Current collector design method for reducing inflow distortion of F-type centrifugal fan

Abstract

The invention discloses a current collector design method for reducing inflow distortion of an F-type centrifugal ventilator, which specifically comprises the following steps: establishing a prototype current collector: the molded line of the prototype current collector comprises a contraction section and a diffusion section, the section of the contraction section of the current collector is a straight line, and the straight line rotates a circle around a central axis to form a conical barrel shape; the rear end of the current collector contraction section is smoothly connected with the current collector diffusion section through a curve; optimized design is carried out on the basis of a prototype current collector, the geometric structure of the improved current collector is established according to three parameters, and the design parameters are the inlet position of a flow guide plate, the outlet angle of the flow guide plate and the throat height variation of the current collector. By effectively controlling flowing in the current collector, the total pressure distortion index of the outlet section of the current collector is reduced, high-strength vortex structures in the current collector and the volute are reduced, the flowing loss in the current collector and the volute is greatly reduced, and the operation efficiency and the total pressure of the centrifugal fan are greatly improved under the designed flow working condition.

Description

Technical Field

[0001] The invention belongs to the technical field of fan collector design, and in particular relates to a collector design method for reducing inflow distortion of an F-type centrifugal fan. Background Art

[0002] Fans are widely used in various fields, and their power consumption accounts for about 10% of the total power consumption. Improving fan efficiency and reducing fan energy consumption are of great significance for energy conservation and emission reduction. In industry, due to limitations such as installation space, centrifugal fans often use F-type air inlets, that is, the air inlet makes a 90° turn at its outlet, causing the fan's inflow distortion. This distorted inflow makes the fan's internal flow field more complicated, which in turn causes great flow losses. Therefore, it is necessary to reduce the flow losses caused by the inflow distortion of the F-type centrifugal fan and improve the operating efficiency of the F-type centrifugal fan.

[0003] The collector is one of the important components of the centrifugal fan. Its function is to guide the gas to the impeller. The geometric shape of the collector, the type and size of the gap between the collector and the impeller inlet all affect the performance of the fan. Therefore, proposing a new design method for the F-type centrifugal fan collector and developing an optimized design to reduce the flow loss caused by inflow distortion is one of the important ways to improve the efficiency of the centrifugal fan. Summary of the invention

[0004] The purpose of the present invention is to provide a design method for a collector for reducing inflow distortion of an F-type centrifugal fan, thereby solving the problem of low operating efficiency of the existing F-type centrifugal fan.

[0005] The technical solution adopted by the present invention is a design method for a collector for reducing inflow distortion of an F-type centrifugal fan, which is specifically implemented according to the following steps:

[0006] Step 1, establish a prototype collector: the prototype collector profile includes a contraction section and a diffusion section, the cross section of the collector contraction section is a straight line, the straight line rotates around the central axis to form a cone, the collector contraction section gradually contracts from the air inlet to the air outlet; the rear end of the collector contraction section is connected to the collector diffusion section by a smooth curve;

[0007] Step 2, optimize the design based on the prototype collector, and establish the geometric structure of the improved collector according to three parameters, whose design parameters are: guide plate inlet position a, guide plate outlet angle θ, and collector throat height change b.

[0008] The present invention is also characterized in that:

[0009] In step 1, the cross section of the collector contraction section is a straight line, and the angle between it and the collector inlet cross section is

[0010] In step 1, the collector diffusion section is an arc of R = 80.23 mm, and the angle between the outlet diffusion angle and the horizontal line is

[0011] In step 1, the arc line of the current collector diffusion section is tangent to the straight line of the current collector contraction section.

[0012] In step 2, the guide plate inlet position a is defined as the distance between the guide plate inlet height and the horizontal center line, and a is dimensionless using the collector outlet diameter D3; the value range of the guide plate inlet position a is 0 to 0.186D3.

[0013] In step 2, the guide plate outlet angle θ is defined as the angle between the guide plate outlet tangent and the horizontal line. The value range of the guide plate outlet angle θ is -15° to 20°.

