A structural optimization design method for variable frequency condensate pumps

Abstract

This invention provides a method for optimizing the design of a variable-frequency condensate pump structure. This method establishes a functional relationship between the rotor structure's natural frequency and the number of impeller blades, number of impellers, and impeller wheelbase. Using the range of values ​​for these parameters as constraints, the optimization solution is performed with the maximum range within which the condensate pump can reduce its frequency from rated power without resonance as the target value. Matlab programming is used to calculate the optimal combination of blade number, number of impellers, and impeller wheelbase. This method analyzes multiple factors, taking into account the mutual influence of these factors, and collaboratively optimizes each parameter under these constraints. This method ensures that the condensate pump can operate within the maximum range within which it can reduce its frequency without resonance with the rotor, providing theoretical and technical guidance for the optimal design of condensate pumps.

Description

Technical field:

[0001] The present invention belongs to the technical field of power generation equipment, and in particular relates to a method for optimizing the structure of a variable frequency condensate pump. Background technology:

[0002] Thermal power plants consume a significant portion of their electricity from the system's auxiliary equipment, of which the condensate pump is a key component. In response to national energy conservation and consumption reduction policies, Chinese power companies have in recent years implemented variable frequency drive technology upgrades for these auxiliary equipment. Reducing the condensate pump's speed and flow rate can achieve energy savings. However, actual condensate pump variable frequency drive technology upgrades have revealed that most condensate pumps experience resonance after speed reduction, due to the rotor's natural frequency approaching the pump's natural frequency. Current research, such as patents CN 215566913U and CN 211343380U, aims to adjust the pump's natural frequency by modifying the stiffness of the support structure. However, due to the inherent structural limitations of the condensate pump system, these adjustments often have limited effectiveness.

[0003] Some solutions, such as patent CN 105041663A, achieve vibration reduction by removing the first-stage impeller and polishing the impeller outlet blade edge. However, this solution is only applicable to the optimization of condensate pumps that originally include a four-stage impeller.

[0004] In view of this, the purpose of the present invention is to provide a variable frequency condensate pump structure optimization design method to address the resonance problem that occurs during the reduced frequency operation of the condensate pump, perform multi-parameter collaborative optimization, and use finite element analysis software such as ANSYS and ABAQUS to study the influence of the number of blades, the number of impellers, and the impeller wheelbase on the rotor natural frequency, and establish corresponding functional relationships. Through MATLAB, each parameter is collaboratively optimized under constraints to ensure that the condensate pump has a maximum range of reduced frequency operation without resonance with the rotor. Summary of the invention:

[0005] The purpose of the present invention is to provide a variable frequency condensate pump structure optimization design method to address the deficiencies of the existing technology, establish a functional relationship between the first five natural frequencies of the rotor and multiple influencing factors, seek the optimal solution of the objective function within the feasible domain, and obtain the optimal combination scheme of different influencing factors.

[0006] The present invention adopts the following technical solutions:

[0007] A method for optimizing the structure of a variable frequency condensate pump comprises the following steps:

[0008] S1. Establish a three-dimensional finite element model for modal analysis of the condensate pump, and perform parametric modeling on the number of blades, number of impellers, and impeller wheelbase of the condensate pump;

[0009] S2. Determine the range of blade numbers, impeller numbers, and impeller wheelbase, use orthogonal test methods to determine different design schemes, and perform numerical simulations on each scheme to calculate the first five natural frequencies of the condensate pump;

[0010] S3, the function is the first five natural frequencies of the condensate pump f1, f2, f3, f4, f5, and the variable is the number of blades x i 、Impeller number y i , the wheelbase z between the first-stage impeller and the second-stage impeller i , the wheelbase z between the secondary impellers i ', the rated frequency of the condensate pump rotor is f, the minimum operating frequency is f0, and the total wheelbase length available for installing the impeller on the condensate pump is l. A quadratic response surface model is established between the first five natural frequencies of the condensate pump and the four variables:

[0011]

[0012]

[0013]

[0014]

[0015]

[0016] Among them, a i , b i , c i , d i , e i is the coefficient, i = 0, 1, 2, ..., 14, and its value is solved by the least squares method;

[0017] S4, respectively determine whether the first five frequencies f1, f2, f3, f4, and f5 are the frequencies closest to the rated frequency f within the variable frequency operation range, i.e., f i <f<f i+1 , then f i This is the desired frequency; the objective function optimization model is: minf i , set constraints and find the optimal solution;

[0018] S5. Seek the optimal solution for the above objective function. When f i When the value is minimum, ff i Maximum, thus ensuring that the condensate pump has the largest range of reduced frequency operation without resonance. The four parameter values ​​corresponding to the optimal solution are the optimal design scheme of the variable frequency condensate pump. The above calculation process is realized by Matlab programming.

[0019] Furthermore, in S4, the constraints are:

[0020] Furthermore, when the optimal solution corresponds to f i When <f0, there is no frequency that resonates with the rotor within the normal variable frequency operation range of the condensate pump.

[0021] Furthermore, in S5, the calculation process of the four parameter values ​​is implemented by Matlab programming.

[0022] Beneficial effects of the present invention:

[0023] (1) The present invention discloses a method for optimizing the structure of a variable frequency condensate pump. By establishing a functional relationship between the natural frequency of the rotor structure and the number of impeller blades, the number of impellers, and the impeller wheelbase, the method uses the value range of the relevant parameters as a constraint condition, and takes the maximum range in which the condensate pump can reduce the frequency from the rated power without resonance as the target value for optimization and solution. The method calculates the optimal combination of the number of blades, the number of impellers, and the impeller wheelbase through MATLAB programming. The present invention jointly analyzes multiple factors, considers the mutual influence between different factors, and coordinately optimizes each parameter under the constraint condition to ensure that the condensate pump can reduce the frequency and operate in the maximum range without resonance with the rotor.

