RU2515573C2 - Method for control of stability improvement in cavitator operation - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: invention is referred to the field of electric engineering and operation of systems with asynchronous electric motor and frequency control, in particular to control of rotation speed and prevention of critical operation modes. Technical result of the method lies in that reliability of the cavitator is improved; its stable operation is maintained by means of operation mode correction when the detected sign proves potential stalling with change in the electric motor rotation speed. The method for control of stability improvement in cavitator operation includes liquid passing in a gap between the rotor and stator and subsequent conversion of the received energy into thermal energy, control by the heating process. The claimed method for control of the cavitator operation modes is based on the analysis of higher harmonics ratio in the electric mains, its comparing with the threshold value and shaping of the control signal for frequency control unit which controls the rotation speed of the electric motor.

EFFECT: control method allows reaching maximum efficiency for activation of process liquids for the purpose of their use in different processes of chemical production such as dilution, heat generation, and synthesis.

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Description

The invention relates to the field of electrical engineering and operation of systems with an asynchronous electric motor and a frequency controller, in particular to regulating the speed of rotation and preventing critical operating modes.

Known technical solution according to patent No. 2416853, IPC H02J 3/01, RU, METHOD FOR REDUCING THE LEVEL OF HIGH HARMONICS. The method can be used in power supply systems of industrial enterprises with a constant load due to the placement of additional reactors, representing high resistance for higher harmonics, in the electrical network. Since the network contains both inductive and capacitive elements, the proposed method is based on changing the amplitude-frequency characteristics of the network node.

The advantage is to reduce the influence of higher harmonics on electrical equipment.

However, the disadvantage of this method is the inability to analyze changes in the characteristics of higher harmonics, and, therefore, the adjustment and optimization of the operating modes of electrical equipment.

A technical solution is known according to the patent No. 2427937, IPC G21C 17/00, RU, METHOD FOR DIAGNOSTIC OF THE ORIGIN OF INTERCHANNEL INSTABILITY IN A REACTOR WITH WATER UNDER PRESSURE. The method relates to nuclear energy, in particular to the field of control of the coolant in the reactor core with pressurized water, and is intended to control the occurrence of inter-channel instability (regular flow pulsations) in the core in real time. Signals from off-band neutron flux sensors (ionization chambers) are recorded. The recorded neutron flux signal is converted into a neutron power signal, decomposed into a frequency spectrum, a harmonic series with a known fundamental harmonic frequency is detected, which characterizes the occurrence of interchannel instability by amplitude-frequency discrimination. According to a previously known dependence on the reactor power level, the automatic change in the amplitude discrimination level is proportional to the spectral noise level in the measuring path, in case of detecting non-zero amplitudes in the power signal spectrum, a diagnostic signal “Inter-channel instability occurrence” is generated, which is transmitted to the input of the reactor control system.

The advantage is the reduction in the probability of false positives.

However, the method is provided by a large number of sensors, which is material-intensive.

Known technical solution according to patent No. 2413140, IPC F24J3 / 00, RU, METHOD FOR HEATING TECHNOLOGICAL LIQUIDS AND DEVICE FOR ITS IMPLEMENTATION. A method for heating process fluids involves passing a fluid in the gap between the rotor and the stator and then converting the received energy to heat, in order to reduce the power consumption and regulate the process of heating fluids with different viscosities, the heating is carried out in self-oscillating mode, determining the processing modes from the dependence:

BT = 2 · n _p · h ² · Z · ν ^-1 ,

where BT is the ratio of the Reynolds (Re) and Strouhal (Str) criteria, BT 8600;

n _p is the number of revolutions of the rotor, s ^-1 ;

h is the depth of the holes on the rotor, m;

Z is the number of holes on the rotor;

ν is the kinematic viscosity of the treated medium, m ² / s,

and control the onset of a self-oscillating process by the magnitude of the drop in power consumption by the device by an average of 20-30%.

The method of regulating the heating process when using media with different viscosities is carried out by changing the depth of the holes on the rotor.

However, the method does not provide the maximum heating efficiency of process fluids, since the maximum heating efficiency is achieved at cavitator rotor speeds close to critical, and at a critical rotor speed, flow stalls and a sharp drop in heating efficiency occurs.

Mechanical regulation does not automatically maintain the maximum effective speed of rotation of the rotor of the cavitator and prevent the stall of the fluid flow.

The technical result of the proposed method is to increase the reliability of the cavitator, ensuring the maintenance of its stable operation by correcting the operation mode in case of detection of a sign indicating the approach of the occurrence of flow stall - a change in the rotation speed of the electric motor.

