Method for calculating air volume of tuyere through static pressure of main pipe

Abstract

The invention discloses a method for obtaining tuyere air volume through main pipe static pressure calculation, and belongs to the technical field of air volume calculation, and the method comprises the steps: obtaining a relational expression of an outflow angle alpha and a flow coefficient mu of a target tuyere after an air system is simulated through finite element analysis software, and installing a pressure transmitter at a to-be-measured point of a main pipe in front of each tuyere, static pressure of each to-be-measured point is read through an electric signal of the pressure transmitter, the total air volume of the system is obtained, and finally the outflow air volume of each air opening is calculated. The relation between the flow coefficient mu and the outflow angle alpha is established, no dynamic pressure needs to be measured, all static pressure measuring points are located on the main pipe, the flow of each air opening can be obtained finally, the composition of an air system is basically not changed, only the static pressure transmitter is additionally arranged, and the resistance influence on the air system is small; precision is high and measurement is convenient; the static pressure transmitter directly outputs electric signals, field reading is not needed, and debugging and later operation and maintenance are facilitated.

Description

Technical Field

[0001] The invention belongs to the technical field of air volume calculation, and in particular relates to a method for obtaining the air volume of an air outlet by calculating the static pressure of a main pipe. Background Art

[0002] In ventilation and dust removal projects, it is necessary to measure and adjust the wind pressure, wind speed and air volume in the system to ensure that the system can work under normal operating conditions. Traditional air volume measurement methods, such as thermal anemometers, directly measure the average wind speed of the duct section. In some cases, such as when measuring on site, the distance between the pipes is very short, and it is not easy to find a relatively stable measurement section; it is difficult to measure flow using the dynamic pressure method. It is necessary to measure the dynamic pressure at multiple points on the section, calculate the root mean square, and then convert the flow rate to obtain the air volume. This method has high accuracy, but the process is more cumbersome than thermal anemometer measurement; there are currently a small number of static pressure methods for measuring air volume. They need to add additional resistance parts in the air duct, and then calculate the air volume of the air duct through the pressure difference on both sides of the resistance part, but this method increases the resistance of the system and cannot measure the air volume of short air ducts. It is obviously not suitable for engineering applications.

[0003] Therefore, it is necessary to propose a method for calculating the air volume of the tuyere by the static pressure of the main pipe to solve the above problem. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide a method for calculating the air volume at the air outlet through the static pressure of the main pipe, which basically does not change the composition of the wind system, only adds a static pressure transmitter, and has little effect on the resistance of the wind system; it has high accuracy and avoids measuring any wind speed, and the static pressure measuring points are all set on the stable section of the main pipe; it is convenient to measure; the static pressure transmitter directly outputs electrical signals, does not require on-site readings, and is convenient for debugging and later operation and maintenance.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention provides a method for calculating the air volume of an air outlet by using the main pipe static pressure, comprising the following steps:

[0007] S1: Install a pressure transmitter at the main pipe test point in front of each air outlet, then turn on the fan and directly read the total air volume L of the fan. 01 , during the operation of the fan, the static pressure of each point to be measured is read through the electrical signal of the pressure transmitter;

[0008] S2: Use Fluent analysis software to perform finite element simulation analysis on the outlet flow angle α and flow coefficient μ of the tuyere, obtain the outlet flow angle α and flow coefficient μ of the target tuyere, and fit to obtain the following relationship:

[0009] μ n =k nα+c n

[0010] In the formula, μ n is the flow coefficient of the nth air outlet, α is the outflow angle, k n and c n is a constant;

[0011] S3: Calculate the outflow volume L of each air outlet by the following formula n :

[0012]

[0013] In the formula, p jn is the static pressure of the point to be measured in front of the nth tuyere, f n is the cross-sectional area of ​​the main pipe in front of the nth tuyere, L 0n is the remaining air volume of the main pipe before the nth air outlet, S n is the area of ​​the nth tuyere, and ρ is the density of air.

[0014] Furthermore, the outflow angle α is calculated by the following formula:

[0015]

[0016] Where P j is the static pressure of the main pipe before the tuyere, P d is the initial dynamic pressure of the main pipe.

