A Strength Assessment Method for Double-Layer Turbine Blades with Reverse Rotation Function

Abstract

The object of the present invention is to provide a strength assessment method for a double-layer turbine blade with a reverse rotation function, comprising the following steps: establishing a three-dimensional coupled model of the double-layer turbine blade and the disk; determining the forward rotation rated operating parameters, reverse rotation rated operating parameters, and gas switching transient operating parameters of the double-layer turbine blade; calculating the forward rotation operating condition; calculating the reverse rotation operating condition; calculating the transient condition of gas switching; and performing strength assessment for all positions of the double-layer turbine blade under the three operating conditions. The present invention takes into account the special double-layer structure characteristics and operating environment characteristics of the double-layer turbine blade, and considers the influence of heat generation due to friction between the blade and air on the blade temperature field, as well as the influence of the gas switching transient condition on the double-layer turbine blade in the strength calculation. This makes the strength calculation of the double-layer turbine blade more comprehensive and accurate.

Description

Technical Field

[0001] The present invention relates to a strength assessment method, specifically a strength assessment method for a gas turbine turbine. Background Art

[0002] Reversible gas turbines have been favored by various countries due to their large reverse power density and rapid startup, and have become one of the main power devices for ships. The reversible gas turbine adopts the design concept of a double gas channel + double-layer turbine blades. The outer channel is the reverse channel, and the inner channel is the forward channel. The distribution of the gas flow route is realized through the gas switching mechanism at the front end. When the gas only flows through the lower-layer turbine blades, the turbine rotor rotates forward. When the gas only flows through the upper-layer turbine blades, the turbine rotor rotates in the reverse direction. As the core component in the reversible gas turbine, the reliability of the operation of the double-layer turbine blades is directly related to the safety of the entire gas turbine. Therefore, during the design process, it is necessary to perform strength calculations on the double-layer turbine blades, eliminate the weak strength positions, and enable the double-layer turbine blades to obtain as large a strength reserve as possible to meet the long-term use requirements.

[0003] When the gas only flows through the lower-layer turbine blades, the turbine rotor rotates forward. At this time, there is no gas flow through the upper-layer turbine blades. The upper-layer turbine blades will rotate against the design direction, continuously stirring the air and generating heat by friction with the air, which affects the temperature field distribution of the double-layer turbine blades. The change in the temperature field will greatly affect the strength of the double-layer turbine blades. When the gas only flows through the upper-layer turbine blades, the turbine rotor rotates in the reverse direction, and a similar situation exists. Therefore, when assessing the strength of the double-layer turbine blades, the influence of the heat generated by the blades stirring the air and friction on the blade strength should also be considered. In addition, under the transitional condition of gas switching, the gas flows through both the upper-layer turbine blades and the lower-layer turbine blades at the same time. At a certain equilibrium position, the torques generated by the gas on the upper-layer turbine blades and the lower-layer turbine blades are equal and opposite in direction. At this position, a strength weak point will be generated at the connection position of the upper-layer turbine blades and the lower-layer turbine blades. Therefore, when assessing the strength of the double-layer turbine blades, in addition to considering the forward rotation condition and the reverse rotation condition, the strength characteristics of the double-layer turbine blades under the transitional condition should also be considered. Due to the special double-layer structure characteristics and operating environment characteristics of the double-layer turbine blades, the traditional strength calculation method for single-layer turbine blades cannot comprehensively evaluate the strength characteristics of the double-layer turbine blades. Summary of the Invention

[0004] The purpose of the present invention is to provide a strength assessment method for double-layer turbine blades with a reverse rotation function that can solve the problem of strength assessment of double-layer turbine blades and obtain a double-layer turbine blade structure with high reliability and a simple structure.

