CN111159792B - Volute molded line generation method of centrifugal fan - Google Patents
Volute molded line generation method of centrifugal fan Download PDFInfo
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- CN111159792B CN111159792B CN202010014412.6A CN202010014412A CN111159792B CN 111159792 B CN111159792 B CN 111159792B CN 202010014412 A CN202010014412 A CN 202010014412A CN 111159792 B CN111159792 B CN 111159792B
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Abstract
The application discloses a volute molded line generating 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 a basic molded line, and obtaining the basic molded line through a spiral line equation; the method also comprises the following steps: 2) Generating a first initial molded line: a third intersection point which is close to the tail end of the basic molded line is obtained by anticlockwise rotation of the X-axis by a certain angle, a first straight line segment which is tangential to the basic molded line is obtained, a second straight line segment is obtained by taking a first outlet point on the first straight line segment as a starting point, then a third straight line segment which is parallel to the first straight line segment is obtained by taking a second outlet point on the second straight line segment as a starting point, and a fourth intersection point of the third straight line segment and the basic molded line is obtained; 3) Generating a second initial molded line: a fourth intersection point on the third straight line segment is shifted clockwise by a certain angle along the first initial molded line to obtain a fifth intersection point, and a second initial molded line is generated; 4) And correcting the second initial molded line to obtain a third initial molded line.
Description
Technical Field
The application relates to a power device, in particular to a volute molded line generating method of a centrifugal fan.
Background
The centrifugal fan volute has two functions, one of which 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 needed potential energy. The volute molded line is a boundary for restricting the movement of fluid in the volute, and 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 noise and 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 common volute base circle D2 is between 50 and 500mm, the circumferential clearance value between the top end of a volute tongue and the outer circumference of an impeller is t= (0.05-0.1) D2, and the circular arc radius of the top end of the volute tongue is r= (0.03-0.05) D2. For small fan systems, the clearance value can only be a minimum value in the recommended range in many cases, and in order to be able to reduce the noise further, a larger volute tongue clearance must be taken.
At present, two methods for increasing the volute tongue clearance exist, namely, the first method is to dynamically adjust the volute tongue clearance: the application discloses a volute tongue disclosed in China patent with the application number of 201711451180.5, which comprises a support frame and a flexible volute tongue wall arranged on the support frame to form the outer contour of the volute tongue, wherein the support frame comprises an upper support body and a lower support body which are arranged at the root of the volute tongue, a variable R cylinder arranged at the head of the volute tongue, and a driving mechanism for driving the variable R cylinder to rotate, so that the variable R adjustment of the volute tongue can be realized by driving the variable R cylinder to rotate, and the gap between the volute tongue and an impeller is changed, thereby improving the performance of a fan or reducing noise, and enabling the volute tongue to be better suitable for various actual conditions. The dynamic adjustment mode has complex mechanism and higher cost.
The second is to use a stepped volute tongue: the utility model provides a slope ladder volute tongue fan spiral case of chinese patent publication of application number 201510782850.6, includes spiral case front bezel, spiral case back bezel and presss from both sides to locate the annular wall between spiral case front bezel, the spiral case back bezel leaves the air outlet of fan on the annular wall, 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 the buffer of multipohasing on the slope ladder volute tongue for the impact of buffering air current to slope ladder volute tongue can make this fan effectively reduce noise. However, the step volute tongue is poor in sound quality due to the fact that the two volute tongues collide at a large flow rate, and meanwhile the step volute tongue is difficult to process and needs to be independently processed and assembled by plastic parts.
Disclosure of Invention
The application aims to solve the technical problem of providing a volute molded line generating method of a centrifugal fan, which is simple and easy to process and has low noise in the case of large flow.
