Water delivery tunnel maintenance ventilation numerical simulation method considering high ground temperature and biological fouling

Abstract

The invention discloses a water delivery tunnel maintenance ventilation numerical simulation method considering high ground temperature and biofouling, which comprises the following steps: carrying out a biologic putrefying gas release characteristic experiment in a high ground temperature environment, fitting a biologic putrefying gas release rate equation in the high ground temperature environment, calculating the required air quantity considering biologic putrefying gas pollution in the high ground temperature environment, and calculating the ventilation quantity of the water delivery tunnel maintenance ventilation numerical simulation method considering biologic putrefying gas pollution in the high ground temperature environment. And ventilation numerical simulation of the deeply-buried water conveyance tunnel in the overhaul period. According to the method, the emission amount and the emission rule of biological decay gas pollutants including organic gas TVOC in the deeply-buried water delivery tunnel in the high-ground-temperature environment are clearly considered; determining the air volume required for purifying biological decay gas pollutants including organic gas TVOC in the deeply-buried water delivery tunnel in the high-ground-temperature environment; biological decay gas release and ventilation numerical simulation of the deeply-buried water delivery tunnel in the overhaul period under the high ground temperature environment are comprehensively considered, the development condition of an air flow field in the tunnel and the migration and distribution rule of harmful gas under the high ground temperature and biological fouling coupling condition are determined, and the method has important significance for guaranteeing ventilation safety of the complex water delivery tunnel.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of water conservancy water conveyance tunnel maintenance ventilation, and particularly relates to a water conveyance tunnel maintenance ventilation numerical simulation method considering high ground temperature and biological fouling. BACKGROUND

[0002] With the development of tunnel engineering towards the direction of super depth, super length and super large section, the tunnel thermal environment control problem represented by high ground temperature caused by burial depth or geological structure has gradually become an important part of tunnel design. At the same time, with the increase of the operation life of long-distance water conveyance tunnel, the biological invasion phenomenon of freshwater mussel, river clam and capsule snail and the like in water conveyance engineering is very serious, and after death, it will release ammonia, hydrogen sulfide, methane and other gases with irritating odor or toxic effect under the decomposition of putrefactive bacteria. In view of the fact that high ground temperature can accelerate the biological decomposition process and significantly affect the release amount and rate of harmful gases, in-depth study of the air flow field law and harmful gas migration law of deep-buried water conveyance tunnel under the coupling condition of high ground temperature and biological fouling has important significance for optimizing the ventilation scheme, ensuring the safety of maintenance and the health of workers.

[0003] In the area of ​​biofouling research, Gao Fei et al. predicted the spatiotemporal distribution of freshwater husk fouling and proposed measures and recommendations for mitigating freshwater husk biofouling. Addressing the challenge of freshwater husk control in water supply structures, Yan Juntao et al. developed a novel non-toxic freshwater husk protective coating and studied the behavior of live freshwater husks on the coating surface, providing a new approach for freshwater husk control. Wang Ruonan investigated the release patterns of harmful gases NH3 and H2S from freshwater husk decay during the maintenance period of a water supply project, providing a basis for determining the extent of freshwater husk contamination during this period and developing pollutant control measures. However, current research remains limited, primarily focusing on freshwater husk control, while relatively little research has examined the release patterns of harmful gases from biological decay. Existing studies primarily explore the release patterns of inorganic gases NH3 and H2S released by freshwater husk decay, but the release patterns of organic gases (TVOCs) released during biological decay have not been thoroughly studied. TVOCs are highly hazardous. They comprise a variety of volatile organic compounds (VOCs). When released into the environment, these compounds can pollute the atmosphere, alter local air quality, and impact ecological balance. Furthermore, when their concentrations reach certain levels, they can pose serious health risks to humans, such as respiratory irritation, dizziness, nausea, and other discomfort. Long-term exposure can also damage the immune and nervous systems, and even pose a risk of developing serious diseases such as cancer. Therefore, studying the emission patterns of TVOCs is crucial. Furthermore, existing studies examining the release patterns of biodegradation gases have not fully considered the impact of temperature, a key factor, on gas release. The amount and rate of biodegradation gases released vary significantly under different temperature conditions. Increased temperature typically accelerates the biodegradation process, increasing microbial activity and accelerating the decomposition of organic matter, leading to a significant increase in the release of harmful gases. Furthermore, the gas release rate also increases with temperature, as increased temperature increases the motion of gas molecules, making it easier for them to escape from decaying organisms into the environment. Lower temperatures decrease the amount and rate of release. However, due to the lack of systematic research on the release patterns of harmful gases from corruption at different temperatures, it is currently difficult to accurately predict and evaluate the specific changes in the release of biological corruption gases in actual environments as the temperature changes. This has greatly limited the formulation of effective control and prevention measures for harmful gases from biological corruption.