[0014] In step 2, the change in the height of the collector throat b is defined as the change in the position of the collector throat, and the change in the height of the collector throat b is dimensionless using the collector outlet diameter D3. The range of the change in the height of the collector throat b is -0.017D3 to 0.069D3.

[0015] The beneficial effects of the present invention are as follows: the collector design method for reducing the inlet distortion of an F-type centrifugal fan of the present invention couples flow control with collector optimization, which can significantly reduce the flow loss caused by the inlet distortion of an F-type centrifugal fan; before the method is adopted, a large number of vortices exist in the collector and the volute of the centrifugal fan, and after the design method is adopted, the total pressure distortion index of the collector outlet section is reduced through effective control of the flow in the collector, the high-strength vortex structure in the collector and the volute is reduced, the flow loss in the collector and the volute is significantly reduced, and a significant improvement in the operating efficiency and total pressure of the centrifugal fan under the design flow condition is achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic diagram of the prototype current collector profile in the method of the present invention;

[0017] Figure 2 is a schematic diagram of the three-dimensional geometric structure of the prototype current collector in the method of the present invention;

[0018] Figure 3 is a schematic diagram of an optimized current collector profile in the method of the present invention;

[0019] Figure 4 is a schematic diagram of the three-dimensional geometric structure of the optimized current collector in the method of the present invention;

[0020] Figure 5 is the effect of the guide plate inlet position a on the fan efficiency in the method of the present invention;

[0021] Figure 6 is the effect of the guide plate outlet angle θ on the fan efficiency in the method of the present invention;

[0022] Figure 7 is the effect of the collector throat height b on the fan efficiency in the method of the present invention;

[0023] Figure 8 is a comparison diagram of the full pressure rise characteristics of the prototype and the optimized current collector in the method of the present invention;

[0024] Fig. 9 is a comparison diagram of efficiency characteristics of prototype and optimized current collector in the method of the present invention;

[0025] Fig.10 It is the vortex distribution diagram of the prototype air inlet and the collector in the method of the present invention;

[0026] Fig.11 It is the optimized air inlet and vortex distribution diagram in the collector in the method of the present invention;

[0027] Fig.12 It is the turbulent kinetic energy and velocity streamline distribution diagram of the prototype collector in the method of the present invention;

[0028] Fig.13 It is the distribution diagram of turbulent kinetic energy and velocity streamlines of the optimized collector in the method of the present invention;

[0029] Fig.14 It is the distribution diagram of turbulent kinetic energy and velocity streamlines of the prototype collector outlet section in the method of the present invention;

[0030] Fig.15 It is the distribution diagram of turbulent kinetic energy and velocity streamlines of the optimized collector outlet section in the method of the present invention;

[0031] Fig.16 is a vortex distribution diagram in the prototype volute in the method of the present invention;

[0032] Fig.17 is the vortex distribution diagram in the optimized collector volute in the method of the present invention;

[0033] Fig.18 It is a comparison diagram of the prototype and optimized collector and the vortex distribution in the volute in the method of the present invention. DETAILED DESCRIPTION

[0034] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0035] Example 1

[0036] The collector design method for reducing inflow distortion of an F-type centrifugal fan of the present invention is specifically implemented according to the following steps:

[0037] Step 1, establish a prototype current collector: the prototype current collector profile includes a contraction section and a diffusion section. The cross section of the current collector contraction section is a straight line, and the angle between it and the current collector inlet section is The straight line rotates around the central axis to form a cone shape, and the collector contraction section gradually contracts from the air inlet to the air outlet; the rear end of the collector contraction section is smoothly connected to the collector diffusion section by a curve;

[0038] The collector diffusion section is an arc of R = 80.23 mm, and the angle between the outlet diffusion angle and the horizontal line is The arc of the collector diffusion section is tangent to the straight line of the collector contraction section, such as Figure 1 As shown;

[0039] The prototype current collector profile is as follows Figure 1 As shown by the bold lines in the figure, the prototype current collector can be obtained by rotating the profile line along the horizontal center line of the current collector. The three-dimensional structure of the prototype current collector is shown in Figure 2 As shown;

