A new blade shaping method for energy-saving transformation of axial flow fans with adjustable blades in power stations

Abstract

The present invention discloses a method for shaping new moving blades for energy-saving transformation of an axial flow fan with adjustable moving blades in a power station, comprising: first, determining the fan transformation method based on the technical parameters of the fan before and after the energy-saving transformation of the axial flow fan with adjustable moving blades; second, determining corresponding new moving blade shaping methods for different fan transformation methods; and finally, implementing the fan energy-saving transformation according to the fan transformation scheme and new moving blade shaping method determined above. The present invention shapes the fan moving blades into new energy-saving blades while keeping most of the components of the axial flow fan with adjustable moving blades unchanged. After the shaping is completed, all the original moving blades of the fan are replaced with new moving blades, thereby achieving multiple purposes such as saving investment costs, shortening the investment recovery period, achieving deep energy saving of the fan, and ensuring safe and reliable operation of the fan.

Description

Technical Field

[0001] The invention relates to an axial flow fan with adjustable moving blades used in a flue gas system of a coal-fired power plant, and in particular to a new moving blade shaping method for energy-saving transformation of an axial flow fan with adjustable moving blades in a power station. Background Art

[0002] At present, axial flow fans with adjustable moving blades are the most widely used in various types of thermal power units across the country. However, due to factors such as unreasonable fan selection, large changes in coal quality, and frequent deep peak regulation of units, the fans have various problems in actual operation, such as insufficient fan output, low stall margin, and poor matching with the pipeline system. As a result, the actual operating economy and safety of axial flow fans with adjustable moving blades are often poor, resulting in high energy consumption of thermal power generating units.

[0003] When implementing energy-saving retrofits on axial flow fans with adjustable blades, the solution often involves replacing the entire fan. This not only results in significant investment costs and a long payback period, but also, due to the limited number of blade profiles available from fan manufacturers, optimal compatibility between the fan and the system after the retrofit is difficult. Therefore, when implementing energy-saving retrofits on axial flow fans with adjustable blades, it is necessary to propose new blade shaping methods to achieve multiple goals, such as reducing investment costs, shortening the payback period, achieving deep energy savings, and ensuring safe and reliable operation. Summary of the Invention

[0004] In order to solve the problems existing in the prior art, the present invention proposes a new blade shaping method for energy-saving transformation of an axial flow fan with adjustable blades in a power station. The purpose is to shape the fan blades into a new energy-saving blade shape while keeping most of the components of the axial flow fan with adjustable blades unchanged. After the shaping is completed, all the original blades of the fan are replaced with new blades, so as to achieve multiple goals such as saving investment costs, shortening the investment recovery period, realizing deep energy saving of the fan, and ensuring safe and reliable operation of the fan.

[0005] The present invention is achieved by adopting the following technical solutions:

[0006] A method for energy-saving retrofitting of an axial flow fan with adjustable blades in a power station using a new blade shaping method comprises: first, determining a fan retrofit method based on the technical parameters of the fan before and after the energy-saving retrofitting; second, determining corresponding new blade shaping methods for different fan retrofit methods; and finally, implementing the fan energy-saving retrofit based on the fan retrofit plan and the new blade shaping method determined above.

[0007] A further improvement of the present invention is that for the energy-saving transformation of a single-stage axial flow fan with adjustable blades, a new blade shape is specifically implemented as follows:

[0008] Step 1: Determine the fan transformation technical solution, and calculate the flow coefficient corresponding to the fan TB point selection parameters before the fan with adjustable blades is transformed. Pressure coefficient φ1, flow coefficient corresponding to TB point selection parameter after fan energy-saving transformation The pressure coefficient φ2 determines the technical solution for fan modification;

[0009] Step 2: Determine the new fan blade shaping method. The fan modification technical solutions are divided into two methods: fan blade replacement and fan partial modification.

[0010] A further improvement of the present invention is that the fan modification technical solution is divided into two methods: fan blade replacement and fan partial modification. The two methods are described as follows:

[0011] (1) Fan blade replacement method: when the flow coefficient ratio before and after the fan modification meets the requirements When replacing a fan, only all the fan blades need to be replaced, while the dimensions of other structures such as the fan hub and casing remain unchanged;

[0012] (2) Partial modification of the fan: when the flow coefficient ratio before and after the fan modification meets the requirement When replacing the fan blades, the following changes are required:

[0013] ① Adjust the height H′1 of the wind turbine blades and shorten the height H′1 of the wind turbine blades after the transformation to meet the requirements. Where H1 is the blade height before the fan modification, and H′1 is the blade height after the fan modification, both in mm.

[0014] ②Inner diameter of fan casing R′ shroud Adjust and shorten the inner diameter R' of the fan casing after transformation shroud , so that it satisfies R′ shroud =R shroud +H′1-H1, where R shroud is the inner diameter of the fan casing before modification, R′ shroud is the inner diameter of the fan casing after modification, and the unit is mm. At the same time, the fan blade tip clearance remains unchanged before and after the modification.