[0017] Furthermore, the remaining air volume L of the main pipe before the nth air outlet 0n Calculated by the following formula:

[0018] L 0n =L 0(n-1) -L n-1 , n ≥ 2

[0019] Where, L 0(n-1) is the remaining air volume of the main pipe before the n-1th air outlet, L n-1 is the outflow volume of the n-1th air outlet; when n=1, the residual air volume L of the main pipe before the first air outlet 0n is the total air volume of the fan L 01 .

[0020] Furthermore, the total air volume of the fan Where f is the cross-sectional area of ​​the main pipe before the air outlet, p1 and p2 are the static pressures of the points to be measured before and after the first valve after the fan, and ξ is the local resistance coefficient of the first valve after the fan.

[0021] The beneficial effects of the present invention are:

[0022] The present invention quantifies the relationship between the flow coefficient μ of the air outlet and the outflow angle α μ=kα+c through experiments or simulations, without measuring any dynamic pressure, and all the static pressure measurement points are on the main pipe, but the flow of each air outlet can be obtained in the end; compared with the existing small number of static pressure methods for measuring air volume, they need to add additional resistance parts in the air duct, and then pass the pressure difference on both sides of the resistance part to discharge the air volume of the air duct. However, this method increases the resistance of the system, which is obviously not suitable for engineering applications, and cannot measure the air volume of short air ducts, such as the terminal air volume in this scheme. This scheme basically does not change the composition of the wind system, only adds a static pressure transmitter, which has little effect on the resistance of the wind system; high accuracy, avoiding the measurement of any wind speed, and the static pressure measurement points are all set on the stable section of the main pipe; good economic benefits, the pressure is measured by the static pressure transmitter, and the measurement is convenient; the static pressure transmitter directly outputs electrical signals, does not require on-site readings, and is convenient for debugging and later operation and maintenance; the application range is wide and the ductility is high. For the terminals of the same type and size, only one experiment / simulation is required, and it is applicable in any scenario.

[0023] Other advantages, objectives and features of the present invention will be described in the following description and will be apparent to those skilled in the art to some extent, or those skilled in the art may be taught from the practice of the present invention. The objectives and other advantages of the present invention may be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to make the purpose, technical solution and beneficial effects of the present invention clearer, the present invention provides the following drawings for illustration:

[0025] Figure 1 1 is a relationship diagram between the flow coefficient μ and the outflow angle α of the 200mm*200mm tuyere with a 100mm baffle in the embodiment of the present invention. DETAILED DESCRIPTION

[0026] The present invention provides a method for calculating the air volume of an air outlet by using the main pipe static pressure, comprising the following steps:

[0027] S1: Install a pressure transmitter at the main pipe test point in front of each air outlet, then turn on the fan and directly read the total air volume L of the fan. 01 , during the operation of the fan, the static pressure of each point to be measured is read through the electrical signal of the pressure transmitter;

[0028] in, In the formula, f is the cross-sectional area of ​​the main pipe before the air outlet, p1 and p2 are the static pressures of the points to be measured before and after the first valve after the fan, and ρ is the density of the air;

[0029] S2: Determine the relationship between the flow coefficient μ and the outflow angle α of each air outlet of the air duct through simulation, and determine the local resistance coefficient ξ of the first valve after the fan.

[0030] μ n =k n α+c n

[0031] In the formula, μ n is the flow coefficient of the nth air outlet, α is the outflow angle, k n and c n is a constant (measured through simulation);

[0032] The specific simulation steps include: firstly, modeling the wind system; then, using Fluent, after specifying the boundary conditions of the wind system, finite element simulation analysis is performed on the flow rate of the tuyere, the static pressure of the main pipe in front of the tuyere, the outflow angle α of the tuyere and the flow coefficient μ, and a scatter plot of the target tuyere μ and α is obtained, and finally fitting is performed to obtain the above relationship; Figure 1 Taking a 200mm*200mm air outlet with a 100mm baffle as an example, the relationship is μ=0.4534α+0.2241.