The technical scheme adopted for solving the technical problems is as follows: a volute molded line generating 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 origin of the coordinate system as a circle center, obtaining a base circle with a radius of D2, taking a point in the positive direction of the X axis as a starting point of a basic molded line, obtaining the basic molded line through a spiral line equation, wherein the X axis and the basic molded line are provided with a first intersection point near 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 are provided with a second intersection point, and the second intersection point is positioned in the positive direction of the Y axis and is the highest point of the basic molded line; the method is characterized in that: the method also comprises the following steps:
2) Generating a first initial molded line: the method comprises the steps of rotating an X axis anticlockwise for a certain angle to obtain a third intersection point close to the tail end of a basic molded line, and obtaining a first straight line section tangent to the basic molded line, wherein the first straight line section is tangent to the third intersection point, the inclination angle of the first straight line section is theta 1, the end point of the first straight line section, which is far away from the third intersection point, is a first outlet point of a volute, takes the first outlet point as a starting point, serves as a second straight line section which is parallel to the X axis and extends for a certain distance towards the Y axis, the end point of the second straight line section, which is far away from the first outlet point, is a second outlet point of the volute, and then takes the second outlet point as a starting point, serves as a third straight line section which is parallel to the first straight line section, so that a fourth intersection point of the third straight line section and the basic molded line is obtained, and the first initial molded line generated by the part between the fourth intersection point of the basic molded line and the third intersection point, the first straight line section, the second straight line section and the third straight line section; at the moment, the gap between the fourth intersection point and the base circle is t, and t is more than or equal to t min ，t min Setting a minimum gap value for a standard method;
3) Generating a second initial molded line: if t and t min The difference value of the first and second intersection points is more than 1%D2, so that a fourth intersection point on the third straight line section is offset by a certain angle along the first initial line to obtain a fifth intersection point, and a second initial line generated by the first intersection point is composed of a part between the fifth intersection point and the third intersection point of the basic line, the first straight line section, the second straight line section and the third straight line section; at the moment, the gap between the fifth intersection point and the base circle is t ', and t' is more than or equal to t min ；
4) Generating a third initial molded line: taking a sixth intersection point as a first correction point on the fourth straight line segment, 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 molded line, which is positioned in the second quadrant of the coordinate system, as a second correction point, connecting a fifth intersection point of the second initial molded line and the part between the second correction point by a spline curve between the first correction point and the second correction point so as to generate a third initial molded line, and rounding off at the sixth intersection point to form a volute tongue of the volute.
According to one aspect of the present application, in step 4), a third initial line is generated by an offset dotting method, and the spline curve is a first spline curve, including the steps of:
4.1 The parts of the second initial molded lines in the first quadrant and the second quadrant of the coordinate system are shifted outwards by one or at least two equidistant parallel to the direction away from the center of the circle, the outermost side is a first shifting line, the innermost side is an nth shifting line, n is the number of shifting lines, and the middle of the second initial molded lines from the first shifting line to the nth shifting line are respectively a second shifting line … … and an n-1 shifting line;
4.2 Taking an intersection point of the 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 The offset average line is taken from the sixth intersection point to the second correction point at the same angle relative to the circle center, the number of the offset average lines is 1 added to the number of the offset lines, the first offset average line is overlapped with the fifth straight line segment, the n+1th offset average line is the connection line between the second correction point and the circle center, and the middle offset average lines from the first offset average line to the n+1th offset average line are respectively the second offset average line … … and the n' offset average line; and sequentially taking the intersection point … … of the second offset average line and the second offset line and the intersection point of the nth offset average line and the nth offset line, and connecting the sixth intersection point, the n-1 intersection points of the offset average lines and the corresponding offset lines and the second correction points by using the first spline curve, thereby generating a third initial molded line.
Preferably, the included angle of the connecting line of the second correction point and the circle center relative to 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 application, in step 4), a third initial line is generated by a rotational dotting method, the spline curve being a second spline curve, comprising the steps of:
4.1 Rotating a part between the second correction point and the starting point of the basic molded line at least twice in a direction away from the center of a circle by one or equal angles by taking the second correction point as a rotation center, wherein the rotation angle is the first rotation line with the largest rotation angle, the rotation angle is the mth rotation line with the smallest rotation angle, m is the number of rotation lines, and the m-1 rotation lines from the first rotation line to the mth rotation line in the middle are respectively the second rotation line … …;
4.2 Taking the intersection point of the fourth straight line segment and the first rotation line as the 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 The rotation average line is taken from the sixth intersection point to the second correction point at the same angle relative to the circle center, the number of the rotation average lines is 1 added to the number of the rotation lines, the first rotation average line is overlapped with the fifth straight line segment, the m+1th rotation average line is the connection line between the second correction point and the circle center, and the rotation average lines from the first rotation average line to the m are respectively the second rotation average line … … Nm' rotation average 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, the n-1 intersection points of the rotation average lines and the corresponding rotation lines and the second correction points by using a second spline curve, thereby generating a third initial molded line.
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=0, Y=h, the volute height is h1, h1-h is more than or equal to 20mm, and the Y coordinate of the first outlet point is h1.