[0015] A further improvement of the present invention is that, for the fan blade replacement method, the specific shaping method of the fan new moving blade is as follows:

[0016] (1) Divide the blade into M blade sections along the blade height in the cylindrical coordinate system, where M is an integer between 3 and 8, and expand the blade profile coordinates of the M blade sections into a plane coordinate system;

[0017] (2) determining the modeling method of the M blade sections, wherein the modeling method of each blade section is the same;

[0018] (3) Determine the pressure surface profile PS′ of the i-th blade section of the new moving blade i and suction surface line SS′ i , construct the blade profile line BS′ of the i-th blade section of the new moving blade i , according to the arc line C′ of the new blade section determined in the previous step 1,i The shape line passes through the middle arc line C' 1,i The blade thickness distribution is superimposed on both sides of the profile, and the leading edge and trailing edge of the blade section are formed into the leading edge arc curve and the trailing edge arc curve to determine the pressure surface profile PS′ of the i-th blade section of the new moving blade. i and suction surface line SS′ i ;

[0019] (4) The blade profile line BS′ of the M blade sections of the new moving blade i The new three-dimensional shape of the moving blade is generated by stacking along the blade height direction. According to the blade profile line BS′ of the i-th blade section of the new moving blade i , solve to get the centroid O′ of the i-th blade section i , the blade center of gravity O′ of the M blade sections of the new moving blade i As the control point of the n-order Bezier curve, i = 1, ..., M, n = M-1, O'1 is the starting point, O' M Point is the end point, and the (M-1) order Bezier curve C2 is generated. Then, the blade profile line BS′ of the i-th blade section of the new moving blade is converted to i By stacking the Bezier curve C2 along the blade height direction, the three-dimensional shape of the new moving blade is completed.

[0020] A further improvement of the present invention is that, in step (2), for the i-th blade section, i=1, ..., M, a new blade section modeling method is described as follows:

[0021] ① Using the n-order Bezier curve, the pressure surface line PS of the i-th blade section of the original blade is i , suction surface line SS i For curve fitting, the formula for the n-order Bezier curve is as follows:

[0022]

[0023] During the fitting process, keep the blade leading edge point A i , Blade trailing edge point B i The position remains unchanged, and the mid-camber line C of the i-th blade section is used. 1,i The pressure surface profile PS is affected by applying the same blade thickness distribution on both sides. i , suction surface line SS iPerform curve fitting; use the least square method to fit the Bessel fitting curve and the middle arc C 1,i The principle of minimizing the sum of squared errors between discrete points is used to solve the control point P of the Bezier curve. i , i=0,1,...,n, and obtain the Bezier curve order n, n≥3;

[0024] After fitting is completed, the median arc line C of the i-th blade section of the original blade is obtained 1,i The Bezier fitting curve of the blade thickness distribution is used to obtain the following parameters: the leading edge inlet geometric angle α of the i-th blade section of the original blade i , trailing edge exit geometry angle β i , blade chord length c i The maximum thickness of the blade is a distance from the leading edge of the blade i , maximum blade thickness b max,i parameter;

[0025] ② Adjust the arc line C of the i-th blade section of the original blade 1,i The Bezier fitting curve parameters of the new moving blade are obtained, and the Bezier fitting curve of the arc line of the i-th blade section of the new moving blade is completed. 1,i The shape;

[0026] The Bezier fitting curve parameter of the new rotor blade section is the leading edge inlet geometric angle α′ i , the trailing edge exit geometry angle is β′ i and blade chord length c′ i Determined by the following formula:

[0027]

[0028] Where, k1 is the blade leading edge inlet geometry angle adjustment coefficient, k2 is the blade trailing edge outlet geometry angle adjustment coefficient, and k3 is the blade chord length adjustment coefficient;

[0029] Once the above parameters are determined, the arc line C′ in the section of the new blade profile is uniquely determined. 1,i Type line.

[0030] A further improvement of the present invention is that, in step (3), the specific implementation method is as follows:

[0031] ① Take the leading edge of the blade point A i The coordinate origin is 0, the leading edge of the blade is point A i To blade trailing edge point B i Establish a coordinate system for the positive direction of the x-axis, with the blade center arc C′ 1,iThe distance from a certain point on the x-axis to the coordinate origin 0 in the x-direction is x, and the blade thickness distribution at this point is b(x). According to the Bezier fitting curve of the blade thickness distribution of the i-th blade section of the original blade obtained in the second step, the blade thickness distribution function of this section is obtained: b(x) = f1(x), 0≤x≤c i ,make The blade thickness distribution function is processed dimensionlessly and the function b(j)=f2(j) is obtained, 0≤j≤1;

[0032] ② Keep the thickness distribution of the new moving blade and the original blade at the same relative chord length position at the i-th blade section, that is, assume that the abscissa of the i-th blade section of the new moving blade is x′, and the chord length of the blade section is c′ i ,but It can be organized into the blade thickness distribution function of the i-th blade section of the new moving blade b(x′)=f3(x′), 0≤x′≤c′ i , thus, the blade thickness distribution law of the i-th blade section of the new moving blade is determined;