[0033] in, P j is the static pressure of the main pipe before the tuyere, P d is the dynamic pressure; then we only need to know the initial dynamic pressure of the main pipe (i.e. the initial air volume of the fan), then we can get the outflow angle of the first air outlet, and then calculate, finally calculate the air volume of the first air outlet, and also get the remaining air volume of the main pipe after the first air outlet; and so on, we can calculate the air volume of each air outlet;

[0034] S3: Calculate the outflow volume L of each air outlet by the following formula n :

[0035]

[0036] In the formula, p jn is the static pressure of the point to be measured in front of the nth tuyere, f n is the cross-sectional area of ​​the main pipe in front of the nth tuyere, L 0n is the remaining air volume of the main pipe before the nth air outlet, S n is the area of ​​the nth tuyere, ρ is the density of air;

[0037] Among them, L 0n =L 0(n-1) -L n-1 , n≥2; where L 0(n-1) is the remaining air volume of the main pipe before the n-1th air outlet, L n-1is the outflow volume of the n-1th air outlet; when n=1, the residual air volume L of the main pipe before the first air outlet 0n is the total air volume of the fan L 01 .

[0038] This scheme quantifies the relationship between the flow coefficient μ of the air outlet and the outflow angle α μ=kα+c through experiments or simulations. It does not need to measure any dynamic pressure, and all static pressure measurement points are on the main pipe, but the flow of each air outlet can be obtained in the end. Compared with the existing small number of static pressure methods for measuring air volume, they need to add additional resistance parts in the air duct, and then pass the pressure difference on both sides of the resistance part to discharge the air volume of the air duct. However, this method increases the resistance of the system, which is obviously not suitable for engineering applications, and cannot measure the air volume of short air ducts, such as the terminal air volume in this scheme. This scheme basically does not change the composition of the wind system, but only adds a static pressure transmitter, which has little effect on the resistance of the wind system; it has high accuracy, avoids measuring any wind speed, and the static pressure measurement points are set on the stable section of the main pipe; it has good economic benefits, and the pressure is measured by the static pressure transmitter, which is convenient for measurement; the static pressure transmitter directly outputs electrical signals, does not require on-site readings, and is convenient for debugging and later operation and maintenance; it has a wide range of applications and high ductility. For terminals of the same type and size, only one experiment / simulation is required, and it is applicable in any scenario.

[0039] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. A method for calculating the air volume of the tuyere by the static pressure of the main pipe, characterized in that: The following steps are involved: S1: Install a pressure transmitter at the main pipe test point in front of each air outlet, then turn on the fan and directly read the total air volume L of the fan. 01 , during the operation of the fan, the static pressure of each point to be measured is read through the electrical signal of the pressure transmitter; S2: Use Fluent analysis software to perform finite element simulation analysis on the outlet flow angle α and flow coefficient μ of the tuyere, obtain the outlet flow angle α and flow coefficient μ of the target tuyere, and fit to obtain the following relationship: m n =k n a+c n In the formula, μ n is the flow coefficient of the nth tuyere, α is the outflow angle, k n and c n is a constant; S3: Calculate the outflow volume L of each air outlet by the following formula n : In the formula, p jn is the static pressure of the point to be measured in front of the nth tuyere, f n is the cross-sectional area of ​​the main pipe in front of the nth tuyere, L 0n is the remaining air volume of the main pipe before the nth air outlet, S n is the area of ​​the nth tuyere, and ρ is the density of air.

2. The method for calculating the air volume of the tuyere by the main pipe static pressure according to claim 1, characterized in that: The outflow angle α is calculated by the following formula: Where P j is the static pressure of the main pipe before the tuyere, P d is the initial dynamic pressure of the main pipe.

3. The method for calculating the air volume of the tuyere by the main pipe static pressure according to claim 1, characterized in that: The remaining air volume L of the main pipe before the nth air outlet 0n Calculated by the following formula: L On =L 0(n-1) -L n-1 ,n≥2 Where, L 0(n-1) is the remaining air volume of the main pipe before the n-1th air outlet, L n-1 is the outflow volume of the n-1th air outlet; when n=1, the residual air volume L of the main pipe before the first air outlet 0n is the total air volume of the fan L 01 .

4. The method for calculating the air volume of the tuyere by the main pipe static pressure according to claim 1, characterized in that: Total air volume of the fan Where f is the cross-sectional area of ​​the main pipe before the air outlet, p1 and p2 are the static pressures of the points to be measured before and after the first valve after the fan, and ξ is the local resistance coefficient of the first valve after the fan.

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