The optimization method of Low-pressure axial fan impeller blade
Technical field
The invention belongs to fan impeller technical fields, and in particular to a kind of Low-pressure axial fan impeller blade it is excellent
Change method.
Background technique
Low-pressure axial fan is as ventilation, HVAC, cooling, air-conditioning and the master for the industrial equipments and household electrical appliance such as transporting
Power is wanted, is used widely.The Aerodynamic Characteristics of axial flow blower are that total pressure is low, and air quantity is big, and impeller adiabatic efficiency is low, the reason is that its blade
There is gap between pipeline, there is Secondary Flow on leaf top, and blade root is connected with wheel hub, and separation stream is also very serious, and blade root and leaf top nearby have
A large amount of whirlpool, or even reflux, cause very big flow losses.
In propeller fan, air-flow pass through blade when the pressure loss be it is extremely complex, along the pressure of blade height
Loss distribution is non-uniform.At blade mean radius, the pressure loss is smaller, and the pressure loss is concentrated mainly on blade
In wake flow in very narrow region;In the middle section Ye Dao close to blade mean radius, the pressure loss is also all smaller, and compares
It is more uniform;But near wheel hub and casing, the region of the pressure loss is expanded, and the numerical value of the pressure loss is also increased
Add.That is that then have active force between them since when air-flow flows through Ye Daoshi, there are relative motions between air-flow and blade,
And the pressure of forward face is greater than the pressure on blade convex surface.Therefore, between two adjacent blades, from blade
Concave surface between the convex surface of another blade there are transverse-pressure gradient, this transverse-pressure gradient with lift coefficient increase
And increase.On the other hand, air-flow is then to produce centrifugal force, the side of the centrifugal force by leaf grating in the form of curvilinear motion
To being the concave surface for being directed towards blade from the convex surface of a blade.In the middle section along blade height, between adjacent blades
Transverse-pressure gradient and the centrifugal force of air-flow balanced, so air-flow will not generate the flowing of transverse direction.But in blade
Root and top situation are then different.For example, in root of blade, outside the stream pressure and boundary-layer in hub surface boundary-layer
Stream pressure is identical, and the air velocity inside boundary-layer is to the close of hub surface with reducing, and is intended to
Zero.Thus inside boundary-layer there is transverse-pressure gradients, but without or few air-flows centrifugal force, it is then attached
The transverse gradients pressure of surface layer cannot be balanced, and the gas in boundary-layer, which will appear from the concave surface of a blade, flows to adjacent blades
Convex surface lateral flow, the pressure in the boundary-layer near forward face decreases, and attached on the convex surface of adjacent blades
Closely, pressure but increased, and then form whirlpool.These whirlpools are taken away by primary air, behind blade tail end, these
Whirlpool is gradually converted into heat energy loss and falls, and this loss has in root of blade and top.So the design of axial flow blower and excellent
The target of change seeks to reduce radial velocity, keeps axial velocity more uniform, promotes the axial velocity at wheel hub and wheel cap, and mention
The acting ability etc. for rising blade, so that fan efficiency and total pressure be made to get a promotion.
Summary of the invention
In view of the above-mentioned deficiencies in the prior art, it is an object of the present invention to provide a kind of Low-pressure axial fan impeller blade
Optimization method.
Step of the invention is specific as follows:
Step 1: establishing impeller pattern to be optimized.The wheelboss side wall of impeller and the spacing of blade outer end are n × s.At this
N section and the corresponding molded line in n section of vertical impeller radial direction, two neighboring section spacing are taken on one piece of blade of model
It is s, innermost section and wheelboss side wall are tangent, 3≤n≤20.The chord length b in n section is measured respectivelyi, i=1,2,
3 ..., n, and outlet geometry angle beta2A(i), i=1,2,3 ..., n.Chamfering and fillet all in model are removed, mould is simplified
Type.Grid dividing and numerical simulation calculation are carried out to simplified model with grid dividing software, obtain the complete of impeller pattern to be optimized
Three velocity components of pressure and n section entrance;Speed triangle is drawn according to three velocity components, is cut to obtain n
The inlet air flow angle beta in face1(i), i=1,2,3 ..., n.The total pressure value of the model is assigned to Z1.
