Method for determining air flow and fan parameters along the leaky duct with fans in series with intervals

Abstract

The present invention relates to the technical field of construction tunnel ventilation systems, and in particular to a method for determining the air supply volume and fan parameters along the way when fans are connected in series at intervals on a leaky duct. The method comprises the following steps: providing a first fan, a first leaky duct, and a second fan in series to form a combined air supply device; calculating a pressure rise and air volume variation curve of the combined air supply device, as well as a combined flow resistance and air volume variation curve of the second leaky duct and the tunnel; determining the working point of the combined air supply device by the intersection of the two curves; and further determining the operating parameters of the first and second fans, the air supply volume along the way of the leaky duct, and the air supply volume at the end of the second leaky duct. By accurately calculating the air supply volume and fan operating parameters, the present invention achieves efficient optimization of the construction tunnel ventilation system, significantly reduces energy consumption, and improves the end-point air supply effect, making it suitable for ventilation needs in complex tunnel construction environments.

Description

Technical Field

[0001] The present invention relates to the technical field of construction tunnel ventilation systems, and in particular to a method for determining the air supply volume and fan parameters along a leaky duct when fans are connected in series at intervals. Background Art

[0002] In construction tunnels, due to the complex construction environment and long-distance ventilation requirements, duct leakage becomes a key issue affecting the air supply at the end of forced-flow ventilation ducts. Insufficient air supply at the end of the ducts negatively impacts the air quality of the construction environment. By installing fans in series at regular intervals along the leaking ducts, the air supply capacity and coverage of the forced-flow ventilation system can be significantly improved. Accurately determining the air supply at the end of the ducts and fan operating parameters is crucial for assessing and improving the quality of the construction environment and reducing fan energy consumption.

[0003] The existing technology often uses a single fan or two fans installed in series at the beginning of the air duct to achieve air supply, which is different from the installation position of the first and second fans in this patent. The existing technology fails to fully consider the comprehensive performance of multiple fans connected in series at a certain distance and the influence of duct leakage. The calculation method of the air supply volume at the end of the air duct and the fan operating parameters is not suitable for the situation of this patent, resulting in the following defects:

[0004] It is impossible to accurately calculate the air supply volume at the end of the second leaky duct based on the progress of construction, resulting in the inability to evaluate whether the air supply volume meets the air volume requirements of tunnel construction; it is impossible to accurately evaluate the operating parameters of the first and second fans based on the progress of construction, resulting in low fan operating efficiency and excessively high operating energy consumption; it is impossible to optimize the fan settings and fan spacing based on the progress of construction to meet the terminal air supply volume requirements and reduce the fan operating energy consumption. Summary of the Invention

[0005] In response to the many problems existing in the above-mentioned prior art, the present invention provides a method for determining the air supply volume and fan parameters along the leaky duct under the condition of fans being connected in series at intervals. The present invention connects a correction fan formed by a first fan and a first leaky duct and a second fan in series to form a combined air supply device, dynamically calculates the lift pressure and air volume change curve of the combined air supply device, and the intersection with the joint flow resistance and air volume change curve of the second leaky duct and the tunnel, determines the working point of the combined air supply device, and further accurately calculates the air supply volume along the leaky duct and the operating parameters of the first fan and the second fan, evaluates whether the air supply volume at the end of the duct meets the required air volume of the tunnel, and evaluates the operating energy consumption of the fan at the same time; based on this, further optimizes the setting of the fan and the spacing between the fans, reduces the operating energy consumption of the fan and improves the air supply effect at the end.

