A length simulation method for tunnel ventilation

Abstract

The invention discloses a length simulation method for tunnel ventilation, which measures the radius of the air outlet and the wind speed at the air outlet in the initial state; then removes the adjustment rings from the outside to the inside, and measures the radius of the air outlet and the wind speed at the air outlet each time one is removed, until all the adjustment rings are removed; then the radius of the air outlet is measured in order from large to small. R i , calculate the pressure loss of the tunnel model body H f , then calculate the outlet radius as R i The present invention is easy to operate and can accommodate experiments with tunnel models of varying lengths by adjusting the size of the air outlet, saving experimental costs. This invention not only solves the problem of difficulty in varying tunnel model length within the laboratory, but also allows for direct calculation of the increased equivalent length based on a formula.

Description

Technical Field

[0001] The invention belongs to the technical field of tunnel ventilation, and in particular relates to a length simulation method for tunnel ventilation. Background Art

[0002] One of the main research methods for the ventilation problem of long-distance and large-section tunnels is small-scale model experimental research. Due to the actual length of the tunnel being too long and the limited laboratory space, it is difficult to achieve the same length ratio even if the model is built in a smaller size. Therefore, it is necessary to apply the equivalent simulation method to conduct ventilation physical model tests.

[0003] Currently, the main method for varying the relative length of model tunnels is to alter the airflow resistance using resistance grilles. In 2004, during model testing of the Qinling-Zhongnanshan super-long highway tunnel, Xie Yongli, Wang Yaqiong, Fang Lei, and others used resistance grilles to establish tunnel ventilation physical models at scales of 1:8 and 1:24, respectively. For the Hong Kong-Zhuhai-Macao Cross-Harbour Tunnel, Xie Yongli, Wang Yaqiong, and others from Chang'an University used resistance grilles to establish large-scale 1:9 overall and local physical models. In 2009, based on the Dabie Mountain super-long highway tunnel, Xie Yongli, Wang Yaqiong, and others from Chang'an University used resistance grilles to establish a large-scale 1:10 ventilation physical model. The resistance grilles used in these three tunnel model constructions were conventional, with no specific standard and varying shapes and specifications. This required the implementers to order multiple sets of resistance grilles and frequently replace them to meet the required ventilation resistance to simulate model tunnels of varying lengths. This method was time-consuming and labor-intensive, increasing experimental costs.

[0004] In 2018, Han Jinping et al. published an adjustable underground tunnel resistance model. The main principle is to obtain the corresponding length by installing several resistance grids of the same specifications to obtain equivalent resistance. Compared with traditional grids, this method does not require multiple sets of different resistance grids. However, implementers have to increase or decrease the number of resistance grids to form different ventilation resistances, and the corresponding frames need to be installed before installing the resistance grids. It can be seen that in the specific implementation of this method, there are problems such as the frame not being easy to fit into the tunnel and being easy to detach during the experiment. The operation is inconvenient and time-consuming, which in turn affects the experimental process. Summary of the Invention

[0005] In order to solve the above technical problems, a tunnel ventilation length simulation method is provided, which is flexible and convenient to operate, can reduce the labor intensity of experimenters, and can realize experiments on tunnel models of different lengths by adjusting the size of the air outlet, thereby saving experimental costs.

[0006] The technical solution adopted by the present invention is: a tunnel ventilation length simulation method, which is implemented by using a tunnel ventilation length simulation device. The tunnel ventilation length simulation device includes a tunnel model body and an adjustment device. The tunnel model body is a tubular structure, and the adjustment device is installed at the end of the tunnel model body. The adjustment device includes a plurality of adjustment rings, and the diameters of the plurality of adjustment rings are different. The adjustment rings are arranged in sequence according to the size of the diameters. Adjacent adjustment rings are coaxially connected, and the adjustment ring with a smaller diameter is located outside the adjustment ring with a larger diameter.