[0005] The purpose of the present invention is achieved as follows:

[0006] A strength assessment method for a double-layer turbine blade with a reverse rotation function, characterized in that:

[0007] (1) Establish a three-dimensional coupling model of the double-layer turbine blade and the disk in NX three-dimensional modeling software;

[0008] (2) Determine the forward rotation rated operating parameters, reverse rotation rated operating parameters, and gas switching transient operating parameters of the double-layer turbine blade in a reversible gas turbine, including the gas temperature T, gas pressure P, and rated speed n at the position where the double-layer turbine blade is located;

[0009] (3) Forward rotation operating condition calculation: The gas distribution baffle is in a fully open state, and all the gas flows through the lower layer of blades. The gas drives the double-layer turbine blade to rotate forward, and no gas flows through the position of the upper layer of blades;

[0010] (4) Reverse rotation operating condition calculation: The gas distribution baffle is in a fully closed state, and all the gas flows through the upper layer of blades. The gas drives the double-layer turbine blade to rotate in reverse, and no gas flows through the position of the lower layer of blades;

[0011] (5) Gas switching transient condition calculation: The gas distribution baffle is in an intermediate transition state, and part of the gas flows through the lower layer of blades and part of the gas flows through the upper layer of blades;

[0012] (6) Under the three operating conditions, perform strength assessment for all positions of the double-layer turbine blade respectively, and conduct the assessment with the material creep strength as the index. The ratio of the material creep strength to the maximum equivalent stress in the blade is less than 1.3. If the above requirements are not met, optimize the design of the blade structure. The optimized double-layer turbine blade should be recalculated for strength until the strength requirements are met.

[0013] The present invention may further include:

[0014] 1. The forward rotation operating condition calculation in step (3) is specifically as follows:

[0015] First, establish a fluid-structure interaction calculation model between the upper layer of blades and air. Import the calculation model into the CFX fluid calculation software, complete the mesh generation, set the boundary conditions, and the boundary conditions include the blade material, rotational speed, gas parameters, inlet and outlet pressures. Complete the friction heat generation analysis between the upper layer of blades and air to obtain the temperature load of the upper layer of blades and the pressure load on the surface;

[0016] Second, establish a fluid-structure interaction calculation model between the lower layer of blades, the disk and the gas. Import the calculation model into the CFX fluid calculation software, complete the mesh generation, set the boundary conditions, and the boundary conditions include the materials of the blades and the disk, inlet temperature, inlet pressure, outlet pressure, rotational speed, disk surface temperature and heat transfer coefficient. Complete the fluid-structure interaction calculation to obtain the temperature load of the lower layer of blades and the surface gas pressure load, as well as the disk temperature load;

[0017] The temperature loads and pressure loads of the upper blades, lower blades and disk are input as boundaries into the strength calculation software ANSYS. At the same time, centrifugal loads, displacement constraints, pre-twist constraints, and disk tenon and mortise constraints are applied to the three-dimensional coupling model of the double-layer turbine blades and the disk to complete the strength coupling calculation of the double-layer turbine blades and the disk.

[0018] 2. The specific calculation of the reverse operating condition in step (4) is as follows:

[0019] First, a fluid-structure interaction calculation model of the lower blades and air is established. The calculation model is imported into the CFX fluid calculation software to complete mesh generation, set boundary conditions, including blade material, rotational speed, gas parameters, inlet and outlet pressures, and complete the friction heat generation analysis between the lower blades and air to obtain the temperature load of the lower blades 12 and the pressure load on the surface.

[0020] Second, a fluid-structure interaction calculation model of the upper blades, disk and gas is established. The calculation model is imported into the CFX fluid calculation software to complete mesh generation, set boundary conditions, including the materials of the blades and the disk, inlet temperature, inlet pressure, outlet pressure, rotational speed, disk surface temperature and heat transfer coefficient, complete the fluid-structure interaction calculation, and obtain the temperature load of the upper blades and the gas pressure load on the surface, as well as the temperature load of the disk.

