A tunnel or roadway ventilation resistance calculation method based on the flow velocity of a circular pipe cross section

Abstract

The application discloses a tunnel or roadway ventilation resistance measuring and calculating method based on a circular tube cross-section flow velocity, which is composed of the following steps: calculating average air density and potential pressure difference, calculating wall surface shear stress, calculating reference velocity, calculating reference Reynolds number, calculating integer coefficient n and dimensionless shear stress s, calculating friction resistance coefficient, measuring channel cross-section area and circumference and calculating ventilation resistance; according to the application, the ventilation resistance of tunnel or roadway and rigid wind tube ventilation can be calculated by measuring air volume, pressure gradient and air velocities at two positions in the cross-section, and the measuring time and labor cost are greatly reduced under the premise of ensuring the measuring accuracy.

Description

Technical Field

[0001] This invention belongs to the field of ventilation resistance measurement, and particularly relates to a method for measuring ventilation resistance in tunnels or alleys based on the flow velocity of a circular pipe cross section. Background Technology

[0002] With the development of sensor technology, ventilation monitoring systems for construction tunnels or mines have become increasingly mature. Directly calculating ventilation resistance parameters in tunnels, roadways, and rigid ventilation ducts using monitoring data has become an important part of digital and intelligent ventilation management. Achieving online monitoring and calculation of high-precision ventilation networks is of great practical significance for intelligent control and early warning of ventilation in tunnels and mines.

[0003] Ventilation resistance measurement is a key component of mine ventilation technology management. It provides a scientific basis for the design and renovation of mine ventilation systems, strengthens their management, and offers crucial technical parameters for controlling airflow during disasters. Therefore, the current "Coal Mine Safety Regulations" stipulate that a mine ventilation resistance measurement must be conducted before a new mine is put into operation, and at least once every three years thereafter. A new ventilation resistance measurement must be performed again after a mine transitions to a new production level or after a change in the ventilation system of one wing.

[0004] Currently, there are two main methods for measuring ventilation resistance in tunnels or roadways: the tilt gauge method and the barometer method. The barometer method measures the static pressure and potential pressure at two points separately. Its advantages are convenience, speed, and the need for fewer operators. However, due to the constantly changing air pressure in the roadway and on the ground during measurement, accurate measurement is difficult, leading to significant errors in the data. The tilt gauge method directly measures the difference between the sum of the static pressure and potential pressure at two points, providing accurate results. However, it requires the installation of Pitot tubes, a cumbersome process that consumes a lot of manpower and time. To address the shortcomings of these two methods, several improvements have been developed. For example, patent CN111005762B discloses an improved tilt gauge resistance measurement method that pre-places Pitot tubes on the tunnel or roadway wall to avoid the pipe-laying step during measurement; and patent CN111256939A discloses a ventilation resistance coefficient measurement method that calculates roadway air resistance by repeatedly changing the degree of roadway obstruction. However, the above-mentioned improved methods still have drawbacks such as difficulty in ensuring the connectivity of Pitot tubes, increased maintenance costs, complex installation of obstructions, and inability to effectively utilize ventilation monitoring system data. Summary of the Invention

[0005] The purpose of this invention is to provide a method for calculating ventilation resistance in tunnels or roadways based on the flow velocity of a circular tube cross section, in order to solve the problems of existing calculation methods, such as difficulty in ensuring the connectivity of Pitot tubes, increased maintenance costs, complex installation of obstructions, and inability to effectively utilize ventilation monitoring system data, which in turn lead to large errors and high difficulty in the calculation method.

[0006] This invention adopts the following technical solution: a method for calculating the ventilation resistance of tunnels or roadways based on the flow velocity of a circular pipe cross-section, comprising the following steps:

[0007] Step 1: Select any two sections within the same channel, designated as Section 1 and Section 2, ensuring that Section 1 and Section 2 do not overlap. The channel is a tunnel or alleyway. Measure the first static pressure, first average temperature, and first relative humidity at any point along Section 1. Measure the second static pressure, second average temperature, and second relative humidity at the corresponding measurement points along Section 2. Calculate the average air density and potential pressure difference.

[0008] Step 2: Measure the distance between the first and second cross-sections, and calculate the wall shear stress based on this distance, the potential pressure difference, and the corresponding geometric dimensions of the channel. When the channel cross-section is circular, the corresponding geometric dimension is the radius of the circular cross-section; when the channel cross-section is non-circular, the corresponding geometric dimension is the constant velocity equivalent diameter of the non-circular cross-section.

[0009] Step 3: Calculate the reference velocity based on the wall shear stress and average air density, and then calculate the reference Reynolds number based on the wall shear stress and reference velocity.

