Underground power station energy-saving air duct airflow parameter calculation method and system

Abstract

The invention relates to the technical field of underground power station energy-saving air ducts, and discloses an underground power station energy-saving air duct airflow parameter calculation method and system.The method comprises the steps that a single-air-duct equal-perimeter model and a double-air-duct equal-perimeter model containing a middle partition wall are adopted, and a single-air-duct equal-perimeter model is obtained based on analysis of the heat transfer process of airflow and air duct wall faces in combination with cylindrical coordinates; establishing a mathematical model for underground power station air duct airflow parameter calculation by applying basic formulas of heat transfer theory and thermodynamics; performing time and space discretization on the mathematical model to establish a discrete calculation model; and carrying out hourly dynamic calculation on the air duct airflow parameters by using the discrete calculation model. By analyzing the heat transfer between the airflow and the wall body, the heat storage and release of the rock mass and the change characteristics and the relationship between the airflow and the wall body, a universal, rapid and accurate calculation model for the airflow parameters of the single-air-duct and double-air-duct underground power stations is established, and the airflow parameters of the air ducts are dynamically calculated hourly; the hourly rock mass internal change and the rock mass and airflow convective heat exchange airflow parameter change are obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of energy-saving air ducts in underground power stations, and in particular to a method and system for calculating airflow parameters of energy-saving air ducts in underground power stations. Background Art

[0002] Underground power stations generally introduce fresh air from the outside through ventilation tunnels, traffic tunnels or other underground passages. Due to the temperature and humidity difference between the rock mass and the air, the airflow needs to exchange heat and moisture when passing through the air duct. The airflow temperature in summer is greater than the rock mass temperature, and the airflow temperature in winter is less than the rock mass temperature. Therefore, the air temperature flowing through the air duct in summer decreases, and the air temperature increases in winter, thereby achieving the heating and cooling of the airflow; the air duct of the underground power station is usually arched, and the outdoor airflow enters the underground air duct. Due to the temperature difference between the two, the airflow exchanges heat with the wall of the air duct in a convection heat exchange manner. The air inlet duct of the underground power station is generally more than 1,000 meters long, and the natural cooling effect (warming in winter) of the mountain can be fully utilized. A ventilation and air conditioning scheme with mechanical ventilation as the main and air conditioning and dehumidification as the auxiliary is adopted. The advantages of this scheme are: when the unit is running at full load in the hot season, under the conditions of temperature and humidity in the working area, the mechanical ventilation and air conditioning refrigeration system operate together, which can reduce the air conditioning cooling capacity and reduce the power consumption of the air conditioning system.

[0003] However, for the calculation of airflow parameters of underground air inlets, the method in the "Hydropower Station Electromechanical Design Manual" is a design calculation method commonly used in current projects, which introduces a large number of special functions. In the calculation, there are dozens of intermediate parameters that need to be calculated through these functions, but these functions cannot be calculated directly, and the results must be obtained by looking up charts. This makes the calculation process very complicated and prone to errors. Furthermore, the scope of application of these charts is limited, and they cannot meet the calculation of large-scale, large-volume underground air ducts in large-scale underground power stations. At the same time, they are also prone to introducing chart-looking errors, which reduces the accuracy of the calculation results. Summary of the invention

[0004] In view of this, the present invention provides a method and system for calculating airflow parameters of energy-saving air ducts in underground power stations, which can overcome the defects of low accuracy and poor versatility in the prior art for calculating airflow parameters of energy-saving air ducts in underground power stations.

[0005] In a first aspect, the present invention provides a method for calculating airflow parameters of an energy-saving air duct in an underground power station, the method comprising:

[0006] Convert the underground arched duct model into a cylindrical model with equal perimeter, wherein the cylindrical model with equal perimeter includes a single duct equal perimeter model and a double duct equal perimeter model with a middle partition wall, as a physical model of airflow parameter changes in the duct of the underground power station;

[0007] Based on the analysis of the heat transfer process between the airflow and the duct wall and the cylindrical coordinates, the mathematical model for calculating the airflow parameters of the underground power station duct is established by applying the basic formulas of heat transfer and thermodynamics.

[0008] Discretize the mathematical model in time and space to establish a discrete computing model;

[0009] The discrete calculation model is used to dynamically calculate the airflow parameters of the air duct hour by hour.

[0010] The method for calculating airflow parameters of energy-saving ducts in underground power stations provided by the embodiment of the present invention analyzes the heat transfer between the airflow and the wall, the heat storage and release of the rock mass, and the changing characteristics of the airflow parameters and their relationship with each other, and further establishes airflow parameter calculation models for underground power station ducts of single ducts and double ducts by establishing a single duct equal perimeter model and a double duct equal perimeter model with an intermediate partition wall. The model can realize the dynamic calculation of heat and moisture exchange that cannot be realized by traditional analysis methods. During the operation of the underground power station, the accurate airflow parameter values ​​can be used to monitor and adjust the ventilation system in real time, so that the ventilation system always operates in an efficient state, reducing the extra energy consumed to maintain the normal operating temperature of the power station equipment, and reducing the energy consumption of the auxiliary system on the premise of ensuring the safe and stable operation of the power station equipment, thereby achieving an overall energy-saving effect.

[0011] The embodiment of the present invention converts the underground arched air duct into an equal-perimeter equivalent cylindrical model. The equal-perimeter equivalent cylindrical model has the same trend as the original model for single or double air ducts. The equal-perimeter model ensures that the heat exchange area between the air and the rock mass is equal. The difference between the converted model and the original model result is extremely small, which is conducive to the accurate calculation of the air duct parameters.

[0012] In an optional embodiment, the basic formulas of heat transfer and thermodynamics include: the heat conduction equation inside the rock mass, the convection heat transfer equation between the airflow and the wall, and the heat and moisture balance equation of the airflow;

[0013] The mathematical model for calculating airflow parameters of the underground power station wind duct is established by applying the basic formulas of heat transfer and thermodynamics, including:

[0014] The heat conduction equation inside the rock mass is a one-dimensional unsteady cylindrical heat conduction differential equation. Based on the energy conservation and Fourier's heat conduction law, the one-dimensional cylindrical heat conduction differential equation of the rock mass is derived to obtain the first set of partial differential equations.

[0015] The convection heat transfer equation between the airflow and the wall includes Fourier's heat conduction law and Newton's cooling formula. By combining the analysis of the convection heat transfer process between the airflow and the duct wall, the corresponding second partial differential equation group is obtained.

[0016] The heat and moisture balance equation of airflow includes the basic equation of sensible heat balance and the basic equation of latent heat balance. When condensation does not occur on the wall, the total heat exchange between the air in the duct and the wall is equal to the sensible heat exchange, satisfying the basic equation of sensible heat balance. When condensation occurs on the wall, the heat exchange between the air in the duct and the wall is composed of latent heat and sensible heat exchange. Combined with the analysis of the convective heat transfer process of the airflow and the duct wall, the corresponding third group of partial differential equations is obtained.

[0017] The first group of partial differential equations, the second group of partial differential equations and the third group of partial differential equations together constitute a mathematical model for calculating airflow parameters of the wind duct of an underground power station.

[0018] The embodiment of the present invention analyzes the heat transfer physical model that causes the change of airflow parameters, applies the basic formulas of heat transfer and thermodynamics, and combines the analysis of the convective heat transfer process of the airflow and the duct wall to obtain a series of partial differential equations as a mathematical model for calculating the airflow parameters.

[0019] In an optional implementation, for a single duct equal perimeter model, the mathematical model is spatially discretized, including: discretization along the duct length direction and discretization along the cross-sectional radial direction, wherein:

[0020] The duct is divided into multiple grid units at equal intervals along the length direction of the duct according to the actual length of the duct. The center of the duct is selected as the control node in the airflow area along the length direction of the duct, assuming that the airflow distribution is uniform; it is divided into multiple grid units at equal intervals along the radial direction of the cross section, and the control nodes are located on the grid lines;

[0021] Discretize the mathematical model in time, including: discretize the continuous time of the whole year into time points with preset intervals to calculate the airflow parameters and heat transfer values ​​at each time point;

[0022] For the double duct equal perimeter model, the air in the duct is divided into two parts: air A close to the lining wall and air B close to the partition wall. Air A exchanges heat with the nearby lining wall, and air B exchanges heat with the partition wall surface by convection. The same discrete method as the single duct equal perimeter model is used to grid the various parts of the duct in space and discretize them in time.

