RU2287381C2 - Method for ultrasonic cleaning of heat generating aggregates by removing deposits and apparatus for performing the same - Google Patents

Abstract

FIELD: ultrasonic instrument making, namely prevention of deposit formation on inner and outer surfaces of heat generating aggregates in heat power engineering and other branches, intensifying of manufacturing processes.

SUBSTANCE: method is realized with use of magnetostriction converters in exciting windings of which bursts of power current pulses are generated by means of pairs of switching units while providing detection of emergency mode and forming signal inhibiting feed of control signal to control inlets of switching units. Magnetization current is supplied from DC magnetization source to exciting windings before generation and after termination of burst of power current pulses. Apparatus for performing the method includes magnetostriction converters having in each exciting winding switching capacitor; control circuit in the form of setting generator; supply-line filter; full-wave rectifier connected with outlets of filter; accumulation capacitor whose positive terminal is connected with plus terminal of rectifier and whose negative terminal is connected with minus terminal of rectifier; detector of short circuiting current whose one terminal is connected with minus terminal of accumulation capacitor and whose other terminal is connected with pickup for measuring electric current of power current pulses; power switching transistors. Each magnetostriction converter includes one exciting winding connected between pairs of power switching transistors through insulation capacitor; pickup for measuring current of power current pulses having fixed resistor and variable resistor and connected at one side with common bus and at other side with common sources of power switching units; connected with inlet of control circuit mean outlet terminal of variable resistor of said pickup; DC magnetization source whose outlets through chokes are connected with exciting windings of magnetostriction converters and whose inlets are connected with outlets of accumulation capacitor.

EFFECT: enhanced effectiveness of using magnetostriction converter, lowered energy consumption, increased intensity of ultrasonic oscillation in aggregate, improved efficiency of cleaning it.

4 cl, 5 dwg

Description

The invention relates to the field of ultrasonic instrumentation and is intended to prevent deposits on the inner and outer surfaces of heat exchange units in the power system and other industries, as well as to intensify technological processes.

A known method of ultrasonic cleaning, implemented in a device for ultrasonic cleaning of heat generating units from deposits, and a pulsed ultrasonic generator (RU No. 2196646) is adopted as an analogue. The disadvantage is the limited efficiency of cleaning heat from deposits.

The closest (prototype) is a method of ultrasonic cleaning of heat aggregates from deposits by packs of ultrasonic pulses coming from a magnetostrictive transducer, implemented in a device (RU No. 2141877, class C1 07/13/1997), in which packs of power are formed in the windings of two or more groups of magnetostrictive transducers current pulses using pairs of power switching elements (thyristors).

The disadvantages of this device and method are the large amplitude of the pulses of the unipolar excitation current, to obtain the maximum possible oscillation amplitude of the magnetostrictive converters, as can be seen in the graph of the dependence of the amplitude of the oscillations (λ) on the field strength (H) created by the excitation current pulses (Fig. 1); the inability to simultaneously optimize the constant component of the bias current and the amplitude of the variable component; low accuracy of matching the frequency of the excited oscillations with the frequency of the mechanical resonance of the magnetostrictor installed on the object (heat generator).

The technical result of the invention is to increase the efficiency of using a magnetostrictive transducer, reduce power consumption, increase the intensity of ultrasonic vibrations at the facility (heat generator), which leads to an increase in the efficiency of cleaning heat aggregates from deposits.

To achieve a technical result in the proposed method for ultrasonic cleaning of heat generating units from deposits, consisting in the use of n-magnetostrictive transducers, in the field windings of which form packs of power current pulses using pairs of switching elements, identifying an emergency mode, generating a signal for the prohibition of a control signal to the control inputs switching elements, in the field windings of n-magnetostrictive converters form a pack of power current pulse With the help of switching elements, before the formation and at the end of the pack of power current pulses, the magnetization current is supplied to the excitation winding from the DC bias source. An ultrasonic device for cleaning from deposits, containing n-magnetostrictive transducers, each of which has an excitation winding, a switching capacitor, a control unit made in the form of a master oscillator, further comprises a surge protector, a half-wave rectifier connected to the output terminals of the surge protector, a storage capacitor, connected by a positive terminal to the positive terminal of the rectifier, and by a negative terminal to the negative terminal of the rectifier, short-circuit current sensor, with consisting of a non-saturable inductor with a resistor connected in parallel, connected at one end to the negative terminal of the storage capacitor, and the other to a current sensor of power current pulses, power switching transistors, each of the n-magnetostrictive converters containing one excitation winding, each of which is connected between the pairs power switching transistors through isolation capacitors, respectively, a current sensor of power current pulses, consisting of a constant and variable resistor s, connected at one end to a common bus, and at the other end to the common sources of power switching elements, the middle terminal of a variable resistor of a current sensor of power current pulses, to an input of a control unit containing a control device, control elements and an output pulse generating device, a bias DC source whose outputs are connected via chokes to the field windings of n-magnetostrictive converters, and the inputs to the terminals of the storage capacitor.

