CN112049817B

CN112049817B - Cross-flow fan blade based on bionics

Info

Publication number: CN112049817B
Application number: CN202010810586.3A
Authority: CN
Inventors: 韦红旗; 胡善苗
Original assignee: Southeast University
Current assignee: Southeast University
Priority date: 2020-08-13
Filing date: 2020-08-13
Publication date: 2022-04-12
Anticipated expiration: 2040-08-13
Also published as: CN112049817A

Abstract

The invention discloses a cross-flow fan blade based on bionics, wherein the blade comprises a plurality of blade units which are arranged along the axial direction of an impeller, the front edges of the blade units are convex, the rear edges of the blade units are concave, the middle parts of the upper surfaces of the blade units, close to the front edge, are higher than the two sides, the middle parts of the upper surfaces of the blade units, close to the rear edge, are lower than the two sides, and the middle parts of the upper surfaces of the blade units, close to the front edge, are higher than the middle parts of the upper surfaces of the blade units, close to the rear edge. The cross-flow fan blade based on the bionics can improve the airflow flow of the front edge and the rear edge of the blade, enable eccentric vortexes to move downwards, improve the efficiency of the cross-flow fan and reduce energy consumption.

Description

Cross-flow fan blade based on bionics

Technical Field

The invention belongs to the technical field of air conditioner blades, and particularly relates to a cross-flow fan blade based on bionics.

Background

Along with social development, energy conservation and emission reduction become social consensus, in building energy consumption, the energy consumption of a heating ventilation air-conditioning system accounts for about 65% of the whole energy consumption, and the total energy consumption of air conditioners in China is huge. Under the common condition, in order to apply energy-saving engineering design in a heating ventilation air-conditioning system, the blade of a cross-flow fan widely adopted in the air-conditioning system is always designed and optimized in the prior art, so that the fan achieves the effects of reducing drag and consumption and has important practical value and social significance.

However, the design still has some defects, such as the existing blade has a flat and smooth surface, and the airflow is easy to flow transversely; meanwhile, the front edge and the rear edge of the existing blade are of a long and straight structure, so that a large vortex is easily formed when airflow flows through the long and straight structure, and the pressure difference resistance is large; the air outlet side of the cross-flow fan impeller has eccentric vortexes, the fan efficiency is influenced and reduced, and the flow instability degree is increased. Therefore, there is a strong need for a crossflow blower blade that reduces the swirl zone, reduces differential pressure drag, reduces blower energy consumption, and improves blower efficiency.

Disclosure of Invention

Aiming at the defects, the invention provides the cross-flow fan blade based on the bionics, which can overcome the problems of high energy consumption, low efficiency and the like in the prior art and achieve the effects of reducing resistance and consumption.

In order to solve the technical problem, the embodiment of the invention adopts the following technical scheme:

the utility model provides a cross-flow fan blade based on bionics, the blade includes that a plurality of blade unit forms along impeller axial arrangement, the blade unit leading edge is protruding, and the trailing edge is indent, blade unit upper surface is close to leading edge side mid portion and is higher than both sides, is close to trailing edge side mid portion and is less than both sides, it is higher than close to trailing edge side mid portion to close leading edge side mid portion.

Preferably, the section-shaped line of the blade unit is formed by sequentially intersecting a first arc line, a first straight line, a second arc line, a third straight line and a fourth straight line on the windward side of the front edge; the leeward side of the rear edge is formed by sequentially intersecting a fourth arc line, a fifth straight line, a sixth straight line, a fifth arc line, a seventh straight line and an eighth straight line; the middle section is formed by sequentially intersecting a third arc line, an eleventh arc line, a sixth arc line and a twelfth arc line; the left side surface is formed by sequentially intersecting a first arc line, a seventh arc line, a fourth arc line and an eighth arc line; the right side surface is formed by sequentially intersecting a second arc line, a ninth arc line, a fifth arc line and a tenth arc line.

Preferably, the distance between the vertexes of the front edge protruding structures of two adjacent blade units of the blade is 4-80 mm.

Preferably, the vertical distance from the top point of the protruding structure of the front edge of the blade unit to the straight line of the two end points of the front edge is 1-20 mm.

Preferably, the vertical distance from the vertex of the concave structure on the rear edge of the blade unit to the straight line of the two end points on the rear edge is 0.5-15 mm.

Preferably, the chord length of the cross sections on the two sides of the blade unit is 8-120 mm, the height of the middle parts of the cross sections on the two sides is 1/10 of the chord length, and the height of the end parts of the cross sections on the two sides is 1/12 of the chord length.