[0010] Step 4: Measure the wind speed at any two points a and b outside the first predetermined distance from the center of the first cross section. Measure the wind speed at any two points a and b outside the second predetermined distance from the center of the second cross section. Measurement points a and b on the first and second cross sections correspond to each other. Measure the airflow in the channel, the maximum wind speed at the center of the channel cross section, or the wind speed at a third point outside the corresponding predetermined distance from the center of the first and second cross sections. The third point does not coincide with points a and b. Calculate the integer coefficient n and the dimensionless shear stress s.

[0011] Step 5: Calculate the friction resistance coefficient.

[0012] Step 6: Measure the cross-sectional area and perimeter of the passage and calculate the ventilation resistance.

[0013] Furthermore, the first predetermined distance is 0.5 * the radius of the first cross section, and the second predetermined distance is 0.5 * the radius of the second cross section.

[0014] Furthermore, when the channel cross-section is circular, the equations for calculating the integer coefficient n and the dimensionless shear stress s in step 4 are as follows:

[0015]

[0016]

[0017] In the formula, u ηaThe average wind speed at corresponding measuring points 'a' at a predetermined distance from the center of the circle on the first and second cross sections, in m / s; u ηb η is the average wind speed at corresponding measuring points b on the first and second cross sections, located at predetermined distances from the center of the circle. a =r a / R is the dimensionless radial distance; η b =r b / R is the dimensionless radial distance; R is the radius of the tunnel or roadway cross section, r a r is the distance from measuring point a to the center of the circle, in meters (m). b The distance from measuring point b to the center of the circle, in meters; u max The maximum wind speed at the center of the cross-section is expressed in m / s; n is an integer coefficient ≥ 2; Q is the airflow rate in the channel; u * For reference speed.

[0018] Furthermore, when the channel cross-section is rectangular, the equations for calculating the integer coefficient n and the dimensionless shear stress s in step 4 are as follows:

[0019]

[0020]

[0021]

[0022]

[0023]

[0024] In the formula, η a =r a / R is the dimensionless radial distance; η b =r b / R is the dimensionless radial distance; R is the radius of the tunnel or roadway cross section, r a r is the distance from measuring point a to the center of the equivalent circular cross-section, in meters (m). b The distance from measuring point b to the center of the equivalent circular cross-section, in meters; u max The maximum wind speed at the center of the equivalent circular cross-section, in m / s; y a The y value represents the average perpendicular distance between corresponding measuring points 'a' on the first and second rectangular cross sections, located at a predetermined distance from the center of the equivalent circular cross section, and the tunnel wall, in meters (m). b The distance between the corresponding measuring points b on the first and second rectangular sections, located at a predetermined distance from the center of the equivalent circular section, and the roadway wall is expressed in meters (m). yaThe average wind speed at corresponding measuring points 'a' at a predetermined distance from the center of the equivalent circular cross-section on the first and second rectangular cross-sections, in m / s; u yb Let be the average wind speed at corresponding measuring points b at predetermined distances from the center of the equivalent circular cross-section on the first and second rectangular cross-sections, and let Q be the airflow in the channel; u * The reference velocity is y; k is the Karman universal constant, taken as 0.4; 0,avg denoted as the average equivalent hydraulic wall distance, in meters; e is the width of the rectangular tunnel, f is the height of the rectangular tunnel, and D is the height of the rectangular tunnel. v Let be the equivalent diameter of the rectangular cross-section at constant velocity.

[0025] Furthermore, when the channel cross-section is trapezoidal, the equations for calculating the integer coefficient n and the dimensionless shear stress s in step 4 are as follows:

[0026]

[0027]

[0028]

[0029]

[0030]

[0031] In the formula, η a =r a / R is the dimensionless radial distance; η b =r b / R is the dimensionless radial distance; R is the radius of the tunnel or roadway cross section, r a r is the distance from measuring point a to the center of the equivalent circular cross-section, in meters (m). b The distance from measuring point b to the center of the equivalent circular cross-section, in meters; u max The maximum wind speed at the center of the equivalent circular cross-section, in m / s; y a The y value represents the average vertical distance between corresponding measuring points 'a' on the first and second trapezoidal sections, located at a predetermined distance from the center of the equivalent circular section, and the roadway wall, in meters (m). b The distance between the corresponding measuring points b on the first and second trapezoidal sections, located at a predetermined distance from the center of the equivalent circular section, and the roadway wall is expressed in meters (m). ya The average wind speed at corresponding measuring points 'a' at a predetermined distance from the center of the equivalent circular cross-section on the first and second trapezoidal cross-sections, in m / s; u ybLet be the average wind speed at corresponding measuring points b at predetermined distances from the center of the equivalent circular cross-section on the first and second trapezoidal cross-sections; and let Q be the airflow in the channel. * The reference velocity is y; k is the Karman universal constant, taken as 0.4; 0,avg denoted as , where is the average equivalent hydraulic wall distance, in meters; e is the lower width of the trapezoidal tunnel, in meters; f is the upper width of the trapezoidal tunnel, in meters; and D is... v denoted as the constant velocity equivalent diameter of the trapezoidal cross section, and h as the height of the trapezoidal roadway, both in meters.