[0004] In the field of ventilation research for underground projects, Zhang Qingming et al. studied the distribution patterns of temperature and cooling rate within high-temperature tunnels under two ventilation modes: sidewall pressure ventilation and mixed ventilation. They compared the advantages and disadvantages of the two ventilation modes and determined which ventilation mode has the better cooling effect. Li Ru, using a high-temperature, long, deep-buried tunnel as a research object, analyzed the factors affecting the distribution of ventilation temperature and velocity fields in construction tunnels using numerical simulation. Three air supply parameters, namely air supply temperature, air supply velocity, and the distance from the duct outlet to the tunnel face, were selected for numerical simulation of tunnel ventilation under high-temperature conditions. The effects of various factors on the thermal environment within the tunnel were analyzed under three different air supply modes: sidewall ventilation, vault ventilation, and center ventilation. Le Yusheng et al. conducted numerical simulations based on the standard k-ε model to explore the distribution characteristics of the wind flow field and NH3 harmful gas concentration field during ventilation during the maintenance of long-distance water pipelines. Therefore, scholars have largely focused on numerical simulations of ventilation based on single factors, such as high ground temperature in tunnels or the release of harmful gases from freshwater shellfish. This lacks a comprehensive consideration of multiple factors, including high ground temperature and biofouling. Furthermore, numerical simulations of the migration patterns of organic gases (TVOCs) released by biological decay in ventilation tunnels remain largely unresolved. The impact of high ground temperature on ventilation systems cannot be ignored; it alters air density, flow characteristics, and ventilation equipment performance, thereby affecting ventilation effectiveness. Furthermore, high ground temperature influences the migration patterns of harmful gases. Under high temperatures, harmful gas molecules move more vigorously, accelerating diffusion. Furthermore, differences in the density of different harmful gases significantly influence the development of wind flow fields under high temperatures: harmful gases with a density greater than that of air tend to sink and accumulate under high temperatures, altering local airflow organization; while harmful gases with a density less than that of air tend to rise, affecting the vertical distribution of airflow. Therefore, it is necessary to develop a numerical simulation method for maintenance ventilation in deep water transfer tunnels that comprehensively considers high ground temperature and biofouling. This method can comprehensively analyze the distribution characteristics of wind flow fields and harmful gas concentration fields, enabling more effective ventilation management and maintenance, and effectively protecting the lives of maintenance personnel.

[0005] In summary, current research on the release patterns of harmful gases from biodegradation and numerical simulation of ventilation presents numerous limitations. Existing studies primarily focus on the prevention and control of freshwater shellfish, but the release patterns of organic gases (TVOCs) during biodegradation are largely unresolved. Furthermore, there is a lack of systematic analysis of the impact of temperature, a key factor, making it difficult to accurately predict the dynamic changes in biodegradation gas release in real environments. In the field of numerical simulation of ventilation, most studies focus on a single factor, such as the effects of high ground temperature or harmful gases from spoilage on ventilation systems. Comprehensive studies on the coupled effects of high ground temperature and biofouling are limited, and numerical simulation of TVOC migration patterns in ventilation tunnels remains a rarity. Therefore, numerical simulation of ventilation during maintenance of deep-buried water transfer tunnels, taking into account both high ground temperature and biofouling, is urgently needed. This research aims to further analyze the interaction between wind flow and harmful gas concentrations, optimize ventilation management strategies, and effectively protect the lives of maintenance personnel. Summary of the Invention

[0006] In order to overcome the deficiency in the existing technology of the lack of research on the development of ventilation airflow field and the dynamic migration law of harmful gases such as bio-corruption organic gas TVOC in deep buried water conveyance tunnels during the maintenance period under the dual influence of high ground temperature and biological fouling, the present invention provides a numerical simulation method for maintenance ventilation of water conveyance tunnels considering high ground temperature and biological fouling, which solves the problem of unclear evolution mechanism of ventilation airflow field and dynamic migration characteristics of bio-corruption gases such as organic gas TVOC in deep buried water conveyance tunnels during the maintenance period under the coupled influence of high ground temperature and biological fouling.

[0007] To achieve the aforementioned object of the invention, the technical solutions adopted by the present invention include:

[0008] A numerical simulation method for ventilation of a water tunnel maintenance considering high ground temperature and biofouling includes the following steps:

[0009] (1) Experiment on the characteristics of biological decay gas release in high ground temperature environment: Real-time monitoring of the concentration of decay gas released by dead organisms in high ground temperature environment to understand the characteristics of biological decay gas release under high ground temperature conditions;

[0010] (2) Fitting the biological decay gas release rate equation in high geothermal environment: Combined with the biokinetic model, the biological density, decay time and decay gas concentration data in high geothermal environment were analyzed and processed to fit the biological decay gas release rate equation in high geothermal environment;

[0011] The corruption gas release rate equation is:

[0012]

[0013] Where t is time, s; T is temperature, °C; C is the concentration of harmful gases, mg / m 3;

[0014] (3) Calculation of required air volume considering pollution from biological corruption gases in high ground temperature environments: In high ground temperature environments, the required ventilation volume is calculated based on the need to dilute or remove biological corruption gases, and the required air volume of the preliminary design is revised accordingly; the required air volume of the preliminary design includes the air volume required for maintenance personnel, the air volume required to dilute pollution from maintenance machinery, the air volume required to dilute or remove biological corruption gases, and the air volume required to improve the high ground temperature environment of deep buried tunnels;

[0015] The calculation formula of the air volume required by the maintenance personnel is: Q1=knq;

[0016] The calculation formula for the air volume required to dilute the pollutants of the maintenance machinery is: Q2 = H s q s α s ;

