CN110043744B - Method for determining valve closing rule after pump failure of high-lift water delivery system - Google Patents
Method for determining valve closing rule after pump failure of high-lift water delivery system Download PDFInfo
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- CN110043744B CN110043744B CN201910331645.6A CN201910331645A CN110043744B CN 110043744 B CN110043744 B CN 110043744B CN 201910331645 A CN201910331645 A CN 201910331645A CN 110043744 B CN110043744 B CN 110043744B
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 title claims abstract description 52
- 238000000034 method Methods 0.000 title claims abstract description 17
- 238000004364 calculation method Methods 0.000 claims abstract description 15
- 238000004088 simulation Methods 0.000 claims abstract description 9
- 230000005484 gravity Effects 0.000 claims description 3
- 230000001133 acceleration Effects 0.000 claims description 2
- 230000009471 action Effects 0.000 abstract description 9
- 230000008859 change Effects 0.000 description 6
- 238000005457 optimization Methods 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 238000005086 pumping Methods 0.000 description 2
- 230000007704 transition Effects 0.000 description 2
- 201000004569 Blindness Diseases 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000004880 explosion Methods 0.000 description 1
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
- F16L55/00—Devices or appurtenances for use in, or in connection with, pipes or pipe systems
- F16L55/04—Devices damping pulsations or vibrations in fluids
- F16L55/045—Devices damping pulsations or vibrations in fluids specially adapted to prevent or minimise the effects of water hammer
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F30/00—Computer-aided design [CAD]
- G06F30/20—Design optimisation, verification or simulation
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Abstract
The invention discloses a method for determining the closing rule of a valve after a pump failure of a high-lift water delivery system, which can draw up the initial influence moment of the valve closing according to the numerical simulation result of the pump-stopping water hammer under the condition of valve rejection for the high-lift water delivery system meeting the condition, and further can determine the closing rule of the valve according to the condition which should be met by the initial influence moment. The invention omits complicated numerical simulation trial calculation, quickly determines the valve closing rule considering the water hammer protection requirement, provides a basis for setting the action of the accident valve after the pump and has very great application prospect.
Description
Technical Field
The invention belongs to the field of hydraulic and hydroelectric engineering, and particularly relates to a method for determining a valve closing rule after a pump failure of a high-lift water delivery system.
Background
The valve has the advantages of various types, low price, convenient operation, safety, reliability and the like, and is widely applied to flow regulation and hydraulic control of a water delivery system. The reasonable valve operation can effectively reduce the harm of the transition process, so that the optimization of the valve action rule becomes an important content of the calculation research of the transition process.
For a gravity flow water delivery system, the action of a valve is the main reason for generating water hammer, theoretically, the safety of the system can be ensured as long as the valve is operated properly, so that the determination of the action rule of the valve is relatively simple, and the requirement of a control index can be met as long as the action of the valve is slow enough.
For a pressurized water delivery system, the water hammer is damaged due to the water pumping outage accident of a water pump, at the moment, in order to meet the requirements of system cutoff and water pump reverse rotation speed control, a check valve or a butterfly valve at the back of a pump needs to be closed generally, and at the moment, the water hammer is affected by the action of a valve and the water pump together, so that the determination of the action rule of the valve at the back of the pump becomes difficult.
At present, the valve action rule is preliminarily determined based on past research experience, and trial adjustment and optimization are carried out on the valve closing rule through electric calculation, so that the method is a main method for determining the optimal valve regulation rule of the valve after the pump. However, the method is lack of theoretical analysis and guidance, and has certain blindness, so that the required calculation amount is large, and time and labor are wasted.
Disclosure of Invention
The purpose of the invention is as follows: aiming at the problems, the invention provides a method for determining the closing rule of the valve after the pump is stopped in the high-lift water delivery system, and the closing rule of the valve after the pump is stopped in the pump accident considering the protection requirement of the water hammer is simply and quickly determined based on the water hammer characteristic of the high-lift water delivery system when the pump is stopped.