[0024] (2) The present invention uses computer software to perform parametric modeling of the condensate pump rotor system, which can quickly obtain the modal characteristics of the rotor under different parameters; and coordinately optimize the number of blades, the number of impellers and the impeller wheelbase, providing theoretical and technical guidance for the optimal design of the condensate pump. Description of the drawings:

[0025] Figure 1 It is a schematic diagram of the wheelbase of the condensate pump impeller of the present invention.

[0026] The symbols in the accompanying drawings are:

[0027] 11: Axial length of the first-stage impeller; 12: Axial length of the secondary impeller;

[0028] zi: the wheelbase between the first-stage impeller and the second-stage impeller; zi': the wheelbase between the secondary impellers. Specific implementation method:

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0030] Example 1

[0031] This embodiment provides a method for optimizing the structure of a variable frequency condensate pump, comprising the following steps:

[0032] (1) Establish a three-dimensional finite element model for modal analysis of the condensate pump, and perform parametric modeling on the number of blades, number of impellers, and impeller wheelbase of the condensate pump.

[0033] (2) Determine the range of values ​​for the number of blades, the number of impellers, and the impeller wheelbase, use the orthogonal test method to determine different design schemes, and perform numerical simulation on the different schemes to calculate the first five natural frequencies of the condensate pump; for example, in the orthogonal test method, the number of blades is taken as 2, 5, and 8, the number of impellers is taken as 1, 4, and 7, the wheelbases of the first-stage impeller and the second-stage impeller are taken as (l1+l2) / 2, (l1+l2), and 3(l1+l2) / 2, and the wheelbases between the secondary impellers are taken as l2, 2l2, and 3l2, respectively, and an orthogonal test design is performed on the four variables.

[0034] (3) The function is the first five natural frequencies of the condensate pump f1, f2, f3, f4, f5, and the variable is the number of blades x i 、Impeller number y i , the wheelbase z between the first-stage impeller and the second-stage impeller i , the wheelbase z between the secondary impellers i ', the rated frequency of the condensate pump rotor is f, the minimum operating frequency is f0, and the total wheelbase length available for installing the impeller on the condensate pump is l. A quadratic response surface model is established between the first five natural frequencies of the condensate pump and the four variables:

[0035]

[0036]

[0037]

[0038]

[0039]

[0040] Among them, a i , b i , c i , d i , e i is the coefficient, i = 0, 1, 2, ..., 14, and its value is solved by the least squares method.

[0041] (IV) Determine whether the first five frequencies f1, f2, f3, f4, and f5 are the frequencies closest to the rated frequency f within the variable frequency operation range, i.e., f i <f<f i+1 , then fi This is the desired frequency;

[0042] The objective function optimization model is: minf i

[0043] The constraints are:

[0044]

[0045] (V) Seeking the optimal solution for the above objective function, when f i When the value is minimum, ff i The maximum value is obtained, thereby ensuring that the condensate pump has the largest range of reduced-frequency operation without resonance. The four parameter values ​​corresponding to the optimal solution (number of blades, number of impellers, wheelbase between the first-stage impeller and the second-stage impeller, and wheelbase between the secondary impellers) are the optimal design scheme for the variable-frequency condensate pump. The above calculation process is implemented through Matlab programming.

[0046] (6) When the optimal solution corresponds to f i When <f0, there is no frequency that resonates with the rotor within the normal variable frequency operation range of the condensate pump.

[0047] The above are only preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the scope of protection of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications without departing from the principle of the present invention should be regarded as the scope of protection of the present invention.

Claims

1. A variable frequency condensate pump structure optimization design method, characterized in that: The following steps are involved: S1. Establish a three-dimensional finite element model for modal analysis of the condensate pump, and perform parametric modeling on the number of blades, number of impellers, and impeller wheelbase of the condensate pump; S2. Determine the range of blade numbers, impeller numbers, and impeller wheelbase, use orthogonal test methods to determine different design schemes, and perform numerical simulations on each scheme to calculate the first five natural frequencies of the condensate pump; S3, the function is the first five natural frequencies of the condensate pump f1, f2, f3, f4, f5, and the variable is the number of blades x i 、Impeller number y i , the wheelbase z between the first-stage impeller and the second-stage impeller i , the wheelbase z between the secondary impellers i ', the rated frequency of the condensate pump rotor is f, the minimum operating frequency is f0, and the total wheelbase length available for installing the impeller on the condensate pump is l. A quadratic response surface model is established between the first five natural frequencies of the condensate pump and the four variables: Among them, a i , b i , c i , d i , e i is the coefficient, i = 0, 1, 2, ..., 14, the coefficient is solved by the least squares method; S4, respectively determine whether the first five frequencies f1, f2, f3, f4, and f5 are the frequencies closest to the rated frequency f within the variable frequency operation range, i.e., f i <f<f i+1 , then f i This is the desired frequency; The objective function optimization model is: minf i Set constraints and find the optimal solution; S5. Seek the optimal solution for the above objective function. When f i When the value is minimum, ff i Maximum, thus ensuring that the condensate pump has the largest range of reduced frequency operation without resonance. The four parameter values ​​corresponding to the optimal solution are the optimal design scheme for the variable frequency condensate pump. In S4, the constraints are: When f corresponding to the optimal solution i <f0, there is no frequency that resonates with the rotor within the normal variable-frequency operation range of the condensate pump.

2. The variable frequency condensate pump structure optimization design method according to claim 1 is characterized in that: In S5, the calculation process of the four parameter values ​​is implemented by Matlab programming.

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