Step 2: being assigned to i for 1.
Step 3: skeletonizing, sketch include the first line segment, second line segment, third line segment, the 4th line segment, the 5th line segment,
6th line segment, the first circular arc, the second circular arc, the 7th line segment and the 8th line segment.First line segment and second line segment parallel lines each other, the
For the both ends endpoint of three line segments respectively on the first line segment and second line segment, the length of third line segment is bi.4th line segment and the 6th
Line segment is separately positioned on the two sides of the 5th line segment, the both ends endpoint of the 4th line segment, one end endpoint of the 6th line segment and third line segment
It is respectively superposed.The other end endpoint of 4th line segment is on the 5th line segment.The one of the other end endpoint of 6th line segment and the 5th line segment
Endpoint is held to be overlapped, and the 6th line segment and the 5th line segment are isometric.5th line segment and third line segment intersection.The center of circle of first circular arc is the
The intersection point of four line segments and the 5th line segment, two-end-point, which is respectively the 4th line segment, is not overlapped endpoint with the 5th line segment.Second circular arc
The center of circle is the intersection point of the 5th line segment and the 6th line segment, and two-end-point, which is respectively the 5th line segment, is not overlapped endpoint with the 6th line segment.The
One circular arc the second circular arc clockwise.7th line segment is overlapped with tangent line of first circular arc on the 4th line segment endpoint,
The angle of 7th line segment and the first line segment is β1(i), the 8th line segment is overlapped with tangent line of second circular arc on the 6th line segment endpoint,
8th line segment and the angle of second line segment are β2A(i).The angle of 7th line segment and the 8th line segment is θc, acquire θc=β2A(i)-
β1(i).The angle of 4th line segment and the 5th line segment is α1, take α1=0.6 θc;The angle of 6th line segment and the 5th line segment is α2, take α2
=0.4 θc.The angle of third line segment and the 7th line segment is α1, the angle of third line segment and the 8th line segment is α2。
Step 4: the first circular arc and the second circular arc form Novel wire.Thickness value a, 1mm≤a≤6mm are superimposed to Novel wire,
Obtain circular section;Or a kind of aerofoil profile is chosen in airfoil database, obtain the thickness distribution of aerofoil section, the thickness of aerofoil section
Degree distribution combines Novel wire to obtain aerofoil section.Resulting circular section or aerofoil section are recorded as i-th of section.
Step 5: i increases 1, if i≤n, step three and four is repeated, section obtained by step 4 is circular arc in repetitive process
Tee section is aerofoil section.Otherwise, into next step.
Step 6: resulting n section each adjacent two section distance s are arranged in parallel, and be put into two it is coaxial and half
Diameter difference is between the cylindrical surface of n × s.The geometric center in n section is on a straight line perpendicular to n section, and this is straight
Line is vertically intersected on the axis of two cylindrical surface.N section is successively arranged according to chord length size, and the longest section of chord length is located at most
Inside.The longest section of chord length and diameter are tangent compared with small cylindrical surface.First line segment in n section is parallel to each other, and with two cylinders
The axis in face is vertical.The First Line section in n section is located at the same side.Blade blank is obtained according to n section.Extended blade blank
Both ends so that the outer end of blade blank, which passes completely through, is relatively large in diameter cylindrical surface, the inner end of blade blank pass completely through diameter compared with
Small cylindrical surface.Blade blank between two cylindrical surface is to optimize rear blade.Using two cylindrical surface axis as array center, circumferentially
Uniformly distributed array goes out m pieces of blade, 4≤m≤10.Wheel hub is drawn for m pieces of blade, the impeller pattern after being optimized.
Step 7: taking the n section and the n section of vertical impeller radial direction on one piece of blade of step 6 model built
Corresponding molded line, adjacent sections spacing are s, and innermost section and wheelboss side wall are tangent.The chord length in n section is measured respectively
bi, i=1,2,3 ..., n, and outlet geometry angle beta2A(i), i=1,2,3 ..., n.It removes all in step 6 model built
Chamfering and fillet obtain new simplified model.With grid dividing software to new simplified model grid dividing, and carry out numerical simulation meter
It calculates, obtains the total pressure of step 6 model built and three velocity components of n section entrance;It is drawn according to three velocity components
Speed triangle, to obtain the inlet air flow angle beta in n section1(i), i=1,2,3 ..., n.The total pressure value of the model is assigned
It is worth to Z2.
