CN211121383U - An air flow measuring device arranged in an array - Google Patents

Abstract

The utility model provides an air flow measuring device arranged in an array manner, which comprises a dynamic pressure measuring rod and a static pressure measuring rod, wherein the dynamic pressure measuring rod is arranged on the windward side, a plurality of spiral air self-cleaning measuring units are distributed and arranged on the dynamic pressure measuring rod, an array arrangement structure is formed in a wind channel, and the grid configuration is adopted, the spiral air self-cleaning measuring units are cylinders internally provided with round holes, and the cylinders are welded in the inner cavity of the dynamic pressure measuring rod; each spiral air self-cleaning measuring unit also comprises a measuring rectifying tube, a throttling element and a sampling port, wherein the throttling element and the sampling port are coaxially arranged in the measuring rectifying tube; a plurality of guide grooves are arranged on the sampling port from inside to outside; the static pressure measuring rod is arranged in the opposite direction, differential pressure is formed between the static pressure measuring rod and the dynamic pressure measuring rod, a M20 x 1.5 protruding part is formed at one end of the static pressure measuring rod, and the diameter of an inner hole is 8 cm. The utility model discloses the structure is unique, can make measuring element effectively realize preventing under abominable condition that stifled measuring is and resistance to wears.

Description

An air flow measuring device arranged in an array

technical field

The utility model relates to the technical field of air flow measurement of medium-speed coal pulverizers in the field of thermal power generation, in particular to an air flow measurement device arranged in an array.

Background technique

Medium-speed coal pulverizers are currently the mainstream configuration of units above 300MW in China. The pulverizing system has the advantages of rapid startup, flexible adjustment, and low pulverizing unit consumption. It has strict requirements for primary air volume and secondary air flow. Therefore, proper primary air volume and secondary air flow are of great significance to the normal operation of the coal mill and even the entire unit. In the pulverizing system of power station boilers currently equipped with medium-speed coal mills, non-standard speed measuring components are generally used, such as wing-type air volume measuring devices, Venturi flowmeters, Annubar flowmeters, etc. The inlet flue conducts primary air measurements. At present, in the common layout of the cold and hot primary air ducts in front of the inlet of the medium-speed coal mill in the power plant, the speed measuring element is usually installed on a plane of the pipe section between the hot air/cold air inlet and the coal mill inlet as the flow sensor. flat.

The problem brought by this position makes it difficult to measure the secondary air flow and the primary air of the thermal power plant at present. The fundamental reason is that the medium contains a lot of impurities. At present, most of the differential pressure measuring devices in the industry have poor anti-blocking effect, resulting in inaccurate measurement and large on-site maintenance.

Therefore, it is necessary to design a new air flow measurement device to solve the problem that a large amount of impurities in the medium affect the measurement effect.

Utility model content

In order to overcome the above problems existing in the prior art, the present invention provides an air flow measuring device arranged in an array, including a dynamic pressure measuring rod and a static pressure measuring rod, wherein the dynamic pressure measuring rod is arranged on the windward surface, on which A plurality of spiral air self-cleaning measurement units are distributed and arranged to form an array arrangement structure in the air duct, and a grid configuration is adopted. inside the rod cavity.

Preferably, each spiral air self-cleaning measuring unit further includes a measuring rectifier tube, a throttling member coaxially installed in the measuring rectifier tube and a sampling port.

Preferably, a plurality of guide grooves are arranged inside and outside the sampling port.

Preferably, the static pressure measuring rod is arranged in the opposite direction to form a differential pressure with the dynamic pressure measuring rod, and one end of the static pressure measuring rod is formed with a protrusion of M20*1.5, and the diameter of the inner hole is 8cm.

Preferably, the array type air flow measuring device further includes one or more measuring pitot tubes, and each pitot tube is provided with a plurality of spiral air self-cleaning measuring units.

Preferably, the number of spiral air self-cleaning measuring cells is determined by the cross-sectional size of the measuring environment.

Preferably, the air flow measuring devices arranged in an array are made of 304, 904 stainless steel or 316L stainless steel.

