Water pump cavitation inhibition device and control method thereof

Abstract

The invention discloses a water pump cavitation inhibition device and a control method thereof.The water pump cavitation inhibition device comprises a controller, a circulation pipeline, a steam-water separator, a mixer, a cooling heat exchanger and a pump, and the steam-water separator, the mixer, the cooling heat exchanger and the pump are sequentially arranged on the circulation pipeline; pressure sensors are arranged on the circulating pipeline on the upstream and the downstream of the pump, and the pump is connected with a power sensor. In the invention, the lift of the pump is calculated through the two pressure sensors, the water pump input power of the water pump corresponding to the calculated lift is matched through the basic data in the database, the water pump input power is compared with the power measured by the power sensor, and if the actual power measured by the power sensor is smaller than the matched input power, the pump is started. And judging that the water pump is in a cavitation state.

Description

Technical Field

[0001] The present invention relates to the technical field of water pump application equipment, and more specifically to a water pump cavitation suppression device and a control method thereof. Background Art

[0002] At present, the cooling is only carried out through a single heat exchanger in front of the pump, and no judgment measures are taken. When the working conditions change, the possibility of cavitation of the water pump will be greatly increased. Therefore, the possibility of cavitation can only be reduced to a certain extent, and it is impossible to accurately judge whether the pump has cavitation and make corresponding adjustments.

[0003] The patent document with patent publication number CN 107035726 A discloses a protective device for preventing pump cavitation of an ORC power generation system, including a condenser; the condenser includes a working fluid side flow channel and a cooling water flow channel. According to the working fluid flow direction, the working fluid side flow channel of the condenser is respectively connected to the system working fluid side inlet and the working fluid storage tank through pipelines, the working fluid storage tank is connected to a pre-pump cooling heat exchange device through pipelines, the pre-pump cooling heat exchange device is sequentially connected to a working fluid pump and a system working fluid side outlet through pipelines, according to the cooling water flow direction, the cooling water flow channel of the condenser is respectively connected to the system cooling water side outlet and the pre-pump cooling heat exchange device through pipelines, the pre-pump cooling heat exchange device is sequentially connected to a cooling water circulation pump and a system cooling water side inlet through pipelines; the scheme controls the temperature of the organic working fluid by adjusting the cooling water flow rate to change the heat exchange effect, thereby controlling the effective cavitation margin, the cooling water reduces the temperature of the organic working fluid, ensures that the effective cavitation margin is increased, and solves the cavitation problem of the pump.

[0004] But it is unable to judge whether the water pump is in a cavitation state and accurately eliminate the cavitation phenomenon. Summary of the invention

[0005] The technical problem to be solved by the present invention is how to judge whether a water pump is in a cavitation state and eliminate the cavitation phenomenon.

[0006] The present invention solves the above technical problems through the following technical means: a water pump cavitation suppression device, comprising a controller, a circulation pipeline, and a steam-water separator, a mixer, a cooling heat exchanger, and a pump arranged in sequence on the circulation pipeline, the mixer is also connected to a water supply pipeline, the water supply pipeline is provided with a control valve, the circulation pipelines located upstream and downstream of the pump are provided with pressure sensors, the pump is connected to a power sensor, the circulation pipelines located downstream of the cooling heat exchanger and upstream of the pump are provided with a temperature sensor, the controller is electrically connected to the control valve and the temperature sensor, the pump head is calculated by two pressure sensors, and the water pump input power of the water pump corresponding to the calculated head is matched through basic data in a database, the water pump input power is compared with the power measured by the power sensor, if the actual power measured by the power sensor is less than the matched input power, it is determined that the water pump is in a cavitation state, then the outlet temperature of the circulation pipeline located at the cooling heat exchanger is reduced until the water pump is in a non-cavitation state, if the actual power measured by the power sensor is greater than the matched input power, it is determined that the water pump is in a non-cavitation state.

[0007] As a preferred technical solution, a liquid level sensor is provided on the steam-water separator, and the liquid level sensor is electrically connected to the controller. The controller maintains the liquid level in the steam-water separator at a set liquid level through the liquid level sensor.