[0021] The temperature loads and pressure loads of the upper blades, lower blades and disk are input as boundaries into the strength calculation software ANSYS. At the same time, centrifugal loads, displacement constraints, pre-twist constraints, and disk tenon and mortise constraints are applied to the three-dimensional coupling model of the double-layer turbine blades and the disk to complete the strength coupling calculation of the double-layer turbine blades and the disk.

[0022] 3. The specific calculation of the transition condition of gas switching in step (5) is as follows:

[0023] First, for different positions of the gas distribution baffle, a fluid-structure interaction model of the gas with the upper blades and lower blades is established, imported into the CFX software to complete the flow calculation, obtain the torque of the gas on the relative rotation centerline of the upper blades and lower blades, and determine the torque balance point, at which time the torque of the gas on the relative rotation centerline of the upper blades and lower blades is equal in magnitude and opposite in direction.

[0024] Second, under this state, the temperature loads of the upper blades and lower blades and the gas pressure loads on the surface are input as boundary conditions into the strength calculation software, and at the same time, constraints are applied to the three-dimensional coupling model of the double-layer turbine blades and the disk to complete the strength coupling calculation of the double-layer turbine blades and the disk.

[0025] 4. Under the forward rotation operating condition and the reverse rotation operating condition, there is a situation where the gas does not flow through the first-layer blades. At this time, consider the influence of the heat generated by the agitation and friction between the blades and the air in the gas passage on the temperature field of the double-layer turbine blades, and then the influence on the strength of the double-layer turbine blades.

[0026] 5. In the strength calculation, in addition to considering the forward rotation operating condition and the reverse rotation operating condition, also consider the influence of the gas switching transition condition on the strength of the double-layer turbine blades.

[0027] The advantages of the present invention are as follows: Based on the traditional single-layer blade strength assessment method, considering the special double-layer structure characteristics and operating environment characteristics of the double-layer turbine blades, taking into account the influence of the heat generated by the friction between the blades and the air on the temperature field of the blades, and the influence of the gas switching transition condition on the double-layer turbine blades in the strength calculation. This makes the strength calculation of the double-layer turbine blades more comprehensive and accurate. Description of the Drawings

[0028] Figure 1 It is a schematic diagram of the gas flow in the switching transition condition;

[0029] Figure 2 It is a three-dimensional structure schematic diagram of the double-layer turbine blade with the reverse rotation function;

[0030] Figure 3 It is a flow chart of the present invention;

[0031] Figure 4 It is a three-dimensional model schematic diagram of the 1 / N sector double-layer turbine blade and the disk. Detailed Embodiment

[0032] The following further describes the present invention in detail with reference to the drawings:

[0033] Combined with Figures 1-4 , the core mechanism of the reversible gas turbine is as shown in Figure 1 , mainly composed of a double-layer turbine blade 1, a double-layer guide vane 2, a disk 3, a turbine shaft 4, an electric cylinder 5, a crank-link mechanism 6, a diversion channel 7, a gas distribution baffle 8, and a casing 9. The three-dimensional structure of the double-layer turbine blade 1 is shown in Figure 2As shown in the figure, it mainly consists of an upper layer blade 10, a blade connection section 11, a lower layer blade 12, and a tenon tooth 13. The electric cylinder 5 and the crank and connecting rod mechanism 6 can drive the gas distribution baffle 8 to rotate around point A. When the gas distribution baffle 8 is at the uppermost end, the gas can only pass through the lower layer channel, and the gas drives the double-layer turbine blade 1 to rotate forward. When the gas distribution baffle 8 is at the lowermost end, the gas can only pass through the upper layer channel, and the gas drives the double-layer turbine blade 1 to rotate backward. When the gas distribution baffle 8 is in the middle transition position, a part of the gas flows through the upper layer channel, and the gas generates a reverse torque on the upper layer blade 10. A part of the gas flows through the lower layer channel, and the gas generates a forward torque on the lower layer blade 12. When the gas distribution baffle 8 is at a certain position, the torques generated by the gas on the upper layer blade 10 and the lower layer blade 12 are equal in magnitude and opposite in direction, and it is in a torque balance state.

