Method and system for calculating guided rotating speed of axial flow fan of air cooling unit of direct air cooling condenser of power station

Abstract

The invention relates to an air cooling unit axial flow fan guide rotating speed calculation method and system for a direct air cooling condenser of a power station, and the method comprises the steps: measuring the saturation pressure of steam in a finned tube of an air cooling unit in the direct air cooling condenser, and calculating the steam saturation temperature based on the saturation pressure; measuring the tube wall temperature of the finned tube and the inlet air temperature of the air cooling unit; calculating the cooling air volume of the air cooling unit based on the steam saturation temperature, the pipe wall temperature and the inlet air temperature of the air cooling unit; based on the characteristics of the axial flow fan, constructing a function relationship between the fan guide rotating speed and the fan air volume, and obtaining the fan guide rotating speed based on the cooling air volume by utilizing the function relationship; the system provided by the invention is used for implementing the method. Compared with the prior art, the method for calculating the guided rotating speed of the axial flow fan of the air cooling unit of the direct air cooling condenser is provided.

Description

Technical Field

[0001] This invention relates to the field of direct air-cooled condenser technology for power plants, and in particular to a method and system for calculating the guide speed of the axial flow fan in the air-cooled unit of a direct air-cooled condenser for a power plant. Background Technology

[0002] The direct air-cooled condenser is the core equipment of a direct air-cooled system. In actual operation, to reduce unit back pressure and improve operating efficiency, operators often tend to operate a larger number of axial fans at higher speeds to obtain a greater cooling airflow. When the ambient temperature is high or the unit load is high, this operating strategy can indeed effectively improve cooling and reduce unit back pressure. However, when the unit enters a low-load operating state (such as during initial startup or deep peak shaving), the steam flow into the direct air-cooled condenser will decrease significantly. Or, under conditions of a sharp drop in ambient temperature in winter, this operating strategy can over-cool the heat dissipation tube bundle, causing the inner wall temperature of the tube bundle to drop below freezing point, resulting in large-scale freezing of condensate within the tube bundle. Large-scale freezing of the direct air-cooled condenser not only damages the heat dissipation tube bundle, leading to leaks, increasing safety risks and maintenance costs, but may also cause vacuum failure, forcing the unit to reduce load or even shut down, resulting in significant economic losses. Currently, the determination of the number and speed of axial fans in operation mainly relies on the experience of operators, lacking real-time, quantitative guidance. However, most existing research on the rotational speed of direct air-cooled condensers in power plants focuses on adjusting the speed to prevent equipment failure. For example, the technical solution provided in Chinese patent application CN111473657A mainly relies on the measurement results of a temperature measuring device to control the guide speed of the exhaust fan of the direct air-cooled condenser, without providing a corresponding speed calculation method.

[0003] Therefore, providing an online calculation method for the guide speed of the axial flow fan in the air-cooled unit of a direct air-cooled condenser is of great practical significance and application value for guiding operators to adjust the guide speed of the axial flow fan, preventing freezing accidents in the direct air-cooled system, and ensuring the safe and economical operation of the unit. Summary of the Invention

[0004] The purpose of this invention is to overcome the defects of the prior art by providing a method and system for calculating the guide speed of the axial flow fan in the air-cooled unit of a direct air-cooled condenser in a power plant, providing real-time and quantitative guidance for determining the operating speed of the axial flow fan on site.

[0005] The objective of this invention can be achieved through the following technical solutions: According to a first aspect of the present invention, a method for calculating the guide speed of the axial fan in the air-cooled unit of a direct air-cooled condenser in a power plant is provided, characterized in that the method includes: Measure the saturation pressure of steam inside the finned tubes of the air-cooled unit in the direct air-cooled condenser, and calculate the steam saturation temperature based on the saturation pressure; Measure the tube wall temperature of the finned tube and the inlet air temperature of the air-cooled unit; The cooling air volume of the air-cooled unit is calculated based on the steam saturation temperature, pipe wall temperature, and air inlet temperature of the air-cooled unit. Based on the characteristics of axial flow fans, a functional relationship between the fan's guide speed and air volume is constructed. Using this functional relationship, the fan's guide speed is obtained based on the cooling air volume.