Preferably, the value range of θ1 is preferably 0 to 30 degrees.
Preferably, the length of the second straight line segment is 1.3 to 2.0 times the length between the starting point of the basic molded line and the first intersection point.
Compared with the prior art, the application has the advantages that: the tail end of the spiral basic molded line is prolonged, the outlet is inclined to the volute tongue, the parts positioned in the first quadrant and the second quadrant are corrected by using spline curves, the volute tongue clearance is increased, and the noise is reduced.
Drawings
FIG. 1 is a schematic view of a profile generated in step 1) of a method for generating a volute profile according to an embodiment of the present application;
fig. 2 is a schematic diagram of a molded line generated in step 2) of a method for generating a molded line of a volute according to an embodiment of the present application;
fig. 3 is a schematic diagram of a volute obtained after stretching a molded line generated in step 2) of the method for generating a volute molded line according to an embodiment of the present application;
FIG. 4 is a schematic diagram comparing the rounded shape of the molded line generated in step 2) of the method for generating a molded line of a volute of the embodiment of the application with the prior art;
FIG. 5 is a schematic diagram of a second initial profile generated by the method for generating a volute profile according to an embodiment of the present application;
FIG. 6 is a schematic diagram illustrating a first mode correction of a first initial profile generated by a method for generating a volute profile according to an embodiment of the present application;
FIG. 7 is an enlarged schematic view of portion I of FIG. 6;
FIG. 8 is a schematic diagram of a second modification of a first initial profile generated by a method for generating a volute profile according to an embodiment of the present application;
fig. 9 is an enlarged schematic view of the portion ii of fig. 8.
Detailed Description
Embodiments of the present application are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same 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 application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings are merely for purposes of describing the present application and simplifying the description, and do not indicate or imply that the device or element being referred to must have a specific orientation, be configured and operated in a specific orientation, and because the disclosed embodiments of the present application may be arranged in different orientations, these directional terms are merely for illustration and should not be construed as limitations, such as "upper", "lower" are not necessarily limited to orientations opposite or coincident with the direction of gravity. Furthermore, features defining "first", "second" may include one or more such features, either explicitly or implicitly.
The spiral line of the centrifugal fan is generally a spiral line, and the spiral line equation is known as r=r2×exp (m×θ) through fluid mechanics calculation, wherein R2 is the radius of the outer circle of the impeller, and M is a parameter related to the fluid property. After R2 and M are determined, the basic molded line (spiral line) of the spiral case can be obtained. Or the base profile may be obtained in other existing ways.
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 overall noise and backflow. Hereinafter, counterclockwise means a rotation direction from the positive X-axis direction toward the positive Y-axis direction, and clockwise means a rotation direction from the positive Y-axis direction toward the positive X-axis direction.
A typical feature of the volute is that as the angle increases, the points on the curve are farther and farther from the center point, and the larger the gap in the volute tongue, the lower the noise. The method of the present application is designed based on the above principle.
Example 1
The application relates to a volute molded line generating method of a centrifugal fan, which comprises the following steps:
1) Obtaining a basic molded line L: as shown in fig. 1, a coordinate system is established, an X axis and a Y axis perpendicular to the X axis are determined, and a base circle Q with a radius of D2 is obtained by taking an origin of the coordinate system as a circle center O, wherein the base circle Q is shown by a dotted line in fig. 1 and represents the outer circle of an impeller of the centrifugal fan; taking a point in the positive direction of the X axis as a starting point F of a basic molded line L, obtaining the basic molded line L through the spiral line equation R=D2X EXP (m X theta), wherein theta is an angle of a point on the spiral line relative to the positive direction of the X axis, a first intersection point G is arranged at the position, close to the tail end, of the X axis and the basic molded line L, 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, and the quadrants are defined as a common 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 positioned in the positive direction of the Y axis and is the highest point of the basic molded line L, the coordinates of the second intersection point H are (X=0, Y=h), the height of the reserved volute is H1, H1-H is more than or equal to 20mm, and as a reserved processing space, the total height of the whole volute molded line is correspondingly determined after the height of H1 is fixed. 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 h1.