[0008] As a preferred technical solution, the steam-water separator is connected to an exhaust pipeline and a drain pipeline, the steam-water separator is connected to the mixer through the drain pipeline, and the control valve includes an electric regulating valve 1.

[0009] As a preferred technical solution, a steam generating heat exchanger is provided on the circulation pipeline between the upstream of the steam-water separator and the downstream of the pump, and a first heat exchange pipeline is connected to the steam generating heat exchanger, and the first heat exchange pipeline performs countercurrent heat exchange with the steam generating heat exchanger.

[0010] As a preferred technical solution, the cooling heat exchanger is also connected to a second heat exchange pipeline, the second heat exchange pipeline performs countercurrent heat exchange with the circulation pipeline, and a second electric regulating valve is provided on the second heat exchange pipeline.

[0011] As a preferred technical solution, the exhaust pipeline is connected to the top of the steam-water separator, and the drain pipeline is connected to the bottom of the steam-water separator.

[0012] As a preferred technical solution, the pressure sensor includes a pressure sensor 1 arranged upstream of the pump and a pressure sensor 2 arranged downstream of the pump.

[0013] The control method of the water pump cavitation suppression device comprises the following steps: S1, monitoring the liquid level data by means of a liquid level sensor, so that the liquid level of the steam-water separator is maintained at a set liquid level;

[0014] S2. Enter the basic curve data of the flow rate, head, power, and cavitation of the pump in the control system as the basic data in the database.

[0015] S3. Calculate the head of the water pump through two pressure sensors, and match the pump input power of the water pump corresponding to the calculated head from the basic curve data.

[0016] The head is calculated by the following formula: H = (p2 - p1) / ρg;

[0017] where H is the head; p1 and p2 are the pressure values at the upstream and downstream of the pump; ρ is the liquid density; g is the acceleration due to gravity.

[0018] S4. Compare the pump input power with the power measured by the power sensor. If the actual power measured by the power sensor is less than the matched input power, it is determined that the water pump is in a cavitation state, and then the outlet temperature of the circulating pipeline located at the cooling heat exchanger is reduced until the water pump is in a non-cavitation state. If the actual power measured by the power sensor is greater than the matched input power, it is determined that the water pump is in a non-cavitation state.

[0019] As a preferred technical solution, it further includes:

[0020] S5. Calculate the saturated vapor pressure of the water at the pump inlet through the outlet temperature of the cooling heat exchanger in combination with the following formula:

[0021]

[0022] where:

[0023] P s is the pressure; T is the temperature; A = 7.96681, B = 1668.21, C = 228;

[0024] S6. Calculate and judge whether it is in a cavitation state at present according to the following formula through the required net positive suction head NPSHr of the water pump corresponding to the head calculated in S3 and P s Let P1 - P

[0025] / ρg - NPSHr = X; P1 is the value of the upstream pressure sensor of the pump; s When X ≤ 0, the water pump is in a cavitation state;

[0026] When X ≥ 0.5, the water pump is in a non-cavitation state;

[0027] When 0 < X < 0.5, maintain the current judgment state;

[0028] When 0 < X < 0.5, maintain the current judgment state;

[0029] where ρ and g are the density and acceleration due to gravity of the medium respectively, and g is taken as 9.81 m / s2 When the medium is water, ρ is 1000 kg / m 3 .

[0030] As a preferred technical solution, when any step in S4 and S6 determines that the pump is in a cavitation state, the outlet temperature of the cooling heat exchanger is reduced, otherwise the outlet temperature is increased until the water pump is in a non-cavitation state.

[0031] The beneficial effects of the present invention are:

[0032] (1) In the present invention, the head of the pump is calculated by two pressure sensors, and the water pump input power of the water pump corresponding to the calculated head is matched by the basic data in the database, and the water pump input power is compared with the power measured by the power sensor. If the actual power measured by the power sensor is less than the matched input power, it is determined that the water pump is in a cavitation state, and the outlet temperature of the circulation pipeline located at the cooling heat exchanger is reduced until the water pump is in a non-cavitation state. If the actual power measured by the power sensor is greater than the matched input power, it is determined that the water pump is in a non-cavitation state. It is possible to determine whether the water pump is in a cavitation state and eliminate the cavitation phenomenon.