Step 8: the value of Z2 is assigned to Z1, and repetition step if Z2 subtracts Z1 resulting value greater than k, 3Pa≤k≤8Pa
Two, three, four, five, six and seven.Otherwise, optimization terminates.
The method that blade blank is obtained in step 6 is as follows: the contour line in n section is carried out " putting in solidworks
Sample curved surface " operation, smooth transition generate blade blank.
The method at extended blade blank both ends is as follows in step 6: blade blank is carried out " curved surface in solidworks
Extend " operation.
The aerofoil profile chosen in step 4 is NACA0012.
The value of k is 5Pa in step 8.
The invention has the advantages that:
1, the present invention combines fluid machinery, three-dimensional modeling and CFD, by the chord length of blade profile, inlet air flow angle and goes out
Mouth geometry angle, it will be able to the performance of Low-pressure axial fan be optimized, design time and cost are substantially reduced.
2, the present invention has duplicate Optimization Steps unit, repeats Optimization Steps unit, can be completed to low-pressure shaft
The multiple optimization of streaming blower performance.
3, the present invention executes Optimization Steps unit for the first time, and the total pressure of Low-pressure axial fan is substantially improved, but efficiency
It is declined slightly;Subsequent Optimization Steps unit is executed, the efficiency of Low-pressure axial fan is held essentially constant, and total pressure can be mentioned persistently
It rises.
Detailed description of the invention
Fig. 1 is the perspective view of impeller pattern to be optimized;
Fig. 2 is the sketch that blade profile molded line is drawn in the present invention.
Specific embodiment
Below in conjunction with attached drawing, the invention will be further described.
Specific step is as follows for the optimization method of Low-pressure axial fan impeller blade:
Step 1: establishing impeller pattern to be optimized as shown in Figure 1, the wheelboss side wall of impeller and the spacing of blade outer end are
8s.Take eight sections and the corresponding molded line in eight sections of vertical impeller radial direction on one piece of blade of the model, adjacent section
Interplanar distance is s, and innermost section and wheelboss side wall are tangent.The chord length b in eight sections is measured respectivelyi, i=1,2,3 ...,
8, and outlet geometry angle beta2A(i), i=1,2,3 ..., 8.Chamfering and fillet all in model are removed, model is simplified.With net
Lattice divide software and carry out grid dividing and numerical simulation calculation to simplified model, obtain impeller pattern to be optimized total pressure and eight
Three velocity components of section entrance;Draw speed triangle according to three velocity components, thus obtain eight sections into
Implication stream angle beta1(i), i=1,2,3 ..., 8.The total pressure value of impeller pattern to be optimized is assigned to Z1.
Step 2: being assigned to i for 1.
Step 3: as shown in Fig. 2, skeletonizing, sketch include the first line segment 1, second line segment 2, third line segment the 3, the 4th
Line segment 4, the 5th line segment 5, the 6th line segment 6, the first circular arc 7-1, the second circular arc 7-2, the 7th line segment 8 and the 8th line segment 9.First Line
Section 1 and the parallel lines each other of second line segment 2, the both ends endpoint of third line segment 3 is respectively on the first line segment 1 and second line segment 2, third
The length of line segment 3 is bi.4th line segment 4 and the 6th line segment 6 are separately positioned on the two sides of the 5th line segment 5, the 4th line segment the 4, the 6th
One end endpoint of line segment 6 is respectively superposed with the both ends endpoint of third line segment 3.The other end endpoint of 4th line segment 4 is in the 5th line segment 5
On.The other end endpoint of 6th line segment 6 is overlapped with one end endpoint of the 5th line segment 5, and the 6th line segment 6 and the 5th line segment 5 are isometric.