[0033] ③ The blade thickness distribution law of the i-th blade section of the new moving blade determined in the above steps is superimposed on the center arc line C′ of the blade section 1,i On the profile line, the pressure surface curve and the suction surface curve are generated. Then, the leading edge arc curve and the trailing edge arc curve are constructed on the leading edge and trailing edge of the blade section respectively. The leading edge arc curve and the trailing edge arc curve are both arcs, which are tangent to the pressure surface curve and the suction surface curve generated above, respectively. In this blade section, the arc radius of the new moving blade leading edge arc curve is R′ 1,i Satisfies: 0<R′ 1,i ≤3%·c′ i ; New blade trailing edge arc curve arc radius R' 2,i Satisfies: 0<R′ 2,i ≤2%·c′ i In this way, the pressure surface profile PS′ of the i-th blade section of the new moving blade is determined i and suction surface line SS′ i , the pressure surface profile PS′ i and suction surface line SS′ i Combined together, the blade profile line BS′ of the i-th blade section of the new moving blade is completed. i structure.

[0034] A further improvement of the present invention is that, for the local modification method of the fan, the specific shaping method of the new fan blade is as follows:

[0035] (1) Complete the three-dimensional modeling of the new moving blade according to the contents of parts (1) to (4) of the fan blade replacement method. The original blade height H2 of the new moving blade is consistent with the original blade height H1, that is, H2 = H1;

[0036] (2) Cut the top of the new moving blade to shorten the blade height. From the first step, it can be seen that after the fan is partially modified, the fan blade height must be shortened to H'1. Therefore, the top of the blade is cut, and after the blade is fixed to the hub, a cylindrical coordinate system is used, with the center line of the hub as the axis of rotation, and the top of the blade is cut off by a height of (H2-H′1). H2-H′1=H1-H′1, and the height of the new moving blade is shortened to H′1. The other parts of the blade remain unchanged.

[0037] A further improvement of the present invention is that, for the new moving blade shaping of the two-stage axial flow fan with adjustable moving blades for energy saving, the shaping method of the new moving blades of the first and second stages is the same, and both are shaped according to the shaping method of the new moving blade shaping of the single-stage axial flow fan with adjustable moving blades for energy saving: after the first stage completes the shaping of the new moving blades of the single-stage fan according to the shaping method of the new moving blade shaping of the single-stage axial flow fan with adjustable moving blades for energy saving, the second stage repeats the above process, and the shapes of the fan moving blades of the first and second stages are exactly the same.

[0038] The present invention has at least the following beneficial technical effects:

[0039] The present invention provides a method for shaping new blades for energy-saving retrofits of axial-flow fans with adjustable blades for power plants. The method determines the fan retrofit method based on the fan's technical parameters before and after the retrofit. Then, corresponding new blade shaping methods are determined for each fan retrofit method. Once this is completed, the energy-saving retrofit and new blade shaping of the adjustable-blade axial-flow fan can be implemented according to the determined method.

[0040] This new blade shaping method for an axial flow fan with adjustable blades can be used to develop customized new blades for energy-saving transformation of an axial flow fan with adjustable blades according to actual user needs. After the developed new blades are applied to the axial flow fan with adjustable blades, deep energy saving of the fan can be achieved on the basis of reducing the fan output. At the same time, the fan adjustment performance can be effectively improved, the fan operating range can be expanded, and the fan energy-saving transformation effect is significant. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a schematic diagram of the blade cross-section of the patented invention;

[0042] Figure 2 This is a schematic diagram of the blade thickness distribution of the blade cross section of the patented invention.

[0043] Where M is the total number of blade sections, i is the blade section number, is the flow coefficient corresponding to the TB point selection parameters of the fan before the transformation, φ1 is the pressure coefficient corresponding to the TB point selection parameters of the fan before the transformation, is the flow coefficient corresponding to the TB point selection parameters of the fan after transformation, and φ2 is the pressure coefficient corresponding to the TB point selection parameters of the fan after transformation.

[0044] H1 is the height of the moving blades before the fan is modified, H′1 is the height of the moving blades after the fan is modified, R shroud is the inner diameter of the fan casing before modification, R′ shroud It is the inner diameter of the fan casing after modification. The above units are all in mm.

[0045] n is the order of the Bezier curve, P i is the control point of the Bezier curve, b(x)=f1(x) is the blade thickness distribution function of the i-th blade section of the original blade, b(x)=f2(x) is the dimensionless blade thickness distribution function of the i-th blade section of the original blade, and b(x)=f3(x) is the thickness distribution function of the i-th blade section of the new moving blade.

[0046] Figure 1 are the parameters of the original blade section i, among which A i is the leading edge point of the blade, B i is the trailing edge point of the blade, C 1,i The arc line of the blade, PS i is the pressure surface line of the blade, SS i It is the blade suction surface line.

[0047] α i is the geometric angle of the blade leading edge inlet, β i is the geometric angle of the blade trailing edge outlet, and the above units are all in degrees.

[0048] a i b is the distance from the maximum thickness position of the blade to the leading edge of the blade, max,i is the maximum thickness of the blade, c i is the blade chord length, R 1,i is the radius of the arc curve of the original blade leading edge, R 2,i is the arc radius of the original blade trailing edge arc curve, and the above units are all mm.