[0017] The calculation formula for the air volume required to dilute or remove the biological corruption gas is: Q3 = f(C);

[0018] The calculation formula for the air volume required to improve the high ground temperature environment of the deep buried tunnel is:

[0019] The calculation formula for the total design required air volume during the final pipeline maintenance period is: Q0 = max (Q1, Q2, Q3, Q4);

[0020] Among them, Q1 is the air volume required by construction workers, m 3 / s; k is the air volume reserve coefficient, ranging from 1.1 to 1.2; n is the maximum number of construction workers in the tunnel; q is the amount of fresh air required per person per minute in the tunnel, based on 3.0m 3 / min calculation;

[0021] Q2 is the ventilation volume required to dilute the pollutants of the maintenance machinery, m 3 / s;H s is the total mechanical power, kw; q s The ventilation volume required for the unit power of the maintenance machinery is 2.8 to 8.1 m 3 / (kw·min);α s is the average working efficiency of the machine;

[0022] Q3 is the ventilation volume required to release biological corruption gas, m 3 / s; C is the concentration of harmful gases from biological corruption, mg / m 3 ;

[0023] Q4 is the air volume required to improve the high ground temperature environment of deep buried tunnels, m 3 / s; ρ is the air density, kg / m 3; h is the heat transfer coefficient, W / (m 2 ·℃); ΔT is the difference between the initial temperature of the surrounding rock and the air temperature after cooling, ℃; A is the heat transfer area, m 2 ; c is the specific heat of air, J / (kg·℃); ΔT1 is the change in air temperature, ℃;

[0024] (4) Numerical simulation of ventilation during the maintenance period of deep-buried water tunnels: A three-dimensional non-steady-state mathematical model of ventilation during the maintenance period of deep-buried water tunnels was established to simulate the formation of wind flow fields and the migration patterns of pollutants in deep-buried water tunnels in a high geothermal environment. The three-dimensional non-steady-state mathematical model of ventilation includes continuity equations, momentum conservation equations, energy conservation equations, component transport equations, and turbulence equations.

[0025] The continuity equation is

[0026]

[0027] The momentum conservation equation is

[0028]

[0029] The energy conservation equation is

[0030]

[0031] The component transport equation is

[0032]

[0033] Where ρ is the gas density, kg / m 3 ; t is time, s; u i and u j is the wind speed of the fluid phase in different directions, m / s; x i and x j is the spatial coordinate axis, used to determine the position and change of gas flow and various physical quantities in space, and is the independent variable of spatial change in partial differential equations; p is the gas pressure, Pa; S C is the source term of the momentum equation; v is the three-dimensional velocity vector of the gas, m / s; λ g is the thermal conductivity of the gas, W / (m·K); T g is the temperature, K; c p is the specific heat capacity of gas, J / (kg·K); S T is the source term of the energy equation; c s is the volume fraction of pollutants in the tunnel, %; D s is the diffusion coefficient of the component; S S is the release rate of harmful gases, mg / (m 3 ·s).

[0034] The organism in step (1) is selected from at least one of freshwater shellfish, river clams and capsule snails.

[0035] The corrupt gas in step (1) includes TVOC.

[0036] The corrupt gas in step (1) also includes 1-2 of NH3 and H2S.

[0037] The biokinetic model in step (2) is the Gompertz model improved by Lay;

[0038] The Lay improved Gompertz model is:

[0039]

[0040] Where t is time, s; T is temperature, °C; C is the concentration of harmful gases, mg / m 3 ; A(T) is the saturation value of gas concentration; A(T)=a+k1T+k2T 2 ;

[0041] μ e (T) is the maximum growth rate, reflecting the rate of gas generation; μ e (T) = b + k3T + k4T 2 ; L(T) is the lag time, reflecting the delay in the start of gas generation; L(T)=c+k5T+k6T 2 ;

[0042] a, b, c, k1, k2, k3, k4, k5, k6: Coefficients obtained from fitting the harmful gas release characteristic equation, dimensionless.

[0043] In step (4), the turbulence equation is a standard k-ε turbulence equation, and the standard k-ε turbulence equation includes a turbulent kinetic energy k transport equation and a turbulent kinetic energy dissipation rate ε transport equation;

[0044] The turbulent kinetic energy k transport equation is:

[0045]

[0046] The transport equation for the turbulent kinetic energy dissipation rate ε is:

[0047]

[0048] k is the turbulent kinetic energy of turbulence, m 2 / s 2 ; ε is the turbulent kinetic energy dissipation rate, m 2 / s 3 ; α k and α εis the inverse of the turbulent Prandtl number corresponding to the turbulent kinetic energy k and the dissipation rate ε. In high Reynolds number turbulent motion, α is taken. k =α ε =1.393; μ and μ t are molecular dynamic viscosity coefficient and turbulent dynamic viscosity coefficient, (N·m) / s; G k is the turbulent kinetic energy generated by the average velocity gradient, m 2 / s 2 ;u i ′ and u j ′ is the pulsation value of the speed in each direction, m / s; S k and S ε is the source term of the turbulent kinetic energy transport equation and the turbulent dissipation rate transport equation; η is the dimensionless strain or the time scale ratio of the mean flow to the turbulent flow, which reflects the degree of anisotropy of the flow; C2′ is the modified form of C2; C1, C2, C μ , η0 and β are empirical constants in the equation.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] 1. The method described in the present invention clarifies the emission amount and emission pattern of bio-corruption gas pollutants including organic gas TVOC in deep buried water transfer tunnels in high geothermal environments, making up for the lack of research on the release pattern of harmful gases such as TVOC released by invading biological corruption in high geothermal environments in current water transfer projects.

