Method for determining axial clearance of nuclear steam turbine
By constructing a turbine simulation model and mapping table, the minimum clearance of each cylinder section is calculated, which solves the problem of inaccurate axial clearance design in the existing technology and improves the design efficiency and safety of the turbine.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HARBIN TURBINE
- Filing Date
- 2026-05-08
- Publication Date
- 2026-07-31
AI Technical Summary
The existing design method for axial clearance of steam turbines fails to accurately distinguish the arrangement characteristics of different cylinder sections and the long and short transient expansion differential conditions, resulting in poor accuracy of axial clearance design. This can easily lead to axial rubbing and vibration between the rotor and stationary components, affecting the safety and lifespan of the unit.
By establishing a turbine simulation model to simulate the unit's operation, long-term and short-term transient expansion difference data of each cylinder section are obtained. A mapping table is constructed to calculate the minimum clearance between the moving and stationary components of each cylinder section. A reasonable axial clearance design value is selected according to different operating conditions to avoid the risk of axial rubbing.
It enables precise selection of the dynamic and static axial clearance margins of each cylinder section under different operating conditions, reduces the risk of shaft rubbing, and improves the design efficiency and safety of the unit.
Smart Images
Figure CN122485641A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of steam turbine expansion assessment and analysis technology. Background Technology
[0002] Figure 1 As shown, in the push-pull shaft system structure of a large nuclear power turbine generator set, the high-pressure cylinder HP, the first low-pressure cylinder LP-1, the second low-pressure cylinder LP-2, and the third low-pressure cylinder LP-3 are arranged in series on the entire rotor. The shaft system uses the thrust plate as the axial thermal expansion reference dead point, and the rotor and each cylinder form bidirectional thermal expansion displacement along the adjusting end and the electric end side, respectively.
[0003] Among them, the axial thermal expansion of the steam turbine is the expansion of the components along the steam turbine axis caused by temperature changes compared to the installation condition under design conditions (including possible axial deformation). The axial expansion difference is the difference between the cumulative expansion of the rotating components and the cumulative expansion of the stationary components at a certain position in the axial direction of the steam turbine, with the relative dead point as zero. A positive value indicates that the rotor expansion is greater than the stationary component expansion, and a negative value indicates that the rotor expansion is less than the stationary component expansion.
[0004] The two most dangerous states of a steam turbine are long transient expansion difference and short transient expansion difference (during turbine start-up and shutdown, due to the difference in thermal inertia between the rotor and cylinder, an axial expansion difference occurs). Long transient expansion difference and short transient expansion difference occur at different times and have different characteristics. Generally, long transient expansion difference refers to the rotor expansion exceeding the maximum positive value of the axial dynamic-static expansion difference that can be achieved during unit start-up, shutdown, or partial operation; short transient expansion difference refers to the rotor expansion being less than the maximum negative value of the axial dynamic-static expansion difference that can be achieved during unit start-up, shutdown, or partial operation.
[0005] During start-up, shutdown, or partial operation, the temperature rise rate and expansion of the rotor and cylinder differ significantly, which can easily lead to excessive axial expansion difference. If the dynamic and static axial clearances of each cylinder section are not properly matched, it can cause hidden dangers such as axial rubbing between the rotor and stationary parts, and increased rotor vibration, which seriously affect the operational safety of the unit and the service life of the shaft system.
[0006] To prevent friction between moving and stationary parts caused by thermal expansion, dynamic and static clearances must be set during cold installation to allow for a safety margin in axial expansion differences. While mature algorithms exist for calculating positive and negative expansion differences during start-up and shutdown, the setting of axial clearances is still largely based on empirical judgment.
[0007] Existing clearance design methods mostly adopt a single fixed clearance value, without distinguishing the arrangement characteristics of different cylinder sections, and without taking into account the expansion direction law under different extreme expansion difference conditions in long and short transient states.
[0008] Therefore, the existing gap design method has poor accuracy. Summary of the Invention
[0009] The purpose of this invention is to solve the problem of poor accuracy in existing clearance design methods, and to propose a method for determining the axial clearance of nuclear power turbines.
[0010] A method for determining the axial clearance of a nuclear power turbine, the method comprising the following:
[0011] Step 1: Obtain the long transient expansion difference or short transient expansion difference between each group of moving and stationary components in the steam turbine from the steam turbine structure diagram;
[0012] A steam turbine simulation model is established, and the model is used to simulate the operation of the steam turbine. For moving and stationary components with long transient expansion differences, the long transient expansion difference, rotor shrinkage and cylinder deformation between the moving and stationary components are obtained from the start-up, operation to shutdown stages of the steam turbine.
[0013] For moving and stationary components with short transient expansion differences, the short transient expansion differences between these moving and stationary components are obtained from the turbine's startup, operation, and shutdown stages.