[0040] The contraction angle of the prototype collector is small, and the throat diameter is small, which leads to an excessively large equivalent diffusion angle of the airflow in the diffuser section, resulting in a small flow area. The profile of the diffuser section is poorly matched with the profile of the front disk of the impeller inlet. Under the inflow conditions of the F-type centrifugal fan inlet, the velocity distribution is very uneven when the airflow turns in the air inlet box, and a swirling velocity appears. This situation will continue to the outlet of the air inlet box, thereby affecting the uniformity of the inlet velocity of the collector, resulting in a high airflow velocity and low pressure in the upper half of the collector, and a low airflow velocity and high pressure in the lower half of the collector. The gas generates a large-area vortex inside the collector, which increases the flow loss in the collector. Therefore, improvements are needed to reduce the degree of inflow distortion of the airflow and improve the efficiency of the fan.

[0041] Step 2, based on the prototype collector, an optimization design is performed, and the geometric structure of the improved collector is established according to three parameters. The design parameters are: guide plate inlet position a, guide plate outlet angle θ, and collector throat height change b, specifically:

[0042] Guide plate inlet position a: defined as the distance between the guide plate inlet height and the horizontal centerline, such as Figure 3 As shown in the figure, the guide plate inlet position a mainly affects the flow distribution on both sides of the guide plate. The collector outlet diameter D3 is used to make a dimensionless.

[0043] The value range of the guide plate inlet position a is 0 to 0.186D3;

[0044] Guide plate outlet angle θ: defined as the angle between the guide plate outlet tangent and the horizontal line, such as Figure 3 As shown, the size of θ mainly affects the inlet angle of the airflow into the impeller; the value range of the guide plate outlet angle θ is -15° to 20°;

[0045] The change in the collector throat height b is defined as the change in the collector throat position, such as Figure 3 As shown, the size of b mainly affects the flow area in the collector. The collector outlet diameter D3 is used to make the collector throat height variation b dimensionless. The value range of the collector throat height variation b is -0.017D3 to 0.069D3.

[0046] According to the guide plate inlet position a, the guide plate outlet angle θ, and the change in the collector throat height b, the axial cross-sectional profile of the optimized model collector can be determined, such as Figure 3 As shown;

[0047] The design of the optimized model current collector is similar to that of the prototype current collector. The optimized model current collector profile also includes a contraction section profile and a diffusion section profile. The two sections of the profile rotate around the central axis to form a three-dimensional geometric structure of the current collector, such as Figure 4 As shown;

[0048] Table 1 shows the value range of the optimized collector geometry parameters;

[0049] Table 1 Geometric parameters of current collector

[0050] Optimizing current collector parameters Value range Guide plate inlet position a(mm) <![CDATA[0~0.186D3]]> Guide plate outlet angle θ(°) -15°～20° Change in collector throat height b (mm) <![CDATA[-0.017D3~0.069D3]]>

[0051] Example 2

[0052] The collector design method for reducing inflow distortion of an F-type centrifugal fan of the present invention is specifically implemented according to the following steps:

[0053] Step 1, establish a prototype collector: the prototype collector profile includes a contraction section and a diffusion section, the cross section of the collector contraction section is a straight line, the straight line rotates around the central axis to form a cone, the collector contraction section gradually contracts from the air inlet to the air outlet; the rear end of the collector contraction section is connected to the collector diffusion section by a smooth curve;

[0054] Step 2, optimize the design based on the prototype collector, and establish the geometric structure of the improved collector according to three parameters, whose design parameters are: guide plate inlet position a, guide plate outlet angle θ, and collector throat height change b.

[0055] The DoE (Design of Experiment) method is used to customize the three parameters of the collector, with efficiency as the response factor and the goal as the maximum efficiency. The optimized collector is modeled using the three-dimensional modeling software UG, and the flow field inside the three-dimensional incompressible centrifugal fan is numerically simulated using ANSYS CFX software. The turbulence model is the k-ω model. During the numerical simulation, the inlet boundary condition is the mass flow rate, the outlet boundary condition is the average static pressure, the wall condition is an adiabatic smooth non-slip wall, the reference atmospheric pressure is 101325Pa, and the medium is 25℃ air. The total pressure efficiency characteristics of the centrifugal fan are obtained.

