CN110985442B - Elliptical baffle structure and design method for reducing pressure pulsation of centrifugal pump - Google Patents

Abstract

The present invention discloses an elliptical baffle tongue structure and a design method thereof for reducing pressure pulsation of a centrifugal pump. The centrifugal pump comprises a volute and an impeller, wherein the impeller is eccentrically arranged in a cavity inside the volute, an upper outlet is provided on one side of the volute, and a baffle tongue is formed on the upper side of the cavity near the upper outlet, wherein the inner contour line of the baffle tongue is sequentially arranged into a sine curve and an elliptical line along the direction from the cavity to the bottom of the upper outlet. The present invention can effectively reduce the pressure pulsation in the centrifugal pump, especially the optimization effect at the baffle tongue where the pressure pulsation is most serious is more obvious, so that the dynamic and static interference effect of the impeller and the baffle tongue is reduced to a lower level, and the noise and vibration during the operation of the centrifugal pump are effectively reduced.

Description

Elliptical baffle structure and design method for reducing pressure pulsation of centrifugal pump

Technical Field

The invention relates to an internal structure of a centrifugal pump and a design method thereof in the field of fluid machinery, and in particular to an elliptical baffle tongue design method for reducing pressure pulsation of a centrifugal pump.

Background Art

As an important fluid conveying machine, centrifugal pumps are increasingly widely used in chemical, petroleum, electric power, metallurgy, coal, aerospace and other fields. According to statistics, the power consumption of pumps accounts for about 15% of the total power generation in the country. The stability of centrifugal pump operation is of great significance to the entire working system. However, during the operation of the centrifugal pump, the flow of fluid inside the centrifugal pump is complex, and its pulsation-induced vibration and noise seriously affect the equipment itself and the surrounding environment, which seriously affects the stable operation of the centrifugal pump.

The noise and vibration inside the centrifugal pump are mainly caused by the dynamic and static interference between the volute and the impeller. In particular, the volute baffle is a very important factor affecting the pressure pulsation and radial force of the internal flow field of the centrifugal pump. Traditional designs generally only consider changing the outer diameter of the impeller or the base diameter of the volute to improve the flow of the internal fluid, but the effect is not ideal.

Summary of the invention

In view of the shortcomings of the prior art, the present invention provides a method for designing an elliptical baffle for reducing the pressure pulsation of a centrifugal pump, thereby reducing the internal pressure pulsation of the centrifugal pump and achieving the effect of reducing vibration and noise.

The present invention achieves the above technical objectives through the following technical means.

1. An elliptical tongue structure for reducing pressure pulsation of a centrifugal pump:

The centrifugal pump includes a volute and an impeller. The impeller is eccentrically arranged in a cavity inside the volute. The inner contour line of the volute cavity is a spiral line. An upper outlet is provided on one side of the volute. A baffle is formed on the side of the upper part of the cavity close to the upper outlet. The inner contour line of the baffle is arranged in sequence into a sine curve and an elliptical line along the direction from the cavity to the bottom of the upper outlet.

One end of the sine curve is tangently connected to the inner contour line of the volute cavity, the other end of the sine curve is tangently connected to one end of the ellipse line, and the other end of the ellipse line is connected to the bottom edge of the upper outlet.

The main body of the inner contour line of the partition tongue is an ellipse line, and the ellipse line and the inner contour line of the volute cavity are transitioned through a sine curve.

2. A design method for an elliptical tongue structure to reduce pressure pulsation of a centrifugal pump:

1) Draw a straight line through the center of the impeller at O as the radial line. The radial line forms an acute angle θ with the horizontal line on the upper outlet side. The acute angle θ is set according to the following formula. The radial line intersects the spiral line of the inner contour line of the volute cavity at point B:

Where, t is the maximum curvature of the spiral line of the inner contour line of the volute cavity; r is the base circle radius of the impeller, mm;

2) Draw a straight line perpendicular to line segment OB through point B as the tangent line, and then draw a vertical direction line through the starting point A of the spiral line of the inner contour line of the volute cavity, and then draw a straight line close to point B and at an angle α with the vertical direction line through the starting point A of the spiral line of the inner contour line of the volute cavity as the reference line. The starting point A of the spiral line of the inner contour line of the volute cavity is located on the horizontal line of the upper outlet side. The intersection C of the tangent line and the reference line is the starting point of the volute tongue. The acute angle between line segment OC and line segment OA is the placement angle of the tongue.

