Intelligent control method for centrifugal pump

Abstract

According to the intelligent control method for the centrifugal pump, the running flow, pressure and efficiency of the centrifugal pump can be fed back in real time under the condition that a flow sensor and a pressure sensor are not connected, the target flow and target pressure can be set in the controller to achieve PID control, and whether the centrifugal pump runs in the efficient area range of the pump or not is judged; and more accurate feedback of flow, pressure and efficiency of the centrifugal pump and pump energy efficiency attenuation prompt after long-term operation can be realized after a pressure sensor is connected to an inlet and an outlet of the centrifugal pump. According to the system and the method, a brand new system which can enable the centrifugal pump to feed back in real time, monitor the running state of the pump and carry out PID control under the condition that no sensor is used is formed, precise monitoring and energy efficiency prompting of the pump can be achieved after a pressure sensor is connected, the earlier-stage investment of a user is reduced, and the running energy efficiency of the pump is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of centrifugal pump applications, in particular to intelligent control of centrifugal pumps and a sensorless control method for centrifugal pumps. BACKGROUND

[0002] The control system of the centrifugal pump is currently low in intelligence, lacks monitoring and feedback of the real-time running state of the pump, or needs to use a flow sensor and a pressure sensor for control, and is also relatively single in parameters, which cannot realize real-time monitoring and feedback of flow, head, and efficiency, or needs to increase a flow meter, a pressure sensor, and a power meter in the entire system, which is high in cost. The centrifugal pump test bench is used at present, and it is difficult and high in cost to monitor, feed back, and control the flow and pressure of the pump under conventional working conditions.

[0003] Actual running conditions often deviate from design conditions when a medium is transported. In the case where a pressure sensor and a flow sensor are not installed at the inlet and outlet of the pump, the control system is difficult to monitor the running conditions of the pump in real time, resulting in low running efficiency of the pump.

[0004] In order to improve the working efficiency of the pump system, a Chinese patent application with publication number CN118309644A discloses a pipeline pump running flow monitoring method and system based on digital twinning. Specifically, it relates to a pipeline pump running flow monitoring method based on digital twinning, which comprises a data acquisition layer, a communication network layer, a data processing layer, a digital twinning model layer, a flow monitoring and prediction layer, a decision support and control layer, and a user interface layer. By constructing a digital twinning model of the pipeline pump and combining real-time monitoring of the flow, real-time monitoring, intelligent prediction, precise control, and efficient management of the pipeline pump are realized, thereby effectively improving the running efficiency, stability, and economic benefit of the device, and providing strong support for improving the performance and benefit of the pipeline pump system. A pipeline pump running flow monitoring system based on digital twinning is also disclosed, which is used to realize the above method. The monitoring and feedback of the flow and pressure of the method are realized by the pressure sensor and the flow meter arranged at the inlet and outlet of the pump, and then the pipeline pump is controlled by the control system.

[0005] The present application is directed to the overall working performance monitoring, feedback, and control of the movement of fluid in centrifugal pumps such as single-stage single-suction centrifugal pumps, multi-stage centrifugal pumps, single-stage double-suction centrifugal pumps, and the like, which can be applied in the movement of fluid in, for example, HVAC systems, industrial circulating water systems, water treatment plants, or any other system that combines fluid pumping.

[0006] However, the method of the above system cannot guarantee the application of all centrifugal pumps in a wide range of application conditions (requirements), and flow meters or pressure sensors are still needed for some high-precision centrifugal pump control occasions. SUMMARY

[0007] The technical problem solved by the present application is to overcome the low intelligent degree of the control system of the centrifugal pump in the prior art, the lack of monitoring and feedback of the real-time running state and energy efficiency of the pump, the need to add various sensors for control, and the high cost, and to provide a centrifugal pump intelligent control method.

[0008] The present application solves the above technical problems by the following technical scheme: a centrifugal pump intelligent control method, which comprises: the centrifugal pump is driven by a controller to run in a pipeline system, and the controller monitors the power and the rotating speed of the centrifugal pump in real time to realize real-time monitoring and display of the flow, pressure and efficiency of the centrifugal pump.

[0009] In the specific embodiment of the present application, the highest efficiency, rated rotating speed, flow, head and power parameter points at other rotating speeds of the centrifugal pump are input into the controller to generate the relationship formulas of power P-flow Q, flow Q-head H, and the relationship formulas of flow Q-rotating speed n, head H-rotating speed n, power P-rotating speed n, power P and flow Q, head H and efficiency .

[0010] In the specific embodiment of the present application, the controller monitors the power P r and the rotating speed n r of the centrifugal pump in real time, calculates the current real-time flow Q r , head H r and efficiency r .