[0034] A method for assessing the strength of a double-layer turbine blade with a reverse rotation function in this embodiment, the flowchart is shown in Figure 3 As shown in the figure, it includes the following steps:

[0035] Step 1: Establish a three-dimensional coupling model of the double-layer turbine blade 1 and the disk 3 in the NX three-dimensional modeling software. To simplify the calculation workload, take 1 / N fan segments of the double-layer turbine blade 1 and the disk 3 as the model for subsequent strength calculation (N is the number of blades of the lower layer blade 12).

[0036] Step 2: Determine the forward rotation rated operating parameters, reverse rotation rated operating parameters, and gas switching transition operating parameters of the double-layer turbine blade 1 in the reversible gas turbine. The operating parameters include the gas temperature T, gas pressure P, rated speed n, etc. at the position where the double-layer turbine blade is located.

[0037] Step 3: Forward rotation operating condition calculation: The gas distribution baffle 8 is in a fully open state, and all the gas flows through the lower layer blade 12. The gas drives the double-layer turbine blade 1 to rotate forward, and no gas flows through the position of the upper layer blade 10.

[0038] First, establish a fluid-structure interaction calculation model between the upper layer blade 10 and the air. The calculation model is imported into the CFX fluid calculation software, the mesh is divided, the boundary conditions are set (the boundary conditions include: blade material, rotation speed, gas parameters, inlet and outlet pressures, etc.), and the friction heat generation analysis between the upper layer blade 10 and the air is completed to obtain the temperature load and surface pressure load of the upper layer blade 10.

[0039] Secondly, establish a fluid-structure interaction calculation model for the lower-layer blades 12, the disk 3 and the gas. Import the calculation model into the CFX fluid calculation software, complete the mesh generation, set the boundary conditions (the boundary conditions mainly include: the materials of the blades and the disk, the inlet temperature, the inlet pressure, the outlet pressure, the rotational speed, the surface temperature of the disk and the heat transfer coefficient), complete the fluid-structure interaction calculation, and obtain the temperature load and the surface gas pressure load of the lower-layer blades 12, as well as the temperature load of the disk 3.

[0040] Take the temperature loads and pressure loads of the upper-layer blades 10, the lower-layer blades 12 and the disk 3 as the boundaries and input them into the strength calculation software ANSYS. At the same time, apply centrifugal loads, displacement constraints, pre-twist constraints, and disk tenon and mortise constraints to the three-dimensional coupling model of the double-layer turbine blades 1 and the disk 3 to complete the strength coupling calculation of the double-layer turbine blades 1 and the disk 3.

[0041] Step Four: Calculation of the reverse operating condition: The gas distribution baffle 8 is in a fully closed state, and all the gas flows through the upper-layer blades 10. The gas drives the double-layer turbine blades 1 to rotate in the reverse direction, and no gas flows through the position of the lower-layer blades 12.

[0042] First, establish a fluid-structure interaction calculation model for the lower-layer blades 12 and the air. Import the calculation model into the CFX fluid calculation software, complete the mesh generation, set the boundary conditions (the boundary conditions include: blade material, rotational speed, gas parameters, inlet and outlet pressures, etc.), complete the friction heat generation analysis of the lower-layer blades 12 and the air, and obtain the temperature load and the surface pressure load of the lower-layer blades 12.

[0043] Secondly, establish a fluid-structure interaction calculation model for the upper-layer blades 10, the disk 3 and the gas. Import the calculation model into the CFX fluid calculation software, complete the mesh generation, set the boundary conditions (the boundary conditions mainly include: the materials of the blades and the disk, the inlet temperature, the inlet pressure, the outlet pressure, the rotational speed, the surface temperature of the disk and the heat transfer coefficient), complete the fluid-structure interaction calculation, and obtain the temperature load and the surface gas pressure load of the upper-layer blades 10, as well as the temperature load of the disk 3.