[0006] As a preferred technical solution, pressure measuring points are arranged at the inlet and outlet of the finned tube of the air-cooled unit to collect the inlet pressure and outlet pressure of the finned tube, respectively. The saturation pressure is the average of the inlet pressure and the outlet pressure.

[0007] As a preferred technical solution, the method for measuring the tube wall temperature of the finned tube is as follows: Representative points on the wall of the finned tubes of the air-cooled unit are selected as measuring points. These representative points can be spatially uniformly distributed measuring points, measuring points in different heat load areas, or measuring points in different airflow areas. Spatially uniformly distributed measuring points refer to measuring points evenly arranged in the width and height directions of the air-cooled unit. Measuring points in different heat load areas refer to measuring points arranged within a preset range at the steam inlet and steam outlet. Measuring points in different airflow areas refer to measuring points arranged in the areas directly opposite and opposite to the axial flow fan. Measure the temperature at each measuring point and calculate the arithmetic mean of all the measured temperatures as the pipe wall temperature.

[0008] As a preferred technical solution, the inlet air temperature of the air-cooled unit is equal to the ambient temperature.

[0009] As a preferred technical solution, the method for calculating the cooling air volume is as follows: , in, Indicates the overall heat transfer coefficient of the finned tube bundle; Indicates the heat exchange area; This represents the heat transfer coefficient between steam and finned tubes; This indicates the heat transfer coefficient between the finned tube and the air; Indicates the steam saturation temperature; Indicates the temperature of the finned tube wall; This indicates the specific heat capacity of air at constant pressure. This indicates the inlet air temperature of the air-cooled unit.

[0010] According to a second aspect of the present invention, a system for calculating the guide speed of the axial fan in the air-cooled unit of a direct air-cooled condenser in a power plant is provided for implementing the above-described method.

[0011] Compared with existing technologies, this invention addresses the problem that determining the number and speed of operating fans on-site relies on the experience of operators and lacks real-time quantitative guidance. It proposes a method for calculating the guide speed of axial flow fans in the air-cooled unit of a direct air-cooled condenser in a power plant. This method provides an online calculation method for the guide speed of axial flow fans that meets on-site requirements. It can output accurate guide speeds, providing clear data support for fan operation control, significantly reducing human judgment errors, and improving the scientific and timely nature of control. It also has strong engineering applicability, fully reusing the original measuring points of the direct air-cooled system, greatly reducing the number of new measuring points and facilitating installation. At the same time, it requires fewer tuning parameters and has low tuning difficulty, enabling rapid and accurate calculation of guide wind speed. Attached Figure Description

[0012] Figure 1 This is a flowchart of the method of the present invention; Figure 2 This is a schematic diagram of the heat transfer process of the direct air-cooled condenser air-cooling unit of the present invention. Detailed Implementation

[0013] 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, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0014] Example 1 To address the technical problems existing in the prior art, this invention provides a method for calculating the guide speed of the axial flow fan in the air-cooled unit of a direct air-cooled condenser in a power plant. The process is as follows: Figure 1 As shown, it includes: S1. Measure the saturation pressure of steam in the finned tubes of the air-cooled unit in the direct air-cooled condenser, and calculate the steam saturation temperature based on the saturation pressure.

[0015] S11. Pressure measuring points are arranged at the inlet and outlet of the finned tubes in the air-cooled unit to collect the inlet pressure and outlet pressure of the finned tubes, respectively. The saturation pressure is the average of the inlet and outlet pressures, and its expression is: , in, Indicates the inlet pressure of the finned tube; Indicates the outlet pressure of the finned tube; This represents the saturation pressure.

[0016] S12. Calculate the steam saturation temperature.

[0017] In this step, the data recorded in the "Thermodynamic Properties of Water and Water Vapor Chart" are first fitted with a functional relationship between pressure and temperature. Under the premise of ensuring the accuracy of the fitting, the corresponding functional relationship is a common technique used by those skilled in the art, and there are no restrictions on the form.