[0032] Furthermore, when the channel cross-section is a semi-circular arch, the equations for calculating the integer coefficient n and the dimensionless shear stress s in step 4 are as follows:

[0033]

[0034]

[0035]

[0036]

[0037]

[0038] In the formula, η a =r a / R is the dimensionless radial distance; η b =r b / R is the dimensionless radial distance; R is the radius of the tunnel or roadway cross section, r a r is the distance from measuring point a to the center of the equivalent circular cross-section, in meters (m). b The distance from measuring point b to the center of the equivalent circular cross-section, in meters; u max The maximum wind speed at the center of the equivalent circular cross-section, in m / s; y a The y value represents the average vertical distance between corresponding measuring points 'a' on the first and second semi-circular arched sections, located at a predetermined distance from the center of the equivalent circular section, and the roadway wall, in meters (m). b The distance between the corresponding measuring points b on the first and second semi-circular arched sections, located at a predetermined distance from the center of the equivalent circular section, and the roadway wall is expressed in meters (m). ya The average wind speed, in m / s, is the wind speed at corresponding measuring points 'a' on the first and second semicircular arched sections, at a predetermined distance from the center of the equivalent circular section; u yb Let be the average wind speed at corresponding measuring points b at a predetermined distance from the center of the equivalent circular section on the first and second semicircular arched sections, and let Q be the airflow in the channel; u *The reference velocity is y; k is the Karman universal constant, taken as 0.4; 0,avg denoted as , where is the average equivalent hydraulic wall distance, in meters; e is the width of the semi-circular arched tunnel; f is the wall height of the semi-circular arched tunnel; and D is the wall height of the semi-circular arched tunnel. v It is the constant velocity equivalent diameter of the semi-circular arched cross section.

[0039] Furthermore, the formula for calculating the frictional resistance coefficient in step 5 is as follows:

[0040]

[0041] In the formula, α is the roadway friction resistance coefficient, in Ns. 2 / m 4 Re * The reference Reynolds number is ρ; the average air density is kg / m³. 3 .

[0042] Furthermore, the formula for calculating ventilation resistance in step 6 is: In the formula, R f Wind resistance, unit: Ns 2 / m 8 S is the cross-sectional area of ​​the channel; U is the perimeter of the channel.

[0043] The beneficial effects of this invention are:

[0044] 1. This invention can calculate the ventilation resistance of tunnels or alleys and rigid ventilation ducts by measuring air volume, pressure gradient and wind speed at two locations within the cross section. While ensuring measurement accuracy, it greatly reduces measurement time and labor costs.

[0045] 2. This invention utilizes the velocity distribution pattern within a circular tube to calculate ventilation resistance by measuring the air volume, pressure gradient, and velocity at two locations within the cross-section. This avoids the measurement errors caused by pressure fluctuations in the traditional barometer method and the large amount of manpower and resources required for laying pitot tubes in the differential pressure gauge method. It greatly improves measurement efficiency while ensuring the accuracy of the measurement data.

[0046] 3. The speed, pressure, temperature, humidity and flow measurement point locations determined by this invention guide the installation positions of corresponding sensors in tunnels or ventilation roadways and rigid ventilation ducts. While monitoring relevant parameters, parameters such as friction resistance coefficient and wind resistance can be monitored and calculated in real time, realizing the sharing of measurement parameters. This fully leverages the important role of big data monitoring in the field of tunnel and roadway ventilation, and has significant practical implications for the intelligent control and early warning of ventilation systems. Attached Figure Description

[0047] Figure 1 A schematic diagram showing the location of measuring points on a cross-section of a circular tunnel or ventilation tunnel.

[0048] Figure 2 This diagram illustrates the measuring points for non-circular tunnels or ventilation shafts and their corresponding circular cross-section measuring points; where...