[0011] In the specific embodiment of the present application, the target flow Q v and target pressure P v are set in the controller, and PID control is performed according to the real-time feedback flow Q r and head H r .

[0012] In the specific embodiment of the present application, the efficiency r fed back by the controller in real time is compared with the highest efficiency of the centrifugal pump max , and when the efficiency is lower than 92% of the highest efficiency, the controller prompts that the centrifugal pump deviates from the high-efficiency area.

[0013] In the specific embodiment of the present application, when a pressure sensor is connected to the inlet flange of the centrifugal pump and a pressure sensor is connected to the outlet flange, the controller directly calculates the head H x of the centrifugal pump, and calculates the real-time flow Q according to the relationship formulas of power P-flow Q, flow Q-rotating speed n, head H-rotating speed n, power P-rotating speed n, power P and flow Q, head H and efficiency.x efficiency x .

[0014] In the specific embodiment of the present application, when the calculated real-time efficiency x is greater than 5%, the controller prompts the centrifugal pump energy efficiency degradation. r

[0015] In the specific embodiment of the present application, the controller adopts a frequency conversion controller.

[0016] The positive progress effect of the present application is that in the present application, the running flow, head, and efficiency of the centrifugal pump can be monitored and fed back in real time without a flow pressure sensor, and PID control can be performed according to the flow and pressure, and in the case of connecting a pressure sensor, the calculation accuracy of the flow, head, and efficiency can be improved, and the early warning of the centrifugal pump efficiency degradation and deviation from the high efficiency area can be performed, which greatly improves the running state perception ability of the centrifugal pump and realizes the intelligent control of the centrifugal pump at a low cost. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is the principle diagram of the centrifugal pump without a sensor in the present application.

[0018] Figure 2 is the principle diagram of the centrifugal pump with a pressure sensor in the present application.

[0019] Figure 3 is the flow Q-head H, power P-flow Q curve diagram and relationship of the centrifugal pump in the present application.

[0020] Figure 4 is the PID control flowchart of the present application.

[0021] Figure 5 is the flowchart of the present application. DETAILED DESCRIPTION

[0022] The preferred embodiments of the present application are described below in combination with the drawings to specifically describe the technical solutions of the present application.

[0023] Figure 1 is the principle diagram of the centrifugal pump without a sensor in the present application. Figure 2 is the principle diagram of the centrifugal pump with a pressure sensor in the present application. As shown in Figure 1 and 2 , the system water enters from the inlet flange 3 of the centrifugal pump 2, flows out from the outlet flange 4 after being pressurized by the centrifugal pump, the controller 1 controls the rotating speed of the centrifugal pump to adjust the outlet pressure and flow of the centrifugal pump 2, and the highest efficiency ​max , rated speed n, other speeds n1, n2 (you can also enter several groups) under the flow, head, power parameter points 6 (here 6 is taken as an example, more points can be added to improve the calculation accuracy), the controller 1 generates the power P-flow Q, flow Q-head H relationship, write flow Q-speed n, head H-speed n, power P-speed n, power P and flow Q head H efficiency When the centrifugal pump 2 is running, the controller detects the real-time power P r and speed n r (frequency), the real-time flow rate Q can be calculated through the above relationship r , lift H r , and efficiency r .

[0024] Figure 3 This is the flow rate Q-head H, power P-flow rate Q curve and relationship of the centrifugal pump of the present invention. Figure 3 As shown, the current intelligent controller can monitor the speed n and power P of the centrifugal pump in real time, the flow-head curve and the power-efficiency curve of the centrifugal pump, which can be fitted into a polynomial as follows: When the speed is the rated speed n: (Formula 1) (Formula 2)

[0025] When the speed is n1: (Formula 3) (Formula 4)

[0026] When the speed is n2: (Formula 5) (Formula 6)

[0027] Power calculation formula: (Formula 7) The relationship between flow rate and speed: (Formula 8)

[0028] Relationship between head and speed (Formula 9)

[0029] Power and speed relationship (Formula 10)

[0030] P: Shaft power (kW).

[0031] : Fluid density (kg / m³). 1000 kg / m³ is usually used for clean water. g: Acceleration due to gravity (9.81 m / s²). Q: Flow rate (m³ / h). H: Head (m). : Pump efficiency (dimensionless), which needs to be determined based on actual operating data.

[0032] ： Rotational speed (r / min).

[0033] According to formula 7, the fluid is clean water and 1000 kg / m³ is simplified to: (Formula 11) The current monitoring speed n r , power P r For example, When the speed|n r -n|≤|n r -n1| inputs the curve under rated speed n for calculation, uses formula 1 and formula 2, combines formula 7, formula 8, formula 9, formula 10 to obtain the speed n r Traffic flow at Lift efficiency r .

