Device for measuring nozzle speed of secondary air burner of power station boiler

Abstract

The utility model relates to the technical field of fluid velocity measurement, in particular to a velocity measuring device for a nozzle of a secondary air burner of a power station boiler, which comprises two primary venturi guide plates symmetrically arranged in an air duct. The two second-stage venturi guide plates are arranged in the air duct and are symmetrically arranged between the first-stage venturi guide plates; the third-stage inserting venturi is arranged between the second-stage venturi guide plates, and when dust-containing airflow passes through the interior of the third-stage inserting venturi, the airflow is firstly gathered towards the center and then diffused and discharged, and the third-stage inserting venturi is connected and conducted with a negative pressure output pipe inserted into the air duct; the positive pressure output pipe is inserted into the air duct, and a sampling opening of the positive pressure output pipe located in the air duct is constructed to be an inclined groove right facing incoming air. The flow velocity is increased by utilizing the Venturi principle, and the pressure difference between the positive pressure output pipe and the negative pressure output pipe is acquired to calculate the velocity of the fluid, so that the velocity of the nozzle of the secondary air burner is deduced, and the problem that the section velocity is low and cannot be measured is solved.

Description

Technical Field

[0001] The utility model relates to the technical field of fluid velocity measurement, in particular to a device for measuring the velocity of a secondary air burner nozzle of a power station boiler. Background Art

[0002] At present, my country's domestic energy structure is still dominated by thermal power generation, and the situation of thermal power generation will not change for a long time in the future. The so-called thermal power generation usually refers to the use of raw coal as the primary energy source, the mixture of coal powder and hot air in the boiler for combustion, and water as the medium to absorb the heat released by the coal combustion into high-temperature and high-pressure water vapor, which is sent to the steam turbine generator set to be converted into electrical energy and continuously fed into the power grid. As the main equipment for energy conversion, the safety and economic operation of power station boilers are directly related to the safety of the power grid. With the continuous improvement of the domestic manufacturing level, the single-unit capacity of power station boilers is also increasing. Often a boiler mixes coal powder and hot air and sends them into the boiler for There are dozens of pipes for combustion (the hot air with coal powder is called primary air). The air-powder mixture in dozens of primary air pipes is sprayed into the boiler for combustion through dozens of primary air coal powder burners arranged on the wall of the boiler furnace. According to the combustion characteristics of the boiler, the combustion air is far from enough to rely solely on the primary air mixed with coal powder. A large amount of hot air is also needed to assist combustion (called secondary air). The secondary air also requires dozens of nozzles (called secondary air burner nozzles). When arranging the power station boiler, the primary and secondary air burner nozzles are usually arranged at the four corners of the boiler furnace to form tangential combustion, and the primary and secondary air burners are arranged in layers, one layer of primary air and one layer of secondary air.

[0003] As a key to boiler combustion, monitoring the primary and secondary air velocities at each burner nozzle is particularly important. Poor monitoring and control will affect the safe and economical operation of the boiler. Poor air distribution will first affect the boiler's tangential circle, causing the furnace flame to deviate to one side and cause coking. Poor air distribution can also cause oxygen deficiency or excess oxygen during combustion, preventing complete combustion of pulverized coal and affecting boiler efficiency. Currently, the velocities within dozens of primary air ducts in almost all large power station boilers in China are monitored, presenting no technical difficulties. However, the velocities at the secondary air nozzles of almost all power station boilers are not monitored. The main reason is a lack of monitoring conditions and corresponding equipment. Figure 5 shows the structural diagram of the secondary air burner nozzles and locations of current power station boilers in China. Flow measurement requires corresponding straight pipe sections and installation conditions. Online monitoring of dozens of primary air ducts in power station boilers is achieved because the pipelines have long straight pipe sections, making the placement of measurement devices a problem. However, as shown in Figure 5, there are almost no conditions for monitoring the wind speed at the secondary air nozzle. First, the secondary air from the secondary air main pipe box almost immediately turns and enters the secondary air burner nozzle, with almost no straight pipe section. Second, there is an adjustable damper in front of the secondary air nozzle, which does not allow for installation. Third, the temperature in the area facing the furnace of the secondary air nozzle can reach over 1000 degrees, and the angle of the burner needs to be adjusted at any time according to the operating conditions of the boiler area. In other words, there is no place to arrange measuring points on the burner. According to the structural characteristics of the secondary air burner nozzle, the only place where a measuring device can be installed is at the inlet of the burner and the secondary air main pipe box. There is a small amount of straight pipe section in this area, and the airflow at the inlet connected to the large wind box is relatively stable. However, the flow area of ​​the pipeline in this area is 2 to 3 times that of the secondary air burner nozzle. In other words, the wind speed in the pipeline in this area is very low under normal operating conditions. Nowadays, large-scale generators require large-scale peak regulation, and the speed in the pipeline is even lower at night.