[0049] Figure 2 are the parameters of the original blade's i-th blade section, where the blade leading edge point A i is the coordinate origin 0, x is the blade center arc C′ 1,i The distance of a certain point on the blade from the coordinate origin 0 in the x direction, and b(x) is the blade thickness distribution corresponding to the horizontal coordinate x position.

[0050] The following parameters are all parameters of the i-th blade section of the new moving blade:

[0051] C′ 1,i is the blade mid-camber line, PS′ i is the pressure surface profile of the blade, SS′ i It is the blade suction surface line.

[0052] α′ i is the blade leading edge inlet geometric angle, β′ i is the blade trailing edge exit geometry angle, all in degrees; k1 is the blade leading edge inlet geometry angle adjustment coefficient, and k2 is the blade trailing edge exit geometry angle adjustment coefficient.

[0053] a′ i b′ is the distance from the maximum thickness of the blade to the leading edge of the blade, max,i is the maximum thickness of the blade, c′ i is the blade chord length, R′ 1,i is the arc radius of the leading edge of the blade, R′ 2,i is the arc radius of the blade trailing edge, all units are mm; k3 is the blade chord length adjustment coefficient.

[0054] x′ is the blade center camber line C′ 1,i The distance of a certain point on the surface of the blade from the origin 0 in the x direction, and b(x′) is the blade thickness distribution corresponding to the horizontal coordinate x′.

[0055] O′ i is the centroid of the blade, and C2 is the Bezier curve of the blade along the blade height direction. DETAILED DESCRIPTION

[0056] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art. It should be noted that, unless there is a conflict, the embodiments of the present disclosure and the features described in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0057] A novel blade shaping method for energy-saving transformation of an axial flow fan with adjustable blades in a power station, comprising:

[0058] First, the fan modification method is determined based on the technical parameters of the axial flow fan with adjustable moving blades before and after the energy-saving modification; second, the corresponding new moving blade shaping method is determined for different fan modification methods; finally, the fan energy-saving modification is implemented based on the fan modification plan and the new moving blade shaping method determined above.

[0059] (1) For the energy-saving transformation of a single-stage axial flow fan with adjustable blades into a new blade shape, the specific implementation method is as follows:

[0060] 1. Determine the technical solution for fan transformation. According to the flow coefficient corresponding to the fan TB point selection parameters before the transformation of the adjustable blade axial flow fan Pressure coefficient φ1, flow coefficient corresponding to TB point selection parameter after fan energy-saving transformation The pressure coefficient φ2 determines the technical solution for fan modification. The technical solution for fan modification is divided into two methods: fan blade replacement and fan partial modification. The two methods are described as follows:

[0061] (1) Fan blade replacement method. When the flow coefficient ratio before and after the fan modification meets When replacing a fan, only all the moving blades of the fan need to be replaced, while the dimensions of other structures such as the fan hub and casing remain unchanged.

[0062] (2) Partial modification of the fan. When the flow coefficient ratio before and after the fan modification meets When replacing the fan blades, the following changes are also required:

[0063] ① Adjustment of wind turbine blade height H′1. Shorten the wind turbine blade height H′1 after transformation to meet Where H1 is the blade height before the fan modification, and H′1 is the blade height after the fan modification, both in mm.

[0064] ②Inner diameter of fan casing R′ shroud Adjustment. Shorten the inner diameter R' of the fan casing after modification shroud , so that it satisfies R′ shroud =R shroud +H′1-H1. In the formula, R shroud is the inner diameter of the fan casing before modification, R′ shroud is the inner diameter of the fan casing after modification, in mm. The fan blade tip clearance remains unchanged before and after modification.

[0065] 2. Determine the new fan blade shaping method. As mentioned above, the fan modification technology solutions are divided into two methods: fan blade replacement and fan partial modification. The new fan blade shaping methods of the two methods are different, and they are discussed below.

[0066] I. Regarding the fan blade replacement method, the specific shaping method of the fan new blade is as follows:

[0067] (1) The blade is divided into M blade sections along the blade height in the cylindrical coordinate system, where M is an integer between 3 and 8, and the blade profile coordinates of the M blade sections are expanded into the plane coordinate system.

[0068] (2) Determine the modeling method for the M blade sections. For the M blade sections, the modeling method for each blade section is the same. The following takes the i-th (i=1,…,M) blade section as an example to describe the modeling method for the new rotor blade section as follows:

[0069] ① Using the n-order Bezier curve, the pressure surface line PS of the i-th blade section of the original blade is i , suction surface line SS i Perform curve fitting. The formula for the n-th order Bezier curve is as follows:

[0070]

[0071] During the fitting process, keep the blade leading edge point A i , Blade trailing edge point B i The position remains unchanged, and the mid-camber line C of the i-th blade section is used. 1,i The pressure surface profile PS is affected by applying the same blade thickness distribution on both sides. i , suction surface line SS i Perform curve fitting; use the least square method to fit the Bessel fitting curve and the middle arc C 1,i The principle of minimizing the sum of squared errors between discrete points is used to solve the control point P of the Bezier curve. i , i = 0, 1, ..., n, and obtain the Bezier curve order n (usually, n ≥ 3).