The essence is that in the excitation winding of n-magnetostrictive converters form packs of power current pulses using four switching elements connected in a bridge circuit, before the formation and at the end of the pack of power current pulses, the magnetization current is applied to the excitation winding from a direct current source, shape current of power current pulses is close to trapezoidal, frequency, current of power current pulses and bias current are set depending on the type of magnetostriction converter that allows you to optimize the magnetostrictive transducer operation, and several times to reduce the amount of energy expended on the excitation of a magnetostrictive transducer.

To achieve the named technical result, a device for cleaning from deposits, implemented by n-magnetostrictive converters, each of which contains one excitation winding, a storage capacitor, a control unit made in the form of a master oscillator, an additional network filter, a half-wave rectifier connected to the output terminals are additionally introduced line filter, short-circuit current sensor, consisting of a non-saturable inductor with a resistor connected in parallel and connected at one end to m to the inus output of the storage capacitor, and the other to the current sensor of power current pulses, power switching transistors connected in a bridge circuit, converters containing one field winding, the field windings of which are connected between pairs of power switching transistors through an isolation capacitor, current sensor of current current pulses, consisting of from a constant and variable resistor, connected at one end to a common bus, and the other end to the common sources of power switching elements, the middle the output of a variable resistor to the input of the control unit, with which the current of power current pulses is regulated, a control unit containing a control device, control elements and a device for generating output pulses, a DC bias source, the outputs of which are connected through the inductors to the excitation windings of the converters, and the inputs - to the conclusions of the storage capacitor.

The graph of the dependence of the amplitude of the oscillations (λ) on the field strength (H) created by the pulses of the excitation current (Fig. 2) and in the drawing (Fig. 3) shows a functional diagram of the inventive ultrasonic device that implements the method of ultrasonic cleaning and protection of heat aggregates from deposits.

The device contains a power source, consisting of a mains filter 1, a half-wave rectifier 2 and a storage capacitor 5, switching elements (transistors) 8, 9, 16, 17, 19, 20, at least two magnetostrictive converters, each with one excitation winding 11 12, switching capacitors 15, 18, short-circuit current sensor 6 (Fig. 4), consisting of a non-saturable inductor 21 with a resistor 22 connected in parallel, a current pulse current sensor, consisting of a constant 7 and an alternating 10 resistors, a control unit eniya 3 (5) consisting of a controller 23, control elements 24 and the output pulses forming apparatus device 25, a source of DC bias 4, inductors 13, 14.

The device operates as follows.

The mains source stores energy in the storage capacitor 5 through a line filter 1 and a half-wave rectifier 2, while the line filter 1 limits the surges of the charge current of the storage capacity and prevents the penetration of high-frequency pulses into the network.