[0006] A method for determining the air supply volume and fan parameters along a leaky duct with fans connected in series at intervals, comprising the following steps:

[0007] A combined air supply device is provided for supplying air, wherein the combined air supply device is composed of a first fan, a first air leakage duct, and a second fan connected in series, wherein the first fan and the first air leakage duct are combined to form a correction fan;

[0008] Calculate the pressure rise and air volume variation curve of the combined air supply device, and calculate the combined flow resistance and air volume variation curve of the second air leakage duct and the tunnel;

[0009] The working point of the combined air supply device is determined by the intersection of the curve of the pressure rise and air volume of the combined air supply device and the curve of the combined flow resistance and air volume of the second air leakage duct and the tunnel;

[0010] According to the working point of the combined air supply device, the operating parameters of the first and second fans, the air supply volume along all the leaky air ducts, and the air supply volume at the end of the second leaky air duct are determined.

[0011] Preferably, the first leaky duct and the second leaky duct are provided with a leakage point at fixed intervals along the length direction to simulate the leakage characteristics of the air supply duct, and the fixed distances of the leakage points are dynamically adjusted according to the construction environment.

[0012] Preferably, the number, distribution and leakage amount of the leakage points of the first leaky air duct and the second leaky air duct are determined by analyzing the air circulation requirements of the construction tunnel and the fluid mechanics parameters of the leaky air duct and the tunnel.

[0013] Preferably, the pressure-lift and air volume variation curve of the combined air supply device is obtained by superimposing the pressure-lift and air volume variation curve of the correction fan and the pressure-lift and air volume variation curve of the second fan.

[0014] Preferably, the variation curve of the boost pressure and air volume of the modified fan is determined by the following steps:

[0015] Calculating the changing relationship between the flow resistance and the air volume of the first leaky air duct;

[0016] Determining the lift pressure of the correction fan according to the lift pressure of the first fan minus the flow resistance of the first leaky duct;

[0017] Determining the air volume of the correction fan according to the air volume of the first fan minus the total air leakage volume of the first leaky duct;

[0018] The air volume of the first fan is changed, and the calculation is repeated to obtain a change curve of the boost pressure and air volume of the modified fan.

[0019] Preferably, the variation curve of the combined flow resistance and air volume of the second leaky air duct and the tunnel is determined by adding the flow resistance of the second leaky air duct and the flow resistance of the tunnel.

[0020] Preferably, the flow resistance of the first leaky air duct and the second leaky air duct is obtained by comprehensively calculating the leakage volume of each leakage point along the way and the changes in the air volume, air density, duct diameter, duct roughness and local resistance coefficient along the duct.

[0021] Preferably, the operating parameters of the first fan and the second fan include air volume, boost pressure, power and efficiency, and the operating parameters are determined by the performance curves of the first fan and the second fan and the air volume of the first fan and the second fan; the air volume of the first fan and the second fan is determined by the correspondence with the working point of the combined air supply device.

[0022] Preferably, the distance between the first fan and the second fan and the settings of the first fan and the second fan are dynamically adjusted according to the progress of construction, and the dynamic adjustment is optimized based on the operating parameters of the first fan and the second fan and the air supply volume at the end of the second leakage duct.

[0023] Preferably, the air volume along all leaky ducts is determined by subtracting the air leakage volume at the leakage points along the way from the air volume of the first fan. The air volume at the end of the second leaky duct is determined by subtracting the sum of the air leakage volume at each leakage point along all leaky ducts from the air volume of the first fan.

[0024] Compared with the prior art, the advantages and beneficial effects of the present invention are:

[0025] The present invention achieves accurate determination of the combined air supply device operating point, the first fan operating point, and the second fan operating point by dynamically calculating the change curve of the boost pressure and air volume of the combined air supply device, as well as the change curve of the combined flow resistance and air volume of the second air leakage duct and the tunnel, thus solving the problem of the inability to accurately predict in the prior art.

[0026] The present invention dynamically adjusts the settings of the first and second fans and the distance between the fans according to the progress of construction, thereby reducing the operating costs of the fans.