[0023] In this embodiment, a node discrete equation is established to replace the continuous temperature field with a set of temperatures of discrete points in the space and time coordinate systems on the solution area, and a large number of algebraic equations are used instead of partial differential equations to solve the mathematical model. The solution of partial differential equations usually requires complex numerical methods and huge amount of calculation, which often requires a lot of time and computing resources. Algebraic equations are relatively simple, with relatively small amount of calculation and much faster solution speed. Therefore, the calculation results can be obtained faster, thereby improving work efficiency.

[0024] In an optional implementation, the step of discretizing the mathematical model in time and space to establish a discrete computing model includes:

[0025] Combining the Taylor series expansion method and the heat balance method, the partial differential equation is transformed into an algebraic equation of the control node as a discrete calculation model.

[0026] The embodiment of the present invention utilizes the Taylor series expansion method to transform the partial differential equation into an algebraic equation from a mathematical perspective, and utilizes the thermal balance method to transform the partial differential equation into an algebraic equation with the help of Fourier's law of heat conduction and the law of conservation of energy, so that each parameter has a clear physical meaning and parameter analysis can be conveniently performed, thereby realizing a model that is actually used for calculation.

[0027] In an optional implementation, the step of dynamically calculating the air duct airflow parameters hour by hour using the discrete calculation model includes:

[0028] At the start time of calculation, the outdoor air parameters, ventilation volume and initial temperature of the rock mass are taken as known values. Starting from the first network unit at the entrance along the length of the air duct, the heat conduction inside the rock mass, the convective heat transfer between the rock mass and the airflow, and the changes in the airflow parameters are calculated. The end point of this unit is taken as the starting point of the next unit, and so on until the exit unit, completing the calculation at that moment;

[0029] The rock temperature calculated at the first moment is used as the initial rock temperature when calculating at the second moment, and the outdoor air parameters and ventilation volume at the second moment are taken from the inlet unit to the outlet unit.

[0030] The embodiment of the present invention uses a discrete calculation model to dynamically calculate the airflow parameters of the duct hour by hour, and obtains the moment by moment changes in the rock mass, and the changes in the airflow parameters of the convective heat exchange between the rock mass and the airflow, so as to accurately capture the changes in the airflow parameters of the duct at different times. By analyzing the changes in the airflow parameters moment by moment, the key time points and influencing factors of the convective heat exchange can be found, which provides a basis for selecting air ventilation equipment, improving the ventilation system and controlling the airflow temperature. In engineering decision-making, it can provide real-time airflow parameter information to help engineers make timely adjustments and improvements to ensure the safe and stable operation of the underground power station system.

[0031] In an optional implementation, based on the dual-duct equal-perimeter model, the dual-duct heat exchange process is as follows for the nodes inside the partition wall:

[0032]

[0033] Tw(τ+1,i)=Fo(Tw(τ,i+1)+Tw(τ,i-1))+(1-2Fo)Tw(τ,i)

[0034] in,

[0035] Where Tw(τ,i) represents the temperature of node i in the partition wall at time τ (℃); y3 , y3 Respectively represent the thermal conductivity of the partition material (m 2 / h), density (kg / m 3 ), a y Indicates thermal conductivity (m 2 / h), partition wall layer a y =a y3 ; Δr and Δτ are the grid spacing and time step respectively.

[0036] When considering the heat exchange process of the entire dual air duct in the embodiment of the present invention, it is necessary to additionally consider the convective heat exchange between the air and the rock wall of the air inlet duct, the heat conduction of the air inlet duct, the convective heat exchange between the air and the surface of the air inlet duct partition wall, the heat conduction inside the partition wall, the convective heat exchange between the air and the surface of the exhaust duct partition wall, the heat exchange between the air and the rock wall of the exhaust duct and the heat conduction inside the rock of the exhaust duct. Therefore, the air in the air duct is divided into two parts for analysis, which improves the accuracy of the airflow parameter calculation.

[0037] In a second aspect, the present invention provides a system for calculating airflow parameters of energy-saving air ducts in underground power plants, the system comprising:

[0038] A physical model building module is used to convert the underground arched air duct model into an equal-perimeter cylindrical model, wherein the equal-perimeter cylindrical model includes: a single air duct equal-perimeter model and a double air duct equal-perimeter model with a middle partition wall, which is used as a physical model of airflow parameter changes in the underground power station air duct;

[0039] Mathematical model building module, which is used to establish a mathematical model for calculating airflow parameters in underground power station air ducts based on the analysis of the heat transfer process between airflow and duct wall and cylindrical coordinates, and the application of basic formulas of heat transfer and thermodynamics;

[0040] Discrete module building module, used to discretize mathematical models in time and space to establish discrete calculation models;

[0041] The airflow parameter calculation module is used to dynamically calculate the airflow parameters of the air duct hour by hour using the discrete calculation model.

[0042] In a third aspect, the present invention provides a computer device, comprising: a memory and a processor, the memory and the processor are communicatively connected to each other, the memory stores computer instructions, and the processor executes the method for calculating airflow parameters of energy-saving ducts in underground power stations according to the first aspect or any corresponding embodiment thereof by executing the computer instructions.

[0043] In a fourth aspect, the present invention provides a computer-readable storage medium having computer instructions stored thereon, the computer instructions being used to enable a computer to execute the method for calculating airflow parameters of an energy-saving duct in an underground power station according to the first aspect or any corresponding embodiment thereof.

[0044] In a fifth aspect, the present invention provides a computer program product, including computer instructions, which are used to enable a computer to execute the method for calculating airflow parameters of an energy-saving air duct in an underground power station according to the first aspect or any corresponding embodiment thereof. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0046] Figure 1 is a flow chart of a method for calculating airflow parameters of an energy-saving air duct in an underground power station according to an embodiment of the present invention;

[0047] Figure 2 (a) is a schematic diagram of the geometric structure of a single air duct of an underground power station energy-saving air duct according to an embodiment of the present invention;

[0048] Figure 2 (b) is a schematic diagram of the geometric structure of a double air duct with a middle partition wall of an underground power station energy-saving air duct according to an embodiment of the present invention;

[0049] Figure 3 is a schematic diagram of approximating a single air duct arch to concentric circles according to an embodiment of the present invention;

[0050] Figure 4 is a schematic diagram of the test results before and after the single air duct model is converted according to an embodiment of the present invention;

[0051] Figure 5 is a schematic diagram of approximating the double air duct arch shape to concentric circles with a partition wall boundary line according to an embodiment of the present invention;

[0052] Figure 6 is a schematic diagram of the test results before and after the dual air duct model is transformed according to an embodiment of the present invention;

[0053] Figure 7 is a schematic diagram of a rock mass heat conduction microelement in a cylindrical coordinate system according to an embodiment of the present invention;

[0054] Figure 8is a schematic diagram of spatial discretization of a single air duct equal perimeter model according to an embodiment of the present invention;

[0055] Fig. 9 is a schematic diagram of dividing duct air for a single duct equal perimeter model according to an embodiment of the present invention;

[0056] Fig.10 is a schematic diagram of spatial discretization of a dual-duct equal-perimeter model according to an embodiment of the present invention;

[0057] Fig.11 is a schematic diagram showing the temperature of air A exchanging heat with a rock mass wall as a function of position according to an embodiment of the present invention;

[0058] Fig.12 is a schematic diagram showing the change in temperature of air B exchanging heat with the partition wall surface as a function of position according to an embodiment of the present invention;

[0059] Fig.13 is a comparison diagram of the air temperature change in the air duct and the simulation result according to an embodiment of the present invention;

[0060] Fig.14 is a structural block diagram of an airflow parameter calculation system for an energy-saving air duct in an underground power station according to an embodiment of the present invention;

[0061] Fig.15 It is a schematic diagram of the hardware structure of a computer device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0062] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in 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 those skilled in the art without creative work are within the scope of protection of the present invention.

