A control device for preventing the low-load stall of a fan and improving operation stability

Abstract

The present invention belongs to the technical field of power equipment control, and discloses a control device for preventing the low-load stall of a fan and improving the operation stability. Flow ducts are respectively arranged on the circumferences of the center lines of the inlet and outlet blades of the fan and are evenly distributed on the internal air duct of the fan. A wind speed dynamic pressure measuring tube is arranged on the windward side of the introduced circular flow duct, and a wind speed static pressure measuring tube is arranged on the leeward side of the introduced circular flow duct, and the pipe diameter is half of that of the duct. A stall stability control cabinet is installed outside the fan, and in the interface cabinets of the fan inlet pipe and the outlet pipe, a wind pressure measuring sensor and a micro industrial control computer are arranged inside. A check valve and a flow regulating valve are installed between the outlet flow duct and the inlet flow duct, and control instructions are output after deviation calculation by the industrial control computer. With the aid of the control device of the present invention, the state parameters of the fan deviating from the normal are effectively judged, and according to the characteristic curve of the fan itself, the fan is adjusted to the most stable operation condition by adjusting the recirculation air volume, while ensuring the least unit consumption loss.

Description

Technical Field

[0001] The invention belongs to the technical field of power equipment control, and in particular is a control device for preventing a fan from stalling under low load and improving operation stability. Background Art

[0002] As national policies on environmental protection standards become increasingly stringent, the environmental protection transformation tasks of thermal power plants have become heavier. After the transformation, the resistance characteristics of the boiler tail flue have deviated greatly. Many power plants have been forced to carry out fan transformation, which requires large investments and destroys the original design basis. In addition, they are unable to adapt to changes in policies and environmental protection standards. The types of coal used have changed significantly, resulting in power plants having to carry out technical transformation with strong adjustability to ensure the reliable operation of fans.

[0003] As the capacity of power plants varies, the capacity, margin and operating characteristics of fan designs are also different. There are traditional centrifugal types and new types of stationary blades and moving blades. However, when the type of coal changes, the grid peak-shaving requirements, unit restrictions and load troughs, as well as unstable flue resistance during denitrification and desulfurization modifications, the fan will deviate from its own operating conditions and enter an unstable operating area. Therefore, power plants face the trouble of unsafe fan operation due to changes in flue resistance.

[0004] The conventional modification plan is to modify the entire fan, or replace the impeller, or replace the casing, or install a frequency converter and a hydraulic coupling, but the modification cost is high, and it cannot fundamentally solve the impact of changes in flue resistance on fan characteristics. By changing the flow rate of the fan itself, the fan is guided into normal operating conditions. Although the unit consumption increases, the safety benefits brought are far greater than the increase in unit consumption. Summary of the invention

[0005] The present invention provides a control device for preventing a fan from stalling under low load and improving operation stability. Flow ducts are arranged on the circumference of the center lines of the fan inlet and outlet blades, respectively, and are evenly distributed on the internal flue of the fan. A wind speed dynamic pressure measuring tube is arranged on the windward side of the introduction circular flow duct, and a wind speed static pressure measuring tube is arranged on the leeward side of the lead-out circular flow duct, with the tube diameter being half of the tube. A stall stability control cabinet is installed on the outside of the fan, and the fan inlet and outlet pipes are interfaced in a cabinet, in which a wind pressure measuring sensor and a micro industrial computer are arranged. A check valve and a flow regulating valve are installed between the lead-out flow duct and the introduction flow duct, and a control command is output after the deviation is calculated in the industrial computer. With the help of the control device of the present invention, the state parameters of the fan deviating from the normal state can be effectively judged, and the fan can be adjusted to the most stable operating condition according to the recirculation air volume through the characteristic curve of the fan itself, while ensuring that the unit consumption loss is minimized.

[0006] The technical solution of the present invention is as follows. A control device for preventing a fan from stalling at low load and improving operation stability includes: a fan body, a plurality of air inlet side openings, a plurality of air outlet side openings, pipelines, and a control cabinet; the air inlet side openings are evenly arranged on the same circumference of the fan body close to the air inlet, the air outlet side openings are evenly arranged on the same circumference of the fan body close to the air outlet, the air inlet side openings and the air outlet side openings are connected to the control cabinet through pipelines, and the control cabinet can adjust the air outlet speed.

[0007] Further, the air inlet side openings include a dynamic pressure hole, an inlet dynamic pressure measuring tube hole, a flue gas extraction tube hole, and an introduced flue gas hole whose centers are arranged in sequence on the same straight line; the air outlet side openings include a flue gas discharge hole, a flue gas introduction tube hole, an outlet static pressure measuring tube hole, and a static pressure hole whose centers are arranged in sequence on the same straight line.

