Front disc structure of volute-free centrifugal fan and molded line modification method of front disc structure

Abstract

The invention discloses a front disc structure of a volute-free centrifugal fan and a molded line modification method of the front disc structure. The front disc structure comprises a front disc, blades and a rear disc. The front disc is composed of a flow guide circular ring piece, a plane circular ring piece and a downwards-concave curved surface piece. The diversion circular ring sheet and the concave curved surface sheet are fixed on two sides of the plane circular ring sheet; a plurality of blades evenly distributed in the circumferential direction are fixed between the downwards-concave curved surface piece and the rear disc. The generatrix of the downwards-concave curved surface patch and the molded line of the contact face of the blade and the downwards-concave curved surface patch are consistent in shape, and the molded line of the downwards-concave curved surface patch is accurately controlled through a five-order Bezier curve. In order to better describe the control method, the Bezier curve is placed in a rectangular coordinate system to be quantized, the positions of the end points A and F of the fitted Bezier curve are kept unchanged, and the curve shape is flexibly adjusted by adjusting the coordinates of the control points B, C, D and E, so that the front disc molded line structure is accurately optimized.

Description

Technical Field

[0001] The invention belongs to the field of fluid machinery, and in particular relates to a front disc structure of a volute-free centrifugal fan and a profile modification method thereof. Background Art

[0002] The voluteless centrifugal fan is a machine that relies on input mechanical energy to increase gas pressure and discharge gas. It is a driven fluid machine. Based on the principle of converting mechanical energy into kinetic energy and pressure energy, the voluteless centrifugal fan uses a high-speed rotating impeller to accelerate the gas, increase the kinetic energy and pressure energy of the gas and change its direction of movement, so that the mechanical energy is converted into the kinetic energy and pressure energy of the gas. The pressure increase mainly occurs in the impeller.

[0003] When the voluteless centrifugal fan is running at high speed, the gas velocity at the impeller outlet is high, while the pressure near the impeller front disc is low. There is a large pressure difference here, which causes the impeller outlet gas to flow into the fan. Part of the gas flows back through the impeller front disc to the impeller inlet, generating a reflux at the impeller inlet. The existence of reflux will cause the impeller outlet gas to not flow out fully, affecting the stability of the gas flow in the flow channel.

[0004] In addition, since the pressure at the suction surface of the centrifugal impeller blade is lower, while the pressure at the adjacent blade pressure surface is higher, there is a pressure difference between the blade suction surface and the adjacent blade pressure surface, causing the low-speed fluid near the wall of the blade suction surface to flow separate, and the gas in the flow channel cannot flow out smoothly and orderly, increasing the flow loss and seriously affecting the efficiency of the fan.

[0005] Secondly, in the centrifugal impeller of a voluteless centrifugal fan, the air flow velocity near the outlet of the suction surface of the blade is lower, while the air flow velocity near the outlet of the pressure surface of the adjacent blade is higher, thus forming a circumferentially uneven "jet-wake" flow structure. The greater the difference between the velocity in the wake zone and the velocity in the jet zone, the stronger the "jet-wake" flow structure, and the lower the efficiency of converting the kinetic energy of the airflow into pressure energy, resulting in lower efficiency and greater noise in the centrifugal fan. Summary of the invention

[0006] The purpose of the present invention is to address the deficiencies of the prior art and to provide a front disc structure of a volute-free centrifugal fan and a method for modifying its profile.

[0007] The technical solution adopted by the present invention is:

[0008] The present invention discloses a front disk structure and a profile modification method of a volute-free centrifugal fan, comprising a front disk, blades and a rear disk; the front disk is composed of a guide ring sheet, a plane ring sheet and a concave curved sheet; the guide ring sheet and the concave curved sheet are fixed on both sides of the plane ring sheet; a plurality of blades uniformly distributed along the circumferential direction are fixed between the concave curved sheet and the rear disk; the generatrix of the concave curved sheet and the contact surface profile of the blade and the concave curved sheet are consistent in shape, and the profile of the concave curved sheet is precisely controlled by a fifth-order Bezier curve. In order to better describe the control method, the Bezier curve is placed in a rectangular coordinate system for quantization, the positions of the endpoints A and F of the fitted Bezier curve remain unchanged, and the curve shape is flexibly adjusted by adjusting the coordinates of the control points B, C, D, and E, thereby precisely optimizing the front disk profile structure.

[0009] Preferably, the fifth-order Bezier curve is a parameterized curve based on five control points, which is used to accurately describe complex curve shapes. It is a type of Bezier curve, and its curve shape is determined by the positions of the five control points. The fifth-order Bezier curve has high continuity and smoothness, and is very suitable for fluid design and surface optimization.