[0051] 2. The method described in the present invention clarifies the air volume required for purification of bio-corruption gas pollutants including organic gas TVOC in deep-buried water transfer tunnels in high geothermal environments, which is of great significance for ensuring the safety of construction personnel and the normal operation of mechanical equipment during maintenance periods.

[0052] 3. The method described in the present invention conducts numerical simulation of ventilation during the maintenance period of deep-buried water supply tunnels under comprehensive consideration of the release of biological corruption gases and high geothermal environments, and clarifies the development of the wind flow field in the tunnel and the migration and distribution patterns of harmful gases under the coupled conditions of high geothermal temperature and biological fouling, which is of great significance for ensuring the ventilation safety of complex water supply tunnels. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 It is a technical route flow chart in a specific implementation case of the present invention;

[0054] Figure 2Figure 1 is a schematic diagram of a test device for determining the release characteristics of biogenic spoilage gases in a high-temperature environment, which is composed of an indoor experimental model and a detection system, A - indoor experimental model, B - detection system; 1 - glass tunnel model, 2 - overflow hole, 3 - thermometer hole, 4 - electric blanket, 5 - support, 6 - air inlet hole, 7 - air outlet hole, 8 - multi-purpose hole, 9 - air inlet, 10 - backflow hole, 11 - industrial control system, 12 - gas detection equipment, 17 - rotating support, 18 - rotating handle;

[0055] Figure 3 Figure 2 is a structural schematic diagram of the detection system;

[0056] 13 - TVOC sensor, 14 - NH3 sensor, 15 - H2S sensor, 16 - integrated processing system;

[0057] Figure 4 Figure 3 is a result diagram of the internal air flow direction and average air speed in the water conveying tunnel;

[0058] Figure 5 Figure 4 is a NH3 concentration distribution diagram of the water conveying tunnel section;

[0059] Figure 6 Figure 5 is a TVOC concentration distribution diagram of the water conveying tunnel section. DETAILED DESCRIPTION

[0060] The following examples are exemplary descriptions of the main experimental evidence, rather than limiting the core content and application implementation scope of the disclosed protection due to the amount of evidence. It should be noted that in all these drawings and corresponding descriptions, only the concepts, principles and representative experimental evidence of the disclosed embodiments are exemplarily shown. Without the evidence chain being complete, all specific details and extended details of each embodiment listed by the present application do not need to be shown.

[0061] Unless defined, the technical terms used in the following examples have the same meaning as generally understood by those skilled in the art to which the present application belongs.

[0062] Biological spoilage such as freshwater sponges, river clams and capsule snails in water conveying projects can release harmful gases. Since there are more cases of freshwater sponges causing damage to water conveying systems, freshwater sponges are taken as the research object, and the ventilation numerical simulation of deep buried water conveying tunnel is carried out to study the influence of gas pollution produced by freshwater sponges spoilage under high temperature on water conveying system.

[0063] Example 1: Harmful gas release characteristics experiment of freshwater sponges spoilage

[0064] First, through field investigation, literature review and expert consultation, the attachment pattern of freshwater shellfish in the engineering tunnel was clarified, and the data of its maximum, minimum and average attachment density and cumulative thickness were obtained. According to the attachment pattern of freshwater shellfish and the principle of sample extraction, the density of freshwater shellfish sample experiment was set, and freshwater shellfish samples were collected at the engineering site. Secondly, according to the inner diameter of the deep-buried water diversion tunnel, the experimental device was constructed to simulate the deep-buried water diversion tunnel section, such as Figure 2 As shown. The experimental model has a diameter of 0.8m and a height of 1m. It is wrapped with an industrial electric blanket. The multi-purpose hole has a diameter of 12cm, the thermometer hole, and the air inlet and outlet holes are all 1cm in diameter. The experimental device support is a movable structure with a groove, which allows the upper experimental device to rotate freely. Place the freshwater shellfish into the experimental model through the multi-purpose hole according to the unit space density. The experimental model is rotated by hand by turning the handle to ensure that the freshwater shellfish inside the experimental model is evenly distributed. Use PU air pipes to connect the air inlet of the detection system and the air outlet of the experimental model, and to connect the reflux hole of the detection system and the air inlet of the experimental model.

[0065] In this case, the most unfavorable situation of freshwater shellfish corruption gas pollution is taken as the basis, that is, freshwater shellfish is placed at the maximum spatial density. In this case, the maximum spatial density of freshwater shellfish is 1000g / m 3 The experimental temperature gradient was set at 20°C, 25°C, 30°C, 35°C, 40°C, and 45°C. TVOC was selected as the mandatory indicator, and one or both of NH3 and H2S were selected as monitoring targets, depending on the experimental needs. All three gases are characterized by high volatility, large release volumes, and strong irritation and toxicity. In this case, NH3, H2S, and TVOC were selected as the primary monitoring targets. Each experimental group had a monitoring period of 5 days, with three replicates per group.