[0018] Using this functional relationship and substituting the saturated pressure, the steam saturation temperature is calculated as follows: ,in, Indicates saturated vapor pressure; This represents the functional relationship between pressure and temperature. This indicates the saturation temperature of the steam.

[0019] S2. Measure the tube wall temperature of the finned tube and the inlet air temperature of the air-cooled unit.

[0020] S21. Pipe wall temperature measurement.

[0021] S211. Select representative points on the wall of the finned tubes of the air-cooled unit as measuring points, and measure the temperature of the measuring points using measurement methods including but not limited to resistance thermometers and temperature-sensing cables. The representative points can be selected from one of the following: spatially uniformly distributed measuring points, measuring points in different heat load areas, or measuring points in different airflow areas. Spatially uniformly distributed measuring points refer to measuring points evenly arranged in the width and height directions of the air-cooled unit; measuring points in different heat load areas refer to measuring points arranged within a preset range at the steam inlet and steam outlet; measuring points in different airflow areas refer to measuring points arranged in the areas directly opposite and away from the axial flow fan.

[0022] S212. Measure the temperature at each measuring point and calculate the arithmetic mean of all measuring point temperatures as the pipe wall temperature.

[0023] S22, Measurement of inlet air temperature of air-cooled unit.

[0024] Several ambient temperature measurement points were set up, and the inlet air temperature of the air-cooled unit was assumed to be... Equal to ambient temperature ,Right now .

[0025] S3. Calculate the cooling air volume of the air-cooled unit based on the steam saturation temperature, pipe wall temperature, and air inlet temperature of the air-cooled unit.

[0026] Based on the heat transfer process of the air-cooled unit of the direct air condenser (e.g.) Figure 2 As shown in the figure, the heat transfer model is constructed, which includes the following steps.

[0027] According to the heat transfer equation of the heat exchanger, the heat transfer capacity of the air-cooled unit is... for: , in, Indicates the overall heat transfer coefficient of the finned tube bundle; Indicates the heat exchange area; This indicates the saturation temperature of the steam.

[0028] According to Newton's law of cooling, the heat exchange between the steam inside the finned tube and the tube wall... for: , in, This represents the heat transfer coefficient between steam and finned tubes; This indicates the temperature of the finned tube wall.

[0029] According to Newton's law of cooling, the heat exchange between the finned tube wall and the outside air... for: , in, This indicates the heat transfer coefficient between the finned tube and the air.

[0030] Applying the law of conservation of energy to the air outside the finned tube, we can obtain: , in, Airflow rate, its unit is ; and These are the enthalpy values ​​of the inlet and outlet air of the air-cooled unit, respectively, and their units are... .

[0031] At steady state, we have By combining the above expressions, we can construct the heat transfer model as follows: , .

[0032] Solving the above heat transfer model, the expression for calculating the cooling airflow is obtained as follows: , in, Indicates the overall heat transfer coefficient of the finned tube bundle; Indicates the heat exchange area; This represents the heat transfer coefficient between steam and finned tubes; This indicates the heat transfer coefficient between the finned tube and the air; Indicates the steam saturation temperature; Indicates the temperature of the finned tube wall; This indicates the specific heat capacity of air at constant pressure. This indicates the inlet air temperature of the air-cooled unit.

[0033] S4. Based on the characteristics of axial flow fans, construct a functional relationship between the fan's guide speed and the fan's air volume. Using this functional relationship, obtain the fan's guide speed based on the cooling air volume.

[0034] It should be noted that the functional relationship between the machine's guide speed and the fan's air volume mentioned above can be obtained by those skilled in the art through conventional means, and its functional form is not specifically limited. This process can be expressed as: , in, Indicates rotational speed; This indicates the functional relationship between the machine's operating speed and the fan's air volume; This indicates the cooling airflow.

[0035] In this embodiment, to verify the feasibility of the method provided by the present invention, for a co-current air-cooled unit of a double-A type direct air-cooled condenser of a 2×660MW ultra-supercritical thermal power unit, the online calculation of the axial fan speed of the air-cooled unit can be achieved by following the steps described in the technical solution of the present invention, and the ambient temperature under this operating condition is obtained in advance. Atmospheric pressure is air density is .

