A method for designing a turbine blade with reverse rotation function

Abstract

The application provides a turbine blade design method with reverse rotation function, which fully considers the structural characteristics of the turbine blade with reverse rotation function, namely, after the reverse blade is added, the blade mass and centrifugal force are increased, the difficulty of the turbine structure strength design is increased, the structure characteristics of the approximately symmetrical arrangement of the forward / reverse blade make the structure design of the transition section more complex, in addition, the vibration problem of the turbine blade with reverse rotation function is relatively prominent. The design method provided by the application takes the turbine blade with high reliability, long service life and low stress as the target, and innovatively provides the transition section with pre-twist function, the design method with the shaped reinforcing rib and the like in the design method. The turbine blade with high reliability and long service life can be obtained through the design method provided by the application. The application has the characteristics of simple operation and comprehensive consideration.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of ship gas turbine blade design, and is applied to a turbine blade design method with reverse rotation function. BACKGROUND

[0002] The reversible gas turbine is favored by various countries due to its large reverse power density, rapid start and other characteristics, and becomes one of the main power devices of ships. The reversible gas turbine adopts a design idea of double gas passages + double-layer turbine blades. The outer passage is a reverse passage. The inner passage is a forward passage, and the gas flow route is distributed through a front gas switching mechanism. When the gas only flows through the lower turbine blades, the turbine rotor rotates forward. When the gas only flows through the upper turbine blades, the turbine rotor rotates reversely. The double-layer turbine blade is a core component in the reversible gas turbine, and the reliability of the operation thereof is directly related to the safety of the whole gas turbine.

[0003] Unlike the design method of the traditional single-layer blade, the turbine blade with reverse rotation function has a double-layer structure, so that a transition section structure must be used between the forward blade and the reverse blade. The transition section structure is not only used to connect the forward blade and the reverse blade, but also used to divide the inner and outer passages to prevent the gas from flowing between the two passages. In addition, due to the approximately symmetrical arrangement characteristics of the forward / reverse blades, the design of the transition section structure is more complex. After adding the reverse blade, the blade mass and the centrifugal force increase, and higher requirements are put forward for the design of the tenon and the connecting structure. In addition, due to the complex double-layer blade structure, the vibration problem is relatively prominent, so the vibration reduction design of the blade should be fully considered in the design of the double-layer turbine blade.

[0004] At present, there are almost no researchers at home and abroad to study the turbine blade design method with reverse rotation function, and there are few reports on the turbine blade design method with reverse rotation function. In order to solve the difficulties in the design of the turbine blade with reverse rotation function, the application provides a turbine blade design method with reverse rotation function. SUMMARY

[0005] The application aims to solve the problems encountered in the design of the turbine blade with reverse rotation function, and provides a turbine blade design method with reverse rotation function, so as to obtain a turbine blade with reverse rotation function with high reliability and long service life.

[0006] The application is achieved by the following steps:

[0007] Step one, through pneumatic calculation, the aerodynamic profile, through-flow structure and the number of blades of the forward / reverse blades meeting the performance index requirements are obtained; according to the number of reverse blades and the number of forward blades, the turbine blade with reverse rotation function is determined to be a structure with 1 forward blade and N reverse blades.

[0008] Step two, the turbine blade with reverse rotation function is mainly composed of a forward blade, a reverse blade, a transition section and a tenon, wherein the forward blade and the reverse blade are connected through the transition section to establish a preliminary turbine blade structure with reverse rotation function.

[0009] Step three, in order to reduce the blade mass, the transition section structure is designed as a hollow structure, considering that the reverse blade is located at the top of the forward blade and due to the approximately symmetrical arrangement characteristics of the forward / reverse blades, that is, the blade profile of the reverse blade and the blade profile of the forward blade intersect with each other, which inevitably leads to a large stress concentration area at the position of the transition section, therefore, in addition to using the circumferential reinforcing rib, the transition section structure proposed in the application extends the forward blade to the root of the reverse blade, so that the reinforcing rib of the forward blade is added to the middle position of the transition section, ensuring the structural strength of the transition section.

[0010] Step four, the transition section is rotated by a certain angle, so that the transition section becomes a pre-twisted structure, the transition sections between adjacent blades cooperate with each other to form a whole structure, and the natural frequency of the blade is adjusted by adjusting the pre-twist angle to avoid resonance of the blade.

[0011] Step five, after the reverse blade is added, the blade mass is increased, so that the stress at the connection position of the tenon is deteriorated, therefore, the reverse blade is designed as a hollow structure, and the reinforcing rib is used to connect the blade basin side and the blade back side of the blade body.

[0012] Step six, strength calculation: in the strength calculation of the turbine blade, in addition to the influencing factors considered in the traditional single-layer blade, the heat generation of the turbine blade in the reverse process is also needed to be considered. The reverse heat generation of the turbine blade under the rated working condition is obtained through simulation calculation. Under the premise of considering the reverse heat generation of the turbine blade, the temperature field distribution of the turbine blade under the rated working condition is calculated, and the strength calculation and vibration calculation are completed with temperature load, centrifugal load, aerodynamic load and displacement constraint as the boundary.