[0063] At present, there are mainly engineering calculation method, graphic method, model experiment method and CFD software simulation method for calculating airflow parameters of underground power station duct. The engineering calculation method is based on the calculation method provided in the "Hydropower Station Electromechanical Design Manual". For the two cases of wall condensation and non-condensation, the calculation method of constant air inlet parameters of the duct is given. When the wall does not condense, the summer daily average temperature, winter daily average temperature, summer maximum temperature and winter minimum temperature at any length can be calculated according to the mathematical expression of annual amplitude change value, daily amplitude change value and annual average temperature change of airflow. In the process of outdoor air flowing through the underground duct and contacting the wall in summer, the air first undergoes isohumid cooling and changes. When the air temperature drops and the relative humidity of the air near the wall is close to 100%, the airflow parameters will be carried out according to the cooling and dehumidification process. At this time, condensation occurs on the duct wall. The air change is divided into two processes: isohumid cooling and dehumidification cooling process. The calculation is also divided into two stages. First, according to the isohumid cooling process, the distance from the condensation section to the opening is calculated, and then the various air temperatures are calculated according to the cooling and dehumidification process. However, the calculation results cannot reflect the changes in airflow parameters at different times throughout the year and are inconsistent with the actual situation. In addition, a large number of special functions are introduced in the calculation. Through the chart search, the chart has a very limited scope of application and cannot meet the large-scale and large duct calculations. The model experiment method builds a test bench based on the similarity principle. By simulating the measurement of air temperature in the duct, the airflow parameters under actual conditions are determined according to the measurement data by the similarity principle. By sorting out the relevant data, the empirical formula is obtained. This method has made a lot of simplifications, the operation is relatively complicated, and there are certain limitations in actual engineering applications. Some researchers used fluent software to simulate the heat transfer between airflow and rock mass, and compared the simulated values ​​with the measured values ​​to verify the rationality of the simulation. However, CFD software has many limitations in the application process, such as the difficulty of model grid division and the finer the grid division, the more accurate the results, and the higher the requirements for computer performance.

[0064] At present, the main calculation models at home and abroad regard the heat transfer process between airflow and air duct as steady state or constant heat flow, ignoring the heat transfer of the rock mass along the length direction of the air duct and the moisture transfer between the air and the wall, and not considering the influence of ventilation conditions (such as continuous ventilation and stop ventilation, etc.) on heat and moisture exchange. These calculation models are quite different from the actual situation and cannot meet the requirements of the development of underground power station construction and plant design.

[0065] The embodiment of the present invention provides a method for calculating airflow parameters of an energy-saving air duct of an underground power station, which is a general, fast and accurate method for calculating airflow parameters of an energy-saving air duct of an underground power station. It should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer device such as a set of computer executable instructions, and although a logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in a different order than here.

[0066] In this embodiment, a method for calculating airflow parameters of energy-saving air ducts in underground power plants is provided, which can be used for the above-mentioned computer equipment. Figure 1 FIG. 1 is a flow chart of a method for calculating airflow parameters of an energy-saving air duct in an underground power station according to an embodiment of the present invention. Figure 1 As shown, the process includes the following steps:

[0067] In this embodiment, a method for calculating airflow parameters of energy-saving air ducts in underground power plants is provided, which can be used in the above-mentioned computer equipment, such as Figure 1 As shown, the following steps are included:

[0068] Step S101, converting the underground arched duct model into an equal-perimeter cylindrical model, the equal-perimeter cylindrical model includes: a single duct equal-perimeter model and a double duct equal-perimeter model with a middle partition wall, which serves as a physical model for the change of airflow parameters in the underground power station duct.

[0069] Specifically, the air duct of an underground power station is usually arched. The outdoor air flows into the underground air duct. Due to the temperature difference between the two, the air flows through the duct wall in a convection heat exchange manner. The basis for realizing fast numerical calculation prediction is to abstract the geometry in the actual problem and establish a physical model, and to establish and solve the heat transfer differential equation based on the physical model. To this end, the embodiment of the present invention first extracts the following from the actual problem: Figure 2 (a) The single duct shown Figure 2 (b) shows two cases of double air ducts with a middle partition wall, which are used for subsequent exploration of the physical model of air flow and heat exchange between the rock wall.

[0070] The arch shape of the original air duct has both arc and rectangular sections. If the original arch shape is directly used, the corresponding differential equations of the physical model will be very complicated, which will greatly increase the difficulty and time of solving the problem, and fail to achieve the expected rapid calculation and engineering application value of the project. The results of engineering measurements and theoretical calculations show that the distribution shape of the isotherms on the cross section around the cave has little to do with the geometric shape of the cross section of the cave. Therefore, the arch shape is approximated as concentric circles. Figure 3 As shown. By converting the underground air duct into an equivalent cylindrical model, cylindrical coordinates can be used directly. Using a unified cylindrical coordinate solution model can greatly improve the calculation efficiency. Therefore, the embodiment of the present invention converts the underground arched air duct into an equivalent cylindrical model, and cylindrical coordinates can be used to describe the corresponding heat transfer problem.

[0071] Specifically, the conversion of the arch duct model must not only meet the following two basic physical elements: 1. The ventilation volume must be the same; 2. The heat transfer after the conversion is the same as before the conversion, but also ensure that the model results after the conversion can truly and effectively reflect the results of the original arch model, thereby effectively replacing the original model. The embodiment of the present invention converts the underground arch duct model into an equal-perimeter cylindrical model. The equal-perimeter cylindrical model has the same ventilation volume and similar heat transfer as the underground arch duct model. The equal-perimeter cylindrical model includes: a single-duct equal-perimeter model and a double-duct equal-perimeter model with a middle partition wall.

[0072] Among the many methods of converting arched models to circular models, the equal perimeter model conversion is the method with the highest calculation accuracy and the best calculation efficiency. The conversion connotation is: the perimeter of the converted cylindrical model is equal to that of the original air duct model, so that the heat exchange between the air and the wall is closest. In order to verify the practicality of the equal perimeter model, the embodiment of the present invention will use the CFD simulation method to test the above model, and compare and verify the heat transfer results of the equal perimeter conversion and the actual arch model. The verification method is briefly described as follows:

[0073] The computational fluid dynamics software Fluent was used to build the model, and the transient calculation setting was turned on to calculate the air temperature at the tunnel outlet under the original arch model and the converted equal perimeter model. The reliability of the converted model was verified by comparing the results.

[0074] 1. Single duct equal perimeter model test, the specific setting parameters of the model conversion test case are: the length of the arched single duct is 1000m, the width of the arched wind tunnel section is 2.5m, the height is 4.25m (3m+1.25m), and the rock mass is surrounded by a radial width of 12m. The length of the circular single duct is 1000m, the diameter of the circular wind tunnel section is 3.96m, and the rock mass is also surrounded by a radial width of 12m. A "velocity inlet" is set for the air inlet of the duct, the wind speed of the arched duct is set to 4m / s, and the wind speed of the circular duct is set to 3.23m / s; a "pressure outlet" is set for the air outlet of the duct. Adiabatic boundary conditions are set for the external boundary of the rock mass, and coupling is set for the interface between the rock mass and the air. The initial temperature of the rock mass is 18°C, and the air temperature of the air inlet is 33°C. Figure 4 The figure shows the test results before and after the single duct model conversion. The average temperature of the outlet section of the actual arch model is lower than that of the equivalent cylindrical model after conversion, with a difference of about 0.5°C. The error between the converted equal perimeter model and the original model is small.

[0075] 2. Double duct equal perimeter model test, the double duct transformation idea is similar to the single duct transformation idea, such as Figure 5As shown in the figure, with the partition wall as the dividing line, it can be transformed into an equal perimeter model with a middle partition wall as a whole. In order to verify the transformation results, the CFD model is also used to compare and verify the results before and after the model transformation. The arched double air duct is set to be 1398m long, the arched wind tunnel section is 7.2m wide and 7.2m high (5.2m+2m), and there is a 0.24m partition in the middle to divide the air duct into left and right sides, surrounded by a 12m radial rock mass. The circular double air duct is 1398m long, the circular wind tunnel section is 8m in diameter, and there is a 0.24m partition in the middle to divide the air duct into left and right sides, and there is also a 12m radial rock mass around. "Speed ​​inlet" is set for the air inlets on both sides of the double air duct, the air inlet wind speed on both sides of the arched air duct is set to 2.22m / s, and the air inlet wind speed on both sides of the circular air duct is set to 1.944m / s; "pressure outlet" is set for the air outlet on both sides of the air duct. Adiabatic boundary conditions are set for the outer boundary of the rock mass, coupling is set for the interface between the rock mass and the air, and coupling is set for the interface between the partition and the air. Figure 6 The figure shows the test results before and after the double duct model conversion. It can be seen that the average temperature of the outlet section of the actual model is lower than that of the converted equivalent cylindrical model. The equal perimeter model is very close to the actual situation. The equal perimeter model ensures that the heat exchange area between the air and the rock mass is equal.