[0036] Details include: S1. Measure the saturation pressure of steam in the finned tubes of the air-cooled unit in the direct air-cooled condenser, and calculate the steam saturation temperature based on the saturation pressure.

[0037] S11. Measure the inlet pressure of the finned tube. Finned tube outlet pressure The saturation pressure was calculated. .

[0038] S12. Calculate the steam saturation temperature.

[0039] Since the finned tube is in a saturated state, the saturation temperature of the water vapor inside the finned tube can be calculated using the following formula, based on the thermodynamic properties of saturated water vapor: .

[0040] S2. Measure the tube wall temperature of the finned tube and the inlet air temperature of the air-cooled unit.

[0041] S21. Measure the pipe wall temperature. .

[0042] S22. Measurement of the inlet air temperature of the air-cooled unit: Several ambient temperature measuring points are set up, and it is assumed that the inlet air temperature of the air-cooled unit is... Equal to ambient temperature ,Right now .

[0043] S3. Calculate the cooling air volume of the air-cooled unit based on the steam saturation temperature, pipe wall temperature, and inlet air temperature of the air-cooled unit. The expression is as follows: , in, Indicates the overall heat transfer coefficient of the finned tube bundle; Indicates the heat exchange area; This represents the heat transfer coefficient between steam and finned tubes; This indicates the heat transfer coefficient between the finned tube and the air; Indicates the steam saturation temperature; Indicates the temperature of the finned tube wall; This indicates the specific heat capacity of air at constant pressure. This indicates the inlet air temperature of the air-cooled unit.

[0044] S4. Based on the characteristics of axial flow fans, construct a functional relationship between the fan's guide speed and airflow. Using this functional relationship and the cooling airflow, obtain the fan's guide speed. This process can be expressed as: , in, Indicates rotational speed; This indicates the cooling airflow.

[0045] Based on the dynamic simulation model of the direct air-cooled system, the cooling air volume is obtained. The airflow rate is 730 kg / s, and the fan speed n is 89.4 rpm. Therefore, the relative error of the calculated airflow rate using this method is 11.4%. The reason for this error may be that the online calculation method uses the average inlet and outlet pressures of the finned tube as the saturation pressure of the steam inside the finned tube, and then calculates the saturation temperature of the steam. The resulting steam saturation temperature inevitably has a certain error, ultimately leading to an error in the calculated fan speed. However, this calculation error is still within the acceptable range for engineering applications.

[0046] Example 2 This embodiment provides a system for calculating the guide speed of the axial flow fan in the air-cooled unit of a direct air-cooled condenser in a power plant. The system includes: The saturation pressure measurement module is used to measure the saturation pressure of steam inside the finned tubes of the air-cooled unit in a direct air-cooled condenser.

[0047] The saturation temperature calculation module calculates the steam saturation temperature using the saturation pressure measured by the saturation pressure measurement module.

[0048] Tube wall temperature measurement module, which is used to measure the tube wall temperature of finned tubes.

[0049] Air-cooled unit inlet temperature measurement module, which is used to measure the inlet air temperature of the air-cooled unit.

[0050] The cooling air volume calculation module calculates the cooling air volume of the air-cooled unit based on the steam saturation temperature, pipe wall temperature, and inlet air temperature of the air-cooled unit.

[0051] The guide speed calculation module constructs a functional relationship between the guide speed and the air volume of the fan based on the characteristics of the axial flow fan. Using the functional relationship and the cooling air volume, the guide speed of the fan is obtained.

[0052] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process of the described module can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0053] This invention provides an electronic device including a central processing unit (CPU), which can perform various appropriate actions and processes according to computer program instructions stored in read-only memory (ROM) or loaded from a storage unit into random access memory (RAM). The RAM may also store various programs and data required for device operation. The CPU, ROM, and RAM are interconnected via a bus. Input / output (I / O) interfaces are also connected to the bus.