2) Generating a first initial line L1: referring to fig. 2, a third intersection point a near the end of the base line L is obtained from the counterclockwise rotation angle θ1 of the X-axis, and a first line segment AB (the inclination angle is θ1) tangent to the base line L is obtained, the value range of θ1 is preferably 0-30 degrees, more preferably 12-18 degrees, the first line segment AB is tangent to the base line at the third intersection point a, and the other end point B of the first line segment AB is the first outlet point of the volute. After the basic molded line L is determined, the length between the starting point F and the first intersection point G is fixed, a first outlet point B is taken as the starting point, a second straight line segment BC which is parallel to the X axis and extends towards the Y axis is made, 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, of the length between the starting point F and the first intersection point G, and the initial size which meets the requirement of the external environment is selected according to actual practice; then taking the second outlet point C as a starting point to serve as a third straight line segment CD of a parallel line with the first straight line segment AB, and obtaining a fourth intersection point D with the basic molded line L; detecting a gap t between the fourth intersection point D and the base circle Q, if t is more than or equal to t min (the minimum gap value is set by the standard method, generally 0.035D2), the initial draft can be basically set, and the first initial line L1 is generated up to this point, and is composed of the basic line L, the first line segment AB, the second line segment BC, and the third line segment CD.
At this time, if the overall stretching length B is perpendicular to the first initial line L1, i.e., perpendicular to the paper surface direction of fig. 2, the annular wall 1 of the volute is obtained, and the arrow in fig. 3 indicates the stretching direction; thereafter, the fourth intersection point D is rounded to form a volute tongue, so as to obtain an optimized molded line L4 shown in fig. 4, and referring to fig. 4, the optimized molded line L4 is compared with a volute molded line in the prior art, wherein the straight line segment B1C1 is a volute outlet in the prior art, D1 is a volute tongue position in the prior art, the straight line segment AB1 in the prior art is perpendicular to the X axis, and compared with a molded line in the prior art (in a manner that the second intersection point G is directly and vertically upwards used as an outlet), the optimized molded line L4 is inclined to generate an outlet and a volute tongue, so that the position of the volute tongue is entirely shifted to the Y axis, the volute tongue gap t is increased, and noise is reduced.
The optimized line L4, the radius of the arc at the top end of the volute tongue is r= (0.03-0.05) D2, the stretching length B=1-1.4b, and B is the length of the impeller.
3) Generating a second initial line L2: if the gap t is large, it is larger than t min In order to increase the static pressure by a value of 1% D2 or more, the flow rate may be reduced by shifting the fourth intersection point D of the third straight line segment CD clockwise by a predetermined angle along the first initial line L1 to obtain a fifth intersection point D ', and forming the fourth straight line segment CD' between the second exit point C and the fifth intersection point D ', thereby generating the second initial line L2 composed of the basic 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 smaller than 30 degrees, and the gap t' between the fifth intersection D 'and the base circle Q also satisfies the above requirement, t'. Gtoreq.t min At this time, the outlet of the volute is gradually enlarged, and the effect of reducing the flow speed and increasing the static pressure is achieved.
4) Generating a third initial line L3: in a smaller space, the static pressure needs to be increased and the flow speed needs to be reduced, so that the angles of the third straight line segment CD and the fourth straight line segment CD' need to be enlarged, and the volute tongue clearance necessarily becomes smaller after the angles are enlarged, thereby meaning that the noise is increased. The method described below is applicable to methods that also increase the volute tongue clearance after the fourth straight line segment CD' is angularly fixed. The method is also suitable for other occasions, is limited by the structure or diffusion requirement, and can increase the volute tongue clearance and reduce the noise when the CD angle of the third straight line segment is larger and can not be changed.
Is limited by the installation environment or other constraints such that the range of inclination angles of the first straight line segment AB and the length of the second straight line segment BC is small. Even with maximum, the volute tongue clearance t remains small or the volute tongue is still noisier. The following steps are implemented using offset dotting, see fig. 6 and 7:
4.1 The part of the second initial line L2 positioned in the first quadrant and the second quadrant of the coordinate system is offset outwards in parallel in the direction away from the circle center O, and the gap between the two adjacent offset lines is not excessively large, and the value is between 0.4 and 1mm. One or at least two equal-interval offset lines are outwards offset according to requirements and actual conditions, wherein the outermost side (the farthest from the second basic molded line L) is a first offset line L1, the innermost side (the closest to the second initial molded line L2) is an nth offset line ln, n is the number of offset lines, and the middle offset lines from the first offset line L1 to the nth offset line ln are second offset lines L2 … … and the n-1 offset line ln-1 respectively. In the present embodiment, there are five offset lines, namely, 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 l5.