The technical scheme is as follows: in order to realize the purpose of the invention, the technical scheme adopted by the invention is as follows: a method for determining the closing rule of a valve after a pump failure of a high-lift water delivery system comprises the following steps:
(1) for a high-lift water delivery system meeting the conditions, carrying out numerical simulation calculation under the condition of valve failure to obtain a through-valve flow variation curve;
(2) selecting the flow Q of the valvetThe time at which the valve closes is 0, which is the initial influencing time t of the valve closing;
(3) coefficient of head loss over valve at initial moment of influence t
Wherein,
at time t, the valve opening isτtLower valve head loss coefficient; q0ξ for initial steady state operation0The valve passing head loss coefficient is the valve passing head loss coefficient when the valve is in a fully open state under the condition of initial stable operation; qtThe valve passing flow corresponding to the initial influence moment t of valve closing;
(4) searching the valve overflow characteristic curve according to the valve overflow head loss coefficient at the time t
Obtaining the valve opening tau at the moment tt；
(5) According to the following steps:
the closing rule of the valve after the pump can be obtained as follows:
wherein, tClosing deviceIs a total closing time of a straight line closing valve, t is an initial influence moment, tautIs the valve opening at time t.
In the step 1, the high-lift water delivery system needs to meet the following conditions:
wherein HBIs the water level of the effluent pool HUThe water level of the water inlet tank is a water hammer wave velocity, g is a gravity acceleration, A is the sectional area of the main pipe, and Q isT0Is the total flow of the main pipe under the condition of initial stable operation.
In the step 2, the valve after the water delivery system pump should avoid the situation that the valve passing flow is positive at the initial influence moment, if the valve is closed slowly, the initial influence moment of the valve closing is late, and the valve passing flow is negative, the valve closing will cause the backflow flow to be reduced, so that the pressure behind the valve rises, and therefore the backflow flow passing the valve at the initial influence moment should be small.
In the step 3, the valve passing head loss at the initial influence moment of valve closing is equal to the valve passing head loss under the initial stable operation condition.
Has the advantages that: compared with the conventional method of preliminarily determining the valve action rule through experience and performing trial calculation adjustment and optimization on the valve closing rule through electric calculation, the method provided by the invention is more efficient and rapid due to the omission of complicated numerical simulation calculation, and has great scientific research and practical application values.
Drawings
FIG. 1 is a schematic diagram of a system arrangement;
FIG. 2 is a graph of post-pump valve flow characteristics;
FIG. 3 is a diagram showing a change in flow through a valve in a valve failure state obtained by numerical simulation calculation;
FIG. 4 is a graph comparing the pressure change across the valve when the valve is deactivated and 0.865s is closed;
FIG. 5 is a graph comparing the change in flow through the valve with a valve rejection and a 0.865s valve closure.
Labeled as: the water level measuring device comprises a water inlet pool 1, a water pump 2, a pump rear valve 3, a water outlet pool 4 and an elevation reference 5.
Detailed Description
The technical solution of the present invention is further described below with reference to the accompanying drawings and examples.
The invention discloses a method for determining the valve closing rule after pump failure of a high-lift water delivery system, which comprises the following steps of:
(1) and (4) carrying out numerical simulation calculation on the high-lift water delivery system meeting the conditions under the condition of valve failure to obtain a through-valve flow change curve.
The high-lift water delivery system needs to meet the following conditions:
wherein HBIs the water level of the effluent pool HUThe water level of the intake pool, a is the water hammer wave velocity, g is the weightAcceleration of force, A is the cross-sectional area of the main pipe, QT0The total flow of the main pipe under the condition of initial stable operation;
(2) known from the change curve of the valve flow, if the valve is closed fast, the initial influence moment of the valve closing is earlier, and the valve flow is positive at this moment, then the valve closing will cause the positive flow to reduce to will lead to the pressure drop behind the valve, be unfavorable for the negative pressure protection of pipeline. Considering that the water pump rotates forwards at the moment, the control requirement of the reverse rotation speed of the water pump can be met, and therefore the situation that the flow of the overflow valve is positive at the moment of initial influence is avoided.
If the valve is closed slowly, the initial influence moment of the valve closing is later, and the flow passing through the valve is negative, the valve closing can reduce the backflow flow, so that the pressure behind the valve can be increased, pipe explosion needs to be prevented from occurring in a pipeline, and the backflow flow passing through the valve at the initial influence moment is smaller.
Therefore, the selected flow rate Q of the valvetThe time at which the valve closes is 0, which is the initial influencing time t of the valve closing;
(3) the valve head loss at the initial influence moment of valve closing is equal to the valve head loss under the condition of initial stable operation, and the valve head loss is determined according to the initial influence moment t of valve closing and the corresponding valve flow QtWhen the value is equal to 0, the excess valve head loss coefficient at the time t can be obtained
Wherein,
at time t, the valve opening is tautLower valve head loss coefficient; q0ξ for initial steady state operation0The valve passing head loss coefficient is the valve passing head loss coefficient when the valve is in a fully open state under the condition of initial stable operation; qtThe valve passing flow corresponding to the initial influence moment t of valve closing;
(4) look-up valveThe valve overflow characteristic curve according to the valve head loss coefficient at time t
Obtaining the valve opening tau at the moment tt；
(5) According to the following steps:
the closing rule of the valve after the pump can be obtained as follows:
wherein, tClosing deviceIs a total closing time of a straight line closing valve, t is an initial influence moment, tautIs the valve opening at time t.
