Measurement optimization device and method for primary air multi-dimensional flow field of thermal power plant

Abstract

The invention relates to the technical field of thermal power plant primary air measurement, in particular to a thermal power plant primary air multi-dimensional flow field measurement optimization device and method.The thermal power plant primary air multi-dimensional flow field measurement optimization device comprises a baffling mixer, a flow guide plate, a porous flow equalizing plate and a measuring element which are located in a main air duct, and the baffling mixer, the flow guide plate, the porous flow equalizing plate and the measuring element are located on the upstream of the measuring element. The baffling mixer is arranged on the primary air inlet side of the main air duct and scatters primary air to achieve primary rectification. The guide plate is arranged at the main air duct elbow at the downstream of the baffling mixer and is used for guiding and reducing the resistance of the primary air to finish the second rectification; and the porous flow equalizing plate performs third rectification on the primary air at a position which is a certain distance away from the measuring element, and then the rectified primary air flows through the measuring element to realize air volume measurement, so that the accuracy of primary air volume measurement is improved.

Description

Technical Field

[0001] The invention relates to the technical field of primary wind measurement in thermal power plants, and in particular to a device and method for optimizing the measurement of multi-dimensional flow fields of primary wind in thermal power plants. Background Art

[0002] At present, the on-site layout of thermal power plants is becoming more and more compact, the mixing section of the coal mill inlet air duct is short, and the temperature field and velocity field of the cross section of the online primary air measurement element are unevenly distributed, resulting in inaccurate online primary air velocity and primary air temperature measurements, and ultimately inaccurate primary air volume measurements, and even the situation where the primary air volume and the cold and hot primary air damper damper change in the opposite direction, that is, when the cold and hot primary air damper is opened wide, the primary air volume becomes smaller, causing the coal mill inlet primary air volume measurement to have large deviations and violent fluctuations. There are still a large number of coal-fired boilers in China with distorted coal mill inlet air volume, which makes it impossible to accurately control the coal mill inlet air volume according to the primary air-coal ratio, greatly limiting the performance advantages of large-capacity and high-parameter units.

[0003] The most important factor affecting primary air measurement is the length of the fully developed section upstream and downstream of the measuring element cross section, which is generally required to be at least 5 times the equivalent diameter upstream and at least 2 times the equivalent diameter downstream. However, due to the compact layout of thermal power plants, there is often no such large space, which makes the temperature field and velocity field at the cross section of the primary air measuring element poor, and the primary air measurement error is large. The factors affecting primary air measurement are mainly: there are elbows upstream and downstream of the measuring element, the cold air inlet is too close to the measuring element (the cold and hot air are not fully mixed), and the hot primary air valve is too close to the measuring element. These factors can lead to inaccurate primary air volume measurement.

[0004] The velocity field and temperature field at the cross section of the current thermal power plant measurement element are extremely poor. Due to the small layout space on site, the mixing distance of the cold and hot primary air is extremely short, and it directly reaches the cross section of the measurement element after passing through the elbow, making the primary air volume measurement of the plant inaccurate. In addition, the hot primary air regulating valve is also very close to the measurement element. The hot primary air regulating valve has different disturbances to the primary air at different openings. When the hot primary air regulating valve is opened at a small degree, the primary air will deviate more to one side, resulting in inaccurate primary air measurement. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a device and method for optimizing the multi-dimensional flow field of primary wind in a thermal power plant in view of the deficiencies in the above-mentioned prior art, so as to solve the technical problem of inaccurate primary wind measurement.