[0049] (a) is a schematic diagram of the measuring points of a rectangular roadway and its corresponding circular roadway; (b) is a schematic diagram of the measuring points of a trapezoidal roadway and its corresponding circular roadway; (c) is a schematic diagram of the measuring points of a semi-circular arched roadway and its corresponding circular roadway. Detailed Implementation

[0050] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0051] This invention discloses a method for calculating the ventilation resistance of tunnels or roadways based on the flow velocity of a circular pipe cross-section, comprising the following steps:

[0052] Step 1: Select any two cross sections within the same channel, designated as the first cross section and the second cross section, ensuring that the first and second cross sections do not overlap. The channel is a tunnel or alleyway. Measure the first static pressure, first average temperature, and first relative humidity at any point along the first cross section. Measure the second static pressure, second average temperature, and second relative humidity at the corresponding measurement points along the second cross section. Calculate the average air density and potential pressure difference.

[0053] Step 1 is as follows:

[0054] Select the first and second sections of the tunnel or roadway where ventilation resistance needs to be measured. Measure the static pressures p1 and p2 near the wall at the same location on both sections. Measure the average temperature and relative humidity at both sections, calculate the average air density ρ, and calculate the potential pressure difference ΔP between the first and second sections based on the elevation and static pressure data of the static pressure measurement points on the wall.

[0055] ΔP=(p1-p2)+ρg(h1-h2),

[0056] In the formula, ΔP is the potential pressure difference between the first and second cross sections, in Pa; p1 and p2 are the static pressures near the wall at the same location on the first and second cross sections, in Pa; ρ is the average air density, in kg / m³. 3 g is the local gravitational acceleration, in m / s². 2 h1 and h2 are the absolute elevations of the static pressure measuring points at the wall positions of the first and second sections, respectively.

[0057] Step 2: Measure the distance between the first and second cross-sections, and calculate the wall shear stress based on this distance, the potential pressure difference, and the corresponding geometric dimensions of the channel. When the channel cross-section is circular, the corresponding geometric dimension is the radius of the circular cross-section; when the channel cross-section is non-circular, the corresponding geometric dimension is the constant velocity equivalent diameter of the non-circular cross-section.

[0058] Step 2 is as follows:

[0059] Measure the distance L between the first and second cross sections and the geometric dimensions of the tunnel or roadway (radius R of a circular cross section or equivalent constant velocity diameter D of a non-circular cross section). v ), calculate the wall shear stress τ0;

[0060] In the formula, R is the radius of the tunnel or alleyway cross section.

[0061] Step 3: Calculate the reference velocity based on the wall shear stress and average air density, and then calculate the reference Reynolds number based on the wall shear stress and reference velocity.

[0062] Step 3 specifically involves calculating the reference velocity u from the wall shear stress τ0. * and its corresponding reference Reynolds number Re * :

[0063]

[0064] In the formula, D is used for non-circular cross-sections. v / 2 is a substitute, in meters (m); ν is the kinematic viscosity of air, in meters (m). 2 / s.

[0065] Step 4: Measure the wind speed at any two points a and b outside the first predetermined distance from the center of the first cross section. Measure the wind speed at any two points a and b outside the second predetermined distance from the center of the second cross section. The measuring points a and b of the first and second cross sections correspond to each other. Measure the airflow of the channel, the maximum wind speed at the center of the channel cross section, or the wind speed at a third point outside the corresponding predetermined distance from the center of the first and second cross sections. The third point does not coincide with points a and b. Calculate the integer coefficient n and the dimensionless shear stress s. The first predetermined distance is 0.5 * the radius of the first cross section, and the second predetermined distance is 0.5 * the radius of the second cross section.

[0066] Step 4 is as follows:

[0067] like Figure 1 As shown, when the channel cross-section is circular:

[0068] An ultrasonic flow meter is used to measure the air volume Q in a circular cross-section tunnel or alley, and the wind speed u at points a corresponding to predetermined distances from the center of the first and second cross-sections is measured respectively. ηa The wind speed at point b, u ηb Preferably, point a is selected at a distance of 0.5R from the center of the circle, i.e., η a =0.5, point b is chosen at a distance of 0.75R from the center of the circle, i.e., η b =0.75. The positions of measuring points a and b can be any two points between the upper wall of the cross section and half the radius that are convenient for measurement.

[0069] The wind speed u measured at the respective measuring points of the first and second cross sections ηa and u ηb And the integer coefficients n and dimensionless shear stress s of the empirical formula for calculating the velocity distribution in a two-section circular pipe using the air volume Q:

[0070]

[0071] In the formula, η a =r a / R is the dimensionless radial distance; η b =r b / R is the dimensionless radial distance; R is the radius of the tunnel or roadway cross section, r a r is the distance from measuring point a to the center of the circle, in meters (m). b The distance from measuring point b to the center of the circle, in meters; u max The maximum wind speed at the center of the cross-section is expressed in m / s; u ηa The average wind speed at corresponding measuring points 'a' at a predetermined distance from the center of the circle on the first and second cross sections, in m / s; u ηb Let be the average wind speed at corresponding measuring points b at predetermined distances from the center on the first and second cross sections, where n is an integer coefficient ≥ 2, and Q is the airflow in the channel; u * For reference speed.