The control unit 3 (Figure 5) allows you to generate control pulses in accordance with the selected algorithm and the operating conditions of the device, to control and adjust the magnitude of the current power current pulses, to turn off the power switching transistors in the presence of a signal from the short-circuit current sensor, to control the power switching transistors, the operating mode of the current source, provides control pulses to the power source, the output current of a given value (set by the regulator included in remains a source of DC bias) is first supplied to the field winding 11 of the magnetostrictive transducer 13 through the throttle than is given by the initial displacement field. After 10 ... 20 ms, the control unit includes the switching elements 8 and 17. Upon reaching the power current pulse passing through the field winding and the switching capacitor 15 of a large capacity, specified by the current sensor of magnitude, the switching element 17 is turned off. Since the direction of the power current in the field winding remains unchanged, it closes through the diode of the switched-off switching element 17 and the switched-on element 8, which maintains the magnetic field created by the power current pulse at a constant level (practically the current and field strength continue to increase due to the return of part of the accumulated energy in the choke). After the passage of time equal in duration to the half-period of the resonant frequency of oscillations of the magnetostrictive converter (the frequency is set by the frequency generator of the control unit and tuned to the resonant frequency of the magnetostrictive converter), the switching element 8 is turned off, and the switching elements 9 and 16 are turned on, and the power current pulse passing through the winding excitation magnetostrictive transducer, changes direction. Upon reaching the power current pulse passing through the field winding and the switching capacitor specified by the current sensor 7, 10 magnitude, the switching element 16 is turned off. After the passage of time equal in duration to the second half-cycle of the resonant frequency of oscillations of the magnetostrictive transducer, the switching element 9 is turned off and the cycle of generating current power pulses is repeated. Power current pulses have a shape close to a trapezoidal shape (in practice, the current shape is closer to a sinusoidal shape). The duration of sending power current pulses is determined by the control unit, at the end of which the DC bias source is turned off. After a time of approximately 150 ms (the time required for the accumulation of partially expended energy in the storage capacitor), the control unit 3 supplies control pulses to the power source, the output current of a given magnitude is supplied to the excitation winding of the magnetostrictive transducer 12 through the inductor 14. After 10 ... 20 ms, the control unit includes switching elements 8 and 20. Upon reaching the power current pulse passing through the field winding and the switching capacitor 18 large capacity specified by the current sensor 7, 10 V The magnitude of the switching element 20 is turned off. After the passage of time equal in duration to the half-period of the resonant frequency of oscillations of the magnetostrictive transducer, the switching element 8 is turned off, and the switching elements 9 and 19 are turned on, and the power current pulse passing through the excitation winding changes its direction of motion. Upon reaching the power current pulse passing through the field winding and the switching capacitor specified by the current sensor 7, 10 magnitude, the switching element 19 is turned off. After the passage of time equal in duration to the second half-cycle of the resonant frequency of oscillations of the magnetostrictive transducer, the switching element 9 is turned off and the cycle of generating current power pulses is repeated. At equal intervals of time, power current pulses and a bias current are applied alternately to the transformer windings.

The bias current is set in the middle of the linear part of the magnetostrictor hysteresis loop, and the current current pulse should not reach the lower and upper bends of the magnetostrictor hysteresis loop.

The implementation in the proposed device of a method for exciting a magnetostrictive converter, which consists in the fact that the magnetization current is supplied to the magnetostrictor field winding during the passage of alternating power current pulses, allows to reduce the amplitude of power current pulses with the same amplitude of magnetostrictor vibrations by at least three times (dependence graph the amplitude of the oscillations (λ) versus the field strength (N) created by the pulses of the excitation current in the presence of a magnetizing current, which This is ideal when comparing two graphs (Fig. 1 and Fig. 2) and, as a result, increase the efficiency of using a magnetostrictive transducer, reduce energy consumption, increase the intensity of ultrasonic vibrations at an object (heat generator), which leads to an increase in the efficiency of cleaning heat aggregates from deposits.

Information sources

1. RU No. 2196646, publ. 01/20/2003, No. 2.

2. RU No. 21411877, publ. 11/27/1999, No. 33.

Claims (4)

1. The method of ultrasonic cleaning of heat aggregates from deposits, which consists in the use of n magnetostrictive transducers, in the field windings of which form packs of power current pulses using pairs of switching elements, identifying an emergency mode, generating a signal to prohibit the receipt of a control signal to the control inputs of the switching elements, characterized in that before the formation and at the end of the pack of power current pulses to the field winding from the DC magnetization source I am biased current. 2. An ultrasonic device for cleaning from deposits, containing n magnetostrictive transducers, each of which has an excitation winding, a switching capacitor, a control unit made in the form of a master oscillator, characterized in that it contains a line filter, a half-wave rectifier connected to the output terminals of the line filter , storage capacitor connected by a positive terminal to the positive terminal of the rectifier, and by a negative terminal to the negative terminal of the rectifier, short-circuit current sensor connected at one end to the negative terminal of the storage capacitor, and at the other to the current sensor of power current pulses, power switching transistors, each of n magnetostrictive converters containing one excitation winding, each of which is connected between pairs of power switching transistors through isolation capacitors, respectively, the sensor current of power current pulses, consisting of constant and variable resistors, connected at one end to a common bus, and the other end to a common the currents of the power switching elements, the average output of the variable resistor of the power current pulse current sensor - to the input of the control unit, a DC bias source, the outputs of which are connected via chokes to the field windings of n magnetostrictive converters, and the inputs to the terminals of the storage capacitor. 3. The ultrasonic device for cleaning from deposits according to claim 2, characterized in that the control unit comprises a control device, control elements and a device for generating output pulses. 4. The ultrasonic device for cleaning from deposits according to claim 2, characterized in that the short-circuit current sensor consists of a non-saturated choke with a resistor connected in parallel.

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