3) Take the line BC connecting points B and C as the major axis of the ellipse, and the shortest distance from point B to the impeller contour as the length of the minor semi-axis of the ellipse, and draw an elliptical curve. The elliptical curve and the circle with the impeller center O and radius as the connecting line OB intersect at point D;

4) Draw a perpendicular line through D and intersect the line BC at point E. Draw an elliptical curve with point E as the center of the ellipse, line DE as the minor semi-axis, and line EC as the major semi-axis. The curve segment CD on the elliptical curve is used as the main shape line of the tongue.

5) Set a sine curve between point B and point D, with B as the origin and the direction of line BD as the x-axis, and the direction perpendicular to line BD as the y-axis. Determine the sine curve according to the following formula, and take the first and second period parts of the sine curve as the remaining shape line of the tongue;

Where, n is the speed of the centrifugal pump, r/min;

Q—rated flow rate of centrifugal pump, m ³ /s;

H—rated head of centrifugal pump, m;

L—the distance between point B and point D, mm;

A—sinusoidal amplitude, mm.

The angle α is taken as follows: 2° when the specific speed of the centrifugal pump is between 10 and 80, 3° when the specific speed is greater than 80 to 150, and 5° when the specific speed is greater than 150 to 300.

Beneficial effects of the present invention:

The beneficial effect of the present invention is that according to the centrifugal pumps with different working requirements, the parameters obtained from the centrifugal motion law of the fluid are used to design the tongue-shaped line. The elliptical line at the tongue-shaped part can effectively reduce the pressure pulsation at the tongue-shaped part, thereby reducing vibration and noise; the sinusoidal line between the elliptical curve and the spiral line can effectively reduce the turbulence of the fluid and improve the overall efficiency of the centrifugal pump.

The present invention can effectively reduce the pressure pulsation in the centrifugal pump, especially the optimization effect is more obvious at the diaphragm where the pressure pulsation is most serious, so that the dynamic and static interference effects of the impeller and the diaphragm are reduced to a low level, and the noise and vibration of the centrifugal pump during operation are effectively reduced. The optimization effect is better for high specific speed centrifugal pumps.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a schematic diagram of the overall design of the tongue-shaped line;

FIG2 is a schematic diagram showing the establishment of the angle of the starting endpoint of a sine curve;

FIG3 is a schematic diagram showing the establishment of the terminal points of the tongue-separating elliptic curve;

Fig. 4 is a schematic diagram of an elliptical curve of a tongue partition;

FIG5 is a schematic diagram of a sine curve;

FIG6 is a comparison diagram of pressure fluctuations between the centrifugal pump of the present invention and a standard centrifugal pump;

FIG. 7 is a pressure pulsation spectrum diagram of the centrifugal pump of the present invention and a standard centrifugal pump.

In the figure: volute (1), impeller (2), baffle (3), sinusoidal curve (4) and elliptical line (5).

DETAILED DESCRIPTION

The present invention is further described below in conjunction with the accompanying drawings and specific examples, but the protection scope of the present invention is not limited thereto.

As shown in Figure 1, the centrifugal pump includes a volute 1 and an impeller 2. The impeller 2 is eccentrically arranged in the cavity inside the volute 1. The inner contour line of the cavity of the volute 1 is a spiral line. An upper outlet is provided on one side of the volute 1. A baffle tongue 3 is formed on the side of the upper part of the cavity close to the upper outlet. The inner contour line of the baffle tongue 3 is connected between the direction from the cavity to the bottom of the upper outlet.

The embodiments of the present invention and their implementation are as follows:

1) As shown in FIG2 , in this example, a closed structure centrifugal pump is designed, and the parameters are: rated flow 46.3m ³ /h, rated head 480.6m, impeller speed 14400r/min, impeller outer diameter 116mm, volute base circle radius 62mm. Volute outlet width 80mm. The impeller center is O, and the starting point of the spiral is A.