[0033] (2) In the present invention, a cooling heat exchanger is provided and a mixer is added upstream of the cooling heat exchanger. The mixer is connected to a water supply pipeline. The working fluid in the circulation pipeline can be heat exchanged by water supply. The working fluid in the circulation pipeline can be cooled down for a second time by the cooling heat exchanger. The effective NPSHr is controlled to reduce the working fluid temperature, thereby ensuring that the effective NPSHr increases and solving the cavitation problem of the pump.

[0034] (3) In the present invention, the amount of water replenishment can be controlled by the electric regulating valve 1, and the liquid level in the steam-water separator can also be stabilized, reducing the impact of the change in the liquid level on the pressure sensor 1, thereby improving the control accuracy of the entire system. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 A schematic diagram of the overall structure provided by an embodiment of the present invention;

[0036] Figure 2 Flow rate, head and power curve diagram provided by the embodiment of the present invention;

[0037] Figure numbers: 1. Steam generating heat exchanger; 2. Steam-water separator; 3. Liquid level sensor; 4. Mixer; 5. Electric regulating valve 1; 6. Cooling heat exchanger; 7. Electric regulating valve 2; 8. Temperature sensor; 9. Pressure sensor 1; 10. Pump; 11. Power sensor; 12. Pressure sensor 2. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] See also Figure 1 , a water pump cavitation suppression device and a control method thereof, comprising a circulation pipeline and a steam generating heat exchanger 1, a steam-water separator 2, a mixer 4, a cooling heat exchanger 6, and a pump 10 sequentially arranged on the circulation pipeline. The steam generating heat exchanger 1 is also connected to a first heat exchange pipeline. The heat medium enters the steam generating heat exchanger 1 through the first heat exchange pipeline to cool down and dissipate heat and is output through the first heat exchange pipeline. At the same time, the liquid water in the circulation pipeline is heated to become a two-phase steam-water mixture and flows out to the steam-water separator 1. The overall flow direction is countercurrent heat exchange. It should be noted that countercurrent refers to a flow opposite to the flow direction of the working medium in the circulation pipeline. The working medium takes water as an example, and of course it can also be other working medium materials. The top of the steam-water separator 2 is connected to a steam output pipeline, and the bottom is connected to the mixer 4. The steam-water mixture separates the two-phase steam-water mixture through the steam-water separator. Saturated steam flows out from the top of the steam-water separator 2, and saturated water settles to the bottom, thereby separating the water vapor;

[0040] A liquid level sensor 3 is provided in the steam-water separator 2, and the liquid level sensor is used to monitor the liquid level of the steam-water separator 2 as a signal output. A water supply pipeline is connected to the mixer 4, and the mixer 4 mixes the water from the steam-water separator with the water input from the water supply pipeline. The mixing can cool the water from the steam-water separator, that is, the circulating working medium. An electric regulating valve 5 is provided on the water supply pipeline, and the electric regulating valve 5 is used to control the water supply amount. At the same time, it can also stabilize the liquid level in the steam-water separator 2, reduce the influence of the change of the liquid level on the pressure sensor 9, thereby improving the control accuracy of the whole system;

[0041] The cooling heat exchanger 6 is connected to a second heat exchange pipeline, in which a cooling medium is provided, and the cooling medium is water. The cooling water cools down the mixed water output by the mixer 4, which is a countercurrent heat exchange. An electric regulating valve 2 7 is provided on the second heat exchange pipeline, and the electric regulating valve 2 7 is used to control the flow of the cooling water in the second heat exchange pipeline, thereby adjusting the heat exchange efficiency;

[0042] The circulation pipeline between the cooling heat exchanger 6 and the pump 10 is provided with a temperature sensor 8 and a pressure sensor 9 in sequence along the flow direction of the working medium. The temperature sensor 8 is used to monitor the temperature of the medium entering the pump, and the pressure sensor 9 is used to monitor the pressure of the medium entering the pump. The pump 10 is used as a power device of the circulation pipeline. The pump 10 is connected to a power sensor 11, which is used to monitor the input electrical power of the pump 10. The downstream of the pump 10 is connected to a pressure sensor 12, which is used to monitor the pressure of the working medium leaving the pump 10.