[0006] The objective of the present invention is achieved by the following technical solutions: In a first aspect, the present invention provides a device for measuring and optimizing a multi-dimensional flow field of primary wind in a thermal power plant, comprising: a baffle mixer, a guide plate, a multi-hole flow equalizing plate, and a measuring element arranged in a main air duct; the baffle mixer, the guide plate, and the multi-hole flow equalizing plate are all arranged upstream of the measuring element; The deflector and mixer are arranged at the primary air inlet side of the main air duct, and are used to disperse the primary air in different directions to perform the first rectification; The guide plate is arranged at the elbow of the main air duct downstream of the baffle mixer, and is used to guide the primary air after the first rectification, reduce the resistance of the primary air flow, and obtain the primary air after the second rectification; The multi-hole flow equalizing plate is arranged at a set distance from the measuring element, and performs a third rectification on the primary wind flow field after the second rectification. The rectified wind flows sequentially pass through the measuring element to realize the measurement of the primary wind volume. As a further improvement of the present invention, a secondary air duct is provided on the primary air inlet side of the main air duct, and the cold primary air enters the main air duct through the secondary air duct and mixes with the hot primary air on the primary air inlet side of the main air duct to obtain mixed primary air.

[0007] As a further improvement of the present invention, a deflector mixer is arranged downstream of the secondary air duct inlet side, and the deflector mixer is composed of parallel deflection plates, two adjacent deflection plates are in opposite directions, and there is a set spacing between adjacent deflection plates.

[0008] As a further improvement of the present invention, the set spacing is an optimal spacing determined based on simulation calculations to balance resistance and flow field uniformity.

[0009] As a further improvement of the present invention, the guide plate is arranged at the elbow close to the measuring element side and is arranged parallel to the inner curvature of the elbow.

[0010] As a further improvement of the present invention, the porous flow equalizing plate is a flat plate with honeycomb holes, and the honeycomb holes are evenly arranged.

[0011] As a further improvement of the present invention, the porosity of the hole flow balancing plate is set between 60% and 75%.

[0012] As a further improvement of the present invention, the porous flow balancing plate is arranged 30-50 cm upstream of the measuring element.

[0013] As a further improvement of the present invention, the device also includes a hot primary air regulating gate, which is arranged upstream of the secondary air duct and whose direction is perpendicular to the direction of the deflection plate in the deflector mixer.

[0014] In a second aspect, the present invention provides a method for measuring and optimizing a multi-dimensional flow field of primary wind in a thermal power plant, which is implemented based on the above-mentioned device for measuring and optimizing a multi-dimensional flow field of primary wind in a thermal power plant, and comprises: After the primary air enters the main air duct, it passes through the deflector and mixer, which disperses the primary air in different directions to obtain the primary air after the first rectification; After the first rectification, the primary wind passes through the guide plate, and the primary wind is guided to reduce the resistance of the primary wind flow, thereby obtaining the primary wind after the second rectification; After the second rectification, the primary air is rectified for the third time through the porous flow equalizing plate, and then the air volume of the primary air is measured by the measuring element.

[0015] The beneficial effects of the present invention are as follows: the multi-dimensional flow field measurement and optimization device for primary wind in a thermal power plant of the present invention, through a baffle mixer, breaks up the primary wind in different directions at the primary wind inlet side of the main air duct for the first rectification, preliminarily changes the original chaotic inflow state of the primary wind, and improves the uniformity of the velocity of the entire section. The guide plate guides the primary wind after the first rectification at the elbow of the main air duct downstream of the baffle mixer, further optimizes the flow direction of the wind, reduces the flow resistance, and realizes the second rectification, reduces the resistance of the primary wind flow, and realizes the rectification of the primary wind airflow in the second plane dimension. The porous flow equalizing plate performs a third rectification on the primary wind flow field after the second rectification at a set distance from the measuring element. After these three continuous and targeted rectification operations, an extremely uniform flow field can be formed in front of the measuring element, which greatly improves the accuracy of subsequent air volume measurement. Because the uniform flow field can ensure that the state of the wind received by the measuring element is relatively consistent, the measurement error caused by the uneven flow field is reduced. The stable flow field avoids the measurement deviation caused by uneven conditions such as local wind speed being too fast or too slow, thereby achieving high-precision measurement of primary air volume.