[0072] If it is inconvenient to measure the air volume Q, then it is necessary to supplement the measurement with the maximum wind speed u at the center point of the cross-section. max Alternatively, add a wind speed measuring point c between the wall surface and half the radius.

[0073] like Figure 2 As shown, when the channel cross-section is rectangular:

[0074] η of the cross-section of a non-circular tunnel or alley a and η b The average flow velocity can be obtained by comparing the area of ​​the non-circular cross section enclosed by points with equal wall spacing with the average flow velocity of the inner circle of the equivalent circular cross section, where the radius is the dimensionless distance η to be determined.

[0075] Measure the perpendicular distance y between measuring points a and b on the rectangular cross-section and the tunnel wall. a and y b and the corresponding wind speed u at the measuring point ya u yb The virtual starting point of the wall is calculated based on the non-circular pipe velocity distribution formula, and its average value is calculated to obtain y0:

[0076]

[0077] In the formula: k is the KAMAN universal constant, taken as 0.4; y a y b These are the vertical distances from measuring points a and b on the rectangular cross-section to the tunnel wall, in meters; u ya u yb y1 and y2 are the wind speeds at measuring points a and b on the rectangular cross-section, respectively, in m / s; y0 is the virtual starting point of the wall, y... 0,avg The average equivalent hydraulic wall distance is expressed in meters (m).

[0078] The average gas velocity within the rectangle bounded by points of equal wall spacing is calculated using the velocity distribution formula for non-circular pipes. and

[0079]

[0080]

[0081] In the formula: denoted as , and respectively as the average gas velocity within the rectangle bounded by points with equal wall spacing; e and f are the width and height of the rectangular tunnel, respectively.

[0082] The average velocity of the inner circle with a radius of unknown dimensionless distance η in the equivalent circular cross-section is calculated using the empirical formula for velocity distribution in a circular pipe. and

[0083]

[0084]

[0085] The average gas velocity within a rectangle bounded by points with equal wall spacing is equal to the average velocity of the inner circle of an equivalent circular cross-section with a radius equal to the undetermined dimensionless distance η. have:

[0086]

[0087]

[0088] Calculate η of the circular cross-section corresponding to the given diameter by combining the following five equations. a ηb Maximum velocity u at the center of the cross section max And integer coefficient n and dimensionless shear stress s:

[0089]

[0090]

[0091]

[0092]

[0093]

[0094] In the formula: η a =r a / R is the dimensionless radial distance, η b =r b / R is the dimensionless radial distance, R is the radius of the tunnel or roadway cross section, and r a r is the distance from measuring point a to the center of the equivalent circular cross-section, in meters (m). b The distance from measuring point b to the center of the equivalent circular cross-section, in meters; u max The maximum wind speed at the center of the equivalent circular cross-section, in m / s; y a The y value represents the average perpendicular distance between corresponding measuring points 'a' on the first and second rectangular cross sections, located at a predetermined distance from the center of the equivalent circular cross section, and the tunnel wall, in meters (m). b The distance between the corresponding measuring points b on the first and second rectangular sections, located at a predetermined distance from the center of the equivalent circular section, and the roadway wall is expressed in meters (m). ya The average wind speed at corresponding measuring points 'a' at a predetermined distance from the center of the equivalent circular cross-section on the first and second rectangular cross-sections, in m / s; u yb Let be the average wind speed at corresponding measuring points b at a predetermined distance from the center of the equivalent circular section on the first and second rectangular sections, and let Q be the airflow in the channel, in meters. 3 / s,;u * The reference velocity is y; k is the Karman universal constant, taken as 0.4; 0,avg denoted as the average equivalent hydraulic wall distance, in meters; e is the width of the rectangular tunnel, f is the height of the rectangular tunnel, and D is the height of the rectangular tunnel. v Let be the equivalent diameter of the rectangular cross-section at constant velocity. To ensure accuracy and facilitate verification of the calculation results, the air volume Q in the rectangular tunnel needs to be measured. If measuring the air volume is inconvenient, it can be obtained by integrating the velocity distribution within a non-circular pipe.