The beneficial effects of the present utility model:

Each dynamic pressure sampling port of the measuring device adopts a unique structure to realize spiral air turbulence cleaning, effectively avoiding the deposition and adhesion of impurities in the measured medium in the measuring element. This structure has been continuously tested and improved in repeated simulation environment, and finally finalized, reasonable and very effective. Using a new type of measuring element with a unique shape and structure that has been simulated and calculated, the measuring element can effectively achieve anti-blocking measurement and wear resistance under harsh conditions.

The above and other objects, advantages and features of the present invention will be more apparent to those skilled in the art from the following detailed description of the specific embodiments of the present invention in conjunction with the accompanying drawings.

Description of drawings

Hereinafter, some specific embodiments of the present invention will be described in detail by way of example and not limitation with reference to the accompanying drawings. The same reference numbers in the figures designate the same or similar parts or parts. It will be understood by those skilled in the art that the drawings are not necessarily to scale. Objects and features of the present invention will be more apparent in view of the following description in conjunction with the accompanying drawings, in which:

1 is a cross-sectional view of an air flow measuring device arranged in an array according to an embodiment of the present invention;

2 is a schematic structural diagram of a spiral air self-cleaning measurement unit of an air flow measurement device arranged in an array according to an embodiment of the present invention;

FIG. 3 is a three-dimensional top view of an air flow measuring device arranged in an array according to an embodiment of the present invention.

Detailed ways

The specific embodiments of the present invention are described in detail below with reference to the accompanying drawings, but are not intended to limit the protection scope of the present invention.

Referring to Fig. 1-2, an air flow measuring device arranged in an array includes a dynamic pressure measuring rod 1 and a static pressure measuring rod 2. The dynamic pressure measuring rod 1 is arranged on the windward surface, and a plurality of spiral air auto The cleaning measurement unit 3 forms an array arrangement in the air duct. Each spiral air self-cleaning measurement unit 3 has a sampling port 4. In this embodiment, the aperture of the sampling port 4 is 10 cm. The cylinder of the circular hole is welded in the inner cavity of the dynamic pressure measuring rod. The diameter of the circular hole is 20cm. There are a plurality of guide grooves 5 arranged inside and outside the sampling port 4. When the measured medium flows through the guide grooves 5 , a helical concentrating airflow field is formed near the sampling port, so that the impurities in the medium are removed from the sampling port 4 while the dynamic pressure is measured. differential pressure. In this embodiment, a protrusion of M20*1.5 is formed at one end of the static pressure measuring rod, the diameter of the inner hole is 8cm, and the multiple devices are arranged in an array on the same section, which meets the measurement requirements of the grid method. Requirements are greatly reduced.

For the measurement requirements of the air flow rate by the grid method, the ideal state for measuring the gas flow rate in the pipe is that the inner wall of the pipe is very smooth and has a long straight pipe section, otherwise the gas flow field in the pipe will be uneven, and there will be turbulent flow and swirling flow , affecting the accuracy of the measurement. However, it is almost impossible for the air flue of the power plant boiler to have such ideal conditions. The solution is to use the grid method to arrange multiple measuring points in the air duct to obtain the average wind speed in the air duct. The anti-blocking array air flow measuring device of the utility model is a device for realizing multi-point measurement of gas flow rate, and has a very good function of preventing dust clogging. 316L stainless steel, the choice of material solves the problem of flue gas corrosion.

The number of spiral air self-cleaning measuring units 3 is determined by the cross-sectional size of the measuring environment. The air flow measurement device arranged in an array adopts a standard mathematical model to calculate the air flow (refer to the formula below). The dynamic pressure sampling point in the dynamic pressure measuring rod 1 of the air flow measuring device is linearly matched with the static pressure measuring point of the static pressure measuring rod 2 .