[0054] Multiple components in the device are connected to the I / O interface, including: input units such as keyboards and mice; output units such as various types of displays and speakers; storage units such as disks and optical discs; and communication units such as network interface cards (NICs), modems, and wireless transceivers. The communication unit allows the device to exchange information / data with other devices through computer networks such as the Internet and / or various telecommunications networks.

[0055] The processing unit executes the various methods and processes described above, such as methods S1 to S4. For example, in some embodiments, methods S1 to S4 may be implemented as computer software programs tangibly contained in a machine-readable medium, such as a storage unit. In some embodiments, part or all of the computer program may be loaded and / or installed on the device via ROM and / or a communication unit. When the computer program is loaded into RAM and executed by the CPU, one or more steps of methods S1 to S4 described above may be performed. Alternatively, in other embodiments, the CPU may be configured to execute methods S1 to S4 by any other suitable means (e.g., by means of firmware).

[0056] The functions described above in this document can be performed, at least in part, by one or more hardware logic components. For example, exemplary types of hardware logic components that can be used, without limitation, include: Field Programmable Gate Arrays (FPGAs), Application-Specific Integrated Circuits (ASICs), Application Standard Products (ASSPs), System-on-Chip (SoCs), Complex Programmable Logic Devices (CPLDs), and so on.

[0057] The program code used to implement the methods of the present invention can be written in any combination of one or more programming languages. This program code can be provided to a processor or controller of a general-purpose computer, special-purpose computer, or other programmable data processing device, such that when executed by the processor or controller, the program code causes the functions / operations specified in the flowcharts and / or block diagrams to be implemented. The program code can be executed entirely on the machine, partially on the machine, as a standalone software package partially on the machine and partially on a remote machine, or entirely on a remote machine or server.

[0058] In the context of this invention, a machine-readable medium can be a tangible medium that may contain or store a program for use by or in conjunction with an instruction execution system, apparatus, or device. A machine-readable medium can be a machine-readable signal medium or a machine-readable storage medium. Machine-readable media can include, but are not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatus, or devices, or any suitable combination of the foregoing. More specific examples of machine-readable storage media include electrical connections based on one or more wires, portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fibers, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination of the foregoing.

[0059] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for calculating the guide speed of the axial flow fan in the air-cooled unit of a direct air-cooled condenser in a power plant, characterized in that the method... include: Measure the saturation pressure of steam inside the finned tubes of the air-cooled unit in the direct air-cooled condenser, and calculate the steam saturation temperature based on the saturation pressure; Measure the tube wall temperature of the finned tube and the inlet air temperature of the air-cooled unit; The cooling air volume of the air-cooled unit is calculated based on the steam saturation temperature, pipe wall temperature, and air inlet temperature of the air-cooled unit. Based on the characteristics of axial flow fans, a functional relationship between the fan's guide speed and air volume is constructed. Using this functional relationship, the fan's guide speed is obtained based on the cooling air volume.

2. The method for calculating the guide speed of the axial flow fan in the air-cooled unit of a direct air-cooled condenser in a power plant according to claim 1, characterized in that, Pressure measuring points are arranged at the inlet and outlet of the finned tube of the air-cooled unit to collect the inlet pressure and outlet pressure of the finned tube, respectively. The saturation pressure is the average of the inlet pressure and the outlet pressure.

3. The method for calculating the guide speed of the axial flow fan in the air-cooled unit of a direct air-cooled condenser in a power plant according to claim 1, characterized in that, The method for measuring the tube wall temperature of the finned tube is as follows: Representative points on the wall of the finned tubes of the air-cooled unit are selected as measuring points. These representative points can be spatially uniformly distributed measuring points, measuring points in different heat load areas, or measuring points in different airflow areas. Spatially uniformly distributed measuring points refer to measuring points evenly arranged in the width and height directions of the air-cooled unit. Measuring points in different heat load areas refer to measuring points arranged within a preset range at the steam inlet and steam outlet. Measuring points in different airflow areas refer to measuring points arranged in the areas directly opposite and opposite to the axial flow fan. Measure the temperature at each measuring point and calculate the arithmetic mean of all the measured temperatures as the pipe wall temperature.