[0010] Preferably, the fifth-order Bezier curve formula is expanded as follows:

[0011] B(t)=(1-t) 5 A+5(1-t) 4 tB+10(1-t) 3 t 2 C+10(1-t) 2 t 3 D+5(1-t)t 4 E+t 5 F

[0012] Where A and F are the starting point and end point of the curve respectively; B, C, D, and E are the intermediate points that control the shape of the curve; the parameter t controls the position of the curve, when t=0, B(0)=A; when t=1, B(1)=F.

[0013] Preferably, the boundary line between the guide circular ring piece and the plane circular ring piece is a circle.

[0014] Preferably, the coordinate value ranges of the control points B, C, D, and E of the Bezier curve are determined by the following formula:

[0015]

[0016]

[0017] Where d is the diameter of the rear disc.

[0018] Preferably, point B, point C, point D, point E, the point at the inner edge of the blade and the point at the outer edge of the blade of the curve are fitted by a Bezier curve.

[0019] The working method of the volute-free centrifugal fan with a novel front disc is as follows:

[0020] When the front disk, blades and rear disk rotate synchronously, the airflow enters from the front disk and flows out through the fluid channel between adjacent blades. In this process, the kinetic energy and pressure energy of the gas are increased. In the process of the airflow flowing out from the blade along the fluid channel, the present invention introduces a concave curved surface controlled by a Bezier curve in the design of the front disk. The concave curved surface of the front disk forms a concave arc surface with the contact surface of the blade, so that the fluid channel space near the concave curved surface is more compact than the traditional design. Through the control of the Bezier curve, the shape of the concave curved surface can be accurately adjusted to further optimize the flow environment of the fluid channel. The pressure of the area of ​​the fluid channel close to the concave curved surface increases, thereby reducing the tendency of the gas at the outlet of the fluid channel to flow into the inside of the fluid channel, reducing the backflow phenomenon, and reducing the pressure difference between the pressure surface and the suction surface of adjacent blades; at the same time, the spatial pressure of the fluid channel close to the concave curved surface increases, the fluid velocity increases, effectively resists the adverse pressure gradient, and reduces the gas flow separation phenomenon near the wall of the blade suction surface, so that the difference between the velocity in the wake area and the velocity in the jet area is further reduced. The "jet-wake" flow structure is weakened, the velocity distribution of the airflow at the outlet of the fluid channel is made more uniform, the efficiency of converting gas kinetic energy into pressure energy is improved, and the noise is optimized.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The present invention introduces a concave curved sheet controlled by a Bezier curve into the front disk design, so that the contact surface between the blade and the concave curved sheet forms a concave arc structure. Compared with the traditional fan, this design reduces the space of the fluid channel near the concave curved sheet, resulting in an increase in pressure in this area. This pressure increase effectively reduces the pressure difference between the suction surface and the pressure surface of adjacent blades in the same fluid channel, and further increases the fluid velocity near the front disk position of the suction surface of the blade. The increase in the fluid velocity on the suction surface has a significant optimization effect on the flow, especially it can effectively resist the adverse pressure gradient and reduce the flow separation of the gas near the wall of the blade suction surface. As a result, the flow of gas in the flow channel is more stable and orderly, which significantly improves the flow characteristics of the fan. At the same time, this optimized design not only improves the aerodynamic performance and operating efficiency of the fan, but also effectively reduces the operating noise, providing important support for the efficient and low-noise application of the fan.

[0023] 2. In the present invention, the contact surface between the blade and the front disk is a concave arc surface, which reduces the flow channel space and relatively increases the pressure of the flow channel near the concave part, thereby relatively increasing the air flow velocity in the flow channel, reducing the generation of flow separation vortices on the suction surface and pressure surface of the blade, reducing the speed difference between the wake zone speed and the jet zone speed, thereby weakening the "jet-wake" flow structure, making the velocity distribution of the airflow at the outlet of the centrifugal fan more uniform, optimizing the efficiency of converting gas kinetic energy into pressure energy, improving the efficiency of the fan, and reducing the noise of the fan.

[0024] 3. In the present invention, the contact surface between the blade and the front disk is a concave arc surface, which reduces the flow channel space and increases the pressure, thereby reducing the backflow phenomenon at the blade outlet and reducing the vibration and noise of the fan. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a three-dimensional diagram of the overall structure of the present invention.

[0026] Figure 2 It is a side view of the present invention.

[0027] Figure 3 It is a schematic diagram of a blade of the present invention.

[0028] Figure 4 It is a schematic diagram of the fitting curve when the diameter of the rear disc of the present invention is less than or equal to 400 mm.

[0029] Figure 5 It is a schematic diagram of the fitting curve when the diameter of the rear disc of the present invention is greater than 400 mm and less than 800 mm.