[0027] The present invention accurately calculates the air supply volume at the end of the second leaky air duct and compares it with the air volume required for the construction tunnel, thereby achieving an evaluation of the effectiveness of long-distance air supply;

[0028] The present invention simulates the air circulation characteristics in a complex construction environment and improves the adaptability and stability of the air supply system;

[0029] The calculation method adopted in the present invention can be extended to the case where three or more fans are connected in series on a leaky duct at intervals. Correspondingly, the leaky duct can be divided into a first leaky duct, a second leaky duct, a third leaky duct, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram of the process of the present invention;

[0031] Figure 2 This is a schematic diagram of the calculation principle of the fans in series ventilation in the present invention;

[0032] Figure 3 A diagram for determining the pressure rise and air volume change curves of the combined air supply device of the present invention;

[0033] Figure 4 This is a diagram for determining the working point of the combined air supply device, the working point of the first fan, and the working point of the second fan in the present invention.

[0034] Figure 5 A diagram showing changes in air volume along the leaky duct in the present invention. DETAILED DESCRIPTION

[0035] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present disclosure. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present disclosure. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present disclosure.

[0036] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprise," "include," etc. used herein indicate the presence of the features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0037] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0038] like Figure 1 As shown, a method for determining the air supply volume and fan parameters along a leaky duct with fans connected in series at intervals includes the following steps:

[0039] (1) Division of calculation segments

[0040] In the construction tunnel pressure ventilation system, the first fan and the second fan are connected in series at a certain distance to supply air; draw a calculation diagram ( Figure 2 ) to determine the location of the air leakage point of the pipeline; along the air supply direction, according to the location of the air leakage point, all the air leakage pipelines are numbered as (1), ..., (I), ..., (N) calculation sections in sequence, where the first fan is located outside the (1) section, and the second fan is located between the (J) and (J+1) sections; along the direction from the working face to the tunnel entrance, the tunnels are numbered as (0), (1), ..., (N) calculation sections in sequence.

[0041] (2) Calculation of air volume in the calculation section

[0042] The air volume leaked through each leakage point along the first and second leakage ducts is expressed as q l The air volume along the first and second leaky ducts is expressed as q d , the wind volume along the tunnel is expressed as q t ; They are respectively represented as follows:

[0043] q l =(q l,1 ,…,q l,I ,…q l,N-1 )

[0044] q d =(q d,1 ,…,q d,I ,…q d,N )

[0045] q t =(q t,0 ,…,q t,N-I+1 ,…q t,N )

[0046] Where q l,I is the air leakage volume of any section of the leaking duct (expressed as section (I)), q d,I is the air supply volume of any section of the leaky duct (indicated by section (I)), q t,N-I+1 It is the air volume of the tunnel section (expressed as (N-I+1) section) corresponding to any section of the above-mentioned leaking duct.

[0047] Assume that the duct leakage coefficient is k d , determine the air supply volume and air leakage volume of any section of the leaking duct (represented by section (I)) in turn:

[0048] q d,I =q f,1 (1-k d ) I

[0049] q l,I =q f,1 k d (1-k d ) I

[0050] where q f,1 It is the air volume of the first fan installed at the entrance of the ventilation duct.

[0051] Assuming that the leaked air is fully mixed with the air in the tunnel and flows to the tunnel exit, the air volume in the (N-I+1) section of the tunnel is determined according to the law of conservation of mass:

[0052] q t,N-I+1 =q f,1 (1-k d ) I

[0053] According to the air supply volume of the leakage duct (N) section, determine the air supply volume q at the end of the second leakage duct d,w :

[0054] q d,w =q d,N =q f,1 (1-k d ) N

[0055] (3) Determination of the flow resistance-air volume curve of the first air leakage duct

[0056] Given the air volume of the first fan q f,1 , considering the flow resistance along the way and the local resistance, the flow resistance of the first leaky duct is calculated as follows:

[0057]

[0058] Among them, ⊿P d1 S is the flow resistance of the first air leakage duct. d1 is the flow impedance of the first leaky duct. D d is the equivalent diameter of the first leaky duct. ρ is the air density. d is the length of each calculated section of the leaky duct. in is the local resistance coefficient at the inlet of the first air leakage duct. d λ is the local resistance coefficient of the local resistance points such as the diameter change and the bend in the first air leakage duct (located in the (O1) section). d is the resistance coefficient along the leaky duct.