A straight line is drawn through the center O of the impeller 2 as a radial line. The radial line forms an acute angle θ with the horizontal line on the upper outlet side. The acute angle θ is set according to the following formula. The radial line intersects the spiral line of the inner contour line of the volute 1 cavity at point B:

2) Draw a straight line perpendicular to the line segment OB through point B as the tangent line, and then draw a vertical direction line through the starting point A of the spiral line of the inner contour line of the volute 1 cavity, and then draw a straight line close to point B and at an angle α with the vertical direction line through the starting point A of the spiral line of the inner contour line of the volute 1 cavity as the reference line. The starting point A of the spiral line of the inner contour line of the volute 1 cavity is located on the horizontal line on the upper outlet side, and the intersection C of the tangent line and the reference line is the starting point of the volute baffle. In the specific implementation, the angle α is taken as 5°. 3) As shown in Figure 3, with the line BC connecting points B and C as the major axis of the ellipse, and the shortest distance from point B to the contour of the impeller 2 as the length of the minor semi-axis of the ellipse, draw an elliptical curve, and the elliptical curve and the circle with the center O of the impeller 1 and the radius as the connecting line OB intersect at point D;

4) As shown in FIG4 , a perpendicular line is drawn through D and intersects the line BC at point E, DE⊥BC, and an elliptical curve is drawn with point E as the center of the ellipse, the line DE as the minor semi-axis, and the line EC as the major semi-axis, and the curve segment CD on the elliptical curve is used as the main shape line of the partition tongue 3;

5) As shown in FIG5 , a sine curve is set between point B and point D, with B as the origin and the direction of the connecting line BD as the x-axis, and the direction perpendicular to the connecting line BD as the y-axis. The sine curve is determined according to the following formula, and the first and second period parts of the sine curve are taken as the remaining shape lines of the tongue 3, as shown in FIG5 ;

The centrifugal pump designed according to the above method was subjected to numerical simulation test with the standard centrifugal pump. Twelve monitoring points were arranged in an annular manner in the volute flow passage of the standard centrifugal pump and the centrifugal pump of this design, and unsteady numerical simulation calculations were carried out.

Through the analysis of the test results, as shown in Figure 6, the standard centrifugal pump and the centrifugal pump of this design are subjected to constant numerical simulation calculations at four operating points of flow rate: 0.6Q, 0.8Q, 1.0Q, and 1.2Q. _H1 and _η1 are the head and efficiency of the standard centrifugal pump, and _H2 and _η2 are the head and efficiency of the centrifugal pump of this design. The head of the standard centrifugal pump is 514.92m and the efficiency is 43.82% at 0.6Q; the head is 515.329m and the efficiency is 50.45% at 0.8Q; the head is 512.538m and the efficiency is 55.77% at 1.0Q; and the head is 506.193m and the efficiency is 57.23% at 1.2Q. The centrifugal pump of this design has a head of 533.35m and an efficiency of 43.17% at 0.6Q; a head of 534m and an efficiency of 53.12% at 0.8Q; a head of 531m and an efficiency of 58.04% at 1.0Q; and a head of 510m and an efficiency of 60.81% at 1.2Q. It can be seen that the head of the centrifugal pump of this design is higher than that of the standard centrifugal pump as a whole. The efficiency of the centrifugal pump of this design is slightly lower than that of the standard centrifugal pump under small working flow, but as the flow increases, its efficiency is higher than that of the standard centrifugal pump under most working conditions.

Through the analysis of the test results, as shown in Figure 7, the value is the difference between the pressure value of each monitoring point and the average pressure of the monitoring point in one cycle. It can be seen that the overall pressure fluctuation of the centrifugal pump of this design is smaller than that of the standard centrifugal pump. As shown in Figure 7, the pressure data of each step in the unsteady numerical simulation calculation is extracted for each monitoring point, and a fast Fourier transform is performed. It can be seen that the low-frequency and high-frequency pulsations of the centrifugal pump of this design are greatly improved compared with the standard centrifugal pump. The amplitudes of each monitoring point are reduced. And the amplitude changes at a frequency of about 6000 are very obvious, with good consistency. And the improvement of the centrifugal pump of this design at different points in the same frequency band is also very obvious, especially the improvement effect is most obvious at the tongue where the dynamic and static interference has the strongest influence and the pulsation amplitude is the largest.