[0030] Figure 6 It is a schematic diagram of the fitting curve when the diameter of the rear disc of the present invention is greater than or equal to 800 mm.

[0031] Figure 7 It is a three-dimensional diagram of the overall structure of a traditional ventilator.

[0032] Figure 8 It is a side view of a conventional ventilator. DETAILED DESCRIPTION

[0033] The present invention is further described below in conjunction with the accompanying drawings, wherein welding is preferred for fixing and connecting methods at various locations unless otherwise specified.

[0034] like Figure 1 , Figure 2 and Figure 3As shown, a volute-free centrifugal fan with a novel front disc structure includes a front disc 1, blades 2 and a rear disc 3; the front disc 1 is composed of a guide ring piece 6, a plane ring piece 4 and a concave curved piece 5; the guide ring piece 6 and the concave curved piece 5 are fixed on both sides of the plane ring piece 4; a plurality of (more than three) blades 2 uniformly distributed along the circumferential direction are fixed between the concave curved piece 5 and the rear disc 3; the concave curved piece 5 adopts a body of revolution design, and its generatrix profile is consistent with the contact surface profile of the blade 2 on the concave curved piece 5, and both are controlled by a Bezier curve 10. Through the design of the Bezier curve, the profile of the concave curved piece 5 can be flexibly adjusted to make it more suitable for the fluid flow requirements under different working conditions. The end point position of the Bezier curve is fixed, and the intermediate control point can be adjusted according to the actual application requirements, thereby optimizing the profile structure of the concave curved piece.

[0035] As a preferred embodiment, the fifth-order Bezier curve 10 is a parameterized curve based on five control points, which is used to accurately describe complex curve shapes. It is a type of Bezier curve, and its curve shape is determined by the positions of the five control points. The fifth-order Bezier curve has high continuity and smoothness, and is very suitable for fluid design and surface optimization.

[0036] As a preferred embodiment, the fifth-order Bezier curve formula is expanded as follows:

[0037] B(t)=(1-t) 5 A+5(1-t) 4 tB+10(1-t) 3 t 2 C+10(1-t) 2 t 3 D+5(1-t)t 4 E+t 5 F(1)

[0038] Where A and F are the starting point and end point of the curve respectively; B, C, D, and E are the intermediate points that control the shape of the curve; the parameter t controls the position of the curve, when t=0, B(0)=A; when t=1, B(1)=F.

[0039] As a preferred embodiment, Figure 1 As shown, the boundary line between the guide circular ring piece 6 and the plane circular ring piece 4 is a circle.

[0040] As a preferred embodiment, Figure 4 , Figure 5 and Figure 6 As shown, the coordinate value range of the control points B, C, D, and E of the Bezier curve 10 is determined by the following formula:

[0041]

[0042]

[0043] Wherein, d is the diameter of the rear disc 3 .

[0044] As a preferred embodiment, point B, point C, point D, point E, the point at the inner edge of the blade and the point at the outer edge of the blade of the curve 10 are fitted by a Bezier curve.

[0045] The working method of the volute-free centrifugal fan with a concave front plate is as follows:

[0046] When the front disk 1, blades 2 and rear disk 3 rotate synchronously, the airflow enters from the front disk 1 and flows out through the fluid channel 8 between adjacent blades 2. In this process, the kinetic energy and pressure of the gas can be increased. In the process of the airflow flowing out from the blades 2 along the fluid channel 8, a concave curved surface controlled by a Bezier curve is introduced into the design of the front disk 1. The concave curved surface of the front disk 1 forms a concave arc surface with the contact surface of the blade, making the fluid channel space near the concave curved surface more compact than the traditional design. Through the control of the Bezier curve 10, the profile shape of the concave curved surface can be accurately adjusted to further optimize the flow environment of the fluid channel 8. The pressure in the area of ​​the fluid channel close to the concave curved surface increases, thereby weakening the tendency of the gas at the outlet of the fluid channel to flow into the fluid channel 8, reducing the backflow phenomenon, and reducing the pressure difference between the pressure surface 7 and the suction surface 9 of the adjacent blades; at the same time, the spatial pressure of the fluid channel 8 close to the concave curved surface increases, the fluid velocity increases, effectively resisting the adverse pressure gradient, and weakening the gas flow separation phenomenon near the wall of the blade suction surface 9, thereby further reducing the difference between the velocity in the wake area and the velocity in the jet area. Weakening the "jet-wake" flow structure makes the velocity distribution of the airflow at the outlet of the fluid channel 8 more uniform, improves the efficiency of converting gas kinetic energy into pressure energy, and optimizes noise.