[0066] Example 2: Fitting the characteristic equation for the release of harmful gases from freshwater shellfish corruption

[0067] The biodynamic model used was the Gompertz model modified by Lay (Formula 1). The density gradient of freshwater shellfish was 1000 g / m 3 The data on NH3, H2S, and TVOC concentrations measured in six experimental sets at temperature gradients of 20°C, 25°C, 30°C, 35°C, 40°C, and 45°C were processed to derive the putrefaction gas release rate equation (Equation 2). This clarifies the emission and patterns of harmful gases from the decay of freshwater shellfish in deep-buried water transfer tunnels under different high geothermal environments.

[0068]

[0069] In the above formula,

[0070] t: time, s;

[0071] T: temperature, °C;

[0072] C: harmful gas concentration, mg / m 3 ;

[0073] A(T): saturation value of gas concentration. A(T)=a+k1T+k2T 2 ;

[0074] μ e (T): Maximum growth rate, reflecting the rate of gas generation. μ e (T) = b + k3T + k4T 2 ;

[0075] L(T): Lag time, reflecting the initial delay of gas generation. L(T)=c+k5T+k6T 2 .

[0076] a, b, c, k1, k2, k3, k4, k5, k6: Coefficients obtained from fitting the harmful gas release characteristic equation, dimensionless.

[0077] Example 3: Calculation of ventilation air volume required for maintenance of deep buried water tunnels considering high ground temperature and biofouling

[0078] According to the requirements of the "Construction Code for Underground Excavation of Hydraulic Structures" and gas dilution theory, the air volume required for maintenance personnel (Equation 3) and dilution of maintenance machinery pollutants (Equation 4) is calculated. Combined with the bio-corruption gas release rate equation (Equation 2), the air volume required to dilute or eliminate bio-corruption gases (Equation 5) is calculated. The air volume required to improve the high ground temperature environment of deep-buried tunnels must also be considered (Equation 8). Ultimately, the total design air volume required for the maintenance period of deep-buried water transmission tunnels is obtained (Equation 10).

[0079] 1) Air volume required by maintenance personnel Q1

[0080] The air volume required by maintenance personnel is calculated based on the maximum number of people performing maintenance work in the tunnel at the same time. The calculation formula is as follows:

[0081] Q1=knq (3)

[0082] Where,

[0083] Q1: Air volume required by construction workers, m 3 / s;

[0084] k: air volume reserve coefficient, ranging from 1.1 to 1.2;

[0085] n: the maximum number of construction workers in the tunnel;

[0086] q: The amount of fresh air required per person per minute in the cave, based on 3.0m 3 / min calculation.

[0087] 2) Air volume Q2 required to dilute pollutants from maintenance machinery

[0088] According to the "Handbook of Construction Organization Design for Water Conservancy and Hydropower Projects", the air volume required to dilute the CO emissions from the machines is calculated based on the number of machines undergoing maintenance work in the tunnel. When diesel machines are used for construction in the tunnel, the formula for calculating the ventilation volume required to dilute the diesel engine exhaust is as follows:

[0089] Q2=H s q s α s (4)

[0090] Where,

[0091] Q2: Ventilation volume required to dilute diesel engine exhaust, m 3 / s;

[0092] H s : Total mechanical power, kw;

[0093] q s : The ventilation volume required for the maintenance machinery per unit power is generally 2.8 to 8.1 m 3 / (kw·min);

[0094] α s : Average working efficiency of machinery.

[0095] 3) Air volume Q3 required to dilute harmful gases released by dead and rotting freshwater shellfish

[0096] The required air volume is calculated based on the release rate of harmful gases such as H2S, NH3 and TVOC produced after the death and decay of freshwater shellfish. The release rate of harmful gases is determined through indoor simulation tests.

[0097] Q3=f(C) (5)

[0098] Where,

[0099] Q3: Ventilation volume required to release the decay gas of freshwater shellfish, m 3 / s;

[0100] C: Concentration of harmful gases from biological corruption, mg / m 3 .

[0101] 4) Consider the air volume Q4 required to improve the high ground temperature environment of deep buried tunnels

[0102] During the construction process, the tunnel is a relatively closed space where air cannot flow. At the same time, the surrounding rock dissipates heat into the tunnel, and heat accumulates in the tunnel. Ventilation and cooling in the tunnel is mainly in the form of convection heat transfer, which is usually heat transfer between the fluid and the solid surface, from high temperature to low temperature. Based on the gas-solid heat transfer theory between the wind flow and the surrounding rock, the Newton cooling formula is used to calculate the convection heat transfer. When the low-temperature air flow and the high-temperature wall undergo convection heat transfer, the fluid temperature rises. The gas-solid heat transfer amount Q is calculated according to the following formula: heat .

[0103] q=h·ΔT (6)

[0104] Q heat =q·A·t (7)

[0105] Where,

[0106] q: heat flux, W / m 2 ;

[0107] h: heat transfer coefficient, W / (m 2 ℃);

[0108] ΔT: the difference between the initial temperature of the surrounding rock and the air temperature after cooling, °C;

[0109] Q heat : calories, J;

[0110] A: heat transfer area, m 2 ;

[0111] t: convection time, s.