[0016] Furthermore, the deflector mixer is composed of a structure in which adjacent deflecting plates are parallel and in opposite directions. When the primary air enters the deflector mixer from the downstream side of the secondary air duct inlet, the fluid flows between the adjacent deflecting plates. Since the direction of the deflecting plates changes alternately, the fluid constantly changes its flow direction. This process of repeatedly changing the flow direction will cause strong collisions, shearing and convection between different components inside the fluid. The set spacing between adjacent deflecting plates can constrain and guide the fluid. The flow of the fluid in these spacings can make the flow velocity distribution more uniform. In the absence of a deflector mixer, the fluid may have uneven flow velocity downstream of the secondary air duct inlet due to factors such as inlet conditions, and the deflector mixer can adjust this state.

[0017] Furthermore, this arrangement of the guide plate helps to make the fluid distribution at the elbow more uniform. The guide plate is arranged near the measuring element to ensure that the fluid after passing through the elbow can approach the measuring element in a relatively uniform state. Since the fluid flows in a direction parallel to the guide plate and the inner curvature of the elbow, the fluid unevenness caused by excessively fast or slow local flow velocity is avoided.

[0018] Furthermore, the porous flow equalizing plate with evenly arranged honeycomb holes can evenly disperse the fluid flowing through it. When the fluid passes through the porous flow equalizing plate, due to the even distribution of holes, the fluid is divided into multiple small streams, and these streams will recombine at a relatively uniform speed and direction after passing through the holes. Just like a sieve, the fluid that may have originally had speed and direction differences is combed into a uniform state. When the fluid passes through the honeycomb holes of the porous flow equalizing plate, its flow state will be adjusted. The honeycomb structure makes the flow path of the fluid more regular and reduces the large-scale turbulent structure in the fluid. Because the generation of turbulence is often caused by irregular flow of the fluid and large velocity gradient, the porous flow equalizing plate reduces the possibility of velocity gradient and irregular flow by allowing the fluid to pass through the holes in a more orderly manner.

[0019] Furthermore, accurate control of the flow rate of hot primary air is essential for maintaining the appropriate temperature. This vertically set damper can better meet the demand for hot primary air volume under different working conditions and improve the accuracy of hot primary air flow control. The vertically set hot primary air damper helps the hot primary air enter the baffle mixer in a more regular state. Because the damper can evenly guide the air to the baffle mixer, it avoids the situation where the air is deflected or the local flow rate is too high or too low when entering the baffle mixer. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 Schematic diagram of the structure of a multi-dimensional flow field measurement and optimization device for primary wind in a thermal power plant according to an embodiment of the present invention; Figure 2 is a schematic diagram of the structure of a baffle mixer in an embodiment of the present invention; Figure 3 Schematic diagram of a porous flow balancing plate in an embodiment of the present invention; In the figure, 1-baffle mixer; 2-porous flow equalizing plate; 3-measuring element; 4-coal mill inlet; 5-guide plate; 6-cold primary air; 7-hot primary air damper; 8-hot primary air. DETAILED DESCRIPTION

[0022] In order to make the purpose and technical solution of the present invention clearer and easier to understand, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. The specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0023] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, wherein the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0024] Example 1 like Figure 1-Figure 3 As shown, this embodiment provides a device for measuring and optimizing the multi-dimensional flow field of primary wind in a thermal power plant. Through the combination of the baffle mixer 1, the guide plate 5 and the porous flow equalizing plate 2, the primary wind flow field at the measuring element 3 is reorganized, the mixing of the cold and hot primary winds is accelerated, and the primary wind is rectified to improve the uniformity of the velocity field and the temperature field at the measuring element, and finally improve the accuracy of the primary air volume measurement. The following is a specific implementation method.

[0025] The measuring device comprises a baffle mixer 1, a guide plate 5, a multi-hole flow equalizing plate 2 and a measuring element 3 arranged in a main air duct. The baffle mixer 1, the guide plate 5 and the multi-hole flow equalizing plate 2 are all arranged upstream of the measuring element.

[0026] The deflector and mixer 1 is arranged at the primary air inlet side of the main air duct, and is used to disperse the primary air in different directions to perform the first rectification.

[0027] In this embodiment, a secondary air duct is provided on the primary air inlet side of the main air duct, and the cold primary air 6 enters the main air duct through the secondary air duct and mixes with the hot primary air 8 on the primary air inlet side of the main air duct to obtain mixed primary air.