[0076] After testing, whether it is a single duct or a double duct, the trend of the equal-perimeter equivalent cylindrical model is the same as that of the original model. The equal-perimeter model ensures that the heat exchange area between the air and the rock mass is equal, and the difference between the converted model and the original model is very small. Therefore, when calculating the airflow parameters of the underground power station duct, the equal-perimeter method is used to convert the original arch duct into a circular duct, and the physical mathematical model is established through cylindrical coordinates.

[0077] Step S102, based on analyzing the heat transfer process between the airflow and the wall of the air duct and combining with cylindrical coordinates, a mathematical model for calculating the airflow parameters of the air duct of the underground power station is established by applying basic formulas of heat transfer and thermodynamics.

[0078] Specifically, through the analysis of the heat transfer physical model that causes the change of airflow parameters, it can be known that the basic formulas of heat transfer and thermodynamics used include: the heat conduction equation inside the rock mass, the convection heat transfer equation between the airflow and the wall, and the heat and moisture balance equation of the airflow; the mathematical model for calculating the airflow parameters of the underground power station wind duct established based on the above equations is composed of a series of partial differential equations. Then step S102 specifically includes:

[0079] S1021, the heat conduction equation inside the rock mass is a one-dimensional unsteady cylindrical heat conduction differential equation. Based on the conservation of energy and Fourier's heat conduction law, the one-dimensional cylindrical heat conduction differential equation of the rock mass is derived to obtain the first group of partial differential equations.

[0080] Specifically, the rock mass heat conduction microelement in the cylindrical coordinate system is as follows: Figure 7As shown in the figure, the heat conduction of the microelement in cylindrical coordinates includes three directions: radial direction (r direction), axial direction (z direction), and circumferential direction ( Direction. Since the actual length of the wind duct is much larger than the radius of the wind duct, the axial and circumferential heat conduction in the wall is extremely small for any unit, so it can be considered that the actual rock mass mainly conducts heat in the radial direction. Based on the law of energy conservation and Fourier's law of heat conduction, the radial heat transfer process of the rock mass can be deduced as follows:

[0081] According to the law of energy conservation, the increment of thermodynamic energy in the microelement is equal to the sum of the net heat flow introduced into the microelement and the heat generated by the heat source in the microelement. Since there is no internal heat source in the rock mass studied in this project, the increment of thermodynamic energy in the microelement is equal to the net heat flow introduced into the microelement, and the corresponding energy conservation equation is:

[0082] Conservation of Energy:

[0083] dφ r +dφ v =dU (1)

[0084] Where, dΦ r The net heat flux introduced into the microelement, dΦ v It represents the heat generated by the heat source in the microelement, and dU represents the heat conduction process in the radial r direction (the direction of rock thickness).

[0085] According to Fourier's law of heat conduction:

[0086]

[0087] φ r+dr Perform Taylor expansion at r,

[0088]

[0089] Since there is no internal heat source

[0090] dφ v =0 (5)

[0091] And the energy increment of the microelement per unit time

[0092]

[0093] Among them, m represents mass, ρ represents density, V represents volume, c represents specific heat, and λ is thermal conductivity.

[0094] and

[0095]

[0096] Therefore, the one-dimensional cylindrical heat conduction differential equation of the rock mass can be derived as follows:

[0097]

[0098] in,

[0099]

[0100] Step S1022, the convection heat transfer equation between the airflow and the wall includes Fourier's heat conduction law and Newton's cooling formula, and the convection heat transfer process between the airflow and the duct wall is analyzed to obtain the corresponding second partial differential equation group;

[0101] Specifically, when a fluid flows over a solid surface, heat is mainly exchanged between the fluid and the solid through convection. The convection heat transfer process includes: 1) heat conduction of the fluid close to the wall, and 2) thermal convection of the fluid. The core of studying the convection heat transfer problem is to obtain the convection heat transfer coefficient, which is related to the temperature gradient of the fluid layer flowing through the solid surface, and the temperature gradient of the fluid is related to the velocity gradient. The corresponding basic equation is:

[0102] Heat conduction: Fourier's law of heat conduction

[0103] Thermal convection: Newton cooling formula q = hΔt

[0104] Where: q is the heat flux (W / m 2 );λ is the thermal conductivity of air W / (m·k); r is the distance from a certain point on the wall to the center of the duct (m); h is the convective heat transfer coefficient (w / (m 2 ·k)), Δt is the temperature difference between air and rock mass (℃).

[0105] Air is a viscous gas. When it adheres to the wall, due to the viscosity, the fluid velocity is 0, that is, there is no slip boundary condition. The expression is as follows:

[0106] When r=0, u=0v=0

[0107] Therefore, the heat conduction of the wall fluid layer is:

[0108]

[0109] According to the law of conservation of energy: the convective heat transfer is equal to the heat conduction of the fluid layer attached to the wall

[0110]

[0111] The heat exchange between the fluid and the solid surface causes the temperature of the solid surface to change, which further promotes the internal heat conduction of the object. The internal heat conduction of the object is equal to its convection heat transfer, and its expression is as follows:

[0112]

[0113] Step S1023, the airflow heat and moisture balance equation includes the basic equation of sensible heat balance and the basic equation of latent heat balance. When condensation does not occur on the wall, the total heat exchange between the air in the duct and the wall is equal to the sensible heat exchange, satisfying the basic equation of sensible heat balance; when condensation occurs on the wall, the heat exchange between the air in the duct and the wall is composed of latent heat and sensible heat exchange. Combined with the analysis of the convective heat transfer process between the airflow and the duct wall, the corresponding third group of partial differential equations is obtained. Specifically:

[0114] 1) Basic equation of sensible heat balance

[0115] When condensation does not occur on the wall, the total heat exchange between the air in the duct and the wall is equal to the sensible heat exchange, satisfying the basic equation of sensible heat balance.

[0116] Among them, the change of air energy during sensible heat exchange is:

[0117]

[0118] The heat exchange between the air and the wall in the duct is:

[0119] h[t(τ,R)-T(τ,x)]·S (13)

[0120] Therefore:

[0121]

[0122] Where G represents the mass flow rate of air through the underground air duct (kg / s); C represents the specific heat of air (J / kg·℃); h represents the convective heat transfer coefficient (W / (m 2 K)); S is the circumference of the underground air duct in contact with the air flow (m); x is the distance from a certain point in the cave to the entrance of the air duct (m); R is the equivalent radius of the cave (m); T (τ,x) It represents the temperature of air at the x-axis of the duct at time τ (℃); t(τ,R) represents the temperature at R inside the wall at time τ (℃).

[0123] 2) Basic equation of latent heat (humidity) balance

[0124] In practice, the heat exchange between the wall and the airflow causes the airflow parameters to change along the length of the duct. When the airflow temperature drops to the dew point temperature, condensation will occur on the duct wall, causing a more complex heat and moisture exchange process. It is necessary to establish a mathematical equation that reflects the relationship between the temperature and humidity parameters.

[0125] When condensation occurs on the wall, the heat exchange between the air in the duct and the wall is composed of latent heat and sensible heat exchange. Based on the sensible heat balance equation shown in formula (14), the latent heat exchange required for the condensation of water in the air is:

[0126]

[0127] Where d(τ,x) represents the air humidity at the axial position x in the air duct at time τ (g / kg 干空气 ); γ is the latent heat of vaporization of water (kJ / kg).

[0128] At this time, based on equation (14), the heat and moisture equation including condensation can be changed to:

[0129]

[0130] Combined with formula (16), the air humidity after condensation can be obtained: Combined with formula (17)

[0131]

[0132] In the formula

[0133] C1=-5800.2206, C2=1.3914993, C3=-0.04860239

[0134] C4=0.41764768×10 -4 ,C5=-0.14452093,C6=6.5459673

[0135] represents the relative humidity of outdoor air (%); d represents the moisture content of airflow (kJ / kg), b Indicates the moisture content of saturated air (g / kg 干空气 );P qb represents the partial pressure of saturated water vapor (Pa); B represents the local atmospheric pressure (Pa); and T represents the absolute temperature (K).