The process according to the invention is illustrated below by means of a specific example.
TABLE 1
A certain high-lift water delivery system is shown in fig. 1, parameter statistics are shown in table 1, and the valve overflowing characteristic after pumping is shown in fig. 2. Because the high-lift water delivery system which meets the conditions is obtained through calculation:
therefore, the method is applicable to determining the closing rule of the valve after the pump is stopped due to the pump failure.
Through numerical simulation calculation, the change of the flow through the valve under the condition of valve failure can be obtained as shown in figure 3. As can be seen, when the time is 0.865s, the flow Q of the through valvetThis time is therefore taken as the initial moment of influence of the valve closure.
According to the conditions required to be met at the moment of initial influence, the valve passing head loss coefficient at the moment is as follows:
by looking at the valve over-flow characteristic of fig. 2, the over-valve head loss coefficient corresponds to a valve opening of 0, so the valve closing time after the pump is:
the numerical simulation calculation results of the linear closing of the post-pump valve 0.865s are shown in fig. 4 and 5. As can be seen from fig. 4 and 5, the valve closing at this rate is possible because the minimum pressure value is smaller than the valve failure time and the maximum pressure value is larger than the valve failure time, both of which are within the pressure-bearing range of the pipeline.
In conclusion, the method for determining the valve closing rule after the pump failure of the high-lift water delivery system is feasible, requires a small amount of calculation, and has high convenience.
Claims (1)
1. A method for determining the closing rule of a valve after a pump failure of a high-lift water delivery system is characterized by comprising the following steps of:
(1) for a high-lift water delivery system meeting the conditions, carrying out numerical simulation calculation under the condition of valve failure to obtain a through-valve flow variation curve;
the high-lift water delivery system meets the following conditions:
wherein HBIs the water level of the effluent pool HUThe water level of the water inlet tank is a water hammer wave velocity, g is a gravity acceleration, A is the sectional area of the main pipe, and Q isT0The total flow of the main pipe under the condition of initial stable operation;
(2) the valve after the water delivery system pump is to avoid the situation that the valve-passing flow at the initial influence moment is positive, if the valve is closed slowly, the initial influence moment of the valve closing is late, and the valve-passing flow is negative, the valve closing will cause the backflow flow to be reduced, so that the pressure behind the valve is increased, and the backflow flow of the valve passing at the initial influence moment is selected to be small;
selecting the flow Q of the valvetThe time at which the valve closes is 0, which is the initial influencing time t of the valve closing;
(3) the valve head loss at the initial influence moment of valve closing is equal to the valve head loss under the initial stable operation condition, and the valve head loss coefficient at the initial influence moment t
Wherein,
at time t, the valve opening is tautLower valve head loss coefficient; q0ξ for initial steady state operation0The valve passing head loss coefficient is the valve passing head loss coefficient when the valve is in a fully open state under the condition of initial stable operation; qtThe valve passing flow corresponding to the initial influence moment t of valve closing;
(4) searching the valve overflow characteristic curve according to the valve overflow head loss coefficient at the time t
Obtaining the valve opening tau at the moment tt；
(5) According to the following steps:
the closing rule of the valve after the pump can be obtained as follows:
wherein, tClosing deviceIs a total closing time of a straight line closing valve, t is an initial influence moment, tautIs the valve opening at time t.
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| CN112594554B (en) * | 2020-12-09 | 2021-11-12 | 河海大学 | Valve operation method for solving problem of overlarge positive pressure of high-lift water delivery system |
| CN113705120B (en) * | 2021-08-25 | 2023-09-22 | 山东省调水工程运行维护中心 | Method for formulating optimal regulation and control scheme of back valve of water diversion engineering pump |
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| CH123992A (en) * | 1926-11-27 | 1928-01-02 | Jean Lavanchy | Device for damping the shocks and vibrations occurring in pressure lines. |
| DE617502C (en) * | 1931-10-13 | 1935-08-21 | Joseph Heindorf | Water hammer |
| US3264485A (en) * | 1962-10-02 | 1966-08-02 | Hitachi Ltd | Methods and apparatus for preventing water hammer in tailrace or suction lines |
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