[0028] The function of the baffle mixer 1 is mainly to disperse the primary air in different directions to increase the mixing degree of the primary air. The specific schematic diagram of the baffle mixer 1 is shown in FIG. Figure 2 As shown. When the cold primary air 6 is inserted into the port from one side and preliminarily mixed with the hot primary air 8, the mixing of the cold and hot primary air is poor at this time. The baffle mixer 1 divides the cold and hot primary air into many small streams, and breaks up the preliminarily mixed cold and hot primary air respectively, and guides them to flow in two directions. There will be obvious high-speed and low-speed airflow areas at the original cross section. After being broken up by the baffle mixer 1, the uniformity of the velocity of the entire cross section is improved, and the mixing degree of the cold and hot primary air is also improved, realizing the rectification of the primary airflow in the first plane dimension.

[0029] The baffle mixer is composed of parallel baffle plates, two adjacent baffle plates are in opposite directions, and there is a set spacing between adjacent baffle plates. The set spacing is the optimal spacing determined based on simulation calculations to balance resistance and flow field uniformity. Specifically, the baffle mixer is composed of a series of parallel baffle plates, such as Figure 2 As shown. After passing through the deflection plate, the airflow deflects to one side. The directions of two adjacent deflection plates are opposite. The distance between two adjacent deflection plates can be flexibly adjusted according to the actual situation on site. If the distance between two adjacent deflection plates is the closest (that is, close together), the airflow mixing effect is the best, but the relative resistance is the largest. The distance between two adjacent deflection plates can be farther, but the maximum distance is the width of the deflection plate. The farther the distance, the smaller the resistance, and the airflow mixing effect is relatively weaker.

[0030] In addition, the device also includes a hot primary air damper, which is arranged upstream of the secondary air duct. The direction of the deflection plate is usually perpendicular to the direction of the hot primary air damper. In the actual on-site layout, the primary air flow may deviate to one side, especially in a circular primary air duct. At this time, the direction of the deflection plate can be changed in different directions. The best angle is obtained through numerical simulation calculation.

[0031] The guide plate 5 is arranged at the elbow of the main air duct downstream of the baffle mixer, and is used to guide the primary wind after the first rectification, reduce the resistance of the primary wind flow, and obtain the primary wind after the second rectification. The guide plate 5 is arranged at the elbow close to the measuring element side, and is arranged parallel to the inner curvature of the elbow. The guide plate 5 in this embodiment is a plurality of arc plates arranged in parallel, and its arc is parallel to the inner curvature of the elbow, and can form a plurality of parallel channels in the bend.

[0032] The guide plate 5 at the elbow mainly plays the role of airflow guidance and resistance reduction. The primary air will deflect to one side after passing through the elbow. The guide plate 5 can prevent the deflection and reduce the resistance of the primary air flow, thereby realizing the rectification of the primary air flow in the second plane dimension.

[0033] The porous flow balancing plate 2 is arranged at a set distance from the measuring element 3, and performs a third rectification on the primary wind flow field after the second rectification. The rectified wind flows sequentially through the measuring element 3 to achieve the measurement of the primary wind volume.

[0034] In this embodiment, the primary air is rectified by the porous flow equalizing plate 2, which is a honeycomb plate with many holes. The uniformity of the velocity of the primary air after being rectified by the porous flow equalizing plate 2 will be significantly improved, realizing the rectification of the primary air flow in the third plane dimension.

[0035] The porous flow plate 2 is generally installed 30-50 cm upstream of the measuring element.

[0036] The porous flow plate 2 is Figure 3 As shown, a series of honeycomb holes are opened on a flat plate. The higher the porosity, the smaller the resistance and the weaker the relative rectification effect. The specific porosity requirement is also determined according to the actual situation on site. The requirements for balanced resistance and flow field uniformity are determined specifically through numerical simulation calculations. Numerical simulation calculations can construct a primary wind flow model close to the actual situation based on various parameters provided on site. Through the wind flow model, the flow field changes of the primary wind after passing through the porous flow equalizing plate under different porosities can be simulated, including indicators such as velocity distribution, pressure loss, and uniformity of the flow field. By analyzing and comparing these simulation results, the optimal porosity that meets the requirements of balanced resistance and flow field uniformity can be accurately determined. Generally speaking, the porosity of the porous flow equalizing plate is set between 60% and 75%.