[0008] Further, the flue gas extraction tube hole is connected to the control cabinet through a flue gas extraction tube, the flue gas introduction tube hole is connected to the control cabinet through a flue gas introduction tube, the inlet dynamic pressure measuring tube hole is connected to the control cabinet through an inlet dynamic pressure measuring tube, and the outlet static pressure measuring tube hole is connected to the control cabinet through an outlet static pressure measuring tube.

[0009] Further, a check valve, a flow regulating valve, a wind pressure measuring sensor, and an industrial control computer are arranged in the control cabinet. A check valve and a flow regulating valve are installed between the flue gas extraction tube and the flue gas introduction tube, and the outlet static pressure measuring tube and the inlet dynamic pressure measuring tube hole are connected to the wind pressure measuring sensor.

[0010] Further, the aperture of the inlet dynamic pressure measuring tube hole is half of the aperture of the flue gas extraction tube hole; the aperture of the outlet static pressure measuring tube hole is half of the aperture of the flue gas introduction tube hole.

[0011] Further, both the air inlet side openings and the air outlet side openings have thirty-two.

[0012] A control method for preventing a fan from stalling at low load and improving operation stability

[0013] S1 The wind pressure measuring sensor collects the measurement data of the dynamic pressure and static pressure measurement points;

[0014] S2 According to the measurement data in step S1, calculate the air volume and total pressure data of the fan;

[0015] S3 According to the air volume and total pressure data in step S2, combined with the blade opening position, compare with the performance characteristic curve of the fan, and calculate the deviation and stall state of the fan;

[0016] S4 If a deviation occurs, calculate the flow rate difference from the normal characteristic curve, and by adjusting the flow regulating valve, according to the method of increasing the recirculation flow rate, restore the fan to the normal operating condition range; if no deviation occurs, repeat steps S1 - S3.

[0017] The beneficial effects of the present invention are as follows:

[0018] With the control device of the present invention, the state parameters of the fan deviating from normal can be effectively judged. Through the characteristic curve of the fan itself, the fan is adjusted to the most stable operating condition according to the recirculation air volume, while ensuring the least single - consumption loss. Brief Description of the Drawings

[0019] Figure 1 It is a schematic diagram of the overall structure of the fan of the present invention.

[0020] Figure 2 It is a schematic diagram of the opening structure on the air - inlet side of the present invention.

[0021] Figure 3 It is a schematic diagram of the opening structure on the air - outlet side of the present invention.

[0022] Figure 4 It is a sectional view of the opening arrangement of the fan of the present invention.

[0023] Figure 5 It is a schematic diagram of deviation correction under off - design conditions.

[0024] Legend: 1 - opening on the air - inlet side; 2 - opening on the air - outlet side; 3 - inlet dynamic - pressure velocity - measuring tube; 4 - outlet static - pressure velocity - measuring tube; 5 - flue - gas extraction pipe; 6 - industrial control computer; 7 - check valve; 8 - control cabinet; 9 - flow regulating valve; 10 - flue - gas inlet pipe; 11 - fan body; 12 - wind - pressure measuring sensor; 101 - dynamic - pressure hole; 102 - hole for inlet dynamic - pressure velocity - measuring tube; 103 - hole for flue - gas extraction pipe; 104 - hole for introducing flue - gas; 201 - hole for discharging flue - gas; 202 - hole for flue - gas inlet pipe; 203 - hole for outlet static - pressure velocity - measuring tube; 204 - static - pressure hole. Detailed Embodiments

[0025] A control device for preventing the fan from stalling and improving its operation stability, which prevents the fan from entering the stall region at low load. At the same time, the control device moves the operating condition point of the fan to the safe operating region according to the characteristic curve of the fan, ensuring the long - term safe and reliable operation of the fan. This control device is mainly applicable to the induced draft fan and forced draft fan in thermal power plants, and mainly includes the following structures, see Figure 1

[0026] The flue - gas extraction pipe 5 is arranged on the circumference of the center line of the inlet blades of the fan, and the flue - gas introduction hole 102 is on the leeward side. On the same cross - section of the fan, 32 openings on the air - inlet side 1 and openings on the air - outlet side 2 are evenly distributed respectively, and the internal flue - gas is led out of the fan housing.

[0027] The inlet dynamic - pressure velocity - measuring tube 3 is arranged on the windward side of the flue - gas extraction pipe 5, and is fixedly welded back - to - back with the flue - gas extraction pipe 5. The diameter of the inlet dynamic - pressure velocity - measuring tube 3 is half of that of the flue - gas extraction pipe 5.

[0028] A flue gas inlet pipe 10 is arranged on the circumference of the blade center line at the outlet of the fan. Its form and structure are exactly the same as those of the flue gas outlet pipe, except that the flue gas outlet hole 6 is located on the windward side.

[0029] An outlet static pressure velocity measuring pipe 4 is arranged on the leeward side of the flue gas inlet pipe 10 and is fixedly welded to the back of the flue gas inlet pipe 10. The diameter of the outlet static pressure velocity measuring pipe 4 is half of that of the flue gas inlet pipe 10.