[0007] The steps include:

[0008] 1) Measure the radius of the air outlet and the wind speed at the air outlet in the initial state;

[0009] 2) Remove the adjustment rings from the outside to the inside, and measure the radius of the air outlet and the wind speed at the air outlet after each removal until all the adjustment rings are removed; then count the radius of the air outlet from large to small as R i , i=0,1,2,3,……,n,n is the total number of adjustment rings; and the radius of the air outlet R i The anemometer is v i ;

[0010] 3) Calculate the pressure loss P of the tunnel model body f :

[0011] a) Take the air outlet radius R0 as the control group, where R0 is the original radius of the tunnel model body, and calculate the loss along the control group. The calculation formula is shown in formula (1):

[0012]

[0013] Where, P f(0) —Long-range loss when the outlet radius is R0, Pa;

[0014] λ—along-the-line resistance coefficient, dimensionless number;

[0015] ρ—air density in the tunnel, kg / m 3 ;

[0016] D—inner diameter of the tunnel model body, D=2R0, m;

[0017] v0—wind speed when the outlet radius is R0, m / s;

[0018] L0—equivalent length of the tunnel model body when the outlet radius is R0, m;

[0019] b) Calculate the outlet radius R i , i=1, 2, 3, ..., n, the loss along the way is calculated as shown in formula (2):

[0020]

[0021] Where, P f(i) —The air outlet radius is R i Loss along the way, Pa;

[0022] L i —The air outlet radius is R i The equivalent length relative to the outlet radius R0, m;

[0023] c) Calculate the outlet radius from R0 to R i , i=1, 2, 3, ..., n, the pressure loss consumed is calculated as shown in formula (3):

[0024]

[0025] Where, P f(i-0) —The air outlet radius changes from R0 to R i The pressure loss consumed when , Pa;

[0026] △L i —The air outlet radius changes from R0 to R i The equivalent length increment of the tunnel model body at time , m;

[0027] 4) Calculate the air outlet radius R i The equivalent length increment of the tunnel model body at time:

[0028] a) Change the right side of formula (3) Moving to the left, we obtain formula (4):

[0029]

[0030] b) The left side of formula (4) Moving to the right, we obtain formula (5):

[0031]

[0032] c) Changes in the outlet area will cause changes in local resistance. The local loss calculation formula is shown in formula (6):

[0033]

[0034] Where ξ is the local resistance coefficient;

[0035] d) Due to P f(i-0) =P m , we get formula (7):

[0036]

[0037] e) When the outlet area suddenly decreases, the corresponding local resistance coefficient ξ is expressed as shown in formula (8):

[0038]

[0039] Where A0 is the cross-sectional area of the air outlet when the main body of the tunnel model is not equipped with a regulating device. m 2 ;

[0040] A i —The air outlet radius is R i When the cross-sectional area of the air outlet is m 2 ;

[0041] g) Substitute formula A0, A i Substituting the calculation formula into formula (8) yields formula (9):

[0042]

[0043] h) Substituting formula (9) into formula (7) yields formula (10):

[0044]

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] This invention is easy to operate. Based on the theory of friction equivalence, adjusting rings of varying sizes are stacked at the end of the tunnel model to seal the tunnel exit. When simulating tunnel conditions of a corresponding length, the corresponding ring is removed according to specific needs. The tunnel resistance is adjusted by adjusting the area of the air outlet, thereby achieving the equivalent length effect within the tunnel. By adjusting the size of the air outlet, experiments with tunnel models of varying lengths can be carried out, saving experimental costs. This invention not only solves the problem of difficult tunnel model length changes in the laboratory, but also directly calculates the increased equivalent length based on a formula, avoiding numerical ambiguity that can affect subsequent experimental progress. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 This is a front view of the length simulation device for tunnel ventilation used in the present invention.

[0048] Figure 2 It is a side view of the length simulation device for tunnel ventilation used in the present invention.

[0049] Figure 3 This is the fan characteristic curve.

[0050] Figure 4This is the relationship diagram between the air outlet radius and equivalent length of the tunnel model body.

[0051] In the figure: 1—adjusting ring, 2—self-tapping screw, 3—tunnel model body

[0052] R0 is the original radius of the tunnel model body; R i is the outlet radius, i = 0, 1, 2, 3, ..., n; P f(0) is the loss along the way when the outlet radius is R0; P f(i) The radius of the air outlet is R i The loss along the way; Q (0) is the flow rate when the outlet radius is R0; Q (i) The radius of the air outlet is R i The flow rate at that time. DETAILED DESCRIPTION

[0053] The present invention will be further described below with reference to the accompanying drawings and examples.