[0044] Take the temperature loads and pressure loads of the upper-layer blades 10, the lower-layer blades 12 and the disk 3 as the boundaries and input them into the strength calculation software ANSYS. At the same time, apply centrifugal loads, displacement constraints, pre-twist constraints, and disk tenon and mortise constraints to the three-dimensional coupling model of the double-layer turbine blades 1 and the disk 3 to complete the strength coupling calculation of the double-layer turbine blades 1 and the disk 3.

[0045] Step Five: Calculation of the transitional condition of gas switching: The gas distribution baffle 8 is in an intermediate transitional state, and part of the gas flows through the lower-layer blades 12 and part of the gas flows through the upper-layer blades 10.

[0046] First, when the gas distribution baffle 8 is in different positions, a fluid-structure interaction model of the gas with the upper blade 10 and the lower blade 12 is established, imported into the CFX software to complete the flow calculation, obtain the torques of the gas on the upper blade 10 and the lower blade 12 relative to the rotation center line, and determine the torque balance point. At this time, the torques of the gas on the upper blade 10 and the lower blade 12 relative to the rotation center line are equal in magnitude and opposite in direction.

[0047] Secondly, under this state, the temperature loads of the upper blade 10 and the lower blade 12 and the gas pressure loads on the surfaces are input into the strength calculation software as boundary conditions. At the same time, constraints are applied to the three-dimensional coupling model of the double-layer turbine blade 1 and the disk 3 to complete the strength coupling calculation of the double-layer turbine blade 1 and the disk 3.

[0048] Step 6: Under three working conditions, the strength of all positions of the double-layer turbine blade 1 is respectively examined, and the examination is carried out with the material creep strength as the index. The ratio of the material creep strength to the maximum equivalent stress in the blade should be less than 1.3. If the above requirements are not met, the blade structure should be optimized. After optimization, the double-layer turbine blade 1 should be recalculated for strength until the strength requirements are met.

[0049] The present invention has the following beneficial effects: On the basis of the traditional single-layer blade strength examination method, considering the special double-layer structure characteristics and operating environment characteristics of the double-layer turbine blade, the influence of heat generated by the friction between the blade and the air on the blade temperature field, and the influence of the gas switching transition condition on the double-layer turbine blade are considered in the strength calculation. This makes the strength calculation of the double-layer turbine blade more comprehensive and accurate.

Claims

1. A strength assessment method for a double-layer turbine blade with a reverse rotation function, characterized in that: (1) Establish a three-dimensional coupling model of the double-layer turbine blade and the disk in the NX three-dimensional modeling software; (2) Determine the forward-rated operating parameters, reverse-rated operating parameters, and gas-switching transient operating parameters of the double-layer turbine blade in the reversible gas turbine, including the gas temperature T, gas pressure P, and rated speed n at the position where the double-layer turbine blade is located; (3) Forward-running condition calculation: The gas distribution baffle is in a fully open state, and all the gas flows through the lower-layer blades. The gas drives the double-layer turbine blade to rotate forward, and no gas flows through the upper-layer blade position; (4) Reverse-running condition calculation: The gas distribution baffle is in a fully closed state, and all the gas flows through the upper-layer blades. The gas drives the double-layer turbine blade to rotate backward, and no gas flows through the lower-layer blade position; (5) Gas-switching transient condition calculation: The gas distribution baffle is in an intermediate transition state, and part of the gas flows through the lower-layer blades and part of the gas flows through the upper-layer blades; The specific calculation of the gas-switching transient condition is as follows: First, for different positions of the gas distribution baffle, establish a fluid-structure interaction model of the gas with the upper-layer blades and the lower-layer blades, import it into the CFX software to complete the flow calculation, obtain the torque of the gas on the relative rotation centerline of the upper-layer blades and the lower-layer blades, and determine the torque balance point. At this time, the torque of the gas on the relative rotation centerline of the upper-layer blades and the lower-layer blades is equal in magnitude and opposite in direction; Second, under this state, the temperature load of the upper-layer blades and the lower-layer blades and the gas pressure load on the surface are input into the strength calculation software as boundary conditions. At the same time, constraints are applied to the three-dimensional coupling model of the double-layer turbine blade and the disk to complete the strength coupling calculation of the double-layer turbine blade and the disk; (6) Under the three working conditions, conduct strength assessment for all positions of the double-layer turbine blade respectively, and conduct assessment with the material creep strength as the index. The ratio of the material creep strength to the maximum equivalent stress in the blade is less than 1.

