A Polynomial-Based Forming Method for the Wicker Blade Profile of a Power Turbine

Abstract

The present invention is a method for forming the wicker-shaped profile of a power turbine based on polynomials, which relates to a method for forming the guide vane of a gas turbine power turbine with a long and slender blade body similar to a wicker using polynomials. The purpose of the present invention is to provide a wicker-shaped guide vane shaping method that can effectively reduce the flow loss of the profile, improve the aerodynamic performance of the turbine blade, weaken the exciting force caused by the wake flow, and increase the service life of the downstream moving blade. Thus, it solves the problems that the existing shaping methods are difficult to further improve the turbine efficiency, the exciting force caused by the wake flow is difficult to reduce, and the reliability of the moving blade is poor. The present invention is used in the field of improving the aerodynamic performance of the turbine blades of gas-driven compressor units and marine gas turbines and weakening the exciting force caused by the wake flow.

Description

Technical Field

[0001] The present invention relates to a method for forming a wicker-shaped blade profile of a power turbine based on polynomials. More specifically, the present invention relates to a method for forming a wicker-shaped guide vane of a gas turbine power turbine with a slender blade body, similar to a wicker, small flow loss of the blade profile, and small exciting force caused by wake flow, using polynomials. Background Art

[0002] Due to the advantages of large power density and fast starting speed, gas turbines are widely used in industrial and offshore platform power generation, gas-driven compression, and as the main power device of ships. The efficiency of modern gas turbines has reached a relatively high level, and it is difficult to further improve the efficiency of the unit and components. In addition, a gas turbine is a bladed rotating machine with three-dimensional unsteady flow inside. The unsteady flow caused by factors such as blade wakes will affect the forces on the blades, and then cause unsteady vibration of the blades. When the aerodynamic frequency is equal to the natural frequency of the blade, the blade will resonate, resulting in a reduction in blade life or even blade damage.

[0003] In recent years, with the continuous progress of design technology and the continuous development of computational fluid dynamics, full three-dimensional optimization design methods have been continuously applied in the aerodynamic design process of turbines. Unsteady calculation and design technologies represented by the Clocking effect have played a great role in improving turbine efficiency. The aerodynamic design system, design methods, and techniques of turbines have been continuously enriched and improved. Advanced design technologies and blade profiles have continuously promoted the improvement of turbine aerodynamic performance, and the shape of turbine blades has developed from traditional straight blades to complex shapes such as twisted blades, bowed and twisted blades, and bowed, twisted, and swept blades. In addition, to avoid turbine blade resonance and improve the structural reliability of turbine blades, a large amount of research work has been carried out on the optimization of turbine blade crown structures, the design of turbine blade shroud and root damping structures, and the frequency tuning of turbine blades by domestic and foreign scholars, effectively improving the structural reliability of turbine blades.

[0004] To meet the requirements of energy conservation and emission reduction, modern gas turbines are constantly pursuing performance improvement, requiring continuous improvement of turbine aerodynamic performance and continuous reduction of turbine blade flow loss. However, the advanced optimization design technology based on traditional turbine blades is difficult to further improve turbine aerodynamic performance. To meet the performance improvement, the shape of turbine blades is more complex and the full three-dimensional characteristics are more obvious, which has a greater impact on the structural reliability of the engine and is particularly likely to cause turbine blade vibration problems.

[0005] Although domestic and foreign scholars and researchers have carried out a large number of studies on high-performance turbine aerodynamic design and unsteady flow, and have gained a certain understanding of improving turbine aerodynamic performance and revealing unsteady flow in turbine cascades, these studies have not focused on how to reduce the unsteady blade forces caused by wakes while improving the aerodynamic performance of turbine blades, and there are few reports on improving turbine aerodynamic performance and weakening the unsteady forces caused by wakes by adopting willow leaf profile blade structures. Researchers hope to have an advanced blade forming method that can both improve the performance of turbine blades and effectively weaken the unsteady forces on the moving blades caused by wakes. Summary of the Invention

[0006] The object of the present invention is to provide a willow-shaped guide vane forming method that can effectively reduce the flow loss of the airfoil, improve the aerodynamic performance of turbine blades, weaken the exciting force caused by wake flow, and improve the service life of downstream moving blades, thereby solving the problems that it is difficult to further improve turbine efficiency in the prior art, the exciting force caused by wake flow is difficult to reduce, and the reliability of downstream moving blades is poor.