The working principle of the measuring device of the utility model is as follows:

The array air flow measuring device is based on the S-type pitot tube measurement principle and is designed and manufactured according to the international standard ISO3966:1997 "Measurement of fluid flow in closed pipes/velocity-area method using pitot static tubes". The measuring device is installed on the pipeline, and its pitot tube is inserted into the pipeline. When there is airflow in the pipeline, the windward side is impacted by the airflow, where the kinetic energy of the airflow is converted into pressure energy, so the pressure in the windward side pipe is high, and its pressure is called It is "full pressure". Since the leeward side is not affected by the airflow, the pressure in the pipe is the static pressure in the air pipe, and its pressure is called "static pressure". The difference between the total pressure and the static pressure is called differential pressure. The internal wind speed is related. The greater the wind speed, the greater the differential pressure; the smaller the wind speed, the smaller the differential pressure. The relationship between the wind speed and the differential pressure conforms to the Bernoulli equation. The array air flow measuring device is especially suitable for the working conditions with large dust content, low Reynolds number and dirty medium. The fluid resistance and sharp edge wear are small, and the measurement accuracy is high. The outflow coefficient is stable, and the straight pipe section is shortened by 70% (front straight pipe section <3D, rear straight pipe section <1D). Good pressure equalization effect and low pressure loss. Each set of array air flow measuring device consists of one or more measuring pitot tubes, each pitot tube includes multiple gas flow rate sensors with anti-blocking function, each sensor is a measuring rectifier tube and coaxially installed on the measuring rectifier The throttling part in the pipe and the corresponding sampling port are composed, and the whole device is equivalent to forming a speed measuring array to measure the air volume. When multiple measuring pitot tubes are inserted into the air duct, the full pressure and the full pressure, and the static pressure and the static pressure output by the pitot tubes are connected in parallel, so that the average flow velocity of each measuring point of the air duct section can be accurately measured. This means that if the measuring pitot tubes are arranged in the air duct as much as possible, and each measuring pitot tube is equipped with as many flow velocity sensors as possible, the uneven flow field caused by the swirl and turbulent flow in the air duct can be avoided. influence and reduce measurement errors.

Example:

In order to solve the problem of flue gas corrosion in a power plant, the air flow measurement device is made of 316L stainless steel, which is treated with anti-corrosion spraying. 316L stainless steel is a kind of molybdenum-containing stainless steel, and its molybdenum content is slightly higher than that of 316 stainless steel. Due to the molybdenum in the steel, the overall performance of this steel is better than that of 310 and 304 stainless steel. Of course, the best corrosion-resistant material at present is Hastelloy, However, due to its high price and poor cost performance, it is not recommended for use. The array type air flow measurement device of this embodiment has almost no pressure loss and reliable device performance due to the strict use of standard grid multi-point layout on the air duct section, and the self-cleaning and anti-clogging functions of the measurement device itself. It can ensure stable and accurate flow display. The mathematical operation model for the calculation of the array air flow device is as follows:

Q=3600×A×vm ₃ /h

Among them, A is the area of the air duct, square meters; v represents the airflow speed in the air duct, and the airflow speed in the air duct is:

表示测量截面的平均动压，p表示空气密度。in,

represents the average dynamic pressure of the measuring section, and p represents the air density.

The measurement accuracy and flow coefficient k of the measuring device before leaving the factory are usually obtained through laboratory wind tunnel testing, and are flow data under normal conditions. Therefore, in order to ensure the on-site measurement accuracy of the measuring system and the linearity under different operating conditions, it is necessary and necessary to conduct on-site calibration of the measuring device. On-site verification can be performed in a cold state. If conditions permit, it is best to do 3 working conditions. Generally, the verification of 2 working conditions can meet the requirements. The coal-fired boilers are tested in accordance with GB10184--88 "Power Station Boiler Performance Test Regulations", "ASME Test Regulations" PTC4.1, PTC4.3 and relevant test methods. The on-site calibration adopts a high-precision instrument that meets the standard, and the grid method is applied to measure the flow velocity at multiple points on the section of the air duct, and the average flow velocity of the section of the air duct is calculated. The on-site verification steps are as follows:

(1) The DCS or related instruments can be put into operation normally, the differential pressure transmitter has been calibrated, and the zero point is accurate;

(2) Start the relevant fans and auxiliary equipment according to the operation regulations;

(3) Set the opening of each air door and baffle according to the normal operation mode to maintain the furnace pressure within the allowable range;

⑷ Adjust the air volume of the air duct to be checked to 90-100% of the rated operating conditions;

⑸ Keep the current operating conditions and parameters unchanged, notify the test personnel to start the test, record the output differential pressure of the anti-blocking array air volume measuring device or the indicated value of DCS and related instruments, and record the fan current at the same time;

⑹ Adjust the air volume to 75% and 50% of the rated operating conditions respectively, and continue the test after the operating conditions are stable until the end of the test;

⑺ In the case of special circumstances during the test, the test shall be interrupted immediately and handled in accordance with the operating procedures;

⑻ Calculate and process the test data, provide a mathematical model for the DCS, or set the relevant parameters of the display instrument. The display unit can be selected as m/s, m ³ /h, km ³ /h, Nm ³ /h, kg/ h, t/h, etc.;

⑼ Preparation of test reports, etc.