[0136] Boundary conditions:

[0137] The air parameters at the duct inlet are consistent with the outdoor air:

[0138]

[0139] Where, T(τ,0) represents the air temperature at the duct inlet at time τ (℃), and T1(τ) represents the outdoor air temperature at time τ (℃); Represents the relative humidity of air at the air duct inlet at time τ (%); It represents the relative humidity of outdoor air at time τ (%).

[0140] The relative humidity of the air here can be obtained Combined with the commonly used condensation judgment standards:

[0141]

[0142] It can be obtained whether the air at position x is condensing at time τ. The specific judgment process needs to be combined with discrete methods to judge each cell.

[0143] Step S303, discretizing the mathematical model in time and space to establish a discrete calculation model.

[0144] The mathematical model for calculating the airflow parameters of the underground power station wind duct established in the embodiment of the present invention is composed of a series of partial differential equations. The solution of partial differential equations involves high-order derivatives and complex boundary condition processing, which is difficult to solve and calculate directly. In addition, the outdoor air determined by meteorological data does not change continuously, but is discrete data. For this reason, the embodiment of the present invention adopts the idea of ​​discrete solution, converts the established mathematical model into an algebraic equation and discretizes it in time and space, and obtains the changes in the rock mass internal moment by moment, and the changes in the airflow parameters of the convection heat exchange between the rock mass and the airflow.

[0145] Numerical solution is a method of approximately calculating the temperature distribution of an object at its discrete coordinates through a certain calculation method. Before establishing the discrete equation, the discrete coordinate points must be determined first, that is, the solution area is discretized. For the equivalent cylinder of the underground air duct, it can be considered that heat conduction is divided into three directions, one is heat conduction in the circumferential direction, the second is heat conduction in the radial direction, and the third is heat conduction in the axial direction. However, the length of the air duct is much larger than the inner and outer diameters of the cylinder. At this time, the heat conduction in the axial and circumferential directions can be ignored, and it is considered that only the radial direction conducts heat. Therefore, discretization is performed in the radial direction. In addition, there is convective heat transfer along the direction of the air duct, so it is necessary to discretize the heat conduction direction and calculate each grid point by dividing the grid. Discretization in time is to convert continuous time into moments with a certain time interval.

[0146] The spatial discretization is divided into two directions. First, along the length of the duct, the airflow flows through the duct and exchanges heat and moisture with the wall. Secondly, along the radial direction, the heat conduction inside the rock mass. Finally, a series of partial differential equations established according to the heat transfer process of the underground duct are discretized, and the differential quotient is used instead of the differential quotient to convert the original partial differential equation into a difference equation. Then, the difference equation is brought into the differential equation to obtain the discrete equation of each node. In view of the problem that the partial differential equation can be solved directly in the general mathematical model, the embodiment of the present invention proposes the idea of ​​discrete calculation and establishes a complete discrete calculation model, which is a model that can be actually used for calculation.

[0147] Specifically, since the airflow changes dynamically with the outdoor meteorological parameters, the ventilation condition is not constant. The meteorological data is not continuous, but discrete data at each moment. Therefore, the idea of ​​discrete solution is adopted to perform discrete calculations in space and time on the established mathematical model equation. In the embodiment of the present invention, discrete solution is achieved by converting the partial differential equation into an algebraic equation.

[0148] For the single duct equal perimeter model, the mathematical model is spatially discretized, including: discretization along the duct length direction and discretization along the cross-section radial direction. Figure 8 As shown, the duct is equally divided into multiple grid units along the length direction of the duct (x direction) according to the actual length of the duct. In the airflow area along the length direction of the duct, assuming that the airflow distribution is uniform, the center of the duct is selected as the control node; it is equally divided into multiple grid units along the radial direction of the cross section (r direction), and the control nodes are located on the grid lines.

[0149] Discretize the mathematical model in time, including: discretize the continuous time of the whole year into time points with preset intervals to calculate the airflow parameters and heat transfer values ​​at each time point. For example, if the time of the whole year is discretized into time with an accuracy of up to 5 minutes, any temperature value with a resolution of 5 minutes throughout the year can be predicted.

[0150] After the airflow parameter calculation model is discretized in time and space, the calculation is performed alternately in time and space. At the beginning of the calculation, the outdoor air parameters, ventilation volume and initial temperature of the rock mass are taken as known values. Along the length direction, starting from the first unit at the entrance, the heat conduction inside the rock mass, the convection heat transfer between the rock mass and the airflow and the change of the airflow parameters are calculated, and then the end point of the unit is used as the starting point of the next unit, and so on, until the exit unit, the calculation at that moment is completed. Then the rock mass temperature calculated at the first moment is used as the initial temperature of the rock mass when calculating at the second moment, and the outdoor air parameters and ventilation volume at the second moment are taken from the entrance unit to the exit unit.

[0151] In the embodiment of the present invention, the node discrete equation is established to replace the continuous temperature field with the set of temperatures of discrete points in the space and time coordinate system in the solution area, and a large number of algebraic equations are used to replace differential equations. This study will combine the Taylor series expansion method to transform partial differential equations into algebraic equations and the thermal balance method from a mathematical perspective. The partial differential equations are transformed into algebraic equations with the help of Fourier's heat conduction law and energy conservation, so that each parameter has a clear physical meaning. The discretization process of each key part of the physical model is as follows:

[0152] 1. Differential format of discrete equations at each node

[0153] Taylor series expansion method: Expand the temperature at a certain coordinate according to the Taylor series, ignore the higher-order terms and convert the differential equation of temperature into an algebraic equation of node temperature.

[0154]

[0155] Spatially differencing:

[0156] The temperature of node (τ,i) is t(τ,i), and the temperatures of its adjacent nodes (τ,i+1) and (τ,i-1) are t(τ,i+1) and t(τ,i+1) respectively. Applying Taylor series, t(τ,i+1) is expanded at node (τ,i):

[0157]

[0158] Similarly, put t (τ,i-1) Expanding at the node (τ,i) yields:

[0159]

[0160] Since Δr is a small quantity, discard the high-order terms in equation (20) and move the terms to get:

[0161]

[0162] Add equation (20) and equation (21), move the terms and rearrange them to get:

[0163]

[0164] The temperature of the node (τ,j) is T (τ,j) , the temperature of its adjacent node (τ, j+1) is T(τ, j+1). Applying Taylor series, T(τ, j+1) is expanded at the node (τ, j):

[0165]

[0166] Since Δx is a small quantity, discard the high-order terms in equation (24) and move the terms to get:

[0167]

[0168] The humidity of node (τ, j) is d(τ, j), and the humidity of its adjacent node (τ, j+1) is d(τ, j+1). Applying Taylor series to expand d(τ, j+1) at node (τ, j) yields:

[0169]

[0170] Since Δx is a small quantity, discard the high-order terms in equation (26) and move the terms to get:

[0171]

[0172] Difference in time:

[0173] The temperature of the node (τ, i) is t(τ, i), and the temperature of its adjacent node (τ+1, i) is t(τ+1, i). Applying the Taylor series to expand t(τ+1, i) at the node (τ, i) yields:

[0174]

[0175] Since Δτ is a small quantity, we discard the high-order terms in equation (28) and move the terms to get:

[0176]

[0177] Substituting the above difference expression into the differential equation, we can obtain the discrete equation of each node.

[0178] 2. Discrete equations of each node

[0179] 1) Nodes in rock mass (one-dimensional cylindrical unsteady-state heat conduction)

[0180]

[0181] t(τ+1,i)=(F0+B)t(τ,i+1)+F0t(τ,i-1)+(1-2F0-B)t(τ,i) (31)

[0182] 2) Nodes at the boundary between rock mass and lining

[0183] According to Fourier's law of heat conduction:

[0184]

[0185] From the law of conservation of energy:

[0186]

[0187] Φ=Φ1+Φ2 (35)

[0188]

[0189] Therefore, the discrete equations of the nodes at the boundary between the rock mass and the lining are as follows:

[0190]

[0191] 3) Nodes at the wall

[0192]

[0193] in, 1) Air temperature at each node when there is no condensation

[0194]

[0195]

[0196] T(τ,j+1)=(1-M)T(τ,j)+Mt(τ,i) (45)

[0197] 2) Temperature and humidity of air at each node during condensation

[0198] Air temperature when condensation is considered:

[0199]

[0200] Where T(τ,j) represents the temperature of node j in the air duct at time τ (℃); d(τ,j) represents the moisture content of node j in the air duct at time τ (kg / kg 干空气 ).