3. If the above requirements are not met, optimize the blade structure. The optimized double-layer turbine blade should be recalculated for strength until the strength requirements are met; Under the forward-running condition and the reverse-running condition, there is a situation where the gas does not flow through one layer of blades. At this time, consider the influence of the heat generated by the agitation and friction of the blade with the air in the gas passage on the temperature field of the double-layer turbine blade, and then the influence on the strength of the double-layer turbine blade.

2. The strength assessment method for a double-layer turbine blade with a reverse rotation function according to claim 1, characterized in that: The specific calculation of step (3) forward-running condition is as follows: First, establish a fluid-structure interaction calculation model of the upper-layer blade and the air, import the calculation model into the CFX fluid calculation software, complete the mesh generation, set the boundary conditions, including blade material, rotational speed, gas parameters, inlet and outlet pressures, complete the friction heat generation analysis of the upper-layer blade and the air, and obtain the temperature load of the upper-layer blade and the pressure load on the surface; Secondly, establish a fluid-structure interaction calculation model for the lower-layer blades, disk, and gas. Import the calculation model into the CFX fluid calculation software, complete the mesh generation, and set the boundary conditions. The boundary conditions include the materials of the blades and the disk, inlet temperature, inlet pressure, outlet pressure, rotational speed, disk surface temperature, and heat transfer coefficient. Complete the fluid-structure interaction calculation to obtain the temperature load and surface gas pressure load of the lower-layer blades, as well as the disk temperature load. Use the temperature loads and pressure loads of the upper-layer blades, lower-layer blades, and disk as boundaries and input them into the strength calculation software ANSYS. At the same time, apply centrifugal loads, displacement constraints, pre-twist constraints, and disk tenon-mortise constraints to the three-dimensional coupling model of the double-layer turbine blades and the disk to complete the strength coupling calculation of the double-layer turbine blades and the disk.

3. The strength assessment method for a double-layer turbine blade with a reverse rotation function according to claim 1, characterized in that: The specific calculation of the reverse operating condition in step (4) is as follows: First, establish a fluid-structure interaction calculation model for the lower-layer blades and air. Import the calculation model into the CFX fluid calculation software, complete the mesh generation, and set the boundary conditions. The boundary conditions include blade material, rotational speed, gas parameters, and inlet and outlet pressures. Complete the friction heat generation analysis of the lower-layer blades and air to obtain the temperature load of the lower-layer blades 12 and the surface pressure load. Secondly, establish a fluid-structure interaction calculation model for the upper-layer blades, disk, and gas. Import the calculation model into the CFX fluid calculation software, complete the mesh generation, and set the boundary conditions. The boundary conditions include the materials of the blades and the disk, inlet temperature, inlet pressure, outlet pressure, rotational speed, disk surface temperature, and heat transfer coefficient. Complete the fluid-structure interaction calculation to obtain the temperature load and surface gas pressure load of the upper-layer blades, as well as the disk temperature load. Use the temperature loads and pressure loads of the upper-layer blades, lower-layer blades, and disk as boundaries and input them into the strength calculation software ANSYS. At the same time, apply centrifugal loads, displacement constraints, pre-twist constraints, and disk tenon-mortise constraints to the three-dimensional coupling model of the double-layer turbine blades and the disk to complete the strength coupling calculation of the double-layer turbine blades and the disk.

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