Therefore, compared with the traditional centrifugal pump, the design method proposed by the present invention has better performance in reducing pressure pulsation, improving efficiency, reducing vibration and noise, and has a better optimization effect on high-speed centrifugal pumps.

The examples are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments. Any obvious improvements, substitutions or modifications that can be made by those skilled in the art without departing from the essential content of the present invention belong to the protection scope of the present invention.

Claims (3)

1. A design method of an elliptic partition tongue structure for reducing pressure pulsation of a centrifugal pump is characterized by comprising the following steps of:

The centrifugal pump comprises a volute (1) and an impeller (2), wherein the impeller (2) is eccentrically arranged in a containing cavity in the volute (1), an upper outlet is formed in one side of the volute (1), a partition tongue (3) is formed on one side, close to the upper outlet, of the upper part of the containing cavity, and inner contour lines of the partition tongue (3) are sequentially arranged into a sinusoidal curve (4) and an elliptic line (5) along the direction from the containing cavity to the bottom of the upper outlet;

One end of the sinusoidal curve (4) is in tangential engagement with the inner contour line of the accommodating cavity of the volute (1), the other end of the sinusoidal curve (4) is in tangential engagement with one end of the elliptic line (5), and the other end of the elliptic line (5) is connected to the bottom edge of the upper outlet;

the method comprises the following steps:

1) A straight line is arranged at the circle center O of the impeller (2) and is used as a radial line, the radial line forms an acute angle theta with the horizontal line of the upper outlet side, the acute angle theta is set according to the following mode, and the radial line and a spiral line of an inner contour line of a containing cavity of the volute (1) are intersected at a point B:

Wherein, the maximum curvature of the spiral line of the inner contour line of the accommodating cavity of the t-volute (1); r represents the radius of the base circle of the impeller (2), and mm;

2) The method comprises the steps that a straight line perpendicular to a line segment OB is made through a point B to serve as a tangential line, a starting point A of a spiral line of an inner contour line of a containing cavity of a volute (1) is made to serve as a vertical line, a straight line which is close to the point B and forms an angle alpha with the vertical line is made through the starting point A of the spiral line of the inner contour line of the containing cavity of the volute (1) to serve as a reference line, and an intersection point C of the tangential line and the reference line serves as a position where a volute tongue separating starting point is located;

3) Taking a connecting line BC of the point B and the point C as a long axis of an ellipse, taking the shortest distance from the point B to the outline of the impeller (2) as the length of a short half axis of the ellipse, and taking the circle center O of the impeller and the radius as a connecting line OB as an elliptic curve, wherein the elliptic curve is intersected with the circle at the point D;

4) Making a perpendicular line through D and intersecting the connecting line BC at a point E, taking the point E as the center of an ellipse, taking the connecting line DE as a short half shaft, taking the connecting line EC as a long half shaft to make an elliptic curve, and taking a curve section CD on the elliptic curve as a main body shape line of the partition tongue (3);

5) Setting a sinusoidal curve between a point B and a point D, determining the sinusoidal curve by taking the point B as an origin and taking the direction of a connecting line BD as an x-axis according to the following method, and taking the 1 st and 2 nd period parts of the sinusoidal curve as the rest shape lines of the isolation tongue (3);

Wherein, the rotation speed of the n-centrifugal pump is r/min;

Rated flow of Q-centrifugal pump, m ³/s;

h—rated head, m of centrifugal pump;

L-the distance of the line between the point B and the point D, mm;

a-sinusoidal amplitude, mm.

2. The method for designing an oval-shaped tongue-separating structure for reducing pressure pulsation of a centrifugal pump according to claim 1, wherein: the included angle alpha takes the following value: the specific rotation speed of the centrifugal pump is 2 degrees when the specific rotation speed is 10-80, 3 degrees when the specific rotation speed is more than 80-150, and 5 degrees when the specific rotation speed is more than 150-300.

3. An oval-shaped partition tongue structure for reducing pressure pulsation of a centrifugal pump, which is characterized in that: manufactured by the design method of claim 1.