[0201] Air humidity considering condensation:

[0202] when When , the air in the air duct begins to condense. After condensation, the humidity of the air in the next unit is:

[0203] d(τ,j+1)=0.95*db(τ,j)

[0204] The amount of condensation per unit mass flow of air is:

[0205] Δd=d(τ,j)-d(τ,j+1)

[0206] represents the relative humidity of the air at the j node in the air duct at time τ (%); d(τ,j) represents the air moisture content at the j node in the air duct at time τ (g / kg 干空气 );db(τ,j) represents the saturated air humidity at node j in the air duct at time τ (g / kg 干空气 ).

[0207] The basic equations of the double duct model are similar to those of the single duct, but the double duct of the underground power station consists of two parts, namely the air inlet duct and the exhaust duct, which are connected by a partition wall. When studying the heat exchange process of the entire double duct, it is necessary to additionally consider the convection heat exchange between the air and the rock wall of the air inlet duct, the heat conduction of the air inlet duct, the convection heat exchange between the air and the surface of the air inlet duct partition wall, the heat conduction inside the partition wall, the convection heat exchange between the air and the surface of the exhaust duct partition wall, the heat exchange between the air and the rock wall of the exhaust duct, and the heat conduction inside the rock of the exhaust duct. Fig. 9 As shown, the embodiment of the present invention divides the air in the air duct into two parts: air A close to the lining wall and air B close to the partition wall. Air A exchanges heat with the nearby lining wall, and air B exchanges heat with the partition wall surface by convection.

[0208] Furthermore, each part of the air duct is meshed, such as Fig.10 As shown in Figure 2, the double-duct heat exchange process has an additional partition wall item compared to the single-duct heat exchange process.

[0209] For nodes inside partition walls:

[0210]

[0211] Tw(τ+1,i)=Fo(Tw(τ,i+1)+Tw(τ,i-1))+(1-2Fo)Tw(τ,i) (51)

[0212] in,

[0213] Where Tw(τ,i) represents the temperature of node i in the partition wall at time τ (℃); y3 , y3 Respectively represent the thermal conductivity of the partition material (m 2 / h), density (kg / m 3 ), a y Indicates thermal conductivity (m 2 / h), partition wall layer a y =a y3 ; Δr and Δτ are the grid spacing and time step respectively.

[0214] It should be noted that in the process of establishing the above equations, the errors caused by infinitesimal terms are ignored. As the number of iterations increases, whether the error propagation in the calculation process is amplified or reduced is a question about the stability of the calculation, which is related to whether the calculation results are reasonable. The calculation stability must be judged.

[0215] The discrete process in the embodiment of the present invention adopts the explicit difference format. In the field of mathematics and numerical calculation, relevant scholars have conducted many rigorous discussions on the stability judgment of the explicit difference format and provided judgment methods. Among them, it can be known from the "Heat Transfer" textbook and related literature that: to achieve the stability of solving the system of equations, the coefficients of all node temperatures must be non-negative.

[0216] Here, we take the node equation in the rock mass as an example for specific analysis:

[0217] t(τ+1,i)=(F0+B)t(τ,i+1)+F0t(τ,i-1)+(1-2F0-B)t(τ,i)

[0218] To make the representation clearer and avoid confusion between the symbols t and τ, replace t with u, and use superscripts and subscripts to represent the time and position:

[0219]

[0220] Writing the above expression in the form of a matrix vector, represents the temperature distribution at time τ, and and It is usually given by the boundary conditions and does not need to be listed in the above vector.

[0221] Correspondingly, the coefficient matrix A is a (N-1)×(N-1) tridiagonal matrix with the following non-zero elements:

[0222] A i，i =1-2F0-B,A i,i+1 =F0+B,A i,i-1 =F0

[0223] where i=1,2,...,N-1

[0224] Then, the explicit finite difference scheme can be written as:

[0225] U τ+1 =AU τ

[0226] In order to ensure the stability of the format, it is necessary to ensure that the absolute value of the eigenvalue of matrix A is not greater than 1, that is, the CFL condition:

[0227] 1-2F0-B≥0

[0228] When the above CFL condition is met, that is, the coefficient of the third term of the aforementioned node discrete term expression:

[0229] t(τ+1,i)=(F0+B)t(τ,i+1)+F0t(τ,i-1)+(1-2F0-B)t(τ,i)

[0230] The difference format is shown to be stable. The stability judgment ideas of other node equation solutions are the same as above and will not be repeated here.

[0231] Among the various types:

[0232]

[0233] All meet the requirement of being greater than 0. At this time, the coefficients of each node must meet the following requirements:

[0234]

[0235] At this time, as long as the Then the coefficients of each node are greater than or equal to zero. According to the "Hydropower Station Mechanical and Electrical Design Manual", the a of granite material is y1 Relatively large, a y1 =1.436×10 -6 m 2 / s, then:

[0236]

[0237] Right now:

[0238]

[0239] This can ensure computational stability.

[0240] Based on the previous research experience in related fields, the embodiment of the present invention selects a spatial step size Δr = 0.05m and a time step size Δτ = 300s. Substituting into the equation, we can get Satisfy the requirements of differential format stability.

[0241] Step S104, using a discrete calculation model to dynamically calculate the airflow parameters of the air duct hour by hour.

[0242] Specifically, at the beginning of the calculation, the outdoor air parameters, ventilation volume and initial temperature of the rock mass at that moment are taken as known values, and starting from the first network unit at the entrance along the length of the duct, the heat conduction inside the rock mass, the convective heat transfer between the rock mass and the airflow and the changes in the airflow parameters are calculated, and the end point of the unit is used as the starting point of the next unit, and so on until the exit unit to complete the calculation at that moment; the rock mass temperature calculated at the first moment is used as the initial temperature of the rock mass when calculating at the second moment, and the outdoor air parameters and ventilation volume at the second moment are taken, from the entrance unit to the exit unit.

[0243] In a specific embodiment, the above model is compiled into a program using MATLAB programming, and the air flow temperature and humidity at the outlet can be obtained by inputting the air duct size, inlet air flow temperature and humidity, air volume, and physical parameters of the inlet duct mountain.

[0244] Taking the double air duct as an example, a MATLAB program is written based on the method provided in the embodiment of the present invention, and the running results are as follows: Fig.11 As shown in the figure, the temperature of air A that exchanges heat with the rock wall changes with position. It can be seen that the air in the duct gradually decreases along the way. This is because the air introduced from the outside enters the underground power station duct and undergoes convective heat exchange with the wall, causing the air temperature to drop and the rock wall temperature to rise. The temperature difference gradually decreases along the way, so the heat transfer intensity in the second half is lower than that in the first half. The temperature of air B that exchanges heat with the partition wall surface changes with position as shown in the figure. Fig.12 As shown, the time step is 300s and the space step is 0.04m. Fig.11 and Fig.12 The air temperature changes in the duct when the time step is 300s. Compared with the simulation results, Fig.13 As shown, the calculated result of the air inlet duct differs from the simulated value by 0.47° C., indicating that the dual-duct airflow parameter calculation method provided in the embodiment of the present invention is very close to the simulated value.

[0245] The method for calculating airflow parameters of energy-saving ducts of underground power stations provided by the embodiment of the present invention establishes a general model for calculating airflow parameters of ducts of underground power stations by analyzing the heat transfer between airflow and wall, the heat storage and release of rock mass, and the change characteristics of airflow parameters and their mutual relationship. The model can realize the dynamic calculation of heat and moisture exchange that cannot be realized by traditional analysis methods. During the operation of underground power stations, accurate airflow parameter values ​​can be used to monitor and adjust the ventilation system in real time, so that the ventilation system always operates in an efficient state, reduce the extra energy consumed to maintain the normal operating temperature of power station equipment, and reduce the energy consumption of auxiliary systems on the premise of ensuring the safe and stable operation of power station equipment, thereby achieving an overall energy-saving effect. By calculating the hourly changes in the rock mass and the changes in the airflow parameters of the convective heat exchange between the rock mass and the airflow, the changes in the airflow parameters of the duct at different times can be accurately captured. By analyzing the changes in the airflow parameters at each moment, the key time points and influencing factors of the convective heat exchange can be found, providing a basis for selecting air ventilation equipment, improving the ventilation system and controlling the airflow temperature. In engineering decision-making, real-time airflow parameter information can be provided to help engineers make adjustments and improvements in a timely manner to ensure the safe and stable operation of the underground power station system.