Preferably, the chord length of the middle section of the blade unit is 9-130 mm, the height of the middle section is 1/13 of the chord length, and the height of the end part of the middle section is 1/20 of the chord length.

Preferably, the total width of the blade is 50-800 mm.

Compared with the prior art, the cross-flow fan blade based on the bionics can ensure that the airflow flow of the front edge and the rear edge of the blade is improved, so that the eccentric vortex moves downwards, the energy consumption of the fan is reduced, and the efficiency of the fan is improved. The cross-flow fan blade based on bionics of this embodiment, the blade includes that a plurality of blade unit forms along impeller axial arrangement, blade unit leading edge protrusion, trailing edge indent, blade unit upper surface is close to leading edge side mid portion and is higher than both sides, is close to trailing edge side mid portion and is less than both sides, it is higher than close to trailing edge side mid portion to be close to leading edge side mid portion. The swirl area can be reduced by arranging the convex front edge structure, and the shape resistance is reduced; the concave rear edge structure is arranged to maintain fluid attachment, so that the separation point moves backwards and the pressure difference resistance is reduced; the lateral flow of the airflow is inhibited by utilizing the structural characteristics of the upper surface; the impeller structure formed by the blades in a rotating arrangement can enable the eccentric vortex to move downwards, reduce the energy consumption of the fan and improve the efficiency of the fan.

Drawings

FIG. 1 is a schematic view of a blade according to an embodiment of the present invention;

FIG. 2 is a front view of a blade unit in an embodiment of the invention;

FIG. 3 is a rear view of a blade unit in an embodiment of the invention;

FIG. 4 is a mid-sectional cut-away view of a vane unit in an embodiment of the invention;

FIG. 5 is a dimensional drawing of a blade unit according to an embodiment of the present invention;

FIG. 6 is a top view of a blade in an embodiment of the present invention;

FIG. 7 is a schematic structural view of a segment of an impeller according to an embodiment of the present invention;

FIG. 8 is a schematic structural view of a prior art blade;

FIG. 9 is a streamline distribution cloud for a prior art blade;

FIG. 10 is a cloud of streamlines of a blade in an embodiment of the present invention;

FIG. 11 is a block diagram of an experimental volute model in an embodiment of the invention;

FIG. 12 is a cloud view of a streamline distribution of a prior art crossflow blower;

FIG. 13 is a cloud view of a streamline distribution of a crossflow blower in an embodiment of the present invention.

The figure shows that: the blade unit 1, the leading edge windward side 2, the trailing edge leeward side 3, the left side 4, the right side 5, the middle cross section 6, the first arc 7, the first straight line 8, the second straight line 9, the second arc 10, the third straight line 11, the fourth straight line 12, the third arc 13, the fourth arc 14, the fifth straight line 15, the sixth straight line 16, the fifth arc 17, the seventh straight line 18, the eighth straight line 19, the sixth arc 20, the seventh arc 21, the eighth arc 22, the ninth arc 23, the tenth arc 24, the eleventh arc 25, the twelfth arc 26, the blade 27, the impeller 28, and the existing blade 29.

Detailed Description

The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.

As shown in fig. 1, in the cross-flow fan blade based on bionics according to the embodiment of the present invention, the blade 27 includes a plurality of blade units 1 arranged axially along an impeller 28, a leading edge 2 of each blade unit 1 is convex, a trailing edge 3 of each blade unit 1 is concave, a middle portion of an upper surface of each blade unit 1 near the leading edge 2 is higher than two sides, a middle portion of the upper surface of each blade unit 1 near the trailing edge 3 is lower than two sides, and a middle portion of the upper surface of each blade unit near the leading edge 2 is higher than a middle portion of the upper surface of each blade unit near the trailing edge 3.

The upper surface of the cross-flow fan blade based on the bionics is similar to the surface characteristics of shark scuttle, the middle part of the upper surface of the blade unit 1 close to the front edge 2 side is higher than the two sides, the middle part close to the rear edge 3 side is lower than the two sides, and the middle part close to the front edge 2 side is higher than the middle part close to the rear edge 3 side. The surface characteristics can improve the fluid structure and the flow state of a turbid flow boundary layer flowing through and have better drag reduction effect. The fluid near the middle of the side surface of the trailing edge 3 is calmer than the fluid outside, the wave velocity of the fluid and the kinetic energy of the turbidity current have relatively small values, and when the airflow passes through the surface of the blade 27, the surface structure retards the transverse flow of the airflow, thereby reducing the momentum loss of the fluid in the boundary layer of the turbidity current and reducing the surface friction resistance.