[0030] A stall stability control cabinet 8 is installed outside the fan. The inlet dynamic pressure velocity measuring pipe 3, the outlet static pressure velocity measuring pipe 4, the flue gas outlet pipe 5 and the flue gas inlet pipe 10 are introduced into the stall stability control cabinet 8.

[0031] A wind pressure measuring sensor and a micro industrial control computer 6 are arranged inside the stall stability control cabinet 8. A check valve 7 and a flow regulating valve 9 are installed between the flue gas outlet pipe 5 and the flue gas inlet pipe 10, and control instructions are output after deviation calculation by the industrial control computer 6. With the control device of the present invention, it is possible to effectively judge the state parameters of the fan deviating from the normal state, adjust the fan to the most stable operating condition according to the recirculation air volume through the characteristic curve of the fan itself, and at the same time ensure the least unit consumption loss.

[0032] 32 dynamic pressure and static pressure measuring points are evenly distributed on the circumference of the fan blade center line;

[0033] According to the measurement data of the dynamic pressure and static pressure measuring points, the air volume and total pressure of the fan are calculated, and the blade opening position is transmitted to the control cabinet through a sensor. Through the performance characteristic curve of the fan, the deviation and stall state of the fan are calculated.

[0034] If a deviation occurs, according to the algorithm, the flow difference deviating from the normal characteristic curve is calculated. By adjusting the regulating valves of the inlet conduit and the outlet conduit, and according to the method of increasing the recirculation flow rate, the deviation is minimized and the fan is restored to the normal operating condition point range.

[0035] The illustration method for deviation adjustment: see Figure 5 , the low-load deviation line is the deviation condition, and it is corrected to the normal state after adjustment by increasing the flow rate.

[0036] The distance between the flue gas inlet pipe at the blade center line at the fan inlet and the blade is 1 meter. There are strong brackets on the four sides of the flue gas inlet pipe fixed to the inner shell of the fan. The arrangement of the flue gas outlet pipe is the same. The flue gas outlet pipe and the bound velocity measuring pipe are processed into the shape of a wing through profiling, which does not affect the overall air duct resistance characteristics.

[0037] It should be noted that, in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article or device.

Claims

1. A control device for preventing the low-load stall of a fan and improving the operation stability, characterized in that Including: A fan body, multiple air inlet side openings, multiple air outlet side openings, pipelines and a control cabinet; the air inlet side openings are evenly arranged on the same circumference of the fan body close to the air inlet, the air outlet side openings are evenly arranged on the same circumference of the fan body close to the air outlet, the air inlet side openings and the air outlet side openings are connected to the control cabinet through pipelines, and the control cabinet can adjust the air outlet speed. The air inlet side openings include: a dynamic pressure hole, an inlet dynamic pressure measuring tube hole, a flue gas extraction pipe hole, and a flue gas introduction hole whose centers are arranged in sequence on the same straight line; The air outlet side openings include a flue gas discharge hole, a flue gas introduction pipe hole, an outlet static pressure measuring tube hole, and a static pressure hole whose centers are arranged in sequence on the same straight line. The flue gas extraction pipe hole is connected to the control cabinet through a flue gas extraction pipe, the flue gas introduction pipe hole is connected to the control cabinet through a flue gas introduction pipe, the inlet dynamic pressure measuring tube hole is connected to the control cabinet through an inlet dynamic pressure measuring tube, the outlet static pressure measuring tube hole is connected to the control cabinet through an outlet static pressure measuring tube. A check valve, a flow regulating valve, a wind pressure measuring sensor, and an industrial control computer are arranged in the control cabinet. A check valve and a flow regulating valve are installed between the flue gas extraction pipe and the flue gas introduction pipe. The outlet static pressure measuring tube and the inlet dynamic pressure measuring tube hole are connected to the wind pressure measuring sensor. The aperture of the inlet dynamic pressure measuring tube hole is half of the aperture of the flue gas extraction pipe hole; the aperture of the outlet static pressure measuring tube hole is half of the aperture of the flue gas introduction pipe hole. There are thirty-two air inlet side openings and air outlet side openings respectively.

2. A control method for a control device that prevents a fan from stalling at low load and improves operation stability as described in claim 1, characterized in that, Including the following steps: S1 The wind pressure measuring sensor collects the measurement data of the dynamic pressure and static pressure measurement points; S2 According to the measurement data in step S1, calculate the air volume and total pressure data of the fan; S3 According to the air volume and total pressure data in step S2, combined with the blade opening position, compare with the performance characteristic curve of the fan, and calculate the deviation and stall state of the fan; S4 If deviation occurs, calculate the flow difference deviating from the normal characteristic curve, and by adjusting the flow regulating valve, according to the method of increasing the recirculation flow, restore the fan to the normal operating condition range; If no deviation occurs, repeat steps S1 - S3.

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