JPH03168386A - Measuring device of pump discharge flow - Google Patents

Abstract

PURPOSE:To improve measurement precision by constituting an actual head operation section, a head curve judgement section, a resistance curve judgement section and a flow operation section which operates pump discharge flow corresponding to a pump running point during actual running in accordance with an actual head and a quadratic equation for a head curve and a resistance curve. CONSTITUTION:An actual head operation circuit 7 calculates actual head Ho in accor dance with a difference between the water level Ha of a pump #1 and the water level Hb of discharge #2 detected by level meters 5, 6. A head curve judgement circuit 8 judges a quadratic equation corresponding to the rotating speed detecting signal of a pump 3 from a quadratic equation for a head curve calculated for every rotating speed. A resistance curve judgement circuit 9 judges a quadratic equation corresponding to a discharge valve opening signal at a current point from a resistance curve calcu lated for every valve opening of a discharge valve 4. On the other hand, a flow opera tion circuit 10 operates the discharge flow of the pump corresponding to a running point at which the head curve and the resistance curve are intersected in accordance with an actual head Ho obtained above and a quadratic equation corresponding to the pump head curve and the resistance curve during actual running.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pump discharge flow rate measuring device that is used, for example, in a water pump installed between a pump well and a discharge well of a rainwater pumping station.

[Conventional technology]

In the rainwater pumping station mentioned above, it is necessary to automatically measure the water discharged by the pump from the viewpoint of discharge management.

On the other hand, as a method of measuring the pump discharge flow rate at a pumping station, the discharge flow rate at the pump operating point is determined by calculation from the lift curve of the pump itself and the resistance curve of the water supply pipe including the discharge valve, without using a flow meter. The measurement method described above has already been implemented.

In this case, in the conventional IT measurement method, the head curve and resistance curve of the pump are simulated as a linear equation approximated by a broken line, and the water level difference between the pump well and the flow well is calculated. Pump rotation speed. Based on the detected value of the discharge valve opening, a linear equation is calculated that approximates the actual head of the pump, the head curve and the resistance curve with parameters such as the pump rotation speed and the discharge valve opening. The solution of the operating point for the pump (the intersection of the head curve and the resistance curve) is calculated, and the pump discharge flow rate in that operating state is determined.

[Problems that the invention attempts to solve]

By the way, the conventional pump discharge 2Affl measurement method 2 described above has the disadvantage that the calculation processing program is complicated and the error of 2ii1 obtained by calculation becomes large. In other words, although the pump head characteristic line and the resistance line represented by the pipe friction head loss (proportional to the square of the flow velocity in the pipe) are originally quadratic curves, they can be approximated by a broken line. In order to simulate this as a linear equation, many linear equations are required to represent one curve, and in addition, each rotation speed is calculated using the pump rotation speed and discharge valve opening as parameters. Expressing the head curve and resistance curve corresponding to the valve opening requires an enormous calculation program, and it takes a long time to calculate the flow rate. Furthermore, since the curve is simulated using a linear equation approximating a broken line, the error in the calculated flow rate also becomes large.

The present invention has been made in consideration of the above points, and an object of the present invention is to provide a pump discharge flow rate measuring device that simplifies the program to shorten calculation time and improves flow rate measurement accuracy. Suppose that [Means for Solving the Problems] In order to solve the above problems, the measuring device of the present invention includes an actual head calculation unit that calculates the actual head of the pump from the water level difference between the pump well and the discharge well; Lifting head curve. a head curve determination unit that determines a resistance curve of a pump water supply pipe including a discharge valve as a quadratic equation corresponding to the detected value of the pump rotation speed and the discharge valve opening; and a resistance curve determination unit; and a flow rate calculation unit that calculates the pump discharge flow rate corresponding to the pump operating point during actual operation from the quadratic equation of the head curve and the resistance curve.

[Effect] The discharge flow rate of the pump is the actual head. It can be determined from the operating point, which is the intersection of the pump head curve and the resistance curve, depending on conditions such as the pump rotation speed and the opening degree of the discharge valve. Here, as is well known, the head curve of a pump is determined by the number of revolutions of the pump. If there are multiple pumps, the resistance curve changes depending on the number of pumps in operation, and the resistance curve is a quadratic curve that changes depending on the discharge valve opening condition, so each can be expressed as a quadratic equation.
It has also been confirmed that this quadratic equation matches the actual pump test data. In other words, the lifting head is H. The quadratic equation representing the head curve of the pump, where Q is the flow rate, is as shown in equation (1) below. H=AQ” +BQ10C・1・・・・・・−・−・・・
-・- (1) Regarding the head curve of the pump shown in FIG. 2, three points P. (81, lo+)+Pz(L+Qz)
, Ps(lli,Qs) by solving the following quadratic equation as an inverse matrix, the constant A in the previous equation,
B and C can be found.