4.2 An intersection point of the original fourth straight line segment CD 'and the first offset line l1 is a sixth intersection point D' which is used as a first correction point and is connected with the circle center O to obtain a fifth straight line segment OD ', the second outlet point C is connected with a sixth intersection point D' to obtain a sixth straight line segment CD ', wherein the sixth straight line segment CD' is a part of the original fourth straight line segment CD ', and the X coordinate of the sixth intersection point D' is smaller than the fifth intersection point D ', and the Y coordinate 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 positioned in the second quadrant, wherein the included angle of the 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 E is in the second quadrant, and thus the intersection of the newly generated molded lines is in the second quadrant, and if taken in the first quadrant, it is easy to induce surging and increase noise.
4.3 And taking average lines from the sixth intersection point D' to the seventh intersection point E at equal angles relative to the circle center O, wherein the number of the offset average lines is 1 plus the number of the offset lines. The first offset average line l1 'coincides with the fifth straight line segment OD ", the n+1th offset average line ln+1' is a connection line between the seventh intersection point E and the circle center O, the middle offset average lines ln+1 'from the first offset average line l1' to the n+1th offset average line l1 'are respectively the second offset average line l2' … … and the n 'offset average line ln', in this embodiment, six offset average lines are total, and are respectively the first offset average line l1', the second offset average line l2', the third offset average line l3', the fourth offset average line l4', the fifth offset average line l5 'and the sixth offset average line l6'. And sequentially taking the intersection point … … of the second offset average line L2 'and the second offset line L2, and the intersection point of the nth offset average line ln' and the nth offset line L, connecting a sixth intersection point D 'with n-1 intersection points of the above offset average lines and the corresponding offset lines and a seventh intersection point E by using a first straight line L', wherein the interface part of the first straight line L 'and the second initial line L and the sixth straight line CD' can be subjected to rounding excessive treatment, the minimum distance between the rounded corners is larger than the two offset lines, and the distance between the rounded corners is generally ten times of the offset lines, so that a third initial line L3 is generated, and the third initial line L3 is composed of an EA section, a first straight line AB, a second straight line BC and a sixth straight line CD 'of the first straight line L'. The third initial line L3 increases the volute tongue clearance and can be expanded. In addition, if the distance between the leftmost two points shown in fig. 6 is less than 0.5mm, no treatment is performed. And rounding off at a sixth intersection point D' to form a volute tongue of the volute.
The maximum volute tongue clearance can be increased by 0.01D-0.04D through the offset dotting method, but the clearance is increased by not more than 0.1D2.
Example two
Referring to fig. 8 and 9, in the present embodiment, a third initial line L3 is generated by using a rotational dotting method instead of the offset dotting method described above, which is different from the first embodiment described above. The method comprises the following steps:
4.1 Taking a point I at the part of the second initial molded line L2 positioned in the second quadrant, rotating the curve section IF once or twice at equal angles in the direction away from the circle center O by taking the point I as a rotation center, wherein the rotation center I is taken as a second correction point, the angle delta between the connecting line of the second initial molded line L2 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 rotation angle is the first rotation line N1 with the largest rotation angle, the m rotation line Nm with the smallest rotation angle is the number of rotation lines, and the m-1 rotation line Nm-1 from the first rotation line N1 to the m rotation line Nm in the middle is the second rotation line N2 … … respectively. In the present embodiment, there are five rotation lines, namely, a first rotation line N1, a second rotation line N2, a third rotation line N3, a fourth rotation line N4, and a fifth rotation line N5.
4.2 An intersection point of the original fourth straight line segment CD ' and the first rotation line N1 is a sixth intersection point D ' which is used as a first correction point and is connected with the circle center O to obtain a fifth straight line segment OD ', the second outlet point C is connected with a 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 The rotation average line is taken from the sixth intersection point D' to the rotation center I at the same angle relative to the circle center O, and the number of the rotation average lines is 1 plus the number of the rotation lines. The first rotation average line N1 'coincides with the fifth straight line segment OD ", the m+1th rotation average line nm+1' is a connection line between the rotation center I and the circle center O, the middle rotation average line Nm 'from the first rotation average line N1' to the m rotation average line Nm 'is the second rotation average line N2' … … Nm 'rotation average line Nm', in this embodiment, six rotation average lines are shared, which are the first rotation average line N1', the second rotation average line N2', the third rotation average line N3', the fourth rotation average line N4', the fifth rotation average line N5', and the sixth rotation average line N6', respectively. Sequentially taking the intersection point … … of the second rotation average line N2' and the second rotation line N2, namely the intersection point of the mth rotation average line Nm ' and the mth rotation line Nm, connecting a sixth intersection point D ' by using a second spline curve N ', connecting the above N-1 intersection points of the rotation average lines and the corresponding rotation lines and a rotation center I, and performing rounding corner excessive treatment on the interface part of the second spline curve N ' and the second initial line L and the sixth straight line segment CD ', wherein the distance between the minimum rounded corner and the two offset lines is generally ten times the offset line distance, so that a third initial line L3 is generated, and the third initial line L3 is composed of an IA segment, a first straight line segment AB, a second straight line segment BC and a sixth straight line segment CD '. And rounding off at a sixth intersection point D' to form a volute tongue of the volute.