[0095] When the channel cross-section is trapezoidal, the equations for calculating the integer coefficient n and the dimensionless shear stress s in step 4 are as follows:

[0096]

[0097]

[0098]

[0099]

[0100]

[0101] In the formula, η a =r a / R is the dimensionless radial distance, η b =r b / R is the dimensionless radial distance, R is the radius of the tunnel or roadway cross section, and r a r is the distance from measuring point a to the center of the equivalent circular cross-section, in meters (m). b The distance from measuring point b to the center of the equivalent circular cross-section, in meters; u max The maximum wind speed at the center of the equivalent circular cross-section, in m / s; y a The y value represents the average vertical distance between corresponding measuring points 'a' on the first and second trapezoidal sections, located at a predetermined distance from the center of the equivalent circular section, and the roadway wall, in meters (m). b The distance between the corresponding measuring points b on the first and second trapezoidal sections, located at a predetermined distance from the center of the equivalent circular section, and the roadway wall is expressed in meters (m). ya The average wind speed at corresponding measuring points 'a' at a predetermined distance from the center of the equivalent circular cross-section on the first and second trapezoidal cross-sections, in m / s; u yb Let be the average wind speed at corresponding measuring points b at predetermined distances from the center of the equivalent circular cross-section on the first and second trapezoidal cross-sections; and let Q be the airflow in the channel. * The reference velocity is y; k is the Karman universal constant, taken as 0.4; 0,avg denoted as , where is the average equivalent hydraulic wall distance, in meters; e is the lower width of the trapezoidal tunnel, in meters; f is the upper width of the trapezoidal tunnel, in meters; and D is... v denoted as the constant velocity equivalent diameter of the trapezoidal cross section, and h as the height of the trapezoidal roadway, both in meters.

[0102] When the channel cross-section is a semi-circular arch, the equations for calculating the integer coefficient n and the dimensionless shear stress s in step 4 are as follows:

[0103]

[0104]

[0105]

[0106]

[0107]

[0108] In the formula, η a =r a / R is the dimensionless radial distance, η b =r b / R is the dimensionless radial distance, R is the radius of the tunnel or roadway cross section, and r a r is the distance from measuring point a to the center of the equivalent circular cross-section, in meters (m). b The distance from measuring point b to the center of the equivalent circular cross-section, in meters; u max The maximum wind speed at the center of the equivalent circular cross-section, in m / s; y a The y value represents the average vertical distance between corresponding measuring points 'a' on the first and second semi-circular arched sections, located at a predetermined distance from the center of the equivalent circular section, and the roadway wall, in meters (m). b The distance between the corresponding measuring points b on the first and second semi-circular arched sections, located at a predetermined distance from the center of the equivalent circular section, and the roadway wall is expressed in meters (m). ya The average wind speed, in m / s, is the wind speed at corresponding measuring points 'a' on the first and second semicircular arched sections, at a predetermined distance from the center of the equivalent circular section; u yb Let be the average wind speed at corresponding measuring points b at a predetermined distance from the center of the equivalent circular section on the first and second semicircular arched sections, and let Q be the airflow in the channel; u * The reference velocity is y; k is the Karman universal constant, taken as 0.4; 0,avg denoted as , where is the average equivalent hydraulic wall distance, in meters; e is the width of the semi-circular arched tunnel; f is the wall height of the semi-circular arched tunnel; and D is the wall height of the semi-circular arched tunnel. v It is the constant velocity equivalent diameter of the semi-circular arched cross section.

[0109] Step 5: Calculate the friction resistance coefficient.

[0110] Step 5 specifically involves calculating the frictional resistance coefficient based on the integer coefficient n and the dimensionless shear stress s obtained from the solution. The formula is as follows:

[0111]

[0112] In the formula, α is the roadway friction resistance coefficient, in Ns. 2 / m 4 .

[0113] Step 6: Measure the cross-sectional area and perimeter of the passage and calculate the ventilation resistance.

[0114] Step 6 specifically involves: measuring the cross-sectional area S and perimeter U of the tunnel or roadway, and calculating the wind resistance R. f and pressure drop H f The formula is as follows:

[0115]

[0116] In the formula, R f Wind resistance, unit: Ns 2 / m 8 H f Pressure drop, unit: Pa.

[0117] This invention can calculate the friction resistance coefficient and ventilation resistance of a roadway by measuring the air volume, pressure gradient, and wind speed at two locations on the cross section. It avoids the measurement errors caused by pressure fluctuations in the traditional barometer method and the large amount of manpower and resources required for laying pitot tubes in the differential pressure gauge method. While ensuring the accuracy of the measurement data, it greatly improves the measurement efficiency.