4. The method for calculating the guide speed of the axial flow fan in the air-cooled unit of a direct air-cooled condenser in a power plant according to claim 1, characterized in that, The inlet air temperature of the air-cooled unit is equal to the ambient temperature.

5. The method for calculating the guide speed of the axial flow fan in the air-cooled unit of a direct air-cooled condenser in a power plant according to claim 1, characterized in that, The method for calculating the cooling air volume is as follows: ， in, Indicates the overall heat transfer coefficient of the finned tube bundle; Indicates the heat exchange area; This represents the heat transfer coefficient between steam and finned tubes; This indicates the heat transfer coefficient between the finned tube and the air; Indicates the steam saturation temperature; Indicates the temperature of the finned tube wall; This indicates the specific heat capacity of air at constant pressure. This indicates the inlet air temperature of the air-cooled unit.

6. A system for calculating the guide speed of an axial fan in an air-cooled unit of a direct air-cooled condenser in a power plant, characterized in that, The system includes: Saturation pressure measurement module, which is used to measure the saturation pressure of steam in the finned tubes of the air-cooled unit in a direct air-cooled condenser; The saturation temperature calculation module calculates the steam saturation temperature using the saturation pressure measured by the saturation pressure measurement module. A tube wall temperature measurement module, which is used to measure the tube wall temperature of the finned tube; Air-cooled unit inlet temperature measurement module, which is used to measure the inlet air temperature of the air-cooled unit; The cooling air volume calculation module calculates the cooling air volume of the air-cooled unit based on the steam saturation temperature, pipe wall temperature and air inlet temperature of the air-cooled unit. The guide speed calculation module constructs a functional relationship between the guide speed and the air volume of the fan based on the characteristics of the axial flow fan. Using the aforementioned functional relationship and the cooling air volume, the guide speed of the fan is obtained.

7. The system for calculating the guide speed of the axial flow fan in the air-cooled unit of a direct air-cooled condenser in a power plant according to claim 6, characterized in that, The saturation pressure measurement module arranges pressure measuring points at the inlet and outlet of the finned tube of the air-cooled unit to collect the inlet pressure and outlet pressure of the finned tube, respectively. The saturation pressure is the average of the inlet pressure and the outlet pressure.

8. The system for calculating the guide speed of the axial flow fan in the air-cooled unit of a direct air-cooled condenser in a power plant according to claim 6, characterized in that, The pipe wall temperature measurement module performs the following steps to measure the pipe wall temperature: Representative points on the wall of the finned tubes of the air-cooled unit are selected as measuring points. These representative points can be spatially uniformly distributed measuring points, measuring points in different heat load areas, or measuring points in different airflow areas. Spatially uniformly distributed measuring points refer to measuring points evenly arranged in the width and height directions of the air-cooled unit. Measuring points in different heat load areas refer to measuring points arranged within a preset range at the steam inlet and steam outlet. Measuring points in different airflow areas refer to measuring points arranged in the areas directly opposite and opposite to the axial flow fan. Measure the temperature at each measuring point and calculate the arithmetic mean of all the measured temperatures as the pipe wall temperature.

9. The system for calculating the guide speed of the axial flow fan in the air-cooled unit of a direct air-cooled condenser in a power plant according to claim 6, characterized in that, The air-cooled unit inlet temperature measurement module collects the ambient temperature as the air-cooled unit inlet air temperature.

10. The system for calculating the guide speed of the axial flow fan in the air-cooled unit of a direct air-cooled condenser in a power plant according to claim 6, characterized in that, The method by which the guide speed calculation module calculates the guide speed is as follows: ， in, Indicates the overall heat transfer coefficient of the finned tube bundle; Indicates the heat exchange area; This represents the heat transfer coefficient between steam and finned tubes; This indicates the heat transfer coefficient between the finned tube and the air; Indicates the steam saturation temperature; Indicates the temperature of the finned tube wall; This indicates the specific heat capacity of air at constant pressure. This indicates the inlet air temperature of the air-cooled unit.

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