[0007] The object of the present invention is achieved as follows: The steps are as follows:

[0008] Step 1: Obtain the traditional turbine guide vane modeling parameters according to the turbine aerodynamic parameters, complete the guide vane modeling by using the traditional turbine guide vane modeling method, and perform three-dimensional calculations on the turbine guide vane blades and moving blade blades obtained by using the traditional turbine blade aerodynamic design method by using a full three-dimensional numerical simulation software to obtain the turbine guide vane profile pressure distribution and guide vane outlet total pressure distribution data.

[0009] Step 2: Keep the throat area of the turbine guide vane unchanged, and re-give the willow leaf profile modeling parameters of "1 less, 2 large, 3 small": fewer blade numbers, larger chord lengths, larger axial chord lengths, smaller leading edge radii, smaller trailing edge radii, and smaller maximum thicknesses. Specifically: reduce the number of blades by 50%, increase the chord length by 50%, increase the axial chord length by 20%, reduce the leading edge radius by 50%, reduce the trailing edge radius by 50%, and reduce the maximum thickness by 50%.

[0010] Step 3: Based on the willow leaf profile modeling parameters given in Step 2, adopt the willow leaf profile forming method of "1 reduce, 2 increase, 3 decrease": reduce the number of guide vane blades, increase the blade chord length, increase the blade axial chord length, reduce the leading edge radius, reduce the trailing edge radius, and reduce the maximum thickness, and use a fifth-degree polynomial Construct the pressure surface and suction surface profiles of the guide vane root section and top section, where: x p is the abscissa of the pressure side control point; y p is the ordinate of the pressure side control point; a0, a1, a2, a3, a4, a5 are the coefficients of each order of the fifth-degree polynomial function relationship of the pressure side control point; x s is the abscissa of the suction side control point; ys is the ordinate of the control point on the suction side; b0, b1, b2, b3, b4, and b5 are the coefficients of each order of the fifth-degree polynomial function relationship of the control points on the suction side;

[0011] Step 4: Based on the willow leaf-shaped blade root section and the top section profile designed in Step 3, construct a three-dimensional model of the guide vane blade through the blending function of three-dimensional modeling software;

[0012] Step 5: Based on the blade model obtained in Step 4, keep the root and top dimensions of the inlet and outlet of the meridional flow passage of the turbine guide vane unchanged, and increase the axial width of the meridional flow passage of the guide vane to match the axial width of the profile of the turbine guide vane;

[0013] Step 6: Use a full three-dimensional numerical simulation software to perform a full three-dimensional calculation on the turbine composed of the three-dimensional model of the guide vane blade obtained in Step 4 and the moving blade in Step 1 to obtain the data of the pressure distribution on the profile of the turbine guide vane and the total pressure distribution at the outlet of the guide vane;

[0014] Step 7: If the pressure distribution on the profile of the turbine guide vane obtained in Step 6 conforms to the "rear loading" characteristic and the data of the wake width of the guide vane conforms to the predetermined standard of a 50% reduction compared to the traditional forming method, then the willow leaf-shaped profile of the turbine guide vane is obtained;

[0015] If the pressure distribution on the profile of the turbine guide vane obtained in Step 6 does not conform to the "rear loading" characteristic and the data of the wake width of the guide vane does not conform to the predetermined standard of a reduction compared to the traditional forming method, then repeat Steps 2 to 6 until the pressure distribution on the profile of the guide vane and the data of the total pressure distribution at the outlet of the guide vane reach the predetermined standard.

[0016] Furthermore, the stacking axis formed by the centroid of the root section profile and the centroid of the top section profile is a vertical straight line.

[0017] Furthermore, the full three-dimensional numerical simulation software is NUMECA and CFX software.