[0043] See also Figure 2 , the control method comprises the following steps:

[0044] S1, liquid level control: monitor the liquid level data in real time through the liquid level sensor 3 of the steam-water separator 2, and maintain the liquid level at the set liquid level by controlling the electric regulating valve 5 on the water supply pipeline;

[0045] S2, inputting the basic curve data of flow rate, head, power and cavitation of the pump 10 into the control system as a benchmark;

[0046] S3, calculating the head of the water pump by using the pressure sensor 1 9 and the pressure sensor 2 12, and matching the water pump input power and required NPSHr of the water pump corresponding to the calculated head from the basic curve data;

[0047] The head is calculated using the following formula: H = (p2-p1) / ρg;

[0048] Where H is the head, in m; p1, p2 are the pressures of the liquid at the pump inlet and outlet, i.e. the values ​​at pressure sensor 19 and pressure sensor 212, in Pa; ρ is the liquid density, in kg / m 3 ; g is the acceleration due to gravity, in m / s 2 ;

[0049] S4, by monitoring the operating power of the pump 10 and comparing it with the water pump input power corresponding to the head calculated in S3, if the actual water pump power measured by the power sensor 11 is less than the matched power, it is determined that the water pump is in a cavitation state;

[0050] S5. Calculate the saturated vapor pressure of the pump inlet water by using the outlet temperature of the cooling heat exchanger 6, i.e., the value of the temperature sensor 8, in combination with the following formula;

[0051]

[0052] in:

[0053] P s is pressure, unit kPa; 0.13332 is the unit conversion coefficient when mmhg is converted to kPa; T is temperature, unit ℃;

[0054] A, B, C: coefficients respectively. Different media have different coefficients. In this embodiment, when calculating the saturated vapor pressure of water vapor, A is 7.96681, B is 1668.21, and C is 228;

[0055] S6. The required net positive suction head NPSHr of the water pump corresponding to the lift calculated in S3 and the saturated vapor pressure P calculated in S5 ss Calculate and determine whether it is in the cavitation state according to the following formula;

[0056] Let P1 - P s / ρg - NPSHr = X; P1 is the value of pressure sensor 9;

[0057] When X ≤ 0, the water pump is in the cavitation state;

[0058] When X ≥ 0.5, the water pump is in the non - cavitation state;

[0059] When 0 < X < 0.5, maintain the current judgment state;

[0060] Among them, ρ and g are the density and gravitational acceleration of the medium respectively, where g takes 9.81 m / s 2 , when the medium is water, ρ takes 1000 kg / m 3 , 0.5 is used for adjustment;

[0061] S7. When any step in S4 and S6 determines that the pump is in the cavitation state, increase the opening of the electric control valve 2 to reduce the outlet temperature of the cooling heat exchanger 6, and vice versa, reduce the opening, and finally reach the state where the water pump is in the non - cavitation state.

[0062] 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 foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A water pump cavitation suppression device, characterized in that: The invention comprises a controller, a circulation pipeline, and a steam-water separator, a mixer, a cooling heat exchanger and a pump which are arranged on the circulation pipeline in sequence. The mixer is also connected to a water supply pipeline, and a control valve is arranged on the water supply pipeline. Pressure sensors are arranged on the circulation pipelines located upstream and downstream of the pump, and a power sensor is connected to the pump. A temperature sensor is arranged on the circulation pipelines located downstream of the cooling heat exchanger and upstream of the pump. The controller is electrically connected to the control valve and the temperature sensor. The head of the pump is calculated by two pressure sensors, and the water pump input power of the water pump corresponding to the calculated head is matched by basic data in a database. The water pump input power is compared with the power measured by the power sensor. If the actual power measured by the power sensor is less than the matched input power, it is determined that the water pump is in a cavitation state, and the outlet temperature of the circulation pipeline located at the cooling heat exchanger is reduced until the water pump is in a non-cavitation state. If the actual power measured by the power sensor is greater than the matched input power, it is determined that the water pump is in a non-cavitation state.