[0112] The surrounding rock dissipates heat into the tunnel. Assuming that all the heat is used to heat the low-temperature air flow, then

[0113] Q heat =c·m·ΔT1 (8)

[0114] Where,

[0115] c: specific heat of air, J / (kg·℃);

[0116] m: air mass, kg;

[0117] ΔT1: Change in air temperature, °C.

[0118] According to formulas (6) to (8), the air volume Q4 required to improve the high temperature environment of deep buried tunnels is calculated as follows:

[0119]

[0120] Where,

[0121] Q4: Air volume required to improve high ground temperature environment in deep buried tunnels, m 3 / s;

[0122] ρ: air density, kg / m 3 .

[0123] The air volume required for maintenance of deep-buried water supply tunnels is the maximum value of the air volume required for maintenance personnel, the air volume required to dilute pollutants from maintenance machinery, the air volume required to dilute harmful gases released by the death and decay of freshwater shellfish, and the air volume required to improve the high-altitude environment of the deep-buried tunnel.

[0124] Q0=max(Q1,Q2,Q3,Q4) (10)

[0125] Where,

[0126] Q0: Total required air volume of the tunnel, m 3 / s.

[0127] Example 4: Numerical simulation calculation of maintenance ventilation of deep buried water tunnel considering high ground temperature and biofouling

[0128] Combined with the high geothermal distribution of each maintenance section and the release of harmful gases in the high geothermal environment, a three-dimensional unsteady-state numerical model of maintenance ventilation of deep buried water conveyance tunnels under coupled thermal analysis, component transport analysis and turbulent mode was established, aiming to lay the foundation for the study of the development of wind flow field and the migration law of harmful gases in the high geothermal environment of deep buried water conveyance tunnels.

[0129] Continuity equation:

[0130]

[0131] Momentum conservation equation:

[0132]

[0133] Energy conservation equation:

[0134]

[0135] Component transport equation:

[0136]

[0137] Turbulent kinetic energy k transport equation:

[0138]

[0139] Transport equation of turbulent kinetic energy dissipation rate ε:

[0140]

[0141] in:

[0142]

[0143] Where,

[0144] ρ: gas density, kg / m 3 ;

[0145] t: time, s;

[0146] u i and u j : wind speed of the fluid phase in different directions, m / s;

[0147] x i and x j : The spatial coordinate axis is used to determine the position and changes of gas flow and various physical quantities in space, and is the independent variable of spatial changes in partial differential equations.

[0148] p: gas phase pressure, Pa;

[0149] S C : source term of momentum equation;

[0150] v: gas three-dimensional velocity vector, m / s;

[0151] λ g : thermal conductivity of gas, W / (m·K);

[0152] T g : temperature, K;

[0153] c p : specific heat capacity of gas, J / (kg·K);

[0154] S T : source term of the energy equation;

[0155] c s : Volume fraction of pollutants in the tunnel, %;

[0156] D s : diffusion coefficient of the component;

[0157] S S : Release rate of harmful gases, mg / (m 3 s);

[0158] k: turbulent kinetic energy of turbulence, m 2 / s 2 ;

[0159] ε: turbulent kinetic energy dissipation rate, m 2 / s 3 ;

[0160] α k and α ε: The reciprocal of the turbulent Prandtl number corresponding to the turbulent kinetic energy k and the dissipation rate ε, which is taken as α in high Reynolds number turbulent motion. k =α ε =1.393;

[0161] μ and μ t : molecular dynamic viscosity coefficient and turbulent dynamic viscosity coefficient, (N·m) / s;

[0162] G k : turbulent kinetic energy generated by the mean velocity gradient, m 2 / s 2 ;

[0163] u i ′ and u j ′: velocity pulsation value in each direction, m / s;

[0164] S k and S ε :The source terms of the turbulent kinetic energy transport equation and the turbulent dissipation rate transport equation;

[0165] η: dimensionless strain or the ratio of the mean flow to the time scale of turbulence, reflecting the degree of anisotropy of the flow;

[0166] C2′: a modified form of C2;

[0167] C1, C2, C μ , η0 and β: empirical constants in the equation.

[0168] A deep-buried, long-distance water diversion tunnel project in southern China was used as an example to verify the effectiveness of the proposed method. The tunnel has five sections where the temperature exceeds 28°C, located at XG65+340-XG68+500, XG71+300-XG80+050, XG91+050-XG103+200, XG104+500-XG112+270, and XG112+270.

[0169] —XG121+950, ​​with maximum temperatures in each tunnel section of 33.1°C, 36.4°C, 41.5°C, 35°C, and 37.3°C, respectively. Research on the release characteristics of harmful gases from freshwater shellfish decay shows that the maximum detected concentration of the harmful gas H2S during the decay process is far below the exposure limit defined by the standard, while NH3 and TVOC exceed the standard limits. In this case study, the wind flow and concentration distribution of the harmful gases NH3 and TVOC, produced by biological decay, were specifically considered under the conditions of maximum temperature and corresponding maximum release rate for each high-temperature tunnel section.

[0170] The tunnel section was simulated and calculated based on the numerical simulation method proposed in this patent, and the results are as follows.