Claims (8)
1. A volute molded line generating method of a centrifugal fan comprises the following steps:
1) Obtaining a basic molded line (L): establishing a coordinate system, determining an X axis and a Y axis, taking an origin of the coordinate system as a circle center (O), obtaining 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), obtaining the basic molded line (L) through a spiral line equation, wherein a first intersection point (G) is arranged at the position, close to the tail end, of the X axis and the basic molded line (L), the X coordinate of the first intersection point (G) is larger 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 positioned 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: the method also comprises the following steps:
2) Generating a first initial profile (L1): a third intersection point (A) close to the tail end of the basic molded line (L) is obtained by anticlockwise rotating a certain angle from the X axis, a first straight line segment (AB) tangent to the basic molded line (L) is obtained, the first straight line segment (AB) is tangent to the third intersection point (A) with the basic molded line (L), the inclination angle of the first straight line segment (AB) is theta 1, the end point of the first straight line segment (AB) away from the third intersection point (A) is a first outlet point (B) of the volute, the first outlet point (B) is used as a starting point, a second straight line segment (BC) parallel to the X axis and extending a certain distance towards the Y axis is formed, the end point of the second straight line segment (BC) away from the first outlet point (B) is a second outlet point (C) of the volute, then the second straight line segment (CD) parallel to the first straight line segment (AB) is used as a starting point, and a fourth intersection point (D) of the third straight line segment (CD) with the basic molded line (L) is obtained, and the first initial straight line segment (L1) is formed by the intersection point (D) of the fourth straight line segment (B) and the third straight line segment (A) and the third straight line segment (CD) which are formed by the first intersection point (A) and the third straight line segment (C) is formed; at the moment, the gap between the fourth intersection point (D) and the base circle (Q) is t, and t is more than or equal to t min ，t min Setting a minimum gap value for a standard method;
3) Generating a second initial profile (L2): if the difference between the gaps t and 0.035D2 is greater than 1% D2, the fourth intersection point (D) on the third straight line segment (CD) is along the first initial pointThe initial line (L1) is shifted clockwise by a certain angle to obtain a fifth intersection point (D '), and the generated second initial line (L2) consists of a part between the fifth intersection point (D') and the third intersection point (A) of the basic line (L), a first straight line segment (AB), a second straight line segment (BC) and a third straight line segment (CD); at this time, the gap between the fifth intersection point (D ') and the base circle (Q) is t ', and t '. Gtoreq.t is satisfied min ；
4) Generating a third initial profile (L3): taking a sixth intersection point (D ') as a first correction point on the fourth straight-line segment (CD '), wherein the X coordinate of the sixth intersection point (D ') is smaller than the fifth intersection point (D '), and the Y coordinate is larger than the fifth intersection point (D '); taking a point on the part of the second initial molded line (L2) located in the second quadrant of the coordinate system as a second correction point, connecting a fifth intersection point (D ') of the second initial molded line (L2) and the part between the second correction point by spline curves between the first correction point and the second correction point so as to generate a third initial molded line (L3), and rounding a volute tongue of the volute at a sixth intersection point (D').