[0004] If the actual wind speed in the pipe at the inlet of the secondary air burner can be measured under the conditions of a shorter straight pipe section and lower wind speed at this part, the speed of the secondary air burner nozzle can be deduced according to the principle of equal flow rate and the cross-sectional ratio of the inlet pipe and the secondary air burner nozzle. Utility Model Content

[0005] The utility model aims to solve the above-mentioned defects and provides a device for measuring the nozzle velocity of a secondary air burner of a power station boiler.

[0006] In order to overcome the defects existing in the background technology, the technical solution adopted by the present invention to solve the technical problems is as follows: a device for measuring the nozzle velocity of a secondary air burner of a power station boiler, comprising an air duct, wherein two primary Venturi guide plates are symmetrically arranged inside the air duct, wherein the primary Venturi guide plates are bent so that the dust-laden airflow is first converged toward the center when passing between the primary Venturi guide plates and then diffused and discharged;

[0007] Two secondary Venturi guide plates are provided in the air duct and are symmetrically arranged between the primary Venturi guide plates. The secondary Venturi guide plates are bent so that the dust-laden airflow converges toward the center and then diffuses when passing between the secondary Venturi guide plates. The airflow discharge side is in the same plane as the bend line on the primary Venturi guide plates.

[0008] The third-stage insertion venturi is arranged between the second-stage venturi guide plates, and when the dust-laden airflow passes through, the airflow first converges to the center and then diffuses and discharges. Its airflow output end is in the same plane as the bending line on the second-stage venturi guide plate, and is connected to the negative pressure output pipe inserted into the air duct and is conductive, so as to sample and detect the air pressure at the junction of the airflow convergence and diffusion inside the third-stage insertion venturi;

[0009] A positive pressure output tube is inserted into the air duct, and a sampling port of the positive pressure output tube in the air duct is configured as an oblique cut facing the incoming air.

[0010] A further improvement includes that both the positive pressure output pipe and the negative pressure output pipe adopt a square tube structure.

[0011] Further improvements include that the positive pressure output pipe and the negative pressure output pipe are both perpendicular to the ground, and freely swingable cleaning rods are provided in the positive pressure output pipe and the negative pressure output pipe, and the cleaning rods extend to the outside of the positive pressure output pipe and the negative pressure output pipe respectively.

[0012] A further improvement includes the three-stage insertion venturi being a rectangular frame, wherein one of the two opposite sides of the rectangular frame suddenly turns inward so that the front and rear ends inside the rectangular frame form a horn channel and the middle forms a transition channel, and the negative pressure output pipe is connected to the transition channel inside the three-stage insertion venturi.