[0118] The measurement point locations determined by this invention guide the installation positions of corresponding sensors in tunnels, ventilation roadways, and rigid ventilation ducts. This allows for real-time monitoring and calculation of ventilation parameters such as friction resistance coefficient and wind resistance while ensuring the monitoring of relevant parameters. It also enables the sharing of measurement parameters, fully leveraging the important role of big data monitoring in tunnel and roadway ventilation, and contributing to the construction of a comprehensive and digital ventilation roadway network. Furthermore, by applying computational models and numerical algorithms, the test data can be identified, analyzed, and optimized in real time online, which has significant practical implications for the intelligent control and early warning of ventilation systems.

[0119] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for calculating the ventilation resistance of a tunnel or roadway based on the flow velocity of a circular pipe cross-section, characterized in that, It consists of the following steps: Step 1: Select any two cross sections within the same channel, designated as the first cross section and the second cross section, ensuring that the first and second cross sections do not overlap. The channel is a tunnel or alleyway. Measure the first static pressure, first average temperature, and first relative humidity at any point along the first cross section. Measure the second static pressure, second average temperature, and second relative humidity at the corresponding measurement points along the second cross section. Calculate the average air density and potential pressure difference. Step 2: Measure the distance between the first and second cross-sections, and calculate the wall shear stress based on this distance, the potential pressure difference, and the corresponding geometric dimensions of the channel. When the channel cross-section is circular, the corresponding geometric dimension is the radius of the circular cross-section; when the channel cross-section is non-circular, the corresponding geometric dimension is the constant velocity equivalent diameter of the non-circular cross-section. Step 3: Calculate the reference velocity based on the wall shear stress and average air density, and then calculate the reference Reynolds number based on the wall shear stress and reference velocity. Step 4: Measure the wind speed at any two points a and b outside the first predetermined distance from the center of the first cross section. Measure the wind speed at any two points a and b outside the second predetermined distance from the center of the second cross section. Measurement points a and b on the first and second cross sections correspond to each other. Measure the airflow through the channel, the maximum wind speed at the center of the channel cross section, or the wind speed at a third point outside the corresponding predetermined distance from the center of the first and second cross sections. The third point does not coincide with points a and b. Calculate the integer coefficient n and the dimensionless shear stress s. Step 5: Calculate the friction resistance coefficient. Step 6: Measure the cross-sectional area and perimeter of the passage and calculate the ventilation resistance.

2. The method for calculating the tunnel or roadway ventilation resistance based on the flow velocity of the circular pipe section according to claim 1, characterized in that, The first predetermined distance is 0.5 * the radius of the first cross section, and the second predetermined distance is 0.5 * the radius of the second cross section.

3. The method for calculating the tunnel or roadway ventilation resistance based on the flow velocity of the circular pipe section according to claim 2, characterized in that, When the channel cross-section is circular, the equations for calculating the integer coefficient n and the dimensionless shear stress s in step 4 are as follows: In the formula, u ηa The average wind speed at corresponding measuring points 'a' at a predetermined distance from the center of the circle on the first and second cross sections, in m / s; u ηb η is the average wind speed at corresponding measuring points b on the first and second cross sections, located at predetermined distances from the center of the circle. a =r a / R is the radial dimensionless distance; η b =r b / R is the dimensionless radial distance; R is the radius of the tunnel or tunnel cross-section, r a r is the distance from measuring point a to the center of the circle, in meters (m). b The distance from measuring point b to the center of the circle is in meters. u max is the maximum wind speed of the cross-sectional circle center, unit m / s; n is an integer coefficient ≥ 2, Q is the air volume of the channel; u * is the reference speed.

4. The method for calculating the tunnel or roadway ventilation resistance based on the flow velocity of the circular pipe section according to claim 2, characterized in that, When the channel cross-section is rectangular, the equations for calculating the integer coefficient n and the dimensionless shear stress s in step 4 are as follows: In the formula, η a =r a / R is the dimensionless radial distance; η b =r b / R is the dimensionless radial distance; R is the radius of the tunnel or roadway cross section, r a r is the distance from measuring point a to the center of the equivalent circular cross-section, in meters (m). b The distance from measuring point b to the center of the equivalent circular cross-section is in meters. u max The maximum wind speed at the center of the equivalent circular cross-section, in m / s; y a The y value represents the average perpendicular distance between corresponding measuring points 'a' on the first and second rectangular cross sections, located at a predetermined distance from the center of the equivalent circular cross section, and the tunnel wall, in meters (m). b The distance between the corresponding measuring points b on the first and second rectangular sections, located at a predetermined distance from the center of the equivalent circular section, and the roadway wall is expressed in meters (m). ya The average wind speed at corresponding measuring points 'a' at a predetermined distance from the center of the equivalent circular cross-section on the first and second rectangular cross-sections, in m / s; u yb Let be the average wind speed at corresponding measuring points b at predetermined distances from the center of the equivalent circular cross-section on the first and second rectangular cross-sections, and let Q be the airflow in the channel; u * The reference velocity is y; k is the Karman universal constant, taken as 0.4; 0,avg denoted as the average equivalent hydraulic wall distance, in meters; e is the width of the rectangular tunnel, f is the height of the rectangular tunnel, and D is the height of the rectangular tunnel. v Let be the equivalent diameter of the rectangular cross-section at constant velocity.