[0059] Change the air volume q of the first fan f,1 Repeat the above calculation to get the flow resistance-air volume curve of the first air leakage duct, see Figure 3 .

[0060] (4) Determination of the combined flow resistance-air volume change curve of the second air leakage duct and tunnel

[0061] The combined flow resistance of the second leaky duct and tunnel is:

[0062]

[0063] Among them, ⊿P d2 is the flow resistance of the second leaky duct. t is the flow resistance of the tunnel. d2+t D is the combined flow resistance of the second leaky duct and tunnel. d and D t are the equivalent diameters of the second air leakage duct and the tunnel respectively. ρ is the air density. d is the length of each calculation section of the air leakage duct and tunnel (except section (0)). l0 is the length of section (0) of the tunnel, i.e., the distance between the working face and the outlet of the second air leakage duct. out is the local resistance coefficient of the second air leakage duct outlet or tunnel outlet. d ζ is the local resistance coefficient at the local resistance points such as the diameter change and bend in the second air leakage duct (located in the (O2) section). t is the local resistance coefficient at the local resistance point in the tunnel (located in the (S) section). d and λ t is the resistance coefficient along the second air leakage duct and tunnel. f,2 is the air volume of the second fan, calculated as follows:

[0064] q f,2 =q f,1 (1-k d ) J

[0065] Change the air volume q of the first fan f,1 Repeat the above calculation to obtain the combined flow resistance-air volume curve of the second leaky duct and tunnel, see Figure 3 .

[0066] (5) Determination of the pressure-air volume change curve of the combined air supply device

[0067] like Figure 2 As shown, the combined air supply device is to install the first fan outside the inlet of the first leaky duct, and the second fan is separated by a certain air duct section (length L d1 =Jl d ) is connected in series with the first fan, so the first fan and the first leaky air duct can be connected in series as a whole to form a correction fan; the correction fan and the second fan are connected in series as a whole to form a combined air supply device.

[0068] In a specific embodiment, based on the technical parameters of the fan manufacturer, the following relationship is regressed to obtain the pressure-air volume change curves of the first fan and the second fan, see Figure 3 .

[0069] ΔP f,1 =f1(q f,1 )

[0070] ΔP f,2 =f2(q f,2 )

[0071] like Figure 3 As shown, assuming that the working point of the first fan is point A and the air volume is q f,1 , then the corresponding first fan boost pressure can be determined to be ΔP A =ΔP f,1 =f1(q f,1 ).

[0072] According to the flow resistance-air volume curve of the first air leakage duct, and the air volume of the first fan is q f,1 , we can determine the flow resistance of the first leaky duct to be

[0073] According to the following formula, the total air leakage of the first air leakage duct q can be obtained: l,d1 :

[0074]

[0075] Corrected fan outlet ( Figure 3 Air volume (q) at point C C ) and pressure rise (ΔP C ) can be calculated as:

[0076] q C =q f,1 -q l,d1

[0077] ΔP C =ΔP f,1 -ΔP d1

[0078] There is no air leakage between the correction fan and the second fan, and the two are connected in series to form a combined air supply device. According to the air volume of the correction fan, the working point of the second fan is determined to be Figure 3 Point D, the air volume of the second fan (q f,2 )for:

[0079] q f,2 =q D =q C =q f,1 -q l,d1

[0080] According to the air volume of the second fan and the pressure-air volume curve, the pressure rise of the second fan (ΔP f,2 ):

[0081] ΔP f,2 =ΔP D =f2(q f,2 )

[0082] Combined air supply device outlet ( Figure 3 The air volume at point E) is equal to the air volume of the correction fan and the second fan, so:

