9th INTERNATIONAL WORKSHOP AND TUTORIALS EDM’2008, SESSION V, JULY 1-5, ERLAGOL 267

ISSN 1815-3712 ISBN 978-5-7782-0893-3 © Novosibirsk State Technical University

Ultrasonic Oscillating System for Radiators of Gas Media

Andrey N. Lebedev, Student Member, IEEE, Andrey V. Shalunov, Sergey S. Khmelev, Student Member, IEEE, Nikita V. Kuchin, Student Member, IEEE, Anna V. Shalunova

Biysk Technological Institute (branch) Altai State Technical University after I.I. Polzunov, Biysk, Russia

Abstract – In article the new construction of the mul-tiple-unit piezoelectric transducer with the increased output power and a disk radiator, which has a refined thermal mode is offered. The designing procedure of bending vibration disk radiators is described. The developed constructions are implemented; their tech-nical characteristics and functionality are explored. Index Terms – ultrasound, ultrasonic oscillating sys-tem, disk radiator, multiple-unit transducer, acoustic transducer.

I. INTRODUCTION

S IS KNOWN THAT USE of high-intensity ultrasonic oscillations for influence on differ-

ent media through gas gaps allows to speed up var-ious processes:

• Curdling aerosols and powders [1]; • Drying of productions and materials [2]; • Defoaming [3], etc.

For creating high intensity acoustic vibrations in gas medium aerodynamic radiators or the disk ra-diators of bending vibration are usually used. [4]

Unfortunately, aerodynamic radiators have low efficiency (no more than 40 %), the high noise level at operation and complexity in maintenance.

All existing at present disk radiators are oriented on flaw detection. The constructions presented in [5], are have high weight and sizes, whereas there are some tasks in which the size of a radiator is restricted and it is required to make a high-intensity acoustic field. The radiating power growth will cause magnification of consumed power that will negatively influence on thermal conditions of trans-ducer.

Thus, it is necessary to develop a compact disk radiator for creating high intensity ultrasonic vibra-tions and the high power piezoelectric transducer with a low operating temperature.

II. DEVELOPMENT OF HIGH-POWER PIEZOELECTRIC TRANSDUCER

The increasing of radiating power is imple-mented by increasing of consumed power to the

piezoelectric elements and/or increasing of their number.

The limit of consumed power increasing is re-stricted to performances and sizes of the piezoelec-tric elements and as a rule does not exceed 25 W/cm3.

The simple increasing of number of active ele-ments leads to degradation of ultrasonic oscillating system (UOS) thermal conditions as it is demon-strated in Fig. 1 and 2.

In Fig. 1 results of finite element modeling by temperature distribution in a half-wave oscillating system with two piezoelectric elements are shown. On each piezoelectric element electrical power in 100 W was received. The maximum temperature is 139°C.

Fig. 1. Thermal distribution on half-wave UOS with two piezoe-lectric rings.

In Fig. 2 the analogous oscillating system is pre-

sented under the similar conductions, but with 4 piezoelectric elements. The maximum temperature is 290°C.

Thus, the increase in the number of the piezoe-lectric elements has led to rise of an operating tem-perature more than in 2 times. It should be noted that Curie temperature for the given material is 320°C.

UOS of the half-wave construction diagram is capable to ensure consumption power to 150 – 200 W.

A

268 9th INTERNATIONAL WORKSHOP AND TUTORIALS EDM’2008, SESSION V, JULY 1-5, ERLAGOL

For getting higher technical characteristics it is offered to use a design of the multiple-unit trans-ducer described in [6]. Such constructive scheme allows to provide sufficient power consumption and to manage UOS air cooling. (Fig. 3).

Fig. 2. Thermal distribution on half-wave UOS with four piezoe-lectric rings.

Fig. 3. Schematic view of an ultrasonic oscillatory system with a booster.

The three-half-wave multi-elements ultrasonic

oscillatory system consists of half-wave transducer (1-3), half-wave boost part (4), half-wave horn (6) and disk irradiator (7).

Distinctive feature of such construction is usage of a boost part. Boost part is needed for achieving specified amplification coefficient. The flange with case is mounted in the point of boost part when oscillation amplitude equals zero. First material of boost part is aluminum alloy D16. The experiments showed that material of boost part broke in zone of maximal internal stresses. Therefore, material of boost part was changed to metal with better strength

and limit characteristics (quality steel 45, corrosion-resisting steel 40X13 and instrumental steel U10).

The comparative tests are shown, that it is rea-sonable to use aluminum boost part. It has more closed frequency to a transducer and provides max-imal amplitude. However, as it was noted above to use aluminum alloy is not possible, because of its low mechanical strength.

On the other hand, using of boost part brings in-to construction an additional boundary of materials and threaded connection. It increases mechanical stresses in the connection area. This leads to mis-match and additional loss of acoustic energy.

Taking into account all noted above, it was of-fered to refuse half-wave boost part and to use two-half-wave transducer (produced as one part). It helps to achieve a maximum amplification factor and the optimal frequency matching of a transducer with a concentrator.

Schematic view of ultrasonic oscillatory system construction is shown in Fig. 4.

Fig. 4. Schematic view of an ultrasonic oscillatory system with a two half-wave transducer.

The surface of disk is an irradiating unit (6).

Bending oscillations of disk were made by longitu-dinal oscillations of piezoelectric elements (2). Acoustic coupling in the UOS is possible as piezoe-lectric elements are pressed between a transducer (3) and rear frequency reducing strap (1) with a force that is more than a alternating force produced by piezoelectric elements. The tightening force is ensured by rear frequency reduction straps and double-end bolts (3).