[0072] After fitting is completed, the median arc line C of the i-th blade section of the original blade is obtained 1,i The Bezier fitting curve of the blade thickness distribution is used to obtain the following parameters: the leading edge inlet geometric angle α of the i-th blade section of the original blade i , trailing edge exit geometry angle β i , blade chord length c i The maximum thickness of the blade is a distance from the leading edge of the blade i , maximum blade thickness b max,i parameter.

[0073] ② Adjust the arc line C of the i-th blade section of the original blade 1,i The Bezier fitting curve parameters of the new moving blade are obtained, and the Bezier fitting curve of the arc line of the i-th blade section of the new moving blade is completed. 1,i styling.

[0074] The Bezier fitting curve parameter of the new rotor blade section is the leading edge inlet geometric angle α′ i , the trailing edge exit geometry angle is β′ i and blade chord length c′ i Determined by the following formula:

[0075]

[0076] Where k1 is the blade leading edge inlet geometry angle adjustment coefficient, k2 is the blade trailing edge outlet geometry angle adjustment coefficient, and k3 is the blade chord length adjustment coefficient.

[0077] Once the above parameters are determined, the arc line C′ in the section of the new blade profile is uniquely determined. 1,i Type line.

[0078] (3) Determine the pressure surface profile PS′ of the i-th blade section of the new moving blade i and suction surface line SS′ i , construct the blade profile line BS′ of the i-th blade section of the new moving blade i According to the arc line C′ in the new blade section determined in the previous step 1,i The shape line passes through the middle arc line C' 1,i The blade thickness distribution is superimposed on both sides of the profile, and the leading edge and trailing edge of the blade section are formed into the leading edge arc curve and the trailing edge arc curve to determine the pressure surface profile PS′ of the i-th blade section of the new moving blade. i and suction surface line SS′ i The specific implementation method is as follows:

[0079] ① Take the leading edge of the blade point A i The coordinate origin is 0, the leading edge of the blade is point A i To blade trailing edge point B i Establish a coordinate system for the positive direction of the x-axis, with the blade center arc C′ 1,i The distance from a certain point on the x-axis to the coordinate origin 0 in the x-direction is x, and the blade thickness distribution at this point is b(x). According to the Bezier fitting curve of the blade thickness distribution of the i-th blade section of the original blade obtained in the second step, the blade thickness distribution function of this section can be obtained: b(x) = f1(x), 0≤x≤c i ,make The blade thickness distribution function is dimensionless and the function b(j)=f2(j) is obtained, 0≤j≤1.

[0080] ② The present invention maintains the same thickness distribution of the new moving blade and the original blade at the same relative chord length position of the i-th blade section, that is, assuming that the abscissa of the i-th blade section of the new moving blade is x', and the chord length of the blade section is c' i ,but It can be organized into the blade thickness distribution function of the i-th blade section of the new moving blade b(x′)=f3(x′), 0≤x′≤c′ i In this way, the blade thickness distribution law of the i-th blade section of the new moving blade is determined.

[0081] ③ The blade thickness distribution law of the i-th blade section of the new moving blade determined in the above steps is superimposed on the center arc line C′ of the blade section 1,i On the profile line, generate the pressure surface curve and the suction surface curve. Then, construct the leading edge arc curve and the trailing edge arc curve on the leading edge and trailing edge of the blade section respectively. The leading edge arc curve and the trailing edge arc curve are both arcs, which are tangent to the pressure surface curve and the suction surface curve generated above, respectively. In this blade section, the arc radius of the new moving blade leading edge arc curve is R′ 1,i Satisfies: 0<R′ 1,i ≤3%·c′ i ; New blade trailing edge arc curve arc radius R' 2,i Satisfies: 0<R′ 2,i ≤2%·c′ i In this way, the pressure surface profile PS′ of the i-th blade section of the new moving blade is determined. i and suction surface line SS′ i , the pressure surface profile PS′ i and suction surface line SS′ i Combined together, the blade profile line BS′ of the i-th blade section of the new moving blade is completed. i structure.

[0082] (4) The blade profile line BS′ of the M blade sections of the new moving blade i (i=1,…,M) are stacked along the blade height direction to generate a new three-dimensional shape of the moving blade. According to the blade profile line BS′ of the i-th blade section of the new moving blade i , solve to get the centroid O′ of the i-th blade section i , the blade center of gravity O′ of the M blade sections of the new moving blade i (i=1,…,M) is used as the control point of the n-order (n=M-1) Bezier curve, O′1 is the starting point, O′ M The point is taken as the end point, and the (M-1) order Bezier curve C2 is generated. Then, the blade profile line BS′ of the i-th blade section of the new moving blade is i By stacking the Bezier curve C2 along the blade height direction, the three-dimensional shape of the new moving blade is completed.

