection point of the original fourth straight-line segment CD 'and the first rotating line N1 is a sixth intersection point D' which is used as a first correction point, the sixth intersection point D 'is connected with the circle center O to obtain a fifth straight-line segment OD', the second outlet point C is connected with the sixth intersection point D 'to obtain a sixth straight-line segment CD', and the sixth straight-line segment CD 'is a part of the original fourth straight-line segment CD';
4.3) equally-angled rotation uniform lines are taken from the sixth intersection point D' to the rotation center I relative to the circle center O, and the number of the rotation uniform lines is the number of the rotation lines plus 1. In this embodiment, there are six rotation average dividing lines, which are respectively a first rotation average dividing line N1 ', a second rotation average dividing line N2', a third rotation average dividing line N7 ', a fourth rotation average dividing line N4', a fifth rotation average dividing line N5 'and a sixth rotation average dividing line N6'. And sequentially taking an intersection point … … of a second rotation average line N2 'and a second rotation line N2, connecting an m-th rotation average line Nm' with an m-th rotation line Nm, connecting a sixth intersection point D 'with a second spline curve N', connecting the rotation average lines with N-1 intersection points and a rotation center I of the corresponding rotation line, performing fillet transition treatment between an interface of the second spline curve N 'and a second initial molded line L and a sixth straight line segment CD', wherein the minimum fillet is more than the distance between two offset lines and is generally selected to be ten times of the distance between the offset lines, thereby generating a third initial molded line L3 which is composed of a second spline curve L ', an IA segment of a basic molded line L, a first straight line segment AB, a second straight line segment BC and a sixth straight line segment CD'. And rounding at the sixth intersection point D' to form a volute tongue of the volute.
Claims (8)
1. A volute profile generation method of a centrifugal fan comprises the following steps:
1) base profile (L) was obtained: establishing a coordinate system, determining an X axis and a Y axis, taking an original point of the coordinate system as a circle center (O) to obtain a base circle (Q) with a radius of D2, taking a point in the positive direction of the X axis as a starting point (F) of a basic molded line (L), and obtaining the basic molded line (L) through a spiral line equation, wherein a first intersection point (G) is arranged at the tail end of the X axis and the basic molded line (L), the X coordinate of the first intersection point (G) is greater than the starting point (F), and the tail end of the basic molded line (L) is positioned in a first quadrant of the coordinate system; the Y axis and the basic molded line (L) are provided with a second intersection point (H), and the second intersection point (H) is located in the positive direction of the Y axis and is the highest point of the basic molded line (L); the method is characterized in that: also comprises the following steps:
2) generating a first initial profile (L1): rotating the X axis counterclockwise by a certain angle to obtain a third intersection point (A) close to the tail end of the basic molded line (L) and obtain a first straight line segment (AB) tangent to the basic molded line (L), wherein the first straight line segment (AB) and the basic molded line (L) are tangent to the third intersection point (A), the inclination angle of the first straight line segment (AB) is theta 1, the end point of the first straight line segment (AB) far away from the third intersection point (A) is a first outlet point (B) of the volute, and the first straight line segment (AB) is taken as the first outlet point (B) of the voluteA first outlet point (B) is used as a starting point, a second straight line section (BC) which is parallel to the X axis and extends for a certain distance towards the Y axis is made, the end point of the second straight line section (BC) far away from the first outlet point (B) is used as a second outlet point (C) of the volute, then a third straight line section (CD) which is parallel to the first straight line section (AB) is made by using the second outlet point (C) as a starting point, a fourth intersection point (D) of the third straight line section (CD) and the basic molded line (L) is obtained, and the first initial molded line (L1) generated by the method is composed of a part between the fourth intersection point (D) and the third intersection point (A) of the basic molded line (L), the first straight line section (AB), the second straight line section (BC) and the third straight line section (CD; at the moment, the clearance between the fourth intersection point (D) and the base circle (Q) is t, and t is more than or equal to tmin，tminSetting a minimum clearance value for a standard method;
3) generating a second initial profile (L2): if the difference between the gap t and the gap 0.035D2 is greater than 1% D2 or more, the fourth intersection point (D) on the third straight line segment (CD) is shifted clockwise by a certain angle along the first initial profile (L1) to obtain a fifth intersection point (D '), and the second initial profile (L2) thus generated is composed of a portion between the fifth intersection point (D') and the third intersection point (A) of the base profile (L), the first straight line segment (AB), the second straight line segment (BC) and the third straight line segment (CD); the gap between the fifth intersection point (D ') and the base circle (Q) is t ', and t ' ≧ tmin；
4) Generating a third initial profile (L3): taking a sixth intersection point (D ') on a fourth straight-line segment (CD') as a first correction point, wherein the X coordinate of the sixth intersection point (D ') is smaller than the fifth intersection point (D'), and the Y coordinate of the sixth intersection point (D ') is larger than the fifth intersection point (D'); and taking a point on the part of the second initial profile (L2) positioned in the second quadrant of the coordinate system as a second correction point, connecting the part between a fifth intersection point (D ') replacing the second initial profile (L2) and the second correction point through a spline curve between the first correction point and the second correction point so as to generate a third initial profile (L3), and rounding at the sixth intersection point (D') to form the volute tongue of the volute.