[0014] Step 2: Construct a mapping table of long transient and short transient states with margin. Based on the electric or regulating end of the turbine where each set of moving and stationary components is located, and the long transient expansion difference or short transient expansion difference, select the corresponding margin value from the mapping table of long transient and short transient states with margin.
[0015] Step 3: Calculate the minimum clearance between the corresponding moving and stationary parts during the long transient expansion difference, rotor shrinkage, cylinder deformation and corresponding margin values.
[0016] When the short transient expansion difference is positive, the short transient minimum clearance between the corresponding moving and stationary parts is calculated based on the corresponding margin value.
[0017] When the short transient expansion difference is negative, the short transient minimum clearance between the corresponding moving and stationary parts is calculated based on the short transient expansion difference and the corresponding margin value.
[0018] The beneficial effects of this invention are:
[0019] This invention combines the partitioning of each cylinder section (electric or adjustable end) and the operating conditions of long or short transient expansion differences to construct an axial clearance design mapping table for each cylinder section, adjustable end, or both sides of the electrical disconnection. This enables precise selection of the dynamic and static axial clearance margins for each cylinder section under different operating conditions, avoiding the risk of axial rubbing of the shaft system. Furthermore, based on the data collected during the model's operation, the invention accurately calculates the reserved clearance between each group of dynamic and static components.
[0020] This invention provides a set of feasible axial clearance design values to meet the requirements of improving the quality and efficiency of steam turbines. It fills the theoretical gap in steam turbine axial clearance design, improves unit design efficiency, and reduces steam turbine design time. Attached Figure Description
[0021] Figure 1 This is a schematic diagram of a push-pull structure for a steam turbine.
[0022] Figure 2 This is a schematic diagram of the turbine's dynamic and static clearances;
[0023] Figure 3 for Figure 2 Schematic diagram of the dynamic and static clearance of the steam seal teeth at point I;
[0024] Figure 4 for Figure 2 Schematic diagram of the dynamic and static clearance of the steam seal teeth at point II. Detailed Implementation
[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0026] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the scope of the invention.
[0027] Example:
[0028] A method for determining the axial clearance of a nuclear power turbine, the method comprising the following:
[0029] Step 1: Obtain the long transient expansion difference or short transient expansion difference between each group of moving and stationary components in the steam turbine from the steam turbine structure diagram;
[0030] A steam turbine simulation model is established, and the model is used to simulate the operation of the steam turbine. For moving and stationary components with long transient expansion differences, the long transient expansion difference, rotor shrinkage and cylinder deformation between the moving and stationary components are obtained from the start-up, operation to shutdown stages of the steam turbine.
[0031] For moving and stationary components with short transient expansion differences, the short transient expansion differences between these moving and stationary components are obtained from the turbine's startup, operation, and shutdown stages.
[0032] Step 2: Construct a mapping table of long transient and short transient states with margin. Based on the electric or regulating end of the turbine where each set of moving and stationary components is located, and the long transient expansion difference or short transient expansion difference, select the corresponding margin value from the mapping table of long transient and short transient states with margin.
[0033] Step 3: Calculate the minimum clearance between the corresponding moving and stationary parts during the long transient expansion difference, rotor shrinkage, cylinder deformation and corresponding margin values.
[0034] When the short transient expansion difference is positive, the short transient minimum clearance between the corresponding moving and stationary parts is calculated based on the corresponding margin value.
[0035] When the short transient expansion difference is negative, the short transient minimum clearance between the corresponding moving and stationary parts is calculated based on the short transient expansion difference and the corresponding margin value.
[0036] Specifically, after obtaining the gap between each moving and stationary component using this embodiment, when installing the corresponding moving and stationary components, a corresponding long transient minimum gap or short transient minimum gap is left between the corresponding moving and stationary components.
[0037] Further defining, the clearance between moving and stationary components includes the clearance between the moving blade and the stationary blade, and the clearance at the position of the steam seal teeth.
[0038] Specifically, the clearances between moving and stationary components in a nuclear power turbine refer to the clearances between the moving and stationary blades on HP, LP-1, LP-2, and LP-3, as well as the clearances at the steam seal teeth positions. Whether each clearance is the long transient minimum clearance or the short transient minimum clearance is known and determined by the thrust disk position, such as... Figure 2 As shown, thrust disk 1 is to the right of the moving and stationary blades. Therefore, A and B are the long transient minimum clearances between the moving and stationary blades, and E and F are the short transient minimum clearances between the stationary and moving blades. Figure 3 and Figure 4 For HP, LP-1, LP-2 or LP-3, the dynamic and static clearances of the steam seal teeth are given. G, G1, and M are the long transient minimum clearances, and C and N are the short transient minimum clearances. Therefore, the long transient minimum clearance or the short transient minimum clearance is known for each clearance.