[0018] Furthermore, the three-dimensional modeling software is UG software.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: On the basis of fully considering the traditional design method of gas turbine turbine blades, the present invention applies the slender characteristics of willow branches to the forming process of turbine guide vane blades. By reducing the number of blades, increasing the chord length of the blades, and reducing the radius of the leading edge and trailing edge of the blades, a blade profile similar to that of a slender and uniformly thick willow branch is constructed. Compared with the blades designed by the traditional method, the lowest pressure point on the suction surface is shifted backward by 20%, the "rear loading" characteristic of the blade is more obvious, the adverse pressure gradient section and the adverse pressure gradient are smaller, the adaptability of the blade profile to off-design conditions is strong, and the width of the blade wake is narrowed by 70%. As a result, the flow loss of the blade profile is reduced by 1%, and the aerodynamic efficiency of the turbine is improved. For the blade designed by the slender willow branch blade forming method based on polynomials of the present invention, the blade wake is narrowed, and the excitation force caused by the wake flow is weakened. In addition, the blade designed by the willow branch blade forming method has a longer chord length than the traditional turbine blade profile, and the blade has a stronger ability to control the flow, so that the number of blades is greatly reduced, the number of wakes is reduced, and the excitation force caused by the wake flow is further weakened, improving the stress state of the downstream moving blades. The turbine blade designed by the present invention can reduce the number of blades by 70%, reduce the blade profile loss by 1%, and reduce the total width of the wakes by 70% compared with the traditional turbine blade. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of a guide vane blade designed by a conventional turbine blade aerodynamic design method;

[0021] Figure 2 Schematic diagram of a moving blade designed by a conventional turbine blade aerodynamic design method;

[0022] Figure 3 Schematic diagram of the stacking position of a turbine guide vane designed by a conventional turbine blade aerodynamic design method;

[0023] Figure 4 Schematic diagram of the profile of a turbine guide vane designed by a conventional turbine blade aerodynamic design method;

[0024] Figure 5 Design flow chart of a willow leaf profile forming method based on polynomials;

[0025] Figure 6 Schematic diagram of a power turbine willow leaf profile designed by the present invention;

[0026] Figure 7 Schematic diagram of a power turbine guide vane blade designed by the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] The present invention will be further described in detail below in conjunction with the drawings and the specific embodiments.

[0028] Specific Embodiment 1: The specific process of a method for forming a wicker leaf profile of a power turbine based on polynomials is as follows:

[0029] The method for forming a wicker leaf profile of a power turbine based on polynomials in the present invention is based on the existing conventional turbine blade aerodynamic design method. After the conventional turbine blade aerodynamic design method, the turbine stage blades (such as Figure 1 , Figure 2 ) without the wicker leaf profile treatment based on polynomials are obtained, including the guide vane blade 1 and the moving vane blade 2.

[0030] As shown in Figure 3 , the guide vane blade 1 is constructed by the root section profile 4 and the tip section profile 5. The stacking axis 8 formed by the centroid 6 of the root section profile 4 and the centroid 7 of the tip section profile 5 is a vertical straight line. The root section profile 4 and the tip section profile 5 are as shown in Figure 4 , with a relatively large number of blades, a relatively small chord length and axial chord length, and relatively large leading edge radius, trailing edge radius and maximum thickness.

[0031] On this basis, the following steps are also required (see Figure 5 ):

[0032] Step 1: Use a full three-dimensional numerical simulation software (such as NUMECA, CFX, etc.) to perform full three-dimensional calculations on the turbine guide vane blade 1 and the moving vane blade 2 obtained by the turbine blade aerodynamic design method (see Figure 1 , Figure 2 ) to obtain the pressure distribution on the turbine guide vane profile and the total pressure distribution data at the guide vane outlet, and use this data result as the comparison basis for the wicker leaf profile;