[0047] In contrast, the contact surface between the front disk 1 and the blade 2 of the conventional fan is a plane. Figure 7 and Figure 8

[0048] This design results in a lower pressure at the blade suction surface 9 and a higher pressure at the adjacent blade pressure surface 7, thereby forming a larger pressure difference in the fluid channel 8. This pressure difference will cause the blade suction surface 9 to

[0049] The low-speed fluid near the wall undergoes flow separation, which in turn forms a circumferentially non-uniform "jet-wake" flow.

[0050] In addition, the gas velocity at the outlet is high, while the pressure near the front disk 1 is low, resulting in a large pressure difference in this area, causing part of the outlet gas to flow back into the fan. This backflow phenomenon not only reduces the efficiency of converting the kinetic energy of the airflow into pressure energy, but also causes the efficiency of the centrifugal fan to decrease, while increasing the operating noise.

Claims

1. A front disc structure of a volute-free centrifugal fan and a method for modifying its profile, comprising a front disc, blades and a rear disc; the front disc is composed of a guide ring sheet, a plane ring sheet and a concave curved sheet; the guide ring sheet and the concave curved sheet are fixed on both sides of the plane ring sheet; a plurality of blades uniformly distributed along the circumferential direction are fixed between the concave curved sheet and the rear disc; the generatrix of the concave curved sheet and the contact surface profile of the blade and the concave curved sheet are consistent in shape, and the profile of the concave curved sheet is precisely controlled by a fifth-order Bezier curve. In order to better describe the control method, the Bezier curve is placed in a rectangular coordinate system for quantization, the positions of the endpoints A and F of the fitted Bezier curve remain unchanged, and the curve shape is flexibly adjusted by adjusting the coordinates of the control points B, C, D, and E, thereby precisely optimizing the front disc profile structure.

2. According to claim 1, a front disc structure of a volute-free centrifugal fan and a method for modifying its profile, characterized in that: The fifth-order Bezier curve is a parametric curve based on five control points, which is used to accurately describe complex curve shapes. It is a type of Bezier curve, and its curve shape is determined by the positions of the five control points. The fifth-order Bezier curve has high continuity and smoothness, and is very suitable for fluid design and surface optimization.

3. The front disc structure and profile modification method of a volute-free centrifugal fan according to claim 1, characterized in that: The fifth-order Bezier curve formula is expanded as follows: B(t)=(1-t) 5 A+5(1-t) 4 tB+10(1-t) 3 t 2 C+10(1-t) 2 t 3 D+5(1-t)t 4 E+t 5 F Where A and F are the starting point and end point of the curve respectively; B, C, D, and E are the intermediate points that control the shape of the curve; the parameter t controls the position of the curve, when t=0, B(0)=A; when t=1, B(1)=F.

4. The front disc structure of a volute-free centrifugal fan and the method for modifying its profile according to claim 1, characterized in that: The boundary line between the guide circular ring piece and the plane circular ring piece is a circle.

5. The front disc structure of a volute-less centrifugal fan and the method for modifying its profile according to claim 1, characterized in that: The coordinate value range of the control points B, C, D, and E of the Bezier curve is determined by the following formula: Where d is the diameter of the rear disc.

6. The front disc structure of a volute-less centrifugal fan and the method for modifying its profile according to claim 1, characterized in that: Point B, point C, point D, point E, a point at the inner edge of the blade and a point at the outer edge of the blade of the curve are fitted by a Bezier curve.

7. A working method for modifying the front disc structure and profile of a volute-free centrifugal fan according to any one of claims 1 to 4, characterized in that: The method is as follows: When the front disk, blades and rear disk rotate synchronously, the airflow enters from the front disk and flows out through the fluid channel between adjacent blades. In this process, the kinetic energy and pressure energy of the gas are increased. When the airflow flows out along the fluid channel, since the front disk adopts a concave curved sheet structure designed based on the Bezier curve, the surface in contact with the blade is a concave arc surface, which makes the flow channel space close to the concave curved sheet smaller, resulting in an increase in pressure in this area. The increase in pressure effectively weakens the tendency of the gas at the outlet of the fluid channel to flow into the inside of the fluid channel, reduces the backflow phenomenon, and reduces the pressure difference between the pressure surface and the suction surface of adjacent blades. The increase in pressure in the area of ​​the fluid channel close to the concave curved sheet also brings about an increase in fluid velocity. The increase in fluid velocity can effectively resist the adverse pressure gradient and weaken the flow separation phenomenon near the wall of the blade suction surface, thereby reducing the velocity difference between the wake area and the jet area, weakening the "jet-wake" flow structure, making the airflow velocity distribution at the outlet of the fluid channel more uniform, improving the efficiency of converting gas kinetic energy into pressure energy, and optimizing noise.

Images