[0054] like Figures 1 and 2 As shown, the tunnel ventilation length simulation device used in the present invention includes a tunnel model body 3 and an adjustment device. The tunnel model body 3 is a tubular structure. The adjustment device is installed at the end of the tunnel model body 3 and can adjust the size of the tunnel end opening. The adjustment device includes two adjustment rings 1 (the number of adjustment rings 1 can be more than two) and self-tapping screws 2. The two adjustment rings 1 have different diameters. The adjustment rings are arranged in sequence according to their diameters. Adjacent adjustment rings are coaxially connected by self-tapping screws 2, and the smaller diameter adjustment ring is located outside the larger diameter adjustment ring. The largest diameter adjustment ring is fixed to the end of the tunnel model body 3 by self-tapping screws, thereby fixing the adjustment device to the end of the tunnel model body 3.

[0055] Remove the adjustment rings from small to large, and measure the wind speed and air outlet radius each time you remove an adjustment ring until all the adjustment rings are removed. The air outlet radius from large to small is R i (i=0,1,2,3,……,n,n is the total number of adjustment rings), air outlet radius R i The wind speed at time v i Then, calculate the different outlet diameters R according to the pressure loss formula i The pressure loss under the condition of friction resistance equivalence theory is used to obtain the relative length increase of the tunnel model body △L i The initial length L0 of the tunnel model body plus the relative length increase △L i The equivalent length L of the tunnel model body can be obtained i .

[0056] The specific implementation steps of the present invention are as follows:

[0057] 1) Measure the radius of the air outlet and the wind speed at the air outlet in the initial state;

[0058] 2) Remove the adjustment rings from the outside to the inside, and measure the radius of the air outlet and the wind speed at the air outlet after each removal until all the adjustment rings are removed; then count the radius of the air outlet from large to small as R i , i=0,1,2,3,……,n,n is the total number of adjustment rings; and the radius of the air outlet R i The anemometer is v i ;

[0059] 3) Calculate the pressure loss P of the tunnel model body f :

[0060] a) Take the air outlet radius R0 as the control group, where R0 is the original radius of the tunnel model body, and calculate the loss along the control group. The calculation formula is shown in formula (1):

[0061]

[0062] Where, P f(0) —Long-range loss when the outlet radius is R0, Pa;

[0063] λ—along-the-line resistance coefficient, dimensionless number;

[0064] ρ—air density in the tunnel, kg / m 3 ;

[0065] D—inner diameter of the tunnel model body, D=2R0, m;

[0066] v0—wind speed when the outlet radius is R0, m / s;

[0067] L0—equivalent length of the tunnel model body when the outlet radius is R0, m;

[0068] b) Calculate the outlet radius R i , i=1, 2, 3, ..., n, the loss along the way is calculated as shown in formula (2):

[0069]

[0070] Where, P f(i) —The air outlet radius is R i Loss along the way, Pa;

[0071] L i —The air outlet radius is R i The equivalent length relative to the outlet radius R0, m;

[0072] c) Calculate the outlet radius from R0 to R i , i=1, 2, 3, ..., n, the pressure loss consumed is calculated as shown in formula (3):

[0073]

[0074] Where, P f(i-0) —The air outlet radius changes from R0 to R i The pressure loss consumed when , Pa;

[0075] △L i —The air outlet radius changes from R0 to R i The equivalent length increment of the tunnel model body at time , m;

[0076] 4) Calculate the air outlet radius R i The equivalent length increment of the tunnel model body at time:

[0077] a) Change the right side of formula (3) Moving to the left, we obtain formula (4):

[0078]

[0079] b) The left side of formula (4) Moving to the right, we obtain formula (5):

[0080]

[0081] c) Changes in the outlet area will cause changes in local resistance. The local loss calculation formula is shown in formula (6):

[0082]

[0083] Where ξ is the local resistance coefficient;

[0084] d) Due to P f(i-0) =P m , we get formula (7):

[0085]

[0086] e) When the outlet area suddenly decreases, the corresponding local resistance coefficient ξ is expressed as shown in formula (8):