As shown in fig. 2, 3 and 4, in the cross-sectional line of the crossflow blower blade based on bionics of the above-mentioned embodiment, it is preferable that the section line of the blade unit 1 is a first arc line 7, a first straight line 8, a second straight line 9, a second arc line 10, a third straight line 11 and a fourth straight line 12 which intersect in sequence on the windward side of the leading edge 2; the leeward side of the rear edge 3 is formed by sequentially intersecting a fourth arc line 14, a fifth straight line 15, a sixth straight line 16, a fifth arc line 17, a seventh straight line 18 and an eighth straight line 19; the middle section 6 is formed by intersecting a third arc line 13, an eleventh arc line 25, a sixth arc line 20 and a twelfth arc line 26 in sequence; the left side surface 4 is formed by sequentially intersecting a first arc line 7, a seventh arc line 21, a fourth arc line 14 and an eighth arc line 19; the right flank 5 is formed by the intersection of a second arc line 10, a ninth arc line 23, a fifth arc line 17 and a tenth arc line 24 in that order. The straight line is combined with the arc line to form a protruding structure of the front edge 2, so that the airflow flows along the flow line direction, and the fluid mass points in the boundary layer obtain more kinetic energy for supplement due to the blending effect of turbulent flow, so that the position of the separation point moves backwards, the vortex area is obviously reduced, and the shape resistance is reduced; meanwhile, the rear edge 3 forms a concave structure, the tip points to the direction of the fluid, and the concave structure can generate stronger turbidity current to maintain the attachment of the fluid and prevent the fluid from separating, thereby reducing the pressure difference resistance.

Preferably, the distance between the vertexes of the protruding structures of the front edges 2 of two adjacent blade units 1 of the blades 27 is 4-80 mm.

Preferably, the vertical distance from the top point of the protruding structure of the front edge 2 of the blade unit 1 to the straight line of the two end points of the front edge 2 is 1-20 mm.

Preferably, the vertical distance from the vertex of the concave structure of the trailing edge 3 of the blade unit 1 to the straight line of the two end points of the trailing edge 3 is 0.5-15 mm.

Preferably, the chord length of the cross sections on both sides of the blade unit 1 is 8-120 mm, the height of the middle parts of the cross sections on both sides is 1/10 of the chord length, and the height of the end parts of the cross sections on both sides is 1/12 of the chord length.

Preferably, the chord length of the middle section 6 of the blade unit 1 is 9-130 mm, the height of the middle part of the middle section 6 is 1/13 of the chord length, and the height of the end part of the middle section 6 is 1/20 of the chord length.

Preferably, the total width of the blade 27 is 50 to 800 mm.

The performance of the blade of the embodiment of the invention is tested by a simulation experiment as follows:

the size of the vane unit 1 used in this experiment is shown in fig. 5, and the vertical distance B from the vertex c of the protruding structure of the leading edge 2 of the vane unit 1 to the two end points a (a') is 1.5 mm. The vertical distance C from the end point d of the concave structure of the rear edge 3 of the blade unit 1 to two top points b (b') is 1 mm. The chord length A of the

sections

4 and 5 on the two sides of the blade unit 1 is 10mm, the chord height D of the ninth arc 23 taking the straight lines where the end points a and D are located as chords is 1mm, the height E of the middle part is 1mm, and the height G of the end part is 0.8 mm. The chord length I of the middle section 6 of the blade unit 1 is 10.5mm, the height J of the middle part is 0.8mm, and the height F of the end part is 0.6 mm.

As shown in fig. 6, the total width of the blades 27 formed by arranging the blade units 1 is 60 mm. The distance H between the vertexes of the convex structures of two adjacent blade units 1 of the blades 27 is 6 mm.

As shown in fig. 7, the blades 27 may be combined into an impeller 28 in a circumferential array, wherein a segment of the impeller 28 includes 36 blades 27. The impeller 28 structure formed by the rotary arrangement can enable the eccentric vortex to move downwards and be closer to the volute tongue, thereby improving the efficiency of the fan.

The cross-flow fan blade based on the bionics is subjected to simulation tests by using a single blade 27 structure and a full three-dimensional structure of the cross-flow fan respectively, compared with data of the cross-flow fan blade in the prior art and subjected to three-dimensional numerical simulation calculation by using FLUENT19.0 software.