[0246] In this embodiment, a system for calculating airflow parameters of an energy-saving air duct in an underground power station is also provided. The system is used to implement the above-mentioned embodiments and preferred implementation modes, and the descriptions that have been made will not be repeated. As used below, the term "module" can be a combination of software and / or hardware that implements a predetermined function. Although the system described in the following embodiments is preferably implemented in software, the implementation of hardware, or a combination of software and hardware, is also possible and conceivable.

[0247] This embodiment provides a system for calculating airflow parameters of energy-saving air ducts in underground power plants. Fig.14 As shown, including:

[0248] A physical model building module 1401 is used to convert the underground arched air duct into an equivalent cylindrical model as a physical model of airflow parameter changes in the underground power station air duct;

[0249] The mathematical model building module 1402 is used to build a mathematical model for calculating airflow parameters of the underground power station air duct based on the analysis of the heat transfer process between the airflow and the air duct wall and cylindrical coordinates, and apply the basic formulas of heat transfer and thermodynamics;

[0250] Discrete module building module 1403, used to discretize the mathematical model in time and space to establish a discrete calculation model;

[0251] The airflow parameter calculation module 1404 is used to dynamically calculate the airflow parameters of the air duct hour by hour using the discrete calculation model.

[0252] In some optional embodiments, the underground arched air duct includes: a single air duct and a double air duct with a middle partition wall; converting the underground arched air duct into an equivalent cylindrical model includes: converting the underground arched air duct model into an equal-perimeter cylindrical model, and the equal-perimeter cylindrical model includes: a single-duct equal-perimeter model and a double-duct equal-perimeter model.

[0253] In some optional embodiments, the basic formulas of heat transfer and thermodynamics include: the heat conduction equation inside the rock mass, the convection heat transfer equation between the airflow and the wall, and the heat and moisture balance equation of the airflow;

[0254] The mathematical model for calculating airflow parameters of the underground power station wind duct is established by applying the basic formulas of heat transfer and thermodynamics, including:

[0255] The heat conduction equation inside the rock mass is a one-dimensional unsteady cylindrical heat conduction differential equation. Based on the energy conservation and Fourier's heat conduction law, the one-dimensional cylindrical heat conduction differential equation of the rock mass is derived to obtain the first set of partial differential equations.

[0256] The convection heat transfer equation between the airflow and the wall includes Fourier's heat conduction law and Newton's cooling formula. By combining the analysis of the convection heat transfer process between the airflow and the duct wall, the corresponding second partial differential equation group is obtained.

[0257] The heat and moisture balance equation of airflow includes the basic equation of sensible heat balance and the basic equation of latent heat balance. When condensation does not occur on the wall, the total heat exchange between the air in the duct and the wall is equal to the sensible heat exchange, satisfying the basic equation of sensible heat balance. When condensation occurs on the wall, the heat exchange between the air in the duct and the wall is composed of latent heat and sensible heat exchange. Combined with the analysis of the convective heat transfer process of the airflow and the duct wall, the corresponding third group of partial differential equations is obtained.

[0258] The first group of partial differential equations, the second group of partial differential equations and the third group of partial differential equations together constitute a mathematical model for calculating airflow parameters of the wind duct of an underground power station.

[0259] In some optional implementations, for a single duct equal perimeter model, the mathematical model is spatially discretized, including: discretization along the duct length direction and discretization along the cross-sectional radial direction, wherein:

[0260] The duct is divided into multiple grid units at equal intervals along the length direction of the duct according to the actual length of the duct. The center of the duct is selected as the control node in the airflow area along the length direction of the duct, assuming that the airflow distribution is uniform; it is divided into multiple grid units at equal intervals along the radial direction of the cross section, and the control nodes are located on the grid lines;

[0261] Discretize the mathematical model in time, including: discretize the continuous time of the whole year into time points with preset intervals to calculate the airflow parameters and heat transfer values ​​at each time point;

[0262] For the double duct equal perimeter model, the air in the duct is divided into two parts: air A close to the lining wall and air B close to the partition wall. Air A exchanges heat with the nearby lining wall, and air B exchanges heat with the partition wall surface by convection. The same discrete method as the single duct equal perimeter model is used to grid the various parts of the duct in space and discretize them in time.

[0263] In some optional implementations, the Taylor series expansion method and the heat balance method are combined to transform the partial differential equation into an algebraic equation of the control node as a discrete calculation model.

[0264] In some optional implementations, the step of dynamically calculating the air duct airflow parameters hour by hour using the discrete calculation model includes:

[0265] At the start time of calculation, the outdoor air parameters, ventilation volume and initial temperature of the rock mass are taken as known values. Starting from the first network unit at the entrance along the length of the air duct, the heat conduction inside the rock mass, the convective heat transfer between the rock mass and the airflow, and the changes in the airflow parameters are calculated. The end point of this unit is taken as the starting point of the next unit, and so on until the exit unit, completing the calculation at that moment;

[0266] The rock temperature calculated at the first moment is used as the initial rock temperature when calculating at the second moment, and the outdoor air parameters and ventilation volume at the second moment are taken from the inlet unit to the outlet unit.

[0267] In some optional implementations, based on the dual-duct equal-perimeter model, the dual-duct heat exchange process is as follows for the nodes inside the partition wall:

[0268]

[0269] Tw(τ+1,i)=Fo(Tw(τ,i+1)+Tw(τ,i-1))+(1-2Fo)Tw(τ,i)

[0270] in,

[0271] Where Tw(τ,i) represents the temperature of node i in the partition wall at time τ (℃); y3 , y3 Respectively represent the thermal conductivity of the partition material (m 2 / h), density (kg / m 3 ), a y Indicates thermal conductivity (m 2 / h), partition layer a y =a y3 ; Δr and Δτ are the grid spacing and time step respectively.

[0272] The further functional description of each of the above modules and units is the same as that of the above corresponding embodiments and will not be repeated here.

[0273] The underground power station energy-saving duct airflow parameter calculation system in this embodiment is presented in the form of a functional unit, where the unit refers to an ASIC (Application Specific Integrated Circuit) circuit, a processor and memory that executes one or more software or fixed programs, and / or other devices that can provide the above functions.

[0274] The embodiment of the present invention also provides a computer device having the above Fig.14 The airflow parameter calculation system of the energy-saving air duct of the underground power station is shown.

[0275] See also Fig.15 , Fig.15 is a schematic diagram of the structure of a computer device provided by an optional embodiment of the present invention, such as Fig.15 As shown, the computer device includes: one or more processors 10, memory 20, and interfaces for connecting various components, including high-speed interfaces and low-speed interfaces. Various components utilize different buses to communicate with each other, and can be installed on a common mainboard or installed in other ways as required. The processor can process the instructions executed in the computer device, including instructions stored in the memory or on the memory to display the graphical information of the GUI on an external input / output system (such as, a display device coupled to the interface). In some optional embodiments, if necessary, multiple processors and / or multiple buses can be used together with multiple memories and multiple memories. Similarly, multiple computer devices can be connected, and each device provides part of the necessary operations (for example, as a server array, a group of blade servers, or a multi-processor system). Fig.15 A processor 10 is taken as an example.

[0276] The processor 10 may be a central processing unit, a network processor or a combination thereof. The processor 10 may further include a hardware chip. The hardware chip may be a dedicated integrated circuit, a programmable logic device or a combination thereof. The programmable logic device may be a complex programmable logic device, a field programmable gate array, a general purpose array logic or any combination thereof.

[0277] The memory 20 stores instructions executable by at least one processor 10, so that at least one processor 10 executes the method shown in the above embodiment.

[0278] The memory 20 may include a program storage area and a data storage area, wherein the program storage area may store an operating system, an application required for at least one function; the data storage area may store data created according to the use of the computer device, etc. In addition, the memory 20 may include a high-speed random access memory, and may also include a non-transient memory, such as at least one disk storage device, a flash memory device, or other non-transient solid-state storage device. In some optional embodiments, the memory 20 may optionally include a memory remotely arranged relative to the processor 10, and these remote memories may be connected to the computer device via a network. Examples of the above-mentioned network include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and combinations thereof.