The comparison of two constructions demon-strates (Table 1) that exchange of half-wave trans-ducer and half-wave boost part to two-half-wave transducer will increase oscillations amplitude in

SHALUNOV et al.: ULTRASONIC OSCILLATING SYSTEM FOR RADIATORS OF GAS MEDIA 269

two times. According to field experience loss of acoustical energy were decreased when threaded connection and contact of various materials were excluded.

TABLE I COMPARISON OF TWO CONSTRUCTIONS

With booster Without booster Elements Relative

Ampli-tude

Frequen-cy, kHz

Relative Ampli-tude

Frequen-cy, kHz

Transduc-er 1,5 23,5 1,75 24,0 + booster 1,2 24,03 + horn 2,5 23,48 4,5 23,85 + radiator 2,0 23,01 3,0 23,6

First the horn was of the classical shape representing a body of revolution with two cylin-drical sections of greater and smaller diameter, connected by radial transition. After the beginning of usage of the designed irradiators it was found that the titanic horn did not withstand loads and it was destroyed in a place of connection with a disk radiator. The general view of destroyed horns is shown in Fig. 5.

Fig. 5. General view of destroyed concentrators.

Taking into the consideration stated above the construction of horn was designed. The construc-tion is a body of revolution with three cylindrical areas of various diameters. These areas are con-nected with each other by means of radial transi-tions, and cylinder with minimal diameter is placed in the center (Fig. 6).

Fig. 6. The new design of horn

III. STEPPED-PLATE DISK RADIATOR

Disk radiators of bending vibration are used ex-tensively. One of the reasons of this fact is that

there are not procedures of their calculation and designing.

Analytical calculation of disk radiator perfor-mances is impeded by lack of the analytical forms presenting the shapes and vibrations modes of a stepped-plate disk radiator.

Following the general principles of acoustic ra-diators construction, the approximate designing procedure of disk radiators was offered.

1. The number of mode N on which the radiator will work, a resonant frequency f and radiator di-ameter d are defined. The number of mode N de-pends on quantity of half-waves keeping along ra-diator radius.

2. The disk radiator consists of N+1 parts of dif-ferent thickness and length. The length of each part is equal to half wave length (λ/2) of bending vibra-tion. Lengths of first and last section are in total λ /2. It is necessary to add, that λ depends on material thickness and its properties and is defined from the following expressions:

fcи=λ

(1)

4 2 )1(3 µρπ

−⋅=

Ehfcи (2)

Where ci - speed of a bending vibration in a plate with thickness h, f- frequency of oscillations, λ -wave length, E- Young's modulus, ρ -density, µ -Poisson's ratio.

From (1) and (2) it is obtained:

4 2 )1(3 µρπλ

−⋅=

Efh

(3) 3. Length of each part is defining from expres-

sion (3), disk diameter d and necessity to provide stepped-plate section of a disk. For construction amplification the central part of a disk is made of maximum thickness. To increment oscillation am-plitude the thickness of a disk to edges decreases.

The procedure is illustrated in Fig. 7.

Fig. 7 Sheme stepped – plate disk radiator.

IV. EXPERIMENTAL RESULTS

According to the recommendations stated above, the disk radiators with ultrasonic oscillating system (Fig. 8) has been developed and produced.

Characteristic of the developed radiator was measured and a directivity diagram at a distance of 150 mm and 1000 mm from a radiator was made (Fig. 9, 10).

270 9th INTERNATIONAL WORKSHOP AND TUTORIALS EDM’2008, SESSION V, JULY 1-5, ERLAGOL

Results of experiments indicate that a radiator is capable to create in a chamber isotropic acoustic field with medial intensity of a sound pressure level 136.8 dB. It is sufficient for an intensification of drying, coagulation processes, etc.

Fig. 8. Ultrasonic oscillating system with disk radiator.

120

125

130

135

140

145

150

155

Fig. 9. Directivity diagram at a distance of 150 mm from radiator (the maximum intensity).

100

105

110

115

120

125

130

Fig. 10. Directivity diagram at a distance of 1000 mm from radiator.

The maximum intensity of a sound pressure equals 153 dB at a distance of 150 mm from a ra-diator surface.

Experiments on acoustic vibrations allocation in the closed volume of the cylindrical shape (drying chambers simulator) were carried out. Sound pres-sure was measured along 15 vertical axes. The shift is 100 mm. Intervals between axes are 50 mm.

Height and diameter of a volume is 830 mm. The results are presented in Fig. 11.

Fig. 11. The diagram of distribution sound pressure level.

V. CONCLUSION

The results of this research are following: 1. It was developed an ultrasonic oscillating sys-

tem with the multiple-unit transducer with the in-creasing thermal conductions mode and maximum consumed power 600 VA.

2. A procedure of disk radiators design was of-fered. It helped to construct the radiator with 250 mm diameter. The maximum intensity of a sound pressure level is 153 dB at a distance of 150 mm from radiating surface.

3. The experiments proved high technical cha-racteristic of a radiator and its suitability for indus-trial use.

VI. ACKNOLEDGEMENT

This work was carried out at support of Council of the Russian Federation President grant for gov-ernment support of young Russian scientists (can-didate of science) № MK-383.2008.8.

REFERENCES [1] Strauss W. Industrial Gas Cleaning , USA, Elsevier,

1976, p.632. [