[0056] A single factor analysis was performed on each collector variable. Figure 5 The influence of the guide plate inlet position a on the fan efficiency is given. It can be seen from the figure that with the increase of the guide plate inlet position a, the efficiency first increases and then decreases, and the fan efficiency is the highest when the guide plate inlet position a is 0.143D3. Figure 6 The influence of the guide plate outlet angle θ on the fan efficiency is given. It can be seen from the figure that with the increase of the guide plate outlet angle θ, the efficiency first increases and then decreases, and the difference between the maximum and minimum efficiency values ​​is within 1%. Figure 7 The influence of the change in the collector throat height b on the fan efficiency is given. It can be seen from the figure that with the increase in the collector throat height, the efficiency first decreases, then increases, and then decreases. When the collector throat height b is 0.052D3, the fan efficiency is the highest. The optimal design parameters of the collector can be determined by the DoE method.

[0057] The collector design method for reducing inflow distortion of an F-type centrifugal fan of the present invention can significantly reduce the flow loss caused by inflow distortion of an F-type centrifugal fan. Before the method is adopted, a large number of vortices exist in the collector and volute of the centrifugal fan. After the method is adopted, the total pressure distortion index of the collector outlet boundary section is reduced by effectively controlling the flow in the collector, reducing the high-strength vortex structure in the collector and volute, significantly reducing the flow loss in the collector and volute, and achieving a significant improvement in the operating efficiency and total pressure of the centrifugal fan under the design flow condition.

[0058] Example 3

[0059] The collector design method for reducing the inflow distortion of the F-type centrifugal fan of the present invention is used to optimize the national standard Y4-73 centrifugal fan with an F-type air inlet. The optimized collector geometric parameters are finally determined as follows: guide plate inlet position a: 0.112D3, guide plate outlet angle θ: 10°, collector throat height change b: 0.052D3, and the three-dimensional geometric diagram is as follows: Figure 4 shown.

[0060] Example 4

[0061] Figure 8 This is a comparison chart of the total pressure rise characteristics of the fan between the prototype collector and the optimized model. It can be seen from the figure that the total pressure rise of the optimized model under design conditions is 9.65% higher than that of the prototype. The total pressure rise under large flow conditions and design flow conditions has been significantly improved, and the total pressure rise under small flow conditions is the same as that of the prototype.

[0062] Example 5

[0063] Fig. 9 This is a comparison chart of the fan efficiency characteristics of the prototype collector and the optimized model. It can be seen from the figure that the efficiency of the optimized model in the design condition is 2.21% higher than that of the prototype. The efficiency of the large flow condition and the design flow condition has been significantly improved, and the efficiency of the small flow condition is almost the same as the prototype.

[0064] Example 6

[0065] Fig.10 and Fig.11 The vortex distribution diagrams of the air inlet and collector of the prototype fan and the vortex distribution diagrams of the air inlet and collector of the optimized fan in the method of the present invention are given. It can be seen from the figure that the large-area high-turbulence kinetic energy vortex in the collector of the prototype fan extends from the inner turning point of the bottom of the air inlet to the collector. The vortex inside the collector of the optimized fan is broken up by the guide plate and squeezed to the lower side of the guide plate, and the vortex changes from large-scale vortex I to small-scale vortex II, which increases the effective flow area in the collector and significantly reduces the high-turbulence kinetic energy area in the collector.

[0066] Example 7

[0067] Fig.12 and Fig.13 The transient distribution diagrams of turbulent kinetic energy and limiting streamlines in the prototype collector and the optimized collector in the method of the present invention are given. It can be seen from the figure that a large area of ​​high turbulent kinetic energy appears on the right side of the prototype collector, and the high turbulent kinetic energy area on the right side of the optimized collector is significantly reduced, and the turbulent kinetic energy intensity is also reduced.