5. The method for calculating the tunnel or roadway ventilation resistance based on the flow velocity of the circular pipe section according to claim 2, characterized in that, When the channel cross-section is trapezoidal, the equations for calculating the integer coefficient n and the dimensionless shear stress s in step 4 are as follows: In the formula, η a =r a / R is the dimensionless radial distance; η b =r b / R is the dimensionless radial distance; R is the radius of the tunnel or roadway cross section, r a r is the distance from measuring point a to the center of the equivalent circular cross-section, in meters (m). b The distance from measuring point b to the center of the equivalent circular cross-section is in meters. u max The maximum wind speed at the center of the equivalent circular cross-section, in m / s; y a The y value represents the average vertical distance between corresponding measuring points 'a' on the first and second trapezoidal sections, located at a predetermined distance from the center of the equivalent circular section, and the roadway wall, in meters (m). b The distance between the corresponding measuring points b on the first and second trapezoidal sections, located at a predetermined distance from the center of the equivalent circular section, and the roadway wall is expressed in meters (m). ya The average wind speed at corresponding measuring points 'a' at a predetermined distance from the center of the equivalent circular cross-section on the first and second trapezoidal cross-sections, in m / s; u yb Let be the average wind speed at corresponding measuring points b at predetermined distances from the center of the equivalent circular cross-section on the first and second trapezoidal cross-sections; and let Q be the airflow in the channel. * The reference velocity is y; k is the Karman universal constant, taken as 0.4; 0,avg denoted as , where is the average equivalent hydraulic wall distance, in meters; e is the lower width of the trapezoidal tunnel, in meters; f is the upper width of the trapezoidal tunnel, in meters; and D is... v denoted as the constant velocity equivalent diameter of the trapezoidal cross section, and h as the height of the trapezoidal roadway, both in meters.

6. The method for calculating the ventilation resistance of tunnels or roadways based on the flow velocity of a circular pipe cross-section according to claim 2, characterized in that, When the channel cross-section is a semi-circular arch, the equations for calculating the integer coefficient n and the dimensionless shear stress s in step 4 are as follows: In the formula, η a =r a / R is the dimensionless radial distance; η b =r b / R is the dimensionless radial distance; R is the radius of the tunnel or roadway cross section, r a r is the distance from measuring point a to the center of the equivalent circular cross-section, in meters (m). b The distance from measuring point b to the center of the equivalent circular cross-section is in meters. u max The maximum wind speed at the center of the equivalent circular cross-section, in m / s; y a The y value represents the average vertical distance between corresponding measuring points 'a' on the first and second semi-circular arched sections, located at a predetermined distance from the center of the equivalent circular section, and the roadway wall, in meters (m). b The distance between the corresponding measuring points b on the first and second semi-circular arched sections, located at a predetermined distance from the center of the equivalent circular section, and the roadway wall is expressed in meters (m). ya The average wind speed, in m / s, is the wind speed at corresponding measuring points 'a' on the first and second semicircular arched sections, at a predetermined distance from the center of the equivalent circular section; u yb Let be the average wind speed at corresponding measuring points b at a predetermined distance from the center of the equivalent circular section on the first and second semicircular arched sections, and let Q be the airflow in the channel; u * The reference velocity is y; k is the Karman universal constant, taken as 0.4; 0,avg denoted as , where is the average equivalent hydraulic wall distance, in meters; e is the width of the semi-circular arched tunnel; f is the wall height of the semi-circular arched tunnel; and D is the wall height of the semi-circular arched tunnel. v It is the constant velocity equivalent diameter of the semi-circular arched cross section.

7. A method for calculating the ventilation resistance of a tunnel or roadway based on the flow velocity of a circular pipe cross-section according to any one of claims 3-6, characterized in that, The formula for calculating the friction resistance coefficient in step 5 is: wherein a is the tunnel friction coefficient, in Nsm 2 / m 4 ; Re * is the reference Reynolds number; p is the average air density, in kg / m 3 .

8. The method for calculating the tunnel or roadway ventilation resistance based on the flow velocity of the circular pipe section according to claim 7, characterized in that, The formula for calculating the ventilation resistance is: where R f is the wind resistance, in Ns 2 / m 8 ; S is the cross-sectional area of the passage; and U is the perimeter of the passage.

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