[0013] The beneficial effects of the present utility model are as follows: the present design amplifies the flow rate through the cooperation of the three-stage insertion venturi, the first-stage venturi guide plate and the first-stage venturi guide plate, collects the pressure difference between the positive pressure output pipe and the negative pressure output pipe to calculate the velocity of the fluid, thereby deducing the velocity of the secondary air burner nozzle, and completely solves the problem that the cross-sectional velocity is low and cannot be measured; the three-stage insertion venturi adopts an insertion type, which reduces the pressure loss of the device as much as possible and has a good energy-saving effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0015] Figure 1 It is a top sectional view of the utility model;

[0016] Figure 2 It is a side sectional view of the utility model;

[0017] Figure 3 It is the main view of the utility model;

[0018] Figure 4 This is an axial side view of the three-stage insertion venturi in the utility model;

[0019] FIG5 is a structural diagram of the secondary air burner nozzle and its location of a power station boiler;

[0020] In the figure, 1- air duct, 2- three-stage Venturi insertion, 3- oblique cutout, 4- dust cleaning rod, 5- positive pressure output pipe, 6- negative pressure output pipe, 7- first-stage Venturi guide plate, 8- first-stage Venturi guide plate;

[0021] 201- speaker channel, 202- transition channel. DETAILED DESCRIPTION

[0022] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the embodiments described are part of the embodiments of the present invention, not all of them. The embodiments of the basic utility model and all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present utility model.

[0023] according to Figure 1 、 Figure 2 and Figure 3 As shown, a device for measuring the nozzle velocity of a secondary air burner of a power station boiler includes an air duct 1, in which two primary Venturi guide plates 7 are symmetrically arranged. The primary Venturi guide plates 7 are bent so that the dust-laden airflow converges toward the center when passing between the primary Venturi guide plates 7 and then diffuses and discharges.

[0024] Two secondary Venturi guide plates 8 are provided in the air duct 1 and are symmetrically arranged between the primary Venturi guide plates 7. The secondary Venturi guide plates 8 are bent so that the dust-laden airflow converges toward the center and then diffuses when passing between the secondary Venturi guide plates 8. The airflow discharge side is in the same plane as the bending line on the primary Venturi guide plates 7.

[0025] The third-stage insertion venturi 2 is arranged between the second-stage venturi guide plates 8, and when the dust-laden airflow passes through, the airflow first converges toward the center and then diffuses and discharges. Its airflow output end is in the same plane as the bending line on the second-stage venturi guide plate 8, and is connected and conducted to the negative pressure output pipe 6 inserted into the air duct 1, so as to sample and detect the air pressure at the junction of the convergence and diffusion of the airflow inside the third-stage insertion venturi 2. The sampling port of the negative pressure output pipe 6 is used to detect this area, thereby obtaining a pressure lower than the static pressure in the air duct 1, namely "negative pressure";

[0026] The positive pressure output tube 5 is inserted into the air duct 1 to detect the air pressure in the air duct 1, and the sampling port of the positive pressure output tube 5 located in the air duct 1 is constructed as an oblique cut 3 facing the incoming wind. When the air flow in the air duct 1 blows toward the oblique cut 3 at a certain speed, the speed of the gas will be converted into pressure energy, which will cause the sampling port of the positive pressure output tube 5 to obtain a pressure higher than the static pressure in the air duct 1, which is called "positive pressure".

[0027] The Venturi principle is explained in detail as follows: When gas or liquid flows through a Venturi tube, the dynamic pressure (velocity head) reaches its maximum value and the static pressure (resting pressure) reaches its minimum value at the narrowest point of the tube. The velocity of the gas (liquid) increases due to the decrease in the cross-sectional area of ​​the flow. The entire flow undergoes the process of tube contraction at the same time, causing the pressure to decrease at the same time. By measuring the pressure difference between the positive pressure output pipe 5 and the negative pressure output pipe 6, the fluid velocity can be calculated, and the velocity of the secondary air burner nozzle can be derived. The pressure difference output by this design is 2-3.5 times that of conventional measuring devices, completely solving the problem of low cross-sectional velocity that cannot be measured.

[0028] In this embodiment, the positive pressure output pipe 5 and the negative pressure output pipe 6 both adopt a square tube structure. With this structure, a larger windward surface can be obtained by opening the oblique cut 3 .