[0037] The measuring device of this embodiment can realize adaptive flow field optimization under multiple working conditions with different primary air volumes, and improve the accuracy of air volume measurement under different working conditions of primary air. The corresponding resistance will increase by 300-400Pa, which is within an acceptable range.

[0038] In summary, the multi-dimensional flow field measurement and optimization device for the primary wind of a thermal power plant of this embodiment, through the baffle mixer, breaks up the primary wind in different directions on the primary air inlet side of the main air duct for the first rectification, preliminarily changes the original chaotic inflow state of the primary wind, and improves the uniformity of the velocity of the entire section. The guide plate guides the primary wind after the first rectification at the elbow of the main air duct downstream of the baffle mixer, further optimizes the flow direction of the wind, reduces the flow resistance, and realizes the second rectification, reduces the resistance of the primary wind flow, and realizes the rectification of the primary wind airflow in the second plane dimension. The primary wind flow field after the second rectification is rectified for the third time at a set distance from the measuring element through a porous flow equalizing plate. After these three continuous and targeted rectification operations, an extremely uniform flow field can be formed in front of the measuring element, which greatly improves the accuracy of subsequent air volume measurement. The uniform flow field ensures that the state of the wind received by the measuring element is relatively consistent, reducing the measurement error caused by uneven flow field. The stable flow field avoids the measurement deviation caused by uneven conditions such as local wind speed being too fast or too slow, thereby achieving high-precision measurement of primary air volume.

[0039] Example 2 According to the device for measuring and optimizing the multi-dimensional flow field of primary wind in a thermal power plant described in Example 1, this embodiment provides a method for measuring and optimizing the multi-dimensional flow field of primary wind in a thermal power plant, and the specific implementation method is as follows.

[0040] After the primary air enters the main air duct, it passes through the deflector and mixer, which disperses the primary air in different directions to obtain the primary air after the first rectification.

[0041] The deflector mixer is composed of a series of parallel deflection plates, such as Figure 2 After passing through the deflection plate, the airflow deflects to one side, and the directions of the two adjacent deflection plates are opposite. The distance between the two adjacent deflection plates can be flexibly adjusted according to the actual situation on site.

[0042] The deflecting plates and other components inside the deflector mixer will produce multiple interferences to the primary wind, causing the wind to constantly change direction as it passes through. The originally concentrated airflow is divided into many small tributaries, which interweave and collide with each other, making the primary wind more uniform in speed and direction, thereby obtaining the primary wind after the first rectification.

[0043] After the primary wind after the first rectification passes through the guide plate, the primary wind is guided to reduce the resistance of the primary wind flow, and the primary wind after the second rectification is obtained.

[0044] The guide plate at the elbow mainly plays the role of airflow guidance and resistance reduction. The primary air will deflect to one side after passing through the elbow. The guide plate can prevent the deflection and reduce the resistance of the primary air flow, thereby realizing the rectification of the primary air flow in the second plane dimension.

[0045] After the second rectification, the primary air is rectified for the third time through the porous flow equalizing plate, and then the air volume of the primary air is measured by the measuring element.

[0046] The primary air is rectified by a porous flow equalizing plate, which is a honeycomb plate with many holes. After the primary air is rectified by the porous flow equalizing plate, the uniformity of its velocity will be significantly improved, realizing the rectification of the primary air flow in the third plane dimension.

[0047] The higher the porosity of the honeycomb holes, the smaller the resistance and the weaker the relative rectification effect. The specific porosity requirements are determined based on the actual situation on site, while meeting the requirements of balanced resistance and flow field uniformity.