[0083] q E =q C =q D =q f,1 -q l,d1

[0084] The boost pressure of the combined air supply device is:

[0085] ΔP E =ΔP C +ΔP D =ΔP f,1 -ΔP d1 +ΔP f,2

[0086] Change the air volume at point A (q f,1 ), repeat the above calculation steps to get the corresponding q C and ΔP C The corresponding q can be obtained E and ΔP E Value. ΔP C -q C The change curve of is the modified fan lift pressure-air volume change curve, see Figure 3 ΔP E -q E The change curve of is the pressure-air volume change curve of the combined air supply device, see Figure 3 .

[0087] (6) Determination of the working point of the combined air supply device

[0088] The pressure-air volume change curves of the first fan, the second fan, and the combined air supply device, as well as the combined flow resistance-air volume change curves of the second air leakage duct and the tunnel are plotted on Figure 4 The intersection of the two curves ( Figure 4 Point F) is the working point of the combined air supply device.

[0089] (7) Determination of the operating parameters of the second fan

[0090] Because the air volume of the second fan is equal to that of the combined air supply device, Figure 4 The intersection of the vertical line through point F and the second fan's pressure-air volume curve is the working point of the second fan (F2). The intersection of the vertical line through point F2 and the horizontal axis determines the air volume of the second fan as q f,2 According to the performance curve of the second fan and the air volume of the second fan, the boost pressure, power and efficiency of the second fan can be obtained.

[0091] (8) Determination of the operating parameters of the first fan

[0092] According to the air volume of the second fan (q f,2 ) and the total air leakage of the first air leakage duct (q l,d1 ), we can get the air volume of the first fan (q f,1 ):

[0093] q f,1 =q f,2 +q l,d1

[0094] like Figure 4 As shown, according to the air volume of the first fan (q f,1 ), the working point of the first fan can be determined ( Figure 4 Click F1).

[0095] The boost pressure, power and efficiency of the first fan can be obtained according to the performance curve of the first fan and the air volume of the first fan.

[0096] (9) Determination of air supply volume along the leaking duct

[0097] According to the air volume of the first fan (q f,1 ), and the duct leakage coefficient k d , calculate the air supply volume of any calculated section of the leaky duct in sequence:

[0098] q d,I =q f,1 (1-k d ) I

[0099] The air volume along the leaking duct can be further obtained:

[0100] q d =(q d,1 ,…,q d,I ,…q d,N )

[0101] Changes in air volume along the leaking duct are shown in Figure 5 .

[0102] (10) Determination of air supply volume at the end of the second leaky duct

[0103] According to the air supply volume of the leakage duct (N) section, determine the air supply volume q at the end of the second leakage duct d,w

[0104] q d,w =q d,N =q f,1 (1-k d ) N

[0105] (11) Evaluation of ventilation effectiveness during construction

[0106] During the construction period, as the construction progressed, the length of the air supply duct continued to increase. According to different air supply duct lengths, the above calculations (1)-(10) were repeated to obtain the operating parameters of the first and second fans, as well as the air supply volume at the end of the second leaky duct.

[0107] Based on the fan operating parameters, the fan's operating energy consumption level can be judged.

[0108] Comparing the air volume supplied at the end of the second leaky duct with the required air volume in the tunnel can determine whether forced ventilation can meet the ventilation needs of tunnel construction:

[0109] When the air volume at the end of the second leaky duct exceeds the tunnel's required air volume, forced-in ventilation can meet the tunnel's ventilation needs. When the air volume at the end of the second leaky duct is less than the tunnel's required air volume, forced-in ventilation cannot meet the tunnel's ventilation needs. If forced-in ventilation does not meet the tunnel's ventilation needs, or the fan's operating energy consumption is too high, the following adjustments can be made: Change the configuration of the first and second fans, such as fan speed, fan blade mounting angle, and fan capacity. Change the distance between the first and second fans.