(1) Three-dimensional numerical simulation of single blade structure

Modeling the vane 27 described in the above embodiment, the vane 27 has a basic structure as shown in fig. 1 and dimensions as shown in fig. 5 and 6. The three-dimensional numerical simulation is carried out on the blades 27 in the embodiment by adopting FLUENT19.0 software, the control equation adopts an N-S equation of Reynolds average, the turbulence model adopts a standard k-epsilon model, a standard wall function is adopted near the wall surface, the pressure-velocity coupling adopts a SIMPLE algorithm, the momentum equation, the turbulence kinetic energy and the turbulence dissipation rate adopt second-order windward format dispersion, the boundary condition adopts a velocity inlet and a pressure outlet, the inlet velocity is 10m/S, and the outlet pressure is 0 Pa. When each residual error is less than 10^-5At this time, the calculation of the current operating condition is considered to have converged.

The conventional blade 29 is modeled by using the same procedure, the basic structure of the conventional blade 29 is shown in fig. 8, the front edge and the rear edge of the conventional blade 29 are both long and straight structures, the chord length of the cross section of the two sides of the conventional blade 29 is 10mm, the chord height is 1mm, the middle height is 1mm, and the end height is 1 mm. The existing blade 29 has a total width of 60 mm.

And (4) analyzing results:

as shown in fig. 9, when the airflow passes through the conventional blade 29, a large vortex void is formed on the lower surface by the leading edge structure, and the airflow is separated from the blade surface before the upper surface reaches the trailing edge of the blade.

As shown in fig. 10, in the cross-flow fan blade based on bionics according to the embodiment of the present invention, the leading edge 2 forms a convex structure, so that the airflow flows along the streamline direction, and due to the blending effect of the turbulent flow, the fluid particles in the boundary layer obtain more kinetic energy for supplementation, so that the separation point moves backward, the vortex dead zone is significantly reduced, the airflow is better attached to the surface of the blade 27, the trailing edge 3 at the rear end of the blade 27 forms a concave structure, the tip of the concave structure points to the fluid direction, and the concave structure can generate stronger turbidity current to maintain the attachment of the fluid, thereby preventing the fluid separation.

From the three-dimensional numerical simulation test, the blade front-rear pressure resistance values of the blade 27 of the present invention were obtained as compared with the conventional blade 29, and the results are shown in table 1.

TABLE 1 vane front and rear pressure resistance values

As shown in Table 1, the result of numerical simulation calculation and analysis shows that the vane 27 of the present invention can achieve the resistance reduction result compared with the conventional vane 29, and the pressure resistance is reduced by about 7Pa and relatively reduced by 12.5%.

(2) Three-dimensional numerical simulation of cross-flow fan structure

The cross-flow fan model of the experiment mainly comprises two parts in terms of structure: impeller, spiral case. The model is divided into two parts for separate processing. After the two models are built respectively, the two models are assembled. Volute model as shown in fig. 11, the cross-flow fan impeller structure of the present invention is shown in fig. 7. The main design parameters are as follows: the outer diameter of the impeller is 95.7 mm; a diameter ratio of 0.8114; the height of the middle part of the blade is 1.0 mm; the height of the end part of the blade is 0.8 mm; the effective width of the blade is 60 mm; the number of blades z is 36.

Three-dimensional numerical simulation is carried out on a cross-flow fan consisting of the conventional blades and a cross-flow fan consisting of the blades of the invention by using FLUENT19.0 software. The impeller area is defined as a rotating area, a rotating coordinate system is adopted, the fluid gives a rotating speed, and the rest areas are static areas, and a static coordinate system is adopted. And the calculation solver selects a pressure-based solver, starts a non-steady option, adopts a time dispersion format as a first-Order implicit format, selects a readable k-epsilon turbulence model, adopts a Coupled format for pressure and speed coupling, and activates options of wave-Face Gradient Correction and High Order terminal Relaxation. The pressure is dispersed in a second-order windward format, and the momentum, the turbulent kinetic energy and the turbulent dissipation rate are dispersed in a first-order windward format. The density of air in the flow field was set to 1.225kg/m³Viscosity was set to 1.8X 10^-5kg (m @ s). The rotating speed of the cross-flow fan impeller is 1000r/min, and the unsteady time step length is 0.0002 s. In the boundary conditions, the inlet is set as a speed inlet, the speed is 1m/s, the pressure outlet is set as a boundary condition, the pressure value is the ambient atmospheric pressure, the rest boundaries are wall boundary conditions, and the rest settings in the calculation are default settings.