[0048] Therefore, the determination of porosity is usually achieved by numerical simulation. Numerical simulation can construct a primary wind flow model close to the actual situation based on various parameters provided on site. Through the wind flow model, the flow field changes of the primary wind after passing through the porous flow plate under different porosities can be simulated, including indicators such as velocity distribution, pressure loss, and uniformity of the flow field. By analyzing and comparing these simulation results, the optimal porosity that meets the requirements of balanced resistance and flow field uniformity can be accurately determined.

[0049] Finally, it should be noted that the above 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 with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A device for measuring and optimizing the multi-dimensional flow field of primary air in a thermal power plant, characterized in that: include: A baffle mixer, a guide plate, a multi-hole flow equalizing plate and a measuring element are arranged in the main air duct; the baffle mixer, the guide plate and the multi-hole flow equalizing plate are all arranged upstream of the measuring element; The deflector and mixer are arranged at the primary air inlet side of the main air duct, and are used to disperse the primary air in different directions to perform the first rectification; The guide plate is arranged at the elbow of the main air duct downstream of the baffle mixer, and is used to guide the primary air after the first rectification, reduce the resistance of the primary air flow, and obtain the primary air after the second rectification; The multi-hole flow equalizing plate is arranged at a set distance from the measuring element, and performs a third rectification on the primary wind flow field after the second rectification. The rectified wind flows sequentially pass through the measuring element to realize the measurement of the primary wind volume.

2. The device for measuring and optimizing the primary wind multi-dimensional flow field of a thermal power plant according to claim 1, characterized in that: A secondary air duct is provided on the primary air inlet side of the main air duct, and the cold primary air enters the main air duct through the secondary air duct and mixes with the hot primary air on the primary air inlet side of the main air duct to obtain mixed primary air.

3. The device for measuring and optimizing the primary wind multi-dimensional flow field of a thermal power plant according to claim 2, characterized in that: The deflector mixer is arranged downstream of the inlet side of the secondary air duct, and the deflector mixer is composed of parallel deflection plates, two adjacent deflection plates are in opposite directions, and there is a set interval between adjacent deflection plates.

4. The device for measuring and optimizing the primary wind multi-dimensional flow field of a thermal power plant according to claim 3 is characterized in that: The set spacing is an optimal spacing determined based on simulation calculations to balance resistance and flow field uniformity.

5. The device for measuring and optimizing the primary wind multi-dimensional flow field of a thermal power plant according to claim 1, characterized in that: The guide plate is arranged at the elbow close to the measuring element side and is arranged parallel to the inner curvature of the elbow.

6. The device for measuring and optimizing the primary wind multi-dimensional flow field of a thermal power plant according to claim 1, characterized in that: The porous flow balancing plate is a flat plate with honeycomb holes, and the honeycomb holes are evenly arranged.

7. The device for measuring and optimizing the primary wind multi-dimensional flow field of a thermal power plant according to claim 6, characterized in that: The porosity of the hole flow balancing plate is set between 60% and 75%.

8. The device for measuring and optimizing the primary wind multi-dimensional flow field of a thermal power plant according to claim 1 or 7, characterized in that: The porous flow balancing plate is arranged 30-50 cm upstream from the measuring element.

9. The device for measuring and optimizing the primary wind multi-dimensional flow field of a thermal power plant according to claim 3, characterized in that: The device also includes a hot primary air regulating door, which is arranged upstream of the secondary air duct and is arranged perpendicular to the direction of the deflection plate in the deflector mixer.

10. A method for measuring and optimizing the multi-dimensional flow field of primary wind in a thermal power plant, implemented based on the device for measuring and optimizing the multi-dimensional flow field of primary wind in a thermal power plant according to any one of claims 1 to 9, characterized in that: include: After the primary air enters the main air duct, it passes through the deflector and mixer, which disperses the primary air in different directions to obtain the primary air after the first rectification; After the first rectification, the primary wind passes through the guide plate, and the primary wind is guided to reduce the resistance of the primary wind flow, thereby obtaining the primary wind after the second rectification; After the second rectification, the primary air is rectified for the third time through the porous flow equalizing plate, and then the air volume of the primary air is measured by the measuring element.

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