2. The water pump cavitation suppression device according to claim 1, characterized in that: The steam-water separator is provided with a liquid level sensor, and the liquid level sensor is electrically connected to the controller. The controller maintains the liquid level in the steam-water separator at a set liquid level through the liquid level sensor.

3. The water pump cavitation suppression device according to claim 1, characterized in that: The steam-water separator is connected with an exhaust pipeline and a drain pipeline, the steam-water separator is connected with a mixer through the drain pipeline, and the control valve includes an electric regulating valve 1.

4. The water pump cavitation suppression device according to claim 1, characterized in that: A steam generating heat exchanger is provided on the circulation pipeline between the upstream of the steam-water separator and the downstream of the pump. The steam generating heat exchanger is connected to a first heat exchange pipeline, and the first heat exchange pipeline performs countercurrent heat exchange with the steam generating heat exchanger.

5. The water pump cavitation suppression device according to claim 1, characterized in that: The cooling heat exchanger is also connected to a second heat exchange pipeline, the second heat exchange pipeline performs countercurrent heat exchange with the circulation pipeline, and a second electric regulating valve is arranged on the second heat exchange pipeline.

6. The water pump cavitation suppression device according to claim 3, characterized in that: The exhaust pipeline is connected to the top of the steam-water separator, and the drain pipeline is connected to the bottom of the steam-water separator.

7. The water pump cavitation suppression device according to claim 1, characterized in that: The pressure sensor includes a pressure sensor 1 disposed upstream of the pump and a pressure sensor 2 disposed downstream of the pump.

8. The control method of a water pump cavitation suppression device according to any one of claims 1 to 7, characterized in that: The steps include: S1. Monitor the liquid level data through the liquid level sensor to maintain the liquid level of the steam-water separator at the set liquid level; S2. The basic curve data of the pump flow, head, power and cavitation are input into the control system as the basic data in the database; S3, calculating the head of the water pump by two pressure sensors, and matching the water pump input power of the water pump corresponding to the calculated head from the basic curve data; The head is calculated using the following formula: H = (p2-p1) / ρg; Where H is the head; p1 and p2 are the upstream and downstream pressure values ​​of the pump; ρ is the liquid density; g is the gravitational acceleration; S4. Compare the water pump input power with the power measured by the power sensor. If the actual power measured by the power sensor is less than the matched input power, the water pump is determined to be in a cavitation state. The outlet temperature of the circulation pipeline at the cooling heat exchanger is reduced until the water pump is in a non-cavitation state. If the actual power measured by the power sensor is greater than the matched input power, the water pump is determined to be in a non-cavitation state.

9. The control method of the water pump cavitation suppression device according to claim 8, characterized in that: Also includes: S5. Calculate the saturated vapor pressure of the water at the pump inlet by combining the outlet temperature of the cooling heat exchanger with the following formula: Where: P s is pressure; T is temperature; A=7.96681, B=1668.21, C=228; S6. The pump head corresponding to the head calculated in S3 must have a NPSHr and P s Calculate and use the following formula to determine whether it is currently in the cavitation state; Let P1-P s / ρg-NPSHr=X; P1 is the value of the upstream pressure sensor of the pump; When X ≤ 0, the water pump is in the cavitation state; When X ≥ 0.5, the water pump is in the non-cavitation state; When 0 < X < 0.5, maintain the current judgment state; Among them, ρ and g are the density and gravitational acceleration of the medium, respectively, and g is 9.81m / s 2 When the medium is water, ρ is 1000 kg / m 3 .

10. The control method of the water pump cavitation suppression device according to claim 9, characterized in that: When any step in S4 and S6 determines that the pump is in the cavitation state, lower the outlet temperature of the cooling heat exchanger, and vice versa, raise the outlet temperature until the water pump is in the non-cavitation state.

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