[0171] (1) Analysis of simulation results of ventilation flow field in water supply tunnel maintenance

[0172] like Figure 4 As shown, after the ventilation system is in stable operation, under the coupling of high ground temperature and biofouling, 1 # Branch hole, 2 # Branch hole, 3 # Branch hole, 5 # Branch cave and 6 # The entrance of the branch tunnel is the air inlet, and the wind flows from outside the tunnel to inside the tunnel; the tunnel entrance, 4 # The branch tunnel and tunnel exit are air outlets, and the wind flows from inside the tunnel to outside. # Branch hole—5 # The average wind speed in the branch tunnel section is the largest, which is 1.16m / s; # Branch hole—2 # The average wind speed in the branch tunnel section is the smallest, which is 0.07m / s. This is due to the # The branch tunnel flows into the wind flow of the main tunnel 3 # The diversion in the direction of the branch hole dominates the momentum distribution, making 1 # Branch hole—2 # The branch tunnel section becomes a low-speed stagnant area due to the sharp drop in flow. # Air flow direction of branch tunnel 2 # When the branch tunnel is opened, it is parallel to the main tunnel. # The diversion of the branch tunnel forms a partial reverse flow, resulting in the mutual cancellation of momentum. In addition, the geometric mutation at the intersection of the branch tunnel and the main tunnel will also cause flow separation, increase the turbulence intensity, further accelerate the dissipation of kinetic energy, and lead to the minimum average wind speed in this section.

[0173] (2) Analysis of simulation results of bio-corruption gas concentration field in water supply tunnel maintenance ventilation

[0174] According to Table 1 and Table 2 and Figure 5 and Figure 6 The results show that, considering the maximum temperature in the high ground temperature section and the maximum release rate of harmful gases, the concentration distribution of harmful gases in the water supply tunnel shows obvious gradient changes and local aggregation phenomena. Overall, the maximum concentrations of NH3 and TVOC at the water supply tunnel entrance are relatively low at the tunnel ventilation inlet and relatively high at the tunnel ventilation outlet; the maximum concentrations of NH3 and TVOC inside the tunnel gradually increase along the wind direction and reach 1 # The junction of the branch tunnel and the main tunnel increases significantly due to 1 # Branch hole—2 # The average wind speed in the branch tunnel section is only 0.07m / s, and # Branch cave and 1 # The entrances of the branch tunnels are all air inlets, which makes it difficult for a large amount of harmful gases to be fully discharged, resulting in the phenomenon of local concentration accumulation.# Branch hole—2 # The maximum concentration of NH3 in the branch tunnel section reached 106.00 mg / m 3 The maximum concentration of TVOC reached 297.78 mg / m 3 .

[0175] Table 1 Results of the maximum distribution concentration of harmful gases at each air inlet and outlet of the water diversion tunnel

[0176]

[0177] Table 2 Results of maximum distribution concentration of harmful gases in each section of the water tunnel

[0178]

[0179]

[0180] The results not only provide an accurate basis for the design and optimization of the ventilation system, enabling the rational planning of equipment layout and air duct direction, and ensuring the health and safety of construction and maintenance personnel, but also the simulation results effectively guide the preparation of safety plans, enhance the project's ability to deal with harmful gases, control harmful gas emissions, protect the surrounding environment, improve the project's environmental friendliness and social recognition, and enhance the overall reliability and stability of the project, laying a solid foundation for the smooth implementation, on-time delivery and long-term stable operation of the project.

[0181] It should be understood that the above embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. For those skilled in the art of the present invention, without departing from the concept of the present invention, several changes or substitutions can be made, which should be considered to fall within the scope of protection of the present invention.