[0083] II. Regarding the local modification method of the fan, the specific shaping method of the new fan blade is as follows:

[0084] (1) Complete the three-dimensional modeling of the new moving blade according to the contents of parts (1) to (4) in step I. The original blade height H2 of the new moving blade is consistent with the original blade height H1, that is, H2 = H1.

[0085] (2) Cut the top of the new moving blade to shorten the blade height. From the first step, it can be seen that after the fan is partially modified, the fan blade height should be shortened to H'1 Therefore, the top of the blade needs to be cut. After the blade is fixed to the hub, using a cylindrical coordinate system with the hub centerline as the axis of rotation, the top of the blade is cut off by a height of (H2-H′1) (H2-H′1=H1-H′1). The height of the new rotor blade is shortened to H′1, while the rest of the blade remains unchanged. This completes the three-dimensional shape of the new rotor blade.

[0086] (2) For the new blade shaping of the two-stage axial flow fan with adjustable blades for energy saving, the shaping method for the first and second stages is the same, and both are shaped according to the method of step (1): After the first stage completes the shaping of the new blades of the single-stage fan according to the method of step (1), the second stage repeats the above process, and the blade shapes of the first and second stages are exactly the same. In this way, the shaping of the new blades of the two-stage axial flow fan with adjustable blades for energy saving is completed.

[0087] Example

[0088] The fan of a 600MW unit in China is a single-stage axial flow fan with adjustable blades. The fan has 22 blades, an impeller diameter of 2660mm, and an inner diameter of the fan casing R shroud =1330mm, blade height H1=630mm, motor rated speed is 990r / min, fan TB point flow rate is 232m 3 / s, TB point pressure is 4730Pa, and intake air density is 1.183kg / m 3 After energy-saving transformation, the flow rate of fan TB point is 220m 3 / s, TB point pressure is 3500Pa, and intake air density is 1.146kg / m 3 After calculation, the flow coefficient corresponding to the TB point selection parameters of the fan before transformation is obtained. The pressure coefficient φ1 of the fan TB point selection parameter before the transformation is 0.421, and the flow coefficient of the fan TB point selection parameter after the transformation is After the transformation, the fan TB point selection parameter corresponds to a pressure coefficient of φ2 = 0.321. Follow the steps below to implement the new blade shape of the adjustable blade axial flow fan:

[0089] 1. Flow coefficient ratio before and after fan transformation satisfy Therefore, the fan blade replacement method is adopted to implement fan energy-saving transformation.

[0090] 2. Select M=6, that is, divide the blade into 6 equal sections along the blade height in the cylindrical coordinate system.

[0091] 3. Taking the first blade section (i.e. the blade root section) as an example, implement the modeling of a single blade section:

[0092] (1) The pressure surface profile PS1 and suction surface profile SS1 of the first blade section are fitted using an n-order Bezier curve. The order of the Bezier curve n = 8 is obtained, and the control point P of the Bezier curve is obtained. i , i=0,1,...,8; after the fitting is completed, the camber line C of the first blade section of the original blade is obtained 1,1 The Bezier fitting curve of the blade thickness distribution is obtained, and the following parameters of the first blade section are obtained: the leading edge inlet geometric angle α i =31°, trailing edge exit geometry angle β i =37°, blade chord length c i =348.3mm, the maximum thickness of the blade is a meter away from the leading edge of the blade i =111.5mm, maximum blade thickness b max,i =36.6mm.

[0093] (2) Adjust the arc line C of the first blade section of the original blade 1,1 The Bezier fitting curve parameters are selected, and the blade leading edge inlet geometry angle adjustment coefficient k1 = 0.95, the blade trailing edge outlet geometry angle adjustment coefficient k2 = 0.88, and the blade chord length adjustment coefficient k3 = 0.95 are selected. The leading edge inlet geometry angle of the first blade section of the new moving blade is obtained as α′ i =29.5°, the trailing edge exit geometry angle is β′ i =32.6° and blade chord length c′ i =330.9mm. In this way, the arc line C′ of the first blade section of the new moving blade is completed. 1,1 styling.

[0094] (3) According to the method of step ③ in step (3) of part I, the arc line C′ in the first blade section of the new moving blade is 1,1 Superimpose the blade thickness distribution; then construct the leading edge arc curve (the leading edge arc curve radius R' 1,1 =3.6mm) and the trailing edge arc curve (the radius of the trailing edge arc curve R′ 2,1 =2mm). In this way, the structure of the blade profile line BS′1 of the first blade profile section of the new moving blade is completed.

[0095] 4. Follow the above steps to complete the blade profile BS' of several other blade sections of the new moving blade. i (i=2,...,6) construction.

[0096] 5. According to the method in step (4) of Part I, the blade profile lines BS′ of the six blade sections of the new moving blade are i (i=1,…,6) are stacked along the blade height direction to generate a new three-dimensional shape of the moving blade.

[0097] After completing the above steps, the new blade shape for the energy-saving retrofit of an axial flow fan with adjustable blades was completed. After the developed new blades were applied to the fan, the fan not only met the output requirements of the newly selected operating point after the energy-saving retrofit, but also reduced the fan's overall energy consumption by over 15%, increased the fan blade angle adjustment range by over 10%, and significantly improved the fan's operating economy and equipment applicability. The energy-saving retrofit of this fan was very effective.