[0013] Step seven, the deformation amount of the turbine blade is obtained through the strength calculation, and the through-flow size of the forward / reverse blade is further adjusted.

[0014] Step eight, on the basis of the above results, the turbine blade structure is adjusted.

[0015] Step nine, for large stress position, the turbine blade is optimized in structure. In the tenon position, the axial length of the tenon can be increased, or the tenon profile can be adjusted to reduce the stress of the tenon. In the transition fillet position, the fillet size can be increased to reduce the stress.

[0016] Step ten, re-calculate the strength and vibration, when the results meet the use requirements, the turbine blade design with reverse rotation function is completed, otherwise the turbine blade structure is adjusted again, and the calculation is carried out again until the use requirements are met.

[0017] The application also includes some structural features:

[0018] 1. The profiled stiffener is composed of extending the forward blade to the root of the reverse blade.

[0019] 2. The internal structure of the reverse blade is a hollow structure, and three stiffeners are used to connect the blade basin side and the blade back side of the blade body.

[0020] 3. The transition section can be designed as a pre-twisted structure to adjust the blade vibration frequency.

[0021] 4. The influence of turbine blade reverse rotation heat generation on the strength calculation results is considered in the strength calculation.

[0022] Compared with the prior art, the application has the beneficial effects that: the application provides a turbine blade design method with reverse rotation function, which solves the problems in the design process of the turbine blade with reverse rotation function. The method fully considers the structural characteristics of the turbine blade with reverse rotation function, that is, after the reverse blade is added, the blade mass increases, the centrifugal force increases, and the difficulty of turbine structure strength design is increased. In addition, due to the relatively complex structure of the turbine blade with reverse rotation function, the vibration problem is more prominent. The design method proposed by the application aims to reduce the blade stress, avoid resonance, obtain high reliability and long service life of the turbine blade. In the design method, the transition section with pre-twist function, profiled stiffener and other design methods are innovatively proposed. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 A turbine blade design method with reverse rotation function is provided.

[0024] Figure 2 A three-dimensional structure diagram of a turbine blade with reverse rotation function is provided.

[0025] Figure 3 A front view of a turbine blade with reverse rotation function is provided.

[0026] Figure 4The cross-sectional view of the transition section of the present application;

[0027] Figure 5 The cross-sectional view of the reverse blade of the present application;

[0028] In the figure: reverse blade 1, transition section 2, forward blade 3, tenon tooth 4. DETAILED DESCRIPTION

[0029] The present application will be further described in detail below in combination with the specific embodiments and the accompanying drawings.

[0030] The design method flow of the turbine blade with reverse rotation function of the present application is shown in Figure 1 , which comprises the following steps:

[0031] Step one: through aerodynamic calculation, the aerodynamic profile, through-flow structure and blade number of the forward / reverse blade meeting the performance index requirements are obtained. The number of the reverse blade of the present application is twice the number of the forward blade, that is, the turbine blade with reverse rotation function is a structure of 1 band 2, 1 forward blade band 2 reverse blades.

[0032] Step two: the preliminary turbine blade structure with reverse rotation function is established, which is shown in Figure 2 , Figure 3 . The turbine blade with reverse rotation function mainly comprises the reverse blade 1, the transition section 2, the forward blade 3 and the tenon tooth 4.

[0033] Step three: in order to reduce the blade mass, the transition section 2 is designed as a hollow structure, and the internal structure of the transition section 2 is shown in Figure 4 . The transition section 2 mainly comprises the circumferential reinforcing rib 2-1, the circumferential reinforcing rib 2-2, the circumferential reinforcing rib 2-3 and the conformal reinforcing rib 2-4. Considering that the reverse blade 1 is located at the top of the forward blade 3, and due to the approximately symmetrical arrangement characteristics of the forward blade 3 and the reverse blade 1, that is, the blade profile of the reverse blade 1 and the blade profile of the forward blade 3 intersect with each other, which inevitably leads to a large stress concentration area at the position of the transition section, therefore, the structure of the transition section 2 proposed by the present application adopts the structure form of the circumferential reinforcing rib 2-1, 2-2, 2-3 and the conformal reinforcing rib 2-4, and the conformal reinforcing rib 2-4 extends the forward blade to the root of the reverse blade, so that the reinforcing rib of the forward blade is added to the middle position of the transition section, which ensures the structural strength of the transition section.

[0034] Step four: the transition section 2 is rotated by a certain angle, so that the transition section 2 becomes a pre-twisted structure, and the transition sections 2 between the adjacent blades cooperate with each other to form a whole structure, and the natural frequency of the blade is adjusted by adjusting the pre-twisted angle to avoid resonance of the blade.

[0035] Step five, after adding the reverse blade 1, the blade mass is increased, so that the stress at the tenon tooth 4 connection position is deteriorated, therefore the reverse blade 1 is designed as a hollow structure, the reverse blade 1 cross-section structure is shown as Figure 5 The reinforcing ribs 1-1, 1-2 and 1-3 are used to connect the blade basin side and the blade back side of the blade body in the middle of the reverse blade 1.