[0087]

[0088] Where A0 is the cross-sectional area of the air outlet when the main body of the tunnel model is not equipped with a regulating device. m 2 ;

[0089] A i—The air outlet radius is R i When the cross-sectional area of the air outlet is m 2 ;

[0090] g) Substitute formula A0, A i Substituting the calculation formula into formula (8) yields formula (9):

[0091]

[0092] h) Substituting formula (9) into formula (7) yields formula (10):

[0093]

[0094] The following is a specific embodiment:

[0095] The following data is an experimental measurement of a tunnel model in a laboratory.

[0096] Close all other air outlets, leaving only the air outlet required for the experiment, turn on the fan, and set the fan frequency to 20.8Hz. Other data remain unchanged. Open the control loops one by one and measure the control loop radius. The drag coefficient λ along the way is 0.0065, and the tunnel main length L0 = 10m. Substitute the above values into formula (10) for calculation. The calculation results are shown in Table 1 and Figure 4 shown.

[0097] Table 1

[0098]

Claims

1. A tunnel ventilation length simulation method, implemented using a tunnel ventilation length simulation device. The tunnel ventilation length simulation device comprises a tunnel model body and an adjustment device. The tunnel model body is a tubular structure, and the adjustment device is mounted at the end of the tunnel model body. The adjustment device comprises a plurality of adjustment rings, each having a different diameter. The adjustment rings are arranged sequentially according to their diameters, with adjacent adjustment rings coaxially connected, and the smaller diameter adjustment ring is positioned outside the larger diameter adjustment ring. The steps include: 1) Measure the radius of the air outlet and the wind speed at the air outlet in the initial state; 2) Remove the adjustment rings from the outside to the inside, and measure the radius of the air outlet and the wind speed at the air outlet after each removal until all the adjustment rings are removed; then count the radius of the air outlet from large to small as R i , i=0,1,2,3,……,n,n is the total number of adjustment rings; and the radius of the air outlet R i The anemometer is v i ; 3) Calculate the pressure loss P of the tunnel model body f : a) Take the air outlet radius R0 as the control group, where R0 is the original radius of the tunnel model body, and calculate the loss along the control group. The calculation formula is shown in formula (1): Where, P f(0) —Long-range loss when the outlet radius is R0, Pa; λ—along-the-line resistance coefficient, dimensionless number; ρ—air density in the tunnel, kg / m 3 ; D—inner diameter of the tunnel model body, D=2R0, m; v0—wind speed when the outlet radius is R0, m / s; L0—equivalent length of the tunnel model body when the outlet radius is R0, m; b) Calculate the outlet radius R i , i=1, 2, 3, ..., n, the loss along the way is calculated as shown in formula (2): Where, P f(i) —The air outlet radius is R i Loss along the way, Pa; L i —The air outlet radius is R i The equivalent length relative to the outlet radius R0, m; c) Calculate the outlet radius from R0 to R i , i=1, 2, 3, ..., n, the pressure loss consumed is calculated as shown in formula (3): Where, P f(i-0) —The air outlet radius changes from R0 to R i The pressure loss consumed when , Pa; △L i —The air outlet radius changes from R0 to R i The equivalent length increment of the tunnel model body at time , m; 4) Calculate the outlet radius R i The equivalent length increment of the tunnel model body at time: a) Change the right side of formula (3) Moving to the left, we obtain formula (4): b) The left side of formula (4) Moving to the right, we obtain formula (5): c) Changes in the outlet area will cause changes in local resistance. The local loss calculation formula is shown in formula (6): Where ξ is the local resistance coefficient; d) Due to P f(i-0) =P m , we get formula (7): e) When the outlet area suddenly decreases, the corresponding local resistance coefficient ξ is expressed as shown in formula (8): Where A0 is the cross-sectional area of the air outlet when the main body of the tunnel model is not equipped with a regulating device. m 2 ; A i —The air outlet radius is R i When the cross-sectional area of the air outlet is m 2 ; g) Substitute formula A0, A i Substituting the calculation formula into formula (8) yields formula (9): h) Substituting formula (9) into formula (7) yields formula (10):

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