[0034] When the speed|n r -n|>|n r -n1| inputs the curve under the speed n1 for calculation, uses formula 3 and formula 4, combines formula 7, formula 8, formula 9, formula 10 to obtain the speed n r Traffic flow at Lift efficiency r .

[0035] When the speed|n r - n1|≤|n r -n2| inputs the curve under the speed n1 for calculation, uses formula 3 and formula 4, combines formula 7, formula 8, formula 9, formula 10 to obtain the speed n r Traffic flow at Lift efficiency r .

[0036] When the speed|n r - n1|>|n r -n2| inputs the curve under the speed n2 for calculation, uses formula 5 and formula 6, combines formula 7, formula 8, formula 9, formula 10 to obtain the speed n r Traffic flow at Lift efficiency r .

[0037] like Figure 4 As shown, based on the above flow head efficiency calculation function, the flow, head, efficiency, speed, and power parameters at the current speed can be obtained in real time, and the target flow can be set in the controller. ,pressure , perform PID calculation.

[0038] PID is the abbreviation of Proportional-Integral-Derivative controller, which is a feedback controller widely used in industrial automation control systems. PID controllers adjust the control output by calculating the error (the difference between the set value and the actual value) in real time to achieve the desired system goal. Generally, PID is used to construct a single variable closed-loop system, such as Figure 4 As shown in the figure: r represents the setpoint, y represents the actual value, and y represents the error (e=ry), which is the controller output and also the manipulated variable of the controlled object. G represents the controlled object. The purpose of a PID controller is to control a process variable of the controlled object to the setpoint, the closer the better. For example, suppose we want to control the pressure, the setpoint is r = 0.7 MPa, and the actual measured temperature is y = 0.6 MPa, then the error is 0.1 MPa. The PID controller will adjust the output based on this error, so that the head of the controlled object gradually approaches the setpoint.

[0039] Normally, when the PID function is used, the feedback value of the controlled variable y must be fed back using sensors such as flow, pressure, and temperature. However, this new control method does not require sensors. PID calculation is performed based on the real-time monitoring value of the flow head efficiency calculated by the aforementioned function and the target set value r, thereby controlling the centrifugal pump.

[0040] After long-term operation, the centrifugal pump 2 will rust, abrasion and other conditions will occur, which will reduce the efficiency of the centrifugal pump and increase the energy consumption. For this reason, a pressure sensor 6 is installed on the pump inlet flange 3 (seeFigure 2 ), and a pressure sensor 5 is installed on the outlet flange 4 to monitor the energy efficiency of the pump. The pressure sensor 6 is installed on the inlet flange 3 of the pump to detect the pressure P in , and the pressure sensor 5 is installed on the outlet flange 4 to detect the pressure P out , and the pressure sensor 6 is installed on the inlet flange 3 of the pump to detect the pressure P out -P in。

[0041] When the centrifugal pump 2 is connected to the pressure sensor, the system switches to the following algorithm, and the head H is no longer calculated according to the current flow Q, so as to improve the detection accuracy.

[0042] When the speed is the rated speed n: (Formula 2) When the speed is n1: (Formula 4) When the speed is n2: (Formula 6) Power calculation formula: (Formula 7) Flow and speed relationship: (Formula 8) Head and speed relationship (Formula 9) Power and speed relationship (Formula 10) When the speed is n x , the pressure sensor monitors the pressure P in1 , and P out1 , and the real-time head of the pump is P x =P out1 -P in1 .

[0043] According to the flow head efficiency calculation function, the flow , efficiency x and , efficiency r at the real-time speed can be obtained.

[0044] When the efficiency x deviates or the flow r deviates, the flow and the efficiency When the deviation is greater than 5%, the system prompts that the pump energy consumption is declining.

[0045] Enter the highest efficiency of the centrifugal pump in controller 1 max Regardless of whether the sensor is connected, the real-time efficiency can be calculated based on the x or r , when real-time efficiency x or r Less than optimal max When the system reaches 92%, it prompts that the system is running in a biased working condition and the efficiency is low.

[0046] Take an example to illustrate: the rated speed of this model is 1500rpm, and the efficiency at the highest point is . The parameters of the three groups of measured speeds are as follows:

[0047] From the table above, we can see that at different speeds, the flow rate, head, power and efficiency of the pump are different. At the same speed, there is a certain relationship. According to the above three sets of parameters, we can get the following: Figure 3 The curve graph and corresponding fitting function relationship: from Figure 3 It can be concluded that: When the speed n=1500rpm, PQH satisfies the following relationship: (Formula 12) (Formula 13) When the speed n=1125rpm, PQH satisfies the following relationship: (Formula 14) (Formula 15) When the speed n=750rpm, PQH satisfies the following relationship: (Formula 16) (Formula 17) (1) When the system detects that the real-time speed is 1450 rpm, the power is 42.5 kW. At this time, the relationship H and Q are substituted into the rated speed of 1500 rpm, as shown below: (Formula 12) (Formula 13) According to formula 8, formula 9, formula 10, formula 11 can be derived , that is , into formula 12, 13

[0048]

[0049] Flow and speed relationship: (Formula 8), that is

[0050] Lift and speed relationship: (Formula 9), that is

[0051] (Formula 11), that is

[0052] Therefore, when the system detects the real-time speed of 1450 rpm, the power is 42.5 kW, the system calculates the flow , lift , efficiency .