[0110] Repeat the above calculations (1)-(10) to determine the operating parameters of the first and second fans and the air supply volume at the end of the second leaky duct. Continue the evaluation until the ventilation requirements are met while controlling the fan energy consumption.

[0111] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware.

[0112] The above are merely embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application should be included within the scope of the claims of the present application.

Claims

1. A method for determining the air flow rate and fan parameters along a leaky duct with fans connected in series at intervals, characterized in that: The following steps are involved: A combined air supply device is provided for supplying air, wherein the combined air supply device is composed of a first fan, a first air leakage duct, and a second fan connected in series, wherein the first fan and the first air leakage duct are combined to form a correction fan; Calculate the pressure rise and air volume change curve of the combined air supply device, divide the leaky duct into a first leaky duct and a second leaky duct in sequence, the first leaky duct and the second leaky duct being adjacent to each other, and calculate the combined flow resistance and air volume change curve of the second leaky duct and the tunnel; The pressure rise and air volume variation curve of the combined air supply device is obtained by superimposing the pressure rise and air volume variation curve of the correction fan and the pressure rise and air volume variation curve of the second fan; The variation curve of the lift pressure and air volume of the correction fan is determined by the following steps: calculating the variation relationship between the flow resistance and air volume of the first leaky air duct; determining the lift pressure of the correction fan based on the lift pressure of the first fan minus the flow resistance of the first leaky air duct; determining the air volume of the correction fan based on the air volume of the first fan minus the total air leakage of the first leaky air duct; changing the air volume of the first fan and repeating the calculation to obtain the variation curve of the lift pressure and air volume of the correction fan; The working point of the combined air supply device is determined by the intersection of the curve of the pressure rise and air volume of the combined air supply device and the curve of the combined flow resistance and air volume of the second air leakage duct and the tunnel; A variation curve of the combined flow resistance and air volume of the second leaky air duct and the tunnel is determined by adding the flow resistance of the second leaky air duct and the flow resistance of the tunnel; According to the working point of the combined air supply device, the operating parameters of the first and second fans, the air supply volume along all the leaky air ducts, and the air supply volume at the end of the second leaky air duct are determined; The air supply volume at the end of the second leaky air duct is determined by subtracting the total air leakage volume of each leakage point along all the leaky air ducts from the air volume of the first fan.

2. The method according to claim 1, characterized in that The first leaky air duct and the second leaky air duct are provided with a leakage point at fixed intervals along the length direction to simulate the air leakage characteristics of the air supply duct. The fixed distances of the leakage points are dynamically adjusted according to the construction environment.

3. The method according to claim 2, characterized in that The number, distribution and leakage amount of the leakage points of the first leaky air duct and the second leaky air duct are determined by analyzing the air circulation requirements of the construction tunnel and the fluid mechanics parameters of the leaky air duct and the tunnel.

4. The method according to claim 1, wherein The flow resistance of the first leaky air duct and the second leaky air duct is obtained by comprehensively calculating the air leakage volume at each leakage point along the way and the air volume, air density, duct diameter, duct roughness and local resistance coefficient changes along the duct.

5. The method according to claim 1, wherein The operating parameters of the first fan and the second fan include air volume, boost pressure, power and efficiency. The operating parameters are determined by the performance curves of the first fan and the second fan and the air volume of the first fan and the second fan; the air volume of the first fan and the second fan is determined by the correspondence with the working point of the combined air supply device.

6. The method according to claim 5, characterized in that The distance between the first fan and the second fan and the settings of the first fan and the second fan are dynamically adjusted according to the progress of construction, and the dynamic adjustment is optimized based on the operating parameters of the first fan and the second fan and the air supply volume at the end of the second leaky duct.

7. The method according to claim 1, characterized in that The air supply volume along all leaking ducts is determined by subtracting the air leakage volume at the leakage point along the way from the air volume of the first fan.

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