[0029] Since the sampling ports of the positive-pressure output pipe 5 and the negative-pressure output pipe 6 are prone to dust accumulation in the air duct 1, the reason is that eddies are easily generated at the sampling ports. In order to prevent dust accumulation, in this embodiment, the positive-pressure output pipe 5 and the negative-pressure output pipe 6 are both perpendicular to the ground, and freely swingable cleaning rods 4 are provided in the positive-pressure output pipe 5 and the negative-pressure output pipe 6, and the cleaning rods 4 extend to the outside of the positive-pressure output pipe 5 and the negative-pressure output pipe 6 respectively. When the airflow blows, the free swinging of the cleaning rod 4 will knock down the dust accumulated at the sampling ports of the positive-pressure output pipe 5 and the negative-pressure output pipe 6, thereby ensuring smooth detection.

[0030] In this embodiment, if Figure 4 As shown, in order to avoid dust accumulation inside the three-stage insertion venturi 2 and ensure that the negative pressure output pipe 6 can smoothly sample and detect the connection point where the airflow converges and diffuses inside the three-stage insertion venturi 2, the three-stage insertion venturi 2 is preferably a rectangular frame, and one of the two opposite sides of the rectangular frame suddenly turns inward to form a horn channel 201 at the front and rear ends of the rectangular frame and a transition channel 202 in the middle. The negative pressure output pipe 6 is connected to the transition channel 202 in the three-stage insertion venturi 2, which will make the other two opposite sides of the rectangular frame flat, so that the dust-laden airflow flowing through is not easy to accumulate dust in the horn channel 201.

[0031] The above is only a preferred specific implementation method of the present invention, but the protection scope of the present invention is not limited to this. Any technician familiar with the technical field within the technical scope disclosed by the present invention can make equivalent replacements or changes based on the technical solution and utility model concept of the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A device for measuring the nozzle velocity of a secondary air burner of a power station boiler, characterized in that: It comprises an air duct (1), in which two first-level Venturi guide plates (7) are symmetrically arranged, and the first-level Venturi guide plates (7) are bent so that the dust-laden airflow converges toward the center when passing between the first-level Venturi guide plates (7) and then diffuses and discharges; Two secondary Venturi guide plates (8) are provided in the air duct (1) and are symmetrically arranged between the primary Venturi guide plates (7). The secondary Venturi guide plates (8) are bent so that the dust-laden airflow converges toward the center and then diffuses when passing between the secondary Venturi guide plates (8). The airflow discharge side is on the same plane as the bending line on the primary Venturi guide plates (7); The third-stage insertion venturi (2) is arranged between the second-stage venturi guide plates (8), and when the dust-laden airflow passes through, the airflow first converges toward the center and then diffuses and discharges. The airflow output end is in the same plane as the bending line on the second-stage venturi guide plate (8), and is connected to and conducted with the negative pressure output pipe (6) inserted into the air duct (1) so as to sample and detect the air pressure at the junction of the airflow convergence and diffusion inside the third-stage insertion venturi (2); A positive pressure output tube (5) is inserted into the air duct (1), and a sampling port of the positive pressure output tube (5) located in the air duct (1) is configured as an oblique cutout (3) facing the incoming air.

2. A power station boiler secondary air burner nozzle velocity measuring device according to claim 1, characterized in that: The positive pressure output pipe (5) and the negative pressure output pipe (6) both adopt a square tube structure.

3. The device for measuring the nozzle velocity of a secondary air burner of a power station boiler according to claim 1, characterized in that: The positive pressure output pipe (5) and the negative pressure output pipe (6) are both perpendicular to the ground, and freely swingable cleaning rods (4) are provided in the positive pressure output pipe (5) and the negative pressure output pipe (6), and the cleaning rods (4) extend to the outside of the positive pressure output pipe (5) and the negative pressure output pipe (6), respectively.

4. The device for measuring the nozzle velocity of a secondary air burner of a power station boiler according to claim 1, characterized in that: The three-stage insertion venturi (2) is a rectangular frame, and one of the two opposite sides of the rectangular frame is suddenly inwardly shaped so that the front and rear ends of the rectangular frame form a horn channel (201) and the middle portion forms a transition channel (202). The negative pressure output pipe (6) is connected to the transition channel (202) in the three-stage insertion venturi (2).

Images