[0039] like Figure 1 As shown, HP, LP-1, LP-2 and LP-3 all have symmetrical structures inside the cylinders, and all have a double-flow structure, that is, the air flows from the middle to both sides. Therefore, one side of each cylinder is the electrical terminal and the other side is the adjustment terminal. If the moving and stationary parts are located at the electrical terminal of HP and it is a long transient, then δ is 5.4. The content here is an example of selecting δ.
[0040] For a certain nuclear power turbine, the high-pressure and low-pressure cylinders are symmetrically arranged, and the push-pull structure is shown below. Figure 1 The values of δ can be found in the preset long transient and short transient and margin mapping table:
[0041]
[0042] 4.4 = 2.0 (standard allowance) + 2.0 (installation tolerance) + 0.4 (thrust bearing clearance).
[0043] 5.4 = 2.0 (standard allowance) + 2.0 (installation tolerance) + 0.4 (thrust bearing clearance) + 1.0 (blade misalignment due to long-term operation).
[0044] It is obvious that the skew of the moving blade is towards the side with lower pressure, so it only affects the clearance determination on one side. For locations without moving blades, such as end seals, inlet centerlines, and bearing housings, the minimum clearance design value does not consider blade skew.
[0045] Based on these two expansion differences, this embodiment also considers standard allowances, installation tolerances, thrust bearing clearance, and blade misalignment caused by long-term operation, thereby providing long transient minimum clearance design values and short transient minimum clearance design values.
[0046] Further defined, the minimum clearance during long transient = long transient expansion difference during shutdown + δ + rotor contraction + cylinder deformation, where δ is a margin value.
[0047] Further specifying, when the short transient expansion difference is positive, the short transient minimum gap = δ;
[0048] When the short transient expansion difference is negative, the short transient minimum gap = -short transient expansion difference + δ.
[0049] Further defined, the transient expansion difference during shutdown = 100% expansion of the rotor temperature at the corresponding position - 75% expansion of the stationary component temperature at the corresponding position.
[0050] Further defined, short transient expansion difference = 75% expansion of rotor temperature at the corresponding position - 100% expansion of stationary component temperature at the corresponding position - Poisson effect contraction of rotor at the corresponding position.
[0051] While the invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the invention. Therefore, it should be understood that many modifications can be made to the exemplary embodiments, and other arrangements can be designed without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that different dependent claims and features described herein can be combined in ways different from those described in the original claims. It is also understood that features described in conjunction with individual embodiments can be used in other described embodiments.
Claims
1. A method for determining the axial clearance of a nuclear power turbine, characterized in that, The method includes the following: Step 1: Obtain the long transient expansion difference or short transient expansion difference between each group of moving and stationary components in the steam turbine from the steam turbine structure diagram; A steam turbine simulation model is established, and the model is used to simulate the operation of the steam turbine. For moving and stationary components with long transient expansion differences, the long transient expansion difference, rotor shrinkage and cylinder deformation between the moving and stationary components are obtained from the start-up, operation to shutdown stages of the steam turbine. For moving and stationary components with short transient expansion differences, the short transient expansion differences between these moving and stationary components are obtained from the turbine's startup, operation, and shutdown stages. Step 2: Construct a mapping table of long transient and short transient states with margin. Based on the electric or regulating end of the turbine where each set of moving and stationary components is located, and the long transient expansion difference or short transient expansion difference, select the corresponding margin value from the mapping table of long transient and short transient states with margin. Step 3: Calculate the minimum clearance between the corresponding moving and stationary parts during the long transient expansion difference, rotor shrinkage, cylinder deformation and corresponding margin values. When the short transient expansion difference is positive, the short transient minimum clearance between the corresponding moving and stationary parts is calculated based on the corresponding margin value. When the short transient expansion difference is negative, the short transient minimum clearance between the corresponding moving and stationary parts is calculated based on the short transient expansion difference and the corresponding margin value.
2. The method for determining the axial clearance of a nuclear power turbine according to claim 1, characterized in that, Long transient minimum clearance = long transient expansion difference during shutdown + δ + rotor contraction + cylinder deformation, where δ is a margin value.
3. The method for determining the axial clearance of a nuclear power turbine according to claim 2, characterized in that, When the short transient expansion difference is positive, the short transient minimum gap = δ; When the short transient expansion difference is negative, the short transient minimum gap = -short transient expansion difference + δ.
4. The method for determining the axial clearance of a nuclear power turbine according to claim 1, characterized in that, The clearance between moving and stationary components includes the clearance between the moving blade and the stationary blade, and the clearance at the position of the steam seal teeth.
5. The method for determining the axial clearance of a nuclear power turbine according to claim 1, characterized in that, The transient expansion difference during shutdown = 100% expansion of the rotor at the corresponding position - 75% expansion of the stationary component at the corresponding position.
6. The method for determining the axial clearance of a nuclear power turbine according to claim 1, characterized in that, Short transient expansion difference = 75% expansion of rotor temperature at the corresponding position - 100% expansion of stationary component temperature at the corresponding position - Poisson effect contraction of rotor at the corresponding position.