SU1765529A1 - Centrifugal pump pressure regulator - Google Patents

Abstract

SUMMARY OF THE INVENTION: The magnitude of the pressure in the pressure line is measured and converted into a controlled parameter. Compare the monitored parameter with the specified value. A control signal is formed, according to which the conductivity of the variable hydraulic resistance in the pressure line is controlled, the monitored parameter is determined as the pressure dispersion of the pump. With a given value of pressure value, an additional controlled parameter is determined and compared as a mean square value of pressure. 1 hp f-ly, 2 ill.

Description

The invention relates to the field of hydraulics and can be used in the design of self-tuning pumping systems.

The aim of the invention is to improve the accuracy of regulation.

Fig. 1 is a schematic diagram of a device for implementing a method for controlling the discharge pressure of a centrifugal pump; Fig. 2 shows the dependence of the pressure dispersion on the head at two speeds of rotation of the pump.

The device contains a series 1 pressure sensor 1 of the pump 2, an amplifier (not shown), a pressure dispersion subtractor 3 (including a quad, an integrator and a distributor, not shown), a comparison unit 4, a control unit 5, a correction element 6 and a valve movement mechanism 7. The dial is connected to block 4 (not shown).

The method is carried out as follows.

The sensor 1 measures the instantaneous values of the discharge pressure P (t), which are converted into electrical parameters of the current. These signals are amplified by the amplifier and fed to the calculator 3, where the average current value of pressure mp (t) and its dispersion is calculated. DP (x) C of the calculator 3 signals are fed to the input of block 4, and the required dispersion value is supplied to the second input of block 4

DTR

If the allowable value of the pressure dispersion at the pump outlet is set with respect to the required average pressure, then the dispersion is adjusted relative to this desired value. Know the required mean values of the pressure at the pump outlet and the distribution density f P- (P / t) of its random

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values, it is easy to determine the allowable variance. Then, the calculated value is continuously compared with the set value DRZf of block 4. After the comparison with the setpoint signals, the difference signals are taken into account by the control unit 5, which generates a signal corresponding to zero, positive and negative values of the difference signals. The error signal is processed by the valve 8, which is controlled according to the chosen law with the help of the correction element 6.

Let e (t) be the error in adjusting the pressure dispersion in accordance with the invention, i.e. the deviation of the current value of the pressure dispersion from its given constant or variable value

Ј (t) DPs (t) -DP (t) (1)

 Given that

e (t) DP3 (t) (t) -mp (t), (2) where M is the sign of the expectation operation;

mp (t) is the average current pressure value in the general case, which is a non-stationary random process, with

e (t) -O, we get:

DP3 (t) (t) -mp (t) 2} (3)

Let the mean pressure value mp (t) differ from the desired mpTp (t) and have a variation v P (t) such that

mp (t) mpTp (t) + vP (t) (4)

Then from (3) it follows that the condition Ј - 0 is fulfilled with. D Рз (t) М (t) + v P (t) - mpTp (t) 2} (5)

Because the sum P (t) t v P (t) is the deviation of the pressure not from the current, but from the required (for example, the predetermined pressure), we denote it as

P (t) + v P (t) P1 (t) and we get that

DP3 (t) (t) -mpTp (t) 2} (6)

From this expression it can be seen that if the permissible value of the pressure dispersion at the pump outlet is set with regard to the required average value, then the dispersion is controlled relative to this desired value, i.e. on P (t). Expression (6), therefore, indicates the rule for choosing the value of DP3 (t) required for the implementation of the method. In the particular case of a stationary (in a static sense) random process corresponding to a change in pressure P (t), it is easy to obtain that:

DP3 MflP (t) - mpTp (t) 2}

- 00

mprpffp CP JdP, (7)

and for non-stationary, respectively:

00

DPa (t) (t) - mPrpft) 2 fp (P t) dP (8)

- 00,

Knowing the required mean value of the pressure at the pump outlet and the distribution density fp (Pj t) of its random values, it is easy to determine the allowable value of the pressure dispersion.

Claims (2)

1. A method for controlling the injection pressure of a centrifugal pump at which the pressure value in the pressure line is measured converts it into a monitored parameter and, comparing the latter with its specified value, generates a control signal by which the conductivity of the variable flow resistance is controlled in the pressure line characterized in that, in order to increase the control accuracy, the monitored parameter is determined in the form of a pump pressure dispersion. 2. A method according to claim 1, characterized in that an additional controlled parameter is determined and compared with its predetermined value in the form of an rms pressure value. ttr 2 R, 1