2. The method for generating a volute molded line of a centrifugal fan according to claim 1, wherein: in step 4), a third initial line (L3) is generated by offset dotting, said spline curve being a first spline curve (L'), comprising the steps of:
4.1 The parts of the second initial molded line (L2) in the first quadrant and the second quadrant of the coordinate system are shifted outwards by one or at least two equidistant parallel to the direction away from the center (O), the outermost side is a first shifting line (L1), the innermost side is an nth shifting line (ln), n is the number of shifting lines, and the middle of the second initial molded line (L2) is a second shifting line (L2) … … (ln-1) and the nth shifting line (ln-1) is a second shifting line (L1);
4.2 Taking the intersection point of the fourth straight line segment (CD ') and the first offset line (l 1) to obtain a sixth intersection point (D'), wherein the sixth intersection point (D ') is connected with the 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 Taking offset average lines from the sixth intersection point (D ') to the second correction point at equal angles relative to the circle center (O), wherein the number of the offset average lines is 1 added to the number of offset lines, the first offset average line (l 1') coincides with the fifth straight line segment (OD '), the n+1th offset average line (ln+1') is a connecting line between the second correction point and the circle center (O), and the middle offset average lines (ln+1 ') from the first offset average line (l 1') to the n+1th offset average line (ln ') are respectively second offset average line (l 2') … … th n 'offset average line (ln'); and sequentially taking the intersection point … … of the second offset average line (L2 ') and the second offset line (L2), the intersection point of the nth offset average line (ln') and the nth offset line (ln), and connecting the sixth intersection point (D ') with the n-1 intersection points of the above offset average lines and the corresponding offset lines and the second correction point by using the first spline curve (L'), thereby generating a third initial molded line (L3).
3. The method for generating the volute molded line of the centrifugal fan according to claim 2, wherein: the included angle between the connecting line of the second correction point and the circle center (O) and the Y axis is 3-20 degrees, and the distance between adjacent offset lines is 0.4-1 mm.
4. The method for generating a volute molded line of a centrifugal fan according to claim 1, wherein: in step 4), a third initial line (L3) is generated by a rotational dotting method, the spline curve being a second spline curve (N'), comprising the steps of:
4.1 Rotating a part between the second correction point and the starting point (F) of the basic molded line (L) at least twice in a direction away from the center (O) by one time or at equal angles with the second correction point as a rotation center, wherein the rotation angle is the first rotation line (N1) with the largest rotation angle, the m-th rotation line (Nm) with the smallest rotation angle, the m is the number of rotation lines, and the m-1 rotation lines (Nm-1) from the first rotation line (N1) to the m-th rotation line (Nm) are respectively the second rotation line (N2) … …;
4.2 Taking an intersection point of the fourth straight line segment (CD ') and the first rotation line (N1) as a sixth intersection point (D'), connecting the sixth intersection point (D ') with the circle center (O) to obtain a fifth straight line segment (OD'), and connecting the second outlet point (C) with the sixth intersection point (D ') to obtain a sixth straight line segment (CD');
4.3 Taking rotation average lines from the sixth intersection point (D ') to the second correction point at the same angle relative to the circle center (O), wherein the number of the rotation average lines is 1 added to the number of the rotation lines, the first rotation average line (N1 ') is overlapped with the fifth straight line segment (OD '), the m+1th rotation average line (Nm+1 ') is a connecting line of the second correction point and the circle center (O), and the middle rotation average lines (N1 ') to (Nm ') are respectively second rotation average line (N2 ') … … Nm ' rotation average lines (Nm '); sequentially taking intersection points … … of the second rotation average line (N2 ') and the second rotation line (N2), namely intersection points of the mth rotation average line (Nm') and the mth rotation line (Nm), and connecting a sixth intersection point (D ') with a second spline curve (N'), wherein N-1 intersection points of the rotation average lines and the corresponding rotation lines and a second correction point are connected, so that a third initial molded line (L3) is generated.
5. The method for generating a volute molded line of a centrifugal fan according to claim 4, wherein: the angle delta between the connecting line of the second correction point and the circle center (O) and the Y axis is 0-30 degrees, and the angle range of each rotation is 0.5-2 degrees.
6. The method for generating a volute molded line of a centrifugal fan according to any one of claims 1 to 5, characterized by: the coordinates of the second intersection point (H) are: x=0, Y=h, the height of the volute is h1, h1-h is not less than 20mm, and the Y coordinate of the first outlet point (B) is h1.
7. The method for generating a volute molded line of a centrifugal fan according to any one of claims 1 to 5, characterized by: the value range of theta 1 is 0-30 degrees.
8. The method for generating a volute molded line of a centrifugal fan according to any one of claims 1 to 5, characterized by: the length of the second straight line segment (BC) is 1.3-2.0 times the length between the starting point (F) of the basic molded line (L) and the first intersection point (G).
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