}It = A Q+” 10B Q+ + CH.=A
Q1+BQt+C H. -AQ," +BQ.+C Similarly, the resistance curve can be expressed by the following quadratic equation: H - a Q' + b Q + c -------
-----(2) 3 determined on the resistance curve using the same method as above
By solving the quadratic equation corresponding to the point using an inverse matrix, the constants a, b, and c can be obtained.

Therefore, the actual pump head H0 obtained from the water level difference between the pump well and the downstream discharge well at the pumping station as the difference in water level between the two, and the pump head curve during actual operation determined based on the pump rotation speed detection signal. Find the corresponding quadratic equation ((1) 2) and the quadratic equation ((2) equation) corresponding to the resistance curve determined based on the detection signal of the discharge valve opening, and add the above-mentioned actual hot water to the constant term. By adding the equation H0, connecting these two quadratic equations with equals, and solving the equation, the discharge flow IQ corresponding to the operating point of the pump during actual operation can be determined as follows.

AQ” +BQ+C=aQ” 10bQ+c+H. (A
a) Q” + (B b) Q+ (C
c He) Here, if we set (A-a) 丑 α (B-b) = β (C c He) = γ, then the pump discharge flow IQ can be calculated using the formula for solving the quadratic equation, Q = (1 β±■door=ko rxr)/2α−・−・・(3)
It can be calculated using

〔Example〕

FIG. 1 is a system diagram of a pump discharge flow rate measuring device according to an embodiment of the present invention. In the figure, l is a pump well, 2 is a downstream discharge well, 3 is a pump installed between pump well 1 and discharge well 2, 4 is a discharge valve of pump 3, and the discharge flow rate measuring device is a pump well 1. A water level gauge 5 attached to the discharge well 2, a water level gauge 6 attached to the discharge well 2, an actual head calculation circuit 7 for calculating the actual head H6 of the pump 3, a head curve discrimination circuit 8 for the pump 3, a resistance curve discrimination circuit 9 for the pump water pipe line , and a flow rate calculation circuit lO for determining the discharge flow rate of the pump. Here, the actual head calculation circuit 7 calculates the actual head H0 from the water level difference between the water level Ha of the pump well 1 and the water level 1 lb of the discharge well 2 detected by the water level gauge 5.6. In addition, head curve discrimination time B7
determines the quadratic equation corresponding to the rotational speed detection signal of the pump 4 during actual operation from the quadratic equation of the head curve calculated for each rotational speed.

Furthermore, the resistance curve discriminating circuit 8 discriminates the quadratic equation corresponding to the discharge valve opening signal at that time point from the resistance curve calculated for each valve opening of the discharge valve 5. On the other hand, the flow rate calculation circuit 10 calculates the actual head H. , and the pump head curve during actual operation. Based on the quadratic equation corresponding to the resistance curve, calculate the solution of the simultaneous quadratic equations using the solution formula of equation (3) mentioned above, and find the pump corresponding to the operating point that is the intersection of the head curve and the resistance curve. The discharge flow rate is determined and the calculation result is output to a recorder (not shown) as a measured value of the discharge flow rate. [Effects of the Invention] Since the pump discharge flow rate measuring device according to the present invention is configured as explained above, the calculation program is simpler than the conventional method of measuring using a linear equation approximated by a broken line. The pump discharge flow rate for arbitrary pump operating conditions at a pumping station can be determined with higher accuracy using faster calculations.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of a pump discharge flow rate measuring device according to an embodiment of the present invention, and FIG. 2 is an explanatory diagram for determining a quadratic equation of a pump head curve. In the figure, l: pump well, 2: discharge well, 3: pump, 4: discharge valve, 5.6: water level gauge, 7: actual head calculation circuit, 8: head curve discrimination circuit, 9: resistance curve discrimination circuit, 10: Flow rate calculation circuit.

Claims (1)

[Claims] 1) A device for measuring the discharge flow rate of a water pump installed between a pump well and a discharge well at a pumping station, and an actual head calculation that calculates the actual head of the pump from the water level difference between the pump well and the discharge well. a head curve determination unit that calculates a pump head curve and a resistance curve of a pump water supply pipe line including a discharge valve as a quadratic equation corresponding to detected values of pump rotation speed and discharge valve opening; and a resistance curve determination unit. , a flow rate calculation section which calculates the pump discharge flow rate corresponding to the pump operating point during actual operation from the actual head obtained as described above, and the quadratic equation of the head curve and the resistance curve. measuring device.