Claims

1. A numerical simulation method for maintenance ventilation of water transfer tunnels considering high ground temperature and biofouling, characterized by: The steps include: (1) Experiment on the release characteristics of biological decay gases in high ground temperature environments: Real-time monitoring of the concentration of decay gases released by dead organisms in high ground temperature environments to understand the release characteristics of biological decay gases under high ground temperature conditions; (2) Fitting the biological decay gas release rate equation in high geothermal environment: Combined with the biokinetic model, the biological density, decay time and decay gas concentration data in high geothermal environment were analyzed and processed to fit the biological decay gas release rate equation in high geothermal environment; The corruption gas release rate equation is: Where t is time, s; T is temperature, °C; C is the concentration of harmful gases, mg / m 3 ; (3) Calculation of required air volume considering pollution from biological corruption gases in high ground temperature environments: In high ground temperature environments, the required ventilation volume is calculated based on the need to dilute or remove biological corruption gases, and the required air volume of the preliminary design is revised accordingly; the required air volume of the preliminary design includes the air volume required for maintenance personnel, the air volume required to dilute pollution from maintenance machinery, the air volume required to dilute or remove biological corruption gases, and the air volume required to improve the high ground temperature environment of deep buried tunnels; The calculation formula of the air volume required by the maintenance personnel is: Q1=knq; The calculation formula for the air volume required to dilute the pollutants of the maintenance machinery is: Q2 = H s q s α s ; The calculation formula for the air volume required to dilute or remove the biological corruption gas is: Q3 = f(C); The calculation formula for the air volume required to improve the high ground temperature environment of the deep buried tunnel is: The calculation formula for the total design required air volume during the final pipeline maintenance period is: Q0 = max (Q1, Q2, Q3, Q4); Among them, Q1 is the air volume required by construction workers, m 3 / s; k is the air volume reserve coefficient, ranging from 1.1 to 1.2; n is the maximum number of construction workers in the tunnel; q is the amount of fresh air required per person per minute in the tunnel, based on 3.0m 3 / min calculation; Q2 is the ventilation volume required to dilute the pollutants of the maintenance machinery, m 3 / s;H s is the total mechanical power, kw; q s The ventilation volume required for the unit power of the maintenance machinery is 2.8 to 8.1 m 3 / (kw·min);α s is the average working efficiency of the machine; Q3 is the ventilation volume required to release biological corruption gas, m 3 / s; C is the concentration of harmful gases from biological corruption, mg / m 3 ; Q4 is the air volume required to improve the high ground temperature environment of deep buried tunnels, m 3 / s; ρ is the air density, kg / m 3 ; h is the heat transfer coefficient, W / (m 2 ·℃); ΔT is the difference between the initial temperature of the surrounding rock and the air temperature after cooling, ℃; A is the heat transfer area, m 2 ; c is the specific heat of air, J / (kg·℃); ΔT1 is the change in air temperature, ℃; (4) Numerical simulation of ventilation during the maintenance period of deep buried water conveyance tunnels: A three-dimensional non-steady-state mathematical model of ventilation during the maintenance period of deep buried water conveyance tunnels was established to simulate the formation of wind flow fields and the migration of pollutants in deep buried water conveyance tunnels in a high ground temperature environment; the three-dimensional non-steady-state mathematical model of ventilation includes continuity equations, momentum conservation equations, energy conservation equations, component transport equations, and turbulence equations; the continuity equation is The momentum conservation equation is The energy conservation equation is The component transport equation is Where ρ is the gas density, kg / m 3 ; t is time, s; u i and u j is the wind speed of the fluid phase in different directions, m / s; x i and x j is the spatial coordinate axis, used to determine the position and change of gas flow and various physical quantities in space, and is the independent variable of spatial change in partial differential equations; p is the pressure of the gas phase, Pa; S C is the source term of the momentum equation; v is the three-dimensional velocity vector of the gas, m / s; λ g is the thermal conductivity of the gas, W / (m·K); T g is the temperature, K; c p is the specific heat capacity of gas, J / (kg·K); S T is the source term of the energy equation; c s is the volume fraction of pollutants in the tunnel, %; D s is the diffusion coefficient of the component; S S is the release rate of harmful gases, mg / (m 3 ·s).

2. The numerical simulation method for maintenance ventilation of water transfer tunnels considering high ground temperature and biofouling according to claim 1 is characterized in that: In step (1), the organism is selected from at least one of freshwater shellfish, river clams and capsule snails.

3. The numerical simulation method for maintenance ventilation of water transfer tunnels considering high ground temperature and biofouling according to claim 1 is characterized in that: In step (1), the corrupt gas includes TVOC.

4. The numerical simulation method for maintenance ventilation of water transfer tunnels considering high ground temperature and biofouling according to claim 3 is characterized in that: In step (1), the corrupt gas also includes 1-2 of NH3 and H2S.

5. The numerical simulation method for maintenance ventilation of water transfer tunnels considering high ground temperature and biofouling according to claim 1 is characterized in that: In step (2), the biokinetic model is the Gompertz model improved by Lay; The Lay improved Gompertz model is: Where t is time, s; T is temperature, °C; C is the concentration of harmful gases, mg / m 3 ; A(T) is the saturation value of gas concentration; A(T)=a+k1T+k2T 2 ; μ e (T) is the maximum growth rate, reflecting the rate of gas generation; μ e (T) = b + k3T + k4T 2 ; L(T) is the lag time, reflecting the delay in the start of gas generation; L(T)=c+k5T+k6T 2 ; a, b, c, k1, k2, k3, k4, k5, k6: Coefficients obtained from fitting the harmful gas release characteristic equation, dimensionless.

6. The numerical simulation method for maintenance ventilation of water transfer tunnels considering high ground temperature and biofouling according to claim 1 is characterized in that: In step (4), the turbulence equation is a standard k-ε turbulence equation, which includes a turbulent kinetic energy k transport equation and a turbulent kinetic energy dissipation rate ε transport equation; The turbulent kinetic energy k transport equation is: The transport equation for the turbulent kinetic energy dissipation rate ε is: k is the turbulent kinetic energy of turbulence, m 2 / s 2 ; ε is the turbulent kinetic energy dissipation rate, m 2 / s 3 ; α k and α ε is the inverse of the turbulent Prandtl number corresponding to the turbulent kinetic energy k and the dissipation rate ε. In high Reynolds number turbulent motion, α is taken. k =α ε =1.393; μ and μ t are molecular dynamic viscosity coefficient and turbulent dynamic viscosity coefficient, (N·m) / s; G k is the turbulent kinetic energy generated by the average velocity gradient, m 2 / s 2 ; u i ′ and u j ′ is the pulsation value of the speed in each direction, m / s; S k and S ε is the source term of the turbulent kinetic energy transport equation and the turbulent dissipation rate transport equation; η is the dimensionless strain or the time scale ratio of the mean flow to the turbulent flow, which reflects the degree of anisotropy of the flow; C2′ is the modified form of C2; C1, C2, C μ , η0 and β are empirical constants in the equation.

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