[0098] Although the present invention has been described in detail above using general descriptions and specific embodiments, it will be apparent to those skilled in the art that modifications and improvements may be made based on the present invention. Therefore, such modifications and improvements, which do not depart from the spirit of the present invention, are intended to be within the scope of protection claimed herein.

Claims

1. A new blade shaping method for energy-saving transformation of an axial flow fan with adjustable blades in a power station, characterized in that: include: First, determine the fan modification method based on the fan technical parameters before and after the energy-saving modification of the axial flow fan with adjustable blades; Secondly, according to different fan modification methods, the corresponding new blade shaping method is determined; Finally, according to the fan modification scheme and new blade shaping method determined above, the fan energy-saving modification is implemented; The specific implementation method for energy-saving transformation of single-stage adjustable blade axial flow fans into new blade shapes is as follows: Step 1: Determine the fan transformation technical solution, and calculate the flow coefficient corresponding to the fan TB point selection parameters before the fan with adjustable blades is transformed. Pressure coefficient φ1, flow coefficient corresponding to TB point selection parameter after fan energy-saving transformation The pressure coefficient φ2 determines the technical solution for fan modification; Step 2: Determine the new fan blade shaping method. The fan modification technical solutions are divided into two methods: fan blade replacement and fan partial modification; The technical solutions for fan transformation are divided into two methods: fan blade replacement and fan partial transformation. The two methods are described as follows: (1) Fan blade replacement method: when the flow coefficient ratio before and after the fan modification meets the requirements When replacing a fan, only all the fan blades need to be replaced, while the dimensions of other structures such as the fan hub and casing remain unchanged; (2) Partial modification of the fan: when the flow coefficient ratio before and after the fan modification meets the requirement When replacing the fan blades, the following changes are required: ① Adjust the height H′1 of the wind turbine blades and shorten the height H′1 of the wind turbine blades after the transformation to meet the requirements. Where H1 is the blade height before the fan modification, and H1′ is the blade height after the fan modification, both in mm. ②Inner diameter of fan casing R′ shroud Adjust and shorten the inner diameter R' of the fan casing after transformation shroud , so that it satisfies R′ shroud =R shroud +H′1-H1, where R shroud R′ is the inner diameter of the fan casing before modification shroud is the inner diameter of the fan casing after modification, in mm. At the same time, the fan blade tip clearance remains unchanged before and after modification; Regarding the fan blade replacement method, the specific shaping method of the fan's new moving blade is as follows: (1) Divide the blade into M blade sections along the blade height in the cylindrical coordinate system, where M is an integer between 3 and 8, and expand the blade profile coordinates of the M blade sections into a plane coordinate system; (2) determining the modeling method of the M blade sections, wherein the modeling method of each blade section is the same; (3) Determine the pressure surface profile PS′ of the i-th blade section of the new moving blade i and suction surface line SS′ i , construct the blade profile line BS′ of the i-th blade section of the new moving blade i , according to the arc line C′ of the new blade section determined in the previous step 1,i The shape line passes through the middle arc line C' 1,i The blade thickness distribution is superimposed on both sides of the profile, and the leading edge and trailing edge of the blade section are formed into the leading edge arc curve and the trailing edge arc curve to determine the pressure surface profile PS′ of the i-th blade section of the new moving blade. i and suction surface line SS′ i ; (4) The blade profile line BS′ of the M blade sections of the new moving blade i The new three-dimensional shape of the moving blade is generated by stacking along the blade height direction. According to the blade profile line BS′ of the i-th blade section of the new moving blade i , solve to get the centroid O′ of the i-th blade section i , the blade center of gravity O′ of the M blade sections of the new moving blade i As the control point of the n-order Bezier curve, i = 1, ..., M, n = M-1, O'1 is the starting point, O' M Point is the end point, and the (M-1) order Bezier curve C2 is generated. Then, the blade profile line BS′ of the i-th blade section of the new moving blade is converted to i By stacking the Bezier curve C2 along the blade height direction, the three-dimensional shape of the new moving blade is completed.