The goal is achieved as follows. The method of controlling the process of increasing the stability of the cavitator includes the passage of fluid in the gap between the rotor and the stator and the subsequent conversion of the received energy into heat, regulating the heating process, while the analyzer fixes all the characteristics of the electric power supplied to the electric motor, and sends a signal to the electronic control unit, which calculates coefficient K (for odd harmonics) according to the formula:

where K is the program coefficient for the control unit, characterizing the mode of operation of the cavitator;

V is the value of the harmonic voltage;

n, m is the harmonic sequence number (where n> m, 3≤n, 1≤m≤n-2);

- compare the obtained value of the coefficient with the embedded software standard:

- when K <the reference value, the electronic control unit sends a signal to the frequency controller, which ↑ increases the speed of rotation of the electric motor,

- when K> the reference value, the electronic control unit sends a signal to the frequency controller, which ↓ reduces the speed of rotation of the electric motor

The method is as follows. When the power source (6) is turned on with a voltage of 380 V, power is supplied to the frequency controller (5), which starts the electric motor (2), which rotates the cavitator rotor (1). The analyzer (3) fixes all the characteristics of the electric power supplied to the electric motor (2), and sends a signal to the control unit (4). The control unit, with a resolution of 0.01 sec, calculates the coefficient K (for considering odd harmonics) according to the formula

,

,

where K is the program coefficient for the control unit,

characterizing the mode of operation of the cavitator;

V is the value of the harmonic voltage;

n, m is the harmonic sequence number (n> m, 3≤n, 1≤m≤n-2).

The value of the calculated coefficient K is compared with the value of the embedded software standard:

- when K <the reference value, the electronic control unit sends a signal to the frequency controller, which ↑ increases the speed of rotation of the electric motor,

-for К> of the reference value, the electronic control unit sends a signal to the frequency controller, which ↓ reduces the rotation speed of the electric motor.

1. An example implementation of the method:

A diagram of a device for implementing the proposed method is presented in figure 1, where:

1. The cavitator;

2. The electric motor;

3. The analyzer;

4. The electronic control unit;

5. The frequency regulator;

6. Power source.

Cavitator 1 for optimal operation should maintain a certain (optimal) rotor speed, with an increase in this frequency to a certain limit, a stall of the fluid flow can be observed, which sharply reduces the heating efficiency, to restore normal operation, a complete stop of the cavitator is necessary to completely fill with liquid.

In order to optimize the workflow, the circuit includes an analyzer 3 of higher harmonics in the mains, a frequency regulator 5 of the rotational speed of the electric motor 2 and an electronic control unit. four.

When the operating mode of the cavitator 1 approaches critical, the parameters of the electric motor 2 become different and the current-voltage characteristics of the higher harmonics of the electric network change dramatically. The electronic control unit 4 receives the corresponding signal from the analyzer 3 of higher harmonics in the mains, and that in turn supplies a control signal to the frequency controller 5, which reduces the speed of the electric motor 2. Accordingly, the speed of the rotor of the cavitator 1 decreases, as a result, the heating process of the liquid normalizes without stopping the equipment.

For odd harmonics 3, 5, 7, 9, and 11, which have the largest amplitude and are the most informative, with regard to the processes occurring during the operation of the cavitator, K lies in the range 0.3≤K <1.

The diagram of the ratio of the voltage value of the 9th harmonic to the 3rd when turning on / off the cavitator is shown in Figure 2.

In figure 3, 4 - two areas are selected, corresponding to one cycle (on-off) of the cavitator for a time t = 1 min, at a different value of K, presented

Figure 3 at 0.3≤K is a stable process of the cavitator. In Fig. 4, when K <0.3, a process threatening a stall

The analyzer 3 transmits a signal to the electronic control unit, which, using a frequency controller, reduces the speed of rotation of the electric motor.

The method for controlling the operating modes of the cavitator is based on the analysis of the ratio of higher harmonics in the electric network, comparing it with a threshold value and generating a signal for controlling the speed of rotation of the electric motor.

The inventive control method allows you to automatically maintain the optimal speed of rotation of the rotor of the cavitator to ensure maximum heating efficiency of process fluids. It does not require the use of a large number of sensors and analyzers; it has great reliability and accuracy.

2. An example implementation of the proposed method. A diagram of a device for implementing the proposed method is presented in Figure 5, where:

1-7 - Polymer insulators;

8 - Switchgear with polymer concentration analyzer;

9 - The device of FIG. 1.

The method of cleaning the line of polymerization agents 1-7 during the production of butyl rubber using the process of activating a solvent, for example, saturated hydrocarbons, in which, after the heating process in the device of FIG. 1, it is fed into one polymerizer, where the walls are cleaned and the agitator is removed from the reaction products. Switching to the next polymerizer from the line occurs after reaching the maximum concentration of the polymer (reaction product) in the solvent (saturated hydrocarbon)

Claims (1)

A method of controlling the process of increasing the stability of the cavitator, including
the passage of fluid in the gap between the rotor and the stator and the subsequent conversion of the received energy into heat, regulation of the heating process,
characterized in that
the analyzer fixes all the characteristics of the electric power supplied to the electric motor,
send a signal to the electronic control unit, which for the consideration of odd harmonics calculates the coefficient K by the formula

,
where K is the program coefficient for the control unit,
characterizing the mode of operation of the cavitator;
V is the value of the harmonic voltage;
n, m is the harmonic number (where n> m, 3≤n, 1≤m≤n-2).
- compare the obtained value of the coefficient with the embedded software standard:
- when K <the reference value, the electronic control unit sends a signal to the frequency controller, which increases the speed of rotation of the electric motor,
- when K> the reference value, the electronic control unit sends a signal to the frequency controller, which reduces the speed of rotation of the electric motor.

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