5th line segment 5 intersects with third line segment 3.The center of circle of first circular arc 7-1 is the intersection point of the 4th line segment 4 and the 5th line segment 5, two-end-point
Respectively the 4th line segment 4 is not overlapped endpoint with the 5th line segment 5.The center of circle of second circular arc 7-2 is the 5th line segment 5 and the 6th line segment
6 intersection point, two-end-point, which is respectively the 5th line segment 5, is not overlapped endpoint with the 6th line segment 6.First circular arc 7-1 is in the second circular arc 7-2
Clockwise.7th line segment 8 is overlapped with tangent line of the first circular arc 7-1 on 4 endpoint of the 4th line segment, the 7th line segment 8 with
The angle of first line segment 1 is β1(i), the 8th line segment 9 is overlapped with tangent line of the second circular arc 7-2 on 6 endpoint of the 6th line segment, and the 8th
Line segment 9 and the angle of second line segment 2 are β2A(i).The angle of 7th line segment 8 and the 8th line segment 9 is θc, acquire θc=β2A(i)-
β1(i).The angle of 4th line segment 4 and the 5th line segment 5 is α1, take α1=0.6 θc;The angle of 6th line segment 6 and the 5th line segment 5 is α2,
Take α2=0.4 θc.The angle of third line segment 3 and the 7th line segment 8 is α1, the angle of third line segment 3 and the 8th line segment 9 is α2。
Step 4: the first circular arc 7-1 and the second circular arc 7-2 forms Novel wire.Thickness value a is superimposed to Novel wire, the value of a takes
4mm obtains circular section;Or a kind of aerofoil profile is chosen in airfoil database, the aerofoil profile of selection is NACA0012, obtains aerofoil profile and cuts
The thickness distribution combination Novel wire of the thickness distribution in face, aerofoil section obtains aerofoil section, by resulting circular section or the wing
Type section is recorded as i-th of section.
Step 5: i increases 1, if i≤8, step three and four is repeated, section obtained by step 4 is circular arc in repetitive process
Tee section is aerofoil section.Otherwise, into next step.
Step 6: resulting eight sections each adjacent two section distance s are arranged in parallel, and be put into two it is coaxial and half
Diameter difference is between the cylindrical surface of 8s.The geometric center in eight sections is on a straight line perpendicular to eight sections, and this is straight
Line is vertically intersected on the axis of two cylindrical surface.Eight sections are successively arranged according to chord length size, and the longest section of chord length is located at
Most inner side.The longest section of chord length and the lesser cylindrical surface of diameter are tangent.First line segment 1 in eight sections is parallel to each other, and with
The axis of two cylindrical surface is vertical.First line segment 1 in eight sections is respectively positioned on the same side.The contour line in eight sections is existed
" setting-out curved surface " operation is carried out in solidworks, smooth transition generates blade blank.By blade blank in solidworks
" surface extending " operation is carried out, so that the outer end of blade blank, which passes completely through, is relatively large in diameter cylindrical surface, the inner end of blade blank is complete
Diameter is passed through entirely compared with small cylindrical surface.Blade blank between two cylindrical surface is to optimize rear blade.Using two cylindrical surface axis as battle array
Column center, 60 ° are array angle, and Circle-Array lists six pieces of blades.Wheel hub is drawn for six pieces of blades, the impeller mould after being optimized
Type.First circular arc of blade profile molded line is close to the import of impeller pattern, and the second circular arc is close to the outlet of impeller pattern.
Step 7: taken on one piece of blade of step 6 model built vertical impeller radial direction eight sections and this eight cut
The corresponding molded line in face, two neighboring section spacing is s, and innermost section and wheelboss side wall are tangent.Eight are measured respectively to cut
The chord length b in facei, i=1,2,3 ..., 8, and outlet geometry angle beta2A(i), i=1,2,3 ..., 8.It removes in step 6 model built
All chamferings and fillet, obtain new simplified model.With grid dividing software to new simplified model grid dividing, line number of going forward side by side value
Simulation calculates, and obtains the total pressure of step 6 model built and three velocity components of eight section entrances;According to three speed
Component draws speed triangle, to obtain the inlet air flow angle beta in eight sections1(i), i=1,2,3 ..., 8.By step 6 institute
The total pressure value of established model is assigned to Z2.
Step 8: the value of Z2 is assigned to Z1 if Z2 subtracts Z1 resulting value greater than 5Pa, and repeat Step 2: three,
Four, five, six and seven.Otherwise, optimization terminates.