The same procedure is used to model the prior art, which consists of a circumferential array of existing blades 29.

And (4) analyzing results:

as shown in fig. 12 and 13, compared with the prior art, the cross-flow fan impeller of the present invention has the advantages that the bottom eccentric vortex is significantly reduced, the bottom eccentric vortex is close to the volute tongue, the turbulent backflow near the volute tongue is reduced, the flow field optimization effect is significant, and the gas flow resistance can be effectively reduced.

According to the three-dimensional numerical simulation test, the inlet and outlet pressure resistance values of the crossflow blower of the vane 27 of the present invention are obtained as compared with those of the conventional vane 29, and the results are shown in table 2.

TABLE 2 Cross-flow Fan Inlet and outlet piezoresistive values

As shown in Table 2, through calculation and analysis of numerical simulation results, the blade 27 of the embodiment of the present invention can achieve resistance reduction, and the pressure resistance is reduced by about 4.08Pa, which is relatively reduced by 39%.

Compared with the prior art, the cross-flow fan blade based on the bionics can reduce a vortex area and reduce the shape resistance by arranging the convex front edge structure; the concave rear edge structure is arranged to maintain fluid attachment, so that the separation point moves backwards and the pressure difference resistance is reduced; the upper surface structure features can inhibit airflow from flowing transversely; the impeller structure formed by the blades in a rotating arrangement can enable the eccentric vortex to move downwards, reduce the energy consumption of the fan and improve the efficiency of the fan.

The embodiments of the present invention are merely preferred embodiments of the present invention, and are not intended to limit the scope of the present invention. That is, all equivalent changes and modifications made according to the content of the claims of the present invention should be regarded as the technical scope of the present invention.

Claims

1. A cross-flow fan blade based on bionics is characterized in that the blade (27) comprises a plurality of blade units (1) which are axially arranged along an impeller (28), the front edges (2) of the blade units (1) are protruded, the rear edges (3) are recessed, the middle parts of the upper surfaces of the blade units (1) close to the front edges (2) are higher than two sides, the middle parts of the upper surfaces of the blade units close to the rear edges (3) are lower than two sides, and the middle parts of the upper surfaces of the blade units close to the front edges (2) are higher than the middle parts of the upper surfaces of the blade units close to the rear edges (3);

the section-shaped lines of the blade unit (1) are a first arc line (7), a first straight line (8), a second straight line (9), a second arc line (10), a third straight line (11) and a fourth straight line (12) which are sequentially intersected on the windward side of the front edge (2); the leeward side of the rear edge (3) is formed by sequentially intersecting a fourth arc line (14), a fifth straight line (15), a sixth straight line (16), a fifth arc line (17), a seventh straight line (18) and an eighth straight line (19); the middle section (6) is formed by sequentially intersecting a third arc line (13), an eleventh arc line (25), a sixth arc line (20) and a twelfth arc line (26); the left side surface (4) is formed by sequentially intersecting a first arc line (7), a seventh arc line (21), a fourth arc line (14) and an eighth arc line (22); the right side surface (5) is formed by sequentially intersecting a second arc line (10), a ninth arc line (23), a fifth arc line (17) and a tenth arc line (24).

2. The cross-flow fan blade based on bionics of claim 1, characterized in that, the distance between the vertexes of the protruding structures of the leading edges (2) of two adjacent blade units (1) of the blades (27) is 4-80 mm.

3. The cross-flow fan blade based on the bionics of claim 1, characterized in that, the vertical distance from the top point of the protruding structure of the leading edge (2) of the blade unit (1) to the straight line of the two end points of the leading edge (2) is 1-20 mm.

4. The cross-flow fan blade based on the bionics as claimed in claim 1, wherein a vertical distance from a vertex of the concave structure of the trailing edge (3) of the blade unit (1) to a straight line at two end points of the trailing edge (3) is 0.5-15 mm.

5. The cross-flow fan blade based on bionics of claim 1, characterized in that, the chord length of the cross section of the blade unit (1) is 8-120 mm, the height of the middle part of the cross section is 1/10 of the chord length, and the height of the end part of the cross section is 1/12 of the chord length.

6. The cross-flow fan blade based on bionics of claim 1, characterized in that, the chord length of the middle section (6) of the blade unit (1) is 9-130 mm, the height of the middle section (6) is 1/13 of the chord length, and the height of the end of the middle section (6) is 1/20 of the chord length.

7. The bionic-based crossflow blower blade according to claim 1, wherein the total width of the blade (27) is 50-800 mm.