[0036] Step six, strength calculation: in the strength calculation of the turbine blade, in addition to the influence factors considered by the traditional single-layer blade, the heat generation of the turbine blade in the reverse process of stirring air also needs to be considered. The reverse heat generation of the turbine blade under the rated working condition is obtained through simulation calculation. Under the premise of considering the reverse heat generation of the turbine blade, the temperature field distribution of the turbine blade under the rated working condition is calculated, and the strength calculation and vibration calculation are completed with the temperature load, centrifugal load, aerodynamic load and displacement constraint as the boundary.

[0037] Step seven, the through-flow size of the forward / reverse blade is adjusted through the deformation calculation result.

[0038] Step eight, on the basis of the above results, the turbine blade structure is adjusted.

[0039] Step nine, the turbine blade is structurally optimized for the large stress position. The axial length of the tenon tooth 4 can be increased at the tenon tooth 4 position, or the profile of the tenon tooth 4 is adjusted to reduce the stress level of the tenon tooth 4. The fillet size can be increased at the transition fillet position to reduce the stress.

[0040] Step ten, the strength calculation and vibration calculation are re-performed, when the results meet the use requirements, the turbine blade design with reverse rotation function is completed, otherwise the turbine blade structure is re-adjusted, the calculation is re-performed until the use requirements are met. Although the present application describes the case which is considered to be the most practical and optimized selection by the applicant, the present application is not limited to the structural features described in detail above. But covers the content defined in the claims, and the equivalent methods derived and modified therefrom.

[0041] In summary, the patent application provides a turbine blade design method with reverse rotation function, which fully considers the structural characteristics of the turbine blade with reverse rotation function, that is, the blade mass increases, the centrifugal force increases, and the difficulty of turbine structure strength design increases after adding the reverse blade, and the structure characteristics of the approximately symmetrical arrangement of the forward / reverse blade make the structure design of the transition section more complex, in addition, the vibration problem of the turbine blade with reverse rotation function is relatively prominent. The design method provided by the application aims to reduce the blade stress, avoid resonance, obtain high reliability and long service life of the turbine blade, and innovatively provides a transition section with pre-twist function, a shaped reinforcement rib and other design methods in the design method. The design method provided by the application can obtain a turbine blade with high reliability and long service life. The patent application provides a turbine blade design method with reverse rotation function, which has the characteristics of simple operation and comprehensive consideration.

Claims

1. A method for designing turbine blades with reverse rotation function, characterized in that, The steps are as follows: Step 1: Through aerodynamic calculations, obtain the aerodynamic profile, flow structure, and number of blades for the forward / reverse blades; based on the number of reverse blades and the number of forward blades, determine that the turbine blade with reverse rotation function has a 1-with-N structure, that is, 1 forward blade with N reverse blades. Step 2: The turbine blade with reverse rotation function includes forward blade, reverse blade, transition section, and tenon; the forward blade and reverse blade are connected by the transition section to obtain the preliminary turbine blade structure with reverse rotation function. Step 3: The transition section structure is designed as a hollow structure. Considering that the reversing blade is located at the top of the forward blade and the blade shape of the reversing blade intersects with that of the forward blade, resulting in a large stress concentration area at the transition section, in addition to using circumferential stiffeners, the transition section structure extends the forward blade to the root of the reversing blade, thus adding a stiffener that conforms to the shape of the forward blade in the middle of the transition section. Step 4: Rotate the transition section by a certain angle to make it a pre-twisted structure. The transition sections between adjacent blades cooperate with each other to form a complete ring structure. Adjust the blade's natural frequency by adjusting the pre-twisted angle to avoid blade resonance. Step 5: After adding the reversing blades, the blade mass increases, which worsens the stress at the tenon connection. Therefore, the reversing blades are designed as hollow structures, with reinforcing ribs in the middle connecting the blade body's base side and back side. Step 6, Strength Calculation: When calculating the strength of the turbine blade, the heat generation of the air stirred up by the turbine blade during the reverse rotation is considered. The heat generation of the turbine blade under rated operating conditions is obtained through simulation calculation. The temperature field distribution of the turbine blade under rated operating conditions is calculated. The strength calculation and vibration calculation are completed with temperature load, centrifugal load, aerodynamic load and displacement constraint as boundaries. Step 7: Obtain the turbine blade deformation through strength calculations and adjust the flow path dimensions of the forward / reverse blades; Step 8: Based on the above results, adjust the turbine blade structure; Step 9: For locations with high stress, optimize the turbine blade structure. At the tenon position, increase the axial length of the tenon or adjust the tenon profile to reduce the stress on the tenon. At the transition fillet position, increase the fillet size to reduce stress. Step 10: Recalculate the strength and vibration. If the results meet the requirements, complete the design of the turbine blade with reverse rotation function. Otherwise, readjust the turbine blade structure and recalculate until the requirements are met.

2. The turbine blade design method with reverse rotation function according to claim 1, characterized in that: The conformal reinforcing rib is formed by extending the forward blade to the root of the reverse blade.

3. The turbine blade design method with reverse rotation function according to claim 1, characterized in that: The reversing blade has a hollow internal structure and uses three reinforcing ribs to connect the blade body to the blade back side.

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