[0068] Fig.14 and Fig.15 A comparison diagram of turbulent kinetic energy and limiting streamlines of the prototype and optimized collector outlet sections in the method of the present invention is given. It can be seen from the figure that an obvious vortex and high turbulent kinetic energy area appear on the right side of the prototype collector outlet section, and the large-scale vortex structure in the optimized collector is significantly weakened. The vortex is concentrated on the lower side of the guide plate, and the range of the high turbulent kinetic energy area is significantly reduced.

[0069] Fig.16 and Fig.17The distribution diagram of vortices in the volute of the prototype collector and the optimized collector in the method of the present invention is given. It can be seen from the figure that there is a large-scale vortex structure in the volute of the prototype collector, and a high-turbulent kinetic energy vortex structure appears near the volute tongue. The large-scale vortex structure at the outlet of the volute of the optimized collector is significantly weakened, and the intensity of the high-turbulent kinetic energy vortex at the volute tongue is also reduced.

[0070] Fig.18 A comparison diagram of the vortex distribution in the prototype and optimized model collector and volute in the method of the present invention is given. It can be seen from the figure that the vortex scale in the optimized model collector and volute is reduced by 21.83% and 8.59% respectively.

[0071] The collector design method for reducing the inlet distortion of an F-type centrifugal fan of the present invention can effectively reduce the vortex structure of the collector and the volute outlet, reduce the turbulent kinetic energy intensity at the collector outlet and the volute tongue, reduce the total pressure distortion index of the collector outlet section, and improve the efficiency of the centrifugal fan by reducing the vortex scale in the collector and the volute to reduce the internal flow loss.

[0072] It is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be regarded as exemplary and non-limiting from any point of view, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention, and any reference numerals in the claims should not be regarded as limiting the claims involved.

Claims

1. A flow collector design method for reducing inflow distortion of an F-type centrifugal fan, characterized in that: Follow the steps below to implement it: Step 1, establish a prototype collector: the prototype collector profile includes a contraction section and a diffusion section, the cross section of the collector contraction section is a straight line, the straight line rotates around the central axis to form a cone, the collector contraction section gradually contracts from the air inlet to the air outlet; the rear end of the collector contraction section is connected to the collector diffusion section by a smooth curve; Step 2, optimize the design based on the prototype collector, and establish the geometric structure of the improved collector according to three parameters, whose design parameters are: guide plate inlet position a, guide plate outlet angle θ, and collector throat height change b.

2. The method for designing a collector for reducing inflow distortion of an F-type centrifugal fan according to claim 1, characterized in that: In step 1, the cross section of the current collector contraction section is a straight line, and the angle between it and the current collector inlet cross section is 3. The method for designing a collector for reducing inflow distortion of an F-type centrifugal fan according to claim 2, characterized in that: In step 1, the collector diffusion section is an arc of R = 80.23 mm, and the angle between the outlet diffusion angle and the horizontal line is 4. The method for designing a collector for reducing inflow distortion of an F-type centrifugal fan according to claim 3, characterized in that: In the step 1, the arc line of the current collector diffusion section is tangent to the straight line of the current collector contraction section.

5. The method for designing a collector for reducing inflow distortion of an F-type centrifugal fan according to claim 4, characterized in that: In step 2, the guide plate inlet position a is defined as the distance between the guide plate inlet height and the horizontal center line, and a is dimensionless using the collector outlet diameter D3; the guide plate inlet position a has a value range of 0 to 0.186D3.

6. The method for designing a collector for reducing inflow distortion of an F-type centrifugal fan according to claim 5, characterized in that: In step 2, the guide plate outlet angle θ is defined as the angle between the guide plate outlet tangent and the horizontal line. The value range of the guide plate outlet angle θ is -15° to 20°.

7. The method for designing a collector for reducing inflow distortion of an F-type centrifugal fan according to claim 6, characterized in that: In the step 2, the change in the height of the collector throat b is defined as the change in the position of the collector throat, and the change in the height of the collector throat b is dimensionless using the collector outlet diameter D3.

8. The method for designing a collector for reducing inflow distortion of an F-type centrifugal fan according to claim 7, characterized in that: The value range of the collector throat height change b is -0.017D3 to 0.069D3.

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