2. The method for shaping new blades for energy-saving transformation of an axial flow fan with adjustable blades for a power station according to claim 1, characterized in that: In step (2), for the i-th blade section, i=1,…,M, the new blade section modeling method is described as follows: ① Using the n-order Bezier curve, the pressure surface line PS of the i-th blade section of the original blade is i , suction surface line SS i For curve fitting, the formula for the n-order Bezier curve is as follows: During the fitting process, keep the blade leading edge point A i , Blade trailing edge point B i The position remains unchanged, and the mid-camber line C of the i-th blade section is used. 1,i Applying the same blade thickness distribution on both sides to the pressure surface profile PS i , suction surface line SS i Perform curve fitting; use the least square method to fit the Bessel fitting curve and the middle arc C 1,i The principle of minimizing the sum of squared errors between discrete points is used to solve the control point P of the Bezier curve. s , s=0,1,...,n, and obtain the Bezier curve order n, n≥3; After fitting is completed, the median arc line C of the i-th blade section of the original blade is obtained 1,i The Bezier fitting curve of the blade thickness distribution is used to obtain the following parameters: the leading edge inlet geometric angle α of the i-th blade section of the original blade i , trailing edge exit geometry angle β i , blade chord length c i The maximum thickness of the blade is a distance from the leading edge of the blade i , maximum blade thickness b max,i parameter; ② Adjust the arc line C of the i-th blade section of the original blade 1,i The Bezier fitting curve parameters of the new moving blade are obtained, and the Bezier fitting curve of the arc line of the i-th blade section of the new moving blade is completed. 1,i The shape; The Bezier fitting curve parameter of the new rotor blade section is the leading edge inlet geometric angle α′ i , the trailing edge exit geometry angle is β′ i and blade chord length c′ i Determined by the following formula: Where, k1 is the blade leading edge inlet geometry angle adjustment coefficient, k2 is the blade trailing edge outlet geometry angle adjustment coefficient, and k3 is the blade chord length adjustment coefficient; Once the above parameters are determined, the arc line C′ in the section of the new blade profile is uniquely determined. 1,i Type line.

3. The method for shaping new blades for energy-saving transformation of an axial flow fan with adjustable blades for a power station according to claim 2, characterized in that: In step (3), the specific implementation method is as follows: ① Take the leading edge of the blade point A i The coordinate origin is 0, and the leading edge of the blade is point A. i To blade trailing edge point B i Establish a coordinate system for the positive direction of the x-axis, with the blade center arc C′ 1,i The distance from a certain point on the x-axis to the coordinate origin 0 in the x-direction is x, and the blade thickness distribution at this point is b(x). According to the Bezier fitting curve of the blade thickness distribution of the i-th blade section of the original blade obtained in the second step, the blade thickness distribution function of this section is obtained: b(x) = f1(x), 0≤x≤c i ,make The blade thickness distribution function is processed dimensionlessly and the function b(j)=f2(j) is obtained, 0≤j≤1; ② Keep the thickness distribution of the new moving blade and the original blade at the same relative chord length position at the i-th blade section, that is, assume that the abscissa of the i-th blade section of the new moving blade is x′, and the chord length of the blade section is c′ i ,but It can be organized into the blade thickness distribution function of the i-th blade section of the new moving blade b(x′)=f3(x′), 0≤x′≤c′ i , thus, the blade thickness distribution law of the i-th blade section of the new moving blade is determined; ③ The blade thickness distribution law of the i-th blade section of the new moving blade determined in the above steps is superimposed on the center arc line C′ of the blade section 1,i On the profile line, the pressure surface curve and the suction surface curve are generated. Then, the leading edge arc curve and the trailing edge arc curve are constructed on the leading edge and trailing edge of the blade section respectively. The leading edge arc curve and the trailing edge arc curve are both arcs, which are tangent to the pressure surface curve and the suction surface curve generated above, respectively. In this blade section, the arc radius of the new moving blade leading edge arc curve is R′ 1,i Satisfies: 0<R′ 1,i ≤3%·c′ i ; The radius of the arc curve of the trailing edge of the new moving blade is R′ 2,i Satisfies: 0<R′ 2,i ≤2%·c′ i In this way, the pressure surface profile PS′ of the i-th blade section of the new moving blade is determined i and suction surface line SS′ i , the pressure surface profile PS′ i and suction surface line SS′ i Combined together, the blade profile line BS′ of the i-th blade section of the new moving blade is completed. i structure.

4. The method for shaping new blades for energy-saving transformation of an axial flow fan with adjustable blades for a power station according to claim 3 is characterized in that: For the local modification method of the fan, the specific shaping method of the new fan blade is as follows: (1) Complete the three-dimensional modeling of the new moving blade according to the contents of parts (1) to (4) of the fan blade replacement method. The original blade height H2 of the new moving blade is consistent with the original blade height H1, that is, H2 = H1; (2) Cut the top of the new moving blade to shorten the blade height. From the first step, it can be seen that after the fan is partially modified, the fan blade height must be shortened to H'1. Therefore, the top of the blade is cut, and after the blade is fixed to the hub, a cylindrical coordinate system is used, with the center line of the hub as the axis of rotation, and the top of the blade is cut off by a height of (H2-H′1). H2-H′1=H1-H′1, and the height of the new moving blade is shortened to H′1. The other parts of the blade remain unchanged.

5. The method for shaping new blades for energy-saving transformation of an axial flow fan with adjustable blades for a power station according to claim 4, characterized in that: For the new moving blade shape of the two-stage axial flow fan with adjustable moving blades for energy saving, the shaping method of the new moving blades of the first and second stages is the same, and both are shaped according to the shaping method of the new moving blades of the single-stage axial flow fan with adjustable moving blades for energy saving: after the first stage completes the shaping of the new moving blades of the single-stage fan according to the shaping method of the new moving blades of the single-stage axial flow fan with adjustable moving blades for energy saving, the above process is repeated in the second stage, and the shapes of the moving blades of the first and second stages are exactly the same.

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