[0033] Step 2: Keep the throat area of the turbine guide vane unchanged and re-give the wicker leaf profile shaping parameters of "1 less, 2 larger, 3 smaller": fewer blade numbers, larger chord length, larger axial chord length, smaller leading edge radius, smaller trailing edge radius, and smaller maximum thickness. Specifically: reduce the number of blades by 50%, increase the chord length by 50%, increase the axial chord length by 20%, reduce the leading edge radius by 50%, reduce the trailing edge radius by 50%, and reduce the maximum thickness by 50%;

[0034] Step 3: Use the wicker leaf profile shaping parameters given in Step 2 and adopt the wicker leaf profile forming method of "1 reducing, 2 increasing, 3 decreasing": reduce the number of guide vane blades, increase the blade chord length, increase the blade axial chord length, reduce the leading edge radius, reduce the trailing edge radius, and reduce the maximum thickness. Use a fifth-degree polynomial to construct the pressure surface and suction surface profiles of the guide vane root section and tip section, where: x p is the abscissa of the pressure side control point; y p is the ordinate of the pressure side control point; a0, a1, a2, a3, a4, a5 are the coefficients of each order of the fifth-degree polynomial function relationship of the pressure side control point; x sis the abscissa of the control point on the suction side; y s is the ordinate of the control point on the suction side; b0, b1, b2, b3, b4, b5 are the coefficients of each order of the fifth-degree polynomial function relationship of the control point on the suction side; the wicker leaf profile of the turbine blade is obtained (see Figure 6 );

[0035] Step Four: The leading vane blade three-dimensional model is constructed by using the blending function of the three-dimensional modeling software for the profile lines of the root section and the top section of the wicker leaf profile designed in Step Three (see Figure 7 );

[0036] Step Five: Based on the blade model obtained in Step Four, while keeping the root and top dimensions of the inlet and outlet of the meridional flow passage of the turbine guide vane unchanged, increase the axial width of the meridional flow passage of the guide vane to match the axial width of the wicker leaf profile of the turbine guide vane;

[0037] Step Six: Use a full three-dimensional numerical simulation software (such as NUMECA, CFX, etc.) to perform a full three-dimensional calculation on the turbine composed of the leading vane blade three-dimensional model obtained in Step Four (see Figure 7 ) and the rotor blade 2 in Step One to obtain the pressure distribution on the leading vane profile and the total pressure distribution data at the leading vane outlet;

[0038] Step Seven: If the pressure distribution on the leading vane profile obtained in Step Six conforms to the "rear loading" characteristic and the data of the leading vane wake width conforms to the predetermined standard of a 50% reduction compared to the traditional forming method, then the wicker leaf profile of the turbine guide vane is obtained;

[0039] If the pressure distribution on the leading vane profile obtained in Step Six does not conform to the "rear loading" characteristic and the data of the leading vane wake width does not conform to the predetermined standard of a reduction compared to the traditional forming method, then repeat Steps Two to Six until the pressure distribution on the leading vane profile and the total pressure distribution data at the leading vane outlet reach the predetermined standard.

[0040] Specific Embodiment Two: The difference between this embodiment and Specific Embodiment One is that the stacking axis 8 formed by the centroid 6 of the root section profile 4 and the centroid 7 of the top section profile 5 is a vertical straight line.

[0041] Other steps and parameters are the same as those in Specific Embodiment One.

[0042] Specific Embodiment Three: The difference between this embodiment and one of Specific Embodiments One and Two is that the full three-dimensional numerical simulation software is NUMECA and CFX software.

[0043] Other steps and parameters are the same as those in one of Specific Embodiments One and Two.

[0044] Specific Embodiment Four: The difference between this embodiment and one of Specific Embodiments One to Three is that the three-dimensional modeling software is UG software.

[0045] Other steps and parameters are the same as those in any one of the specific embodiments 1 to 3.

[0046] The present invention may also have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and deformations according to the present invention. However, these corresponding changes and deformations should all fall within the protection scope of the appended claims of the present invention.