[0053] (2) When the pump inlet and outlet flange is connected to the pressure sensor, the detected value is P in =0.0205mpa, P out =0.2751mpa, the system detects the real-time speed of 1450 rpm, the power is 42.5kW, at this time, the relationship formula H and Q of the rated speed of 1500 rpm is brought in.

[0054] Centrifugal pump lift: H=(P out -P in ) =0.2751-0.0205=25.98m.

[0055] According to the calculation of (1) above , into (Formula 11), that is

[0056]

[0057] At this time, the efficiency deviation is greater than 5%, and the system prompts the pump energy efficiency attenuation.

[0058] (3) When the system detects the real-time speed of 1200 rpm, the power is 21.2kW, at this time, the relationship formula H1 and Q1 of the speed of 1125 rpm is brought in The following relationship: The following relationship: (Formula 14) (Formula 15) According to formula 8, formula 9, formula 10, formula 11 That is , substituting formula 14, 15

[0059]

[0060] Flow and speed relationship: (Formula 8) that is

[0061] Head and speed relationship: (Formula 9) that is

[0062] (Formula 11) that is

[0063]

[0064] At this time, the efficiency is lower than the highest efficiency 92%, the system prompts the pump to operate in the partial working condition.

[0065] The following table (Table 1) compares the test data of a certain type of centrifugal pump on the test bench with the data detected by the controller:

[0066] From the above table, it can be seen that in the range of 60-120% of the rated flow of the centrifugal pump, the flow Q, head H and efficiency The deviation of the data detected by the controller from the actual test data on the test bench is about-2% to 2%, according to the 2B level precision specified in the "GBT3216-2016 Rotary Power Pump Hydraulic Performance Acceptance Test 1st, 2nd and 3rd" level, flow ±8%, head ±5%, efficiency-5%, the data detected by this method can better meet the actual engineering application.

[0067] The above shows and describes the basic principles and main features of the present application and the advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above examples, and the above examples and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A centrifugal pump intelligent control method, characterized in that: The centrifugal pump intelligent control method includes: the centrifugal pump is driven by a controller to operate in a pipeline system, and the controller monitors the power and speed of the centrifugal pump in real time during operation, thereby realizing real-time monitoring and display of the flow rate, pressure, and efficiency of the centrifugal pump; Input the centrifugal pump's highest efficiency, rated speed, flow rate, head, and power parameter points at other speeds into the controller to generate the relationship between power P-flow rate Q, flow rate Q-head H, as well as the relationship between flow rate Q-speed n, head H-speed n, power P-speed n, power P and flow rate Q, head H, efficiency The relationship formula.

2. The centrifugal pump intelligent control method according to claim 1, characterized in that: The controller monitors the real-time power P of the centrifugal pump r and speed n r , calculate the current real-time flow Q r , lift H r ,efficiency r .

3. The centrifugal pump intelligent control method according to claim 1, characterized in that: Set the target flow rate Q in the controller v , target pressure P v , according to the real-time feedback flow Q r , lift H r Perform PID control.

4. The centrifugal pump intelligent control method according to claim 1, characterized in that: Efficiency of real-time feedback in the controller r , with the highest efficiency of centrifugal pumps max By comparison, when it is lower than the maximum efficiency of 92%, the controller prompts the centrifugal pump to operate out of the high efficiency zone.

5. The centrifugal pump intelligent control method according to claim 1, characterized in that: When the pressure sensor is connected to the inlet flange of the centrifugal pump and the outlet flange, the controller directly calculates the head H of the centrifugal pump. x , and according to the power P-flow Q relationship, and flow Q-speed n, head H-speed n, power P-speed n, power P and flow Q head H efficiency The relationship is used to calculate the real-time flow Q x ,efficiency x .

6. The centrifugal pump intelligent control method according to claim 2, characterized in that: When the real-time efficiency is calculated x and efficiency r When the deviation is greater than 5%, the controller prompts that the energy efficiency of the centrifugal pump has declined.

7. The centrifugal pump intelligent control method according to claim 1, characterized in that: The controller adopts a variable frequency controller.

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