Implementation of this example:

1. The accuracy is better than ±1.5% of the measured flow,

2. The repeatability is better than ±0.1%;

3. The straight pipe section required for installation is very short, the upstream requires 0 to 3D, and the downstream requires 0 to 1D; there is no need to install a flow regulator in the upstream;

4. Completely solve the problem of signal blockage of the dust-laden airflow air flow measurement device. The air flow measurement device itself has the function of using fluid kinetic energy for self-cleaning and anti-clogging. No matter how big the concentration is, long-term operation and maintenance-free can be achieved.

5. The plug-in arrangement is adopted. For the entire large air duct, the windshield area of the combined air volume measuring device is almost negligible. Therefore, there is almost no pressure loss to the fluid in the entire air duct, and the energy saving effect is very significant, and it is easy to install. It is especially suitable for flow measurement of low static pressure fluids.

Each dynamic pressure sampling port of the measuring device adopts a unique structure to realize spiral air turbulence cleaning, effectively avoiding the deposition and adhesion of impurities in the measured medium in the measuring element. This kind of structure has been continuously tested and improved in repeated simulation environment, and finally finalized, reasonable and very effective. Using a new type of measuring element with a unique shape and structure that has been simulated and calculated, the measuring element can effectively achieve anti-blocking measurement and wear resistance under harsh conditions.

The technical solutions provided by the embodiments of the present utility model have been described in detail above. The principles and implementations of the embodiments of the present utility model are described in this paper by using specific examples. The descriptions of the above embodiments are only suitable for helping the understanding of the present utility model. The principle of the embodiment; at the same time, those of ordinary skill in the art, according to the embodiment of the present utility model, will have changes in the specific implementation and application scope. New type of restriction.

Claims (7)

1. An array-arranged air flow measuring device, characterized in that: the device comprises a dynamic pressure measuring rod (1) and a static pressure measuring rod (2), wherein the dynamic pressure measuring rod (1) is arranged on the windward side, a plurality of spiral air self-cleaning measuring units (3) are distributed on the dynamic pressure measuring rod, an array arrangement structure is formed in an air duct, a gridding configuration is adopted, the spiral air self-cleaning measuring units (3) are cylinders with round holes inside, and the cylinders are welded in the inner cavity of the dynamic pressure measuring rod.

2. An array arrangement of air flow measurement devices according to claim 1, wherein: each spiral air self-cleaning measuring unit (3) also comprises a measuring rectifying tube, a throttling piece and a sampling port (4) which are coaxially arranged in the measuring rectifying tube.

3. An array arrangement of air flow measurement devices according to claim 2, wherein: the sampling port (4) is internally and externally provided with a plurality of guide grooves (5).

4. An array arrangement of air flow measurement devices according to claim 1, wherein: the static pressure measuring rod (2) is arranged in the opposite direction, differential pressure is formed between the static pressure measuring rod (2) and the dynamic pressure measuring rod (1), a protruding part of M20 x 1.5 is formed at one end of the static pressure measuring rod (2), and the diameter of an inner hole is 8 cm.

5. An array arrangement of air flow measurement devices according to claim 1, wherein: the array type air flow measuring device also comprises one or more measuring pitot tubes, and each pitot tube is provided with a plurality of spiral air self-cleaning measuring units (3).

6. An array arrangement of air flow measurement devices according to claim 1, wherein: the number of the spiral air self-cleaning measuring units (3) is determined by the cross-sectional dimension of the measuring environment.

7. An array arrangement air flow measurement device according to claim 1, wherein the array arrangement air flow measurement device is made of 304, 904 stainless steel or 316L stainless steel.

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