[0047] In summary, the present invention relates to a method for forming a guide vane of a gas turbine power turbine with a slender blade body similar to a wicker, using a polynomial. The purpose of the present invention is to provide a wicker-shaped guide vane modeling method that can effectively reduce the flow loss of the blade profile, improve the aerodynamic performance of the turbine blade, weaken the excitation force caused by the wake flow, and improve the service life of the downstream moving blade. Thus, it solves the problems that it is difficult to further improve the turbine efficiency with the existing modeling methods, it is difficult to reduce the excitation force caused by the wake flow, and the reliability of the moving blade is poor. The present invention is used in the field of improving the aerodynamic performance of the turbine blades of a gas-driven compressor unit and a marine gas turbine and weakening the excitation force caused by the wake flow.

Claims

1. A method for forming a wicker blade profile of a power turbine based on polynomials, characterized in that, The steps are as follows: Step 1: Use a full three-dimensional numerical simulation software to perform a full three-dimensional calculation on the turbine guide vane blade (1) and the rotor blade (2) obtained by the traditional turbine blade aerodynamic design method, and obtain the turbine guide vane profile pressure distribution and the total pressure distribution data at the guide vane outlet; Step 2: Keep the throat area of the turbine guide vane unchanged; re-give the wicker leaf profile parameters, specifically: reduce the number of blades by 50%, increase the chord length by 50%, increase the axial chord length by 20%, reduce the leading edge radius by 50%, reduce the trailing edge radius by 50%, and reduce the maximum thickness by 50%; Step 3: Based on the wicker leaf-shaped modeling parameters given in Step 2, adopt the wicker leaf-shaped forming method in Step 2: reduce the number of guide vane blades, increase the blade chord length, increase the axial chord length of the blade, reduce the leading edge radius, reduce the trailing edge radius, reduce the maximum thickness, and use a fifth-degree polynomial to construct the pressure surface and suction surface profiles of the guide vane root section and top section, where: x p is the abscissa of the control point on the pressure side; y p is the ordinate of the control point on the pressure side; a0, a1, a2, a3, a4, a5 are the coefficients of each order of the fifth-degree polynomial function relationship of the control point on the pressure side; x s is the abscissa of the control point on the suction side; y s is the ordinate of the control point on the suction side; b0, b1, b2, b3, b4, b5 are the coefficients of each order of the fifth-degree polynomial function relationship of the control point on the suction side; Step 3: Based on the wicker leaf profile root section and the top section profile lines designed in Step 2, construct a three-dimensional model of the guide vane blade through the blending function of the three-dimensional modeling software; Step 4: Based on the blade model obtained in Step 3, keep the root and top dimensions of the inlet and outlet of the turbine guide vane meridional flow passage unchanged, and increase the axial width of the guide vane meridional flow passage to match the axial width of the turbine guide vane profile; Step 5: Use the full three-dimensional numerical simulation software to perform a full three-dimensional calculation on the turbine composed of the three-dimensional model of the guide vane blade obtained in Step 4 and the rotor blade in Step 1, and obtain the turbine guide vane profile pressure distribution and the total pressure distribution data at the guide vane outlet; Step 6: If the turbine guide vane profile pressure distribution obtained in Step 6 conforms to the "rear loading" characteristic and the guide vane wake width data conforms to the predetermined standard of a 50% reduction compared to the traditional forming method, then obtain the wicker leaf profile of the turbine guide vane; If the turbine guide vane profile pressure distribution obtained in Step 6 does not conform to the "rear loading" characteristic and the guide vane wake width data does not conform to the predetermined standard of a reduction compared to the traditional forming method, then repeat Steps 2 to 6 until the guide vane profile pressure distribution and the total pressure distribution data at the guide vane outlet reach the predetermined standard.

2. The method for forming a wicker blade profile of a power turbine based on polynomials according to claim 1, characterized in that: The stacking axis (8) formed by the centroid (6) of the root section profile (4) and the centroid (7) of the top section profile (5) is a vertical straight line.

3. The method for forming a wicker blade profile of a power turbine based on polynomials according to claim 1 or 2, characterized in that: The full three-dimensional numerical simulation software is NUMECA and CFX software.

4. The method for forming a wicker blade profile of a power turbine based on polynomials according to claim 3, characterized in that: The three-dimensional modeling software is UG software.

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