2. The volute profile generating method of a centrifugal fan according to claim 1, wherein: in step 4), a third initial profile (L3) is generated by an offset dotting method, the spline curve being a first spline curve (L'), comprising the steps of:
4.1) shifting the parts of the second initial profile (L2) in the first quadrant and the second quadrant of the coordinate system outwards in parallel by one or at least two equal intervals in a direction away from the center (O), wherein the outermost part is a first shifting line (L1), the innermost part is an nth shifting line (ln), n is the number of shifting lines, and the middle parts from the first shifting line (L1) to the nth shifting line (ln) are respectively a second shifting line (L2) … … th ln-1 shifting line (ln-1);
4.2) taking the intersection point of a fourth straight line segment (CD ') and a first offset line (l1) to obtain a sixth intersection point (D'), connecting the sixth intersection point (D ') with a circle center (O) to obtain a fifth straight line segment (OD'), and connecting a second outlet point (C) with the sixth intersection point (D ') to obtain a sixth straight line segment (CD');
4.3) taking the deviation average branching line from the sixth intersection point (D ') to the second correction point at an equal angle relative to the circle center (O), wherein the quantity of the deviation average branching lines is the sum of 1 of the quantity of the deviation lines, the first deviation average branching line (l 1') is superposed with the fifth straight line segment (OD '), the n +1 th deviation average branching line (ln + 1') is a connecting line between the second correction point and the circle center (O), and the middle deviation average branching line (ln +1 ') from the first deviation average branching line (l 1') to the n +1 th deviation average branching line (ln +1 ') is respectively a second deviation average branching line (l 2') … … th 'deviation average branching line (ln'); and sequentially taking an intersection … … of the second offset bisector (L2 ') and the second offset bisector (L2), and an intersection of the nth offset bisector (ln ') and the nth offset line (L), and connecting the sixth intersection (D '), the n-1 intersections of the offset bisectors, and the second correction point to the sixth intersection (D '), by using the first spline curve (L '), thereby generating a third initial profile (L3).
3. The method for generating a volute profile of a centrifugal fan according to claim 2, wherein: the included angle of the connecting line of the second correction point and the circle center (O) relative to the Y axis is 3-20 degrees, and the distance between adjacent offset lines is 0.4-1 mm.
4. The volute profile generating method of a centrifugal fan according to claim 1, wherein: in step 4), a third initial profile (L3) is generated by a rotational dotting method, the spline curve being a second spline curve (N'), comprising the steps of:
4.1) rotating the part between the second correction point and the starting point (F) of the basic profile (L) once or at least twice with equal angle in the direction away from the center (O) by taking the second correction point as the rotation center, wherein the part between the second correction point and the starting point (F) of the basic profile (L) is rotated once or twice with equal angle, the part with the largest rotation angle is a first rotation line (N1), the part with the smallest rotation angle is an m-th rotation line (Nm), m is the number of the rotation lines, and the middle rotation lines (N1) to m-th rotation lines (Nm) are respectively a second rotation line (N2) … …, an m-1 rotation line (Nm-1);
4.2) taking the intersection point of a fourth straight line segment (CD ') and a first rotating line (N1) as a sixth intersection point (D'), wherein the sixth intersection point (D ') is connected with a circle center (O) to obtain a fifth straight line segment (OD'), and the second outlet point (C) is connected with the sixth intersection point (D ') to obtain a sixth straight line segment (CD');
4.3) from the sixth intersection point (D ') to the second correction point, the rotation uniform distribution lines are taken at equal angles relative to the circle center (O), the number of the rotation uniform distribution lines is equal to the number of the rotation lines plus 1, the first rotation uniform distribution line (N1') is overlapped with the fifth straight line segment (OD '), the m + 1-th rotation uniform distribution line (Nm + 1') is a connecting line of the second correction point and the circle center (O), and the middle rotation uniform distribution line (Nm ') from the first rotation uniform distribution line (N1') to the m-th rotation uniform distribution line (Nm ') is the second rotation uniform distribution line (N2') … … Nm 'th rotation uniform distribution line (Nm'); a third initial profile (L3) is generated by sequentially taking the intersection point … … of the second rotation bisector (N2 ') and the second rotation bisector (N2), the intersection point of the mth rotation bisector (Nm') and the mth rotation line (Nm), connecting the sixth intersection point (D ') with the second spline curve (N'), and connecting the N-1 intersection points of the rotation bisectors and the second correction points.
5. The method of generating a volute profile for a centrifugal fan according to claim 4, wherein: the angle delta between the connecting line of the second correction point and the center (O) and the Y axis is 0-30 degrees, and the angle range of each rotation is 0.5-2 degrees.
6. The volute profile generation method of the centrifugal fan according to any one of claims 1 to 5, wherein: the coordinates of the second intersection point (H) are: x is 0, Y is h, the height of the volute is h1, h1-h is more than or equal to 20mm, and the Y coordinate of the first outlet point (B) is h 1.
7. The volute profile generation method of the centrifugal fan according to any one of claims 1 to 5, wherein: the preferable value range of theta 1 is 0-30 degrees.
8. The volute profile generation method of the centrifugal fan according to any one of claims 1 to 5, wherein: the length of the second straight line section (BC) is 1.3-2.0 times of the length between the starting point (F) of the basic molded line (L) and the first intersection point (G).
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