[0279] The memory 20 may include a volatile memory, such as a random access memory; the memory may also include a non-volatile memory, such as a flash memory, a hard disk or a solid state drive; the memory 20 may also include a combination of the above types of memory.

[0280] The computer device further comprises a communication interface 30 for the computer device to communicate with other devices or a communication network.

[0281] The embodiment of the present invention also provides a computer-readable storage medium. The method according to the embodiment of the present invention can be implemented in hardware, firmware, or can be implemented as a computer code that can be recorded in a storage medium, or can be implemented as a computer code that is originally stored in a remote storage medium or a non-temporary machine-readable storage medium and will be stored in a local storage medium through a network download, so that the method described herein can be stored in such software processing on a storage medium using a general-purpose computer, a dedicated processor, or programmable or dedicated hardware. Among them, the storage medium can be a magnetic disk, an optical disk, a read-only storage memory, a random access memory, a flash memory, a hard disk or a solid-state hard disk, etc.; further, the storage medium can also include a combination of the above types of memories. It can be understood that a computer, a processor, a microprocessor controller, or programmable hardware includes a storage component that can store or receive software or computer code. When the software or computer code is accessed and executed by a computer, a processor, or hardware, the method shown in the above embodiment is implemented.

[0282] A part of the present invention may be applied as a computer program product, such as a computer program instruction, which, when executed by a computer, can call or provide the method and / or technical solution according to the present invention through the operation of the computer. Those skilled in the art should understand that the existence of the computer program instruction in a computer-readable medium includes, but is not limited to, a source file, an executable file, an installation package file, etc., and accordingly, the way in which the computer program instruction is executed by the computer includes, but is not limited to: the computer directly executes the instruction, or the computer compiles the instruction and then executes the corresponding compiled program, or the computer reads and executes the instruction, or the computer reads and installs the instruction and then executes the corresponding installed program. Here, the computer-readable medium may be any available computer-readable storage medium or communication medium accessible to the computer.

[0283] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A method for calculating airflow parameters of energy-saving air ducts in underground power stations, characterized in that: include: Convert the underground arched duct model into a cylindrical model with equal perimeter, wherein the cylindrical model with equal perimeter includes a single duct equal perimeter model and a double duct equal perimeter model with a middle partition wall, as a physical model of airflow parameter changes in the duct of the underground power station; Based on the analysis of the heat transfer process between the airflow and the duct wall and the cylindrical coordinates, the mathematical model for calculating the airflow parameters of the underground power station duct is established by applying the basic formulas of heat transfer and thermodynamics. Discretize the mathematical model in time and space to establish a discrete computing model; The discrete calculation model is used to dynamically calculate the airflow parameters of the air duct hour by hour.

2. The method according to claim 1, characterized in that: The basic formulas of heat transfer and thermodynamics include: the heat conduction equation inside the rock mass, the convection heat transfer equation between the airflow and the wall, and the heat and moisture balance equation of the airflow; The mathematical model for calculating airflow parameters of the underground power station wind duct is established by applying the basic formulas of heat transfer and thermodynamics, including: The heat conduction equation inside the rock mass is a one-dimensional unsteady cylindrical heat conduction differential equation. Based on the energy conservation and Fourier's heat conduction law, the one-dimensional cylindrical heat conduction differential equation of the rock mass is derived to obtain the first set of partial differential equations. The convection heat transfer equation between the airflow and the wall includes Fourier's heat conduction law and Newton's cooling formula. By combining the analysis of the convection heat transfer process between the airflow and the duct wall, the corresponding second partial differential equation group is obtained. The heat and moisture balance equation of airflow includes the basic equation of sensible heat balance and the basic equation of latent heat balance. When condensation does not occur on the wall, the total heat exchange between the air in the duct and the wall is equal to the sensible heat exchange, satisfying the basic equation of sensible heat balance. When condensation occurs on the wall, the heat exchange between the air in the duct and the wall is composed of latent heat and sensible heat exchange. Combined with the analysis of the convective heat transfer process of the airflow and the duct wall, the corresponding third group of partial differential equations is obtained. The first group of partial differential equations, the second group of partial differential equations and the third group of partial differential equations together constitute a mathematical model for calculating airflow parameters of the wind duct of an underground power station.

3. The method according to claim 1, characterized in that For the single duct equal perimeter model, the mathematical model is spatially discretized, including: discretization along the duct length direction and discretization along the radial direction of the cross section, where: The duct is divided into multiple grid units at equal intervals along the length direction of the duct according to the actual length of the duct. The center of the duct is selected as the control node in the airflow area along the length direction of the duct, assuming that the airflow distribution is uniform; it is divided into multiple grid units at equal intervals along the radial direction of the cross section, and the control nodes are located on the grid lines; Discretize the mathematical model in time, including: discretize the continuous time of the whole year into time points with preset intervals to calculate the airflow parameters and heat transfer values ​​at each time point; For the double duct equal perimeter model, the air in the duct is divided into two parts: air A close to the lining wall and air B close to the partition wall. Air A exchanges heat with the nearby lining wall, and air B exchanges heat with the partition wall surface by convection. The same discrete method as the single duct equal perimeter model is used to grid the various parts of the duct in space and discretize them in time.

4. The method according to claim 3, characterized in that The method of discretizing the mathematical model in time and space to establish a discrete computing model includes: Combining the Taylor series expansion method and the heat balance method, the partial differential equation is transformed into an algebraic equation of the control node as a discrete calculation model.

5. The method according to claim 4, characterized in that The step of dynamically calculating the air duct airflow parameters hour by hour by using the discrete calculation model comprises: At the start time of calculation, the outdoor air parameters, ventilation volume and initial temperature of the rock mass are taken as known values. Starting from the first network unit at the entrance along the length of the air duct, the heat conduction inside the rock mass, the convective heat transfer between the rock mass and the airflow, and the changes in the airflow parameters are calculated. The end point of this unit is taken as the starting point of the next unit, and so on until the exit unit, completing the calculation at that moment; The rock temperature calculated at the first moment is used as the initial rock temperature when calculating at the second moment, and the outdoor air parameters and ventilation volume at the second moment are taken from the inlet unit to the outlet unit.

6. The method according to claim 4, characterized in that Based on the double-duct equal-perimeter model, the double-duct heat exchange process for the nodes inside the partition wall is: Tw(τ+1,i)=Fo(Tw(τ,i+1)+Tw(τ,i-1))+(1-2Fo)Tw(τ,i) in, Where Tw(τ,i) represents the temperature of node i in the partition wall at time τ (℃); y3 , y3 Respectively represent the thermal conductivity of the partition material (m 2 / h), density (kg / m 3 ), a y Indicates thermal conductivity (m 2 / h), partition wall layer a y =a y3 ; Δr and Δτ are the grid spacing and time step respectively.

7. A system for calculating airflow parameters of energy-saving air ducts in underground power stations, characterized in that: The system comprises: A physical model building module is used to convert the underground arched air duct model into an equal-perimeter cylindrical model, wherein the equal-perimeter cylindrical model includes: a single air duct equal-perimeter model and a double air duct equal-perimeter model with a middle partition wall, which is used as a physical model of airflow parameter changes in the underground power station air duct; Mathematical model building module, which is used to establish a mathematical model for calculating airflow parameters in underground power station air ducts based on the analysis of the heat transfer process between airflow and duct wall and cylindrical coordinates, and the application of basic formulas of heat transfer and thermodynamics; Discrete module building module, used to discretize mathematical models in time and space to establish discrete calculation models; The airflow parameter calculation module is used to dynamically calculate the airflow parameters of the air duct hour by hour using the discrete calculation model.

8. A computer device, characterized in that: include: A memory and a processor, wherein the memory and the processor are communicatively connected to each other, the memory stores computer instructions, and the processor executes the method for calculating airflow parameters of energy-saving ducts in underground power stations according to any one of claims 1 to 6 by executing the computer instructions.

9. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer instructions, and the computer instructions are used to enable a computer to execute the method for calculating airflow parameters of energy-saving air ducts in underground power plants according to any one of claims 1 to 6.

10. A computer program product, characterized in that It comprises computer instructions, and the computer instructions are used to enable a computer to execute the method for calculating airflow parameters of energy-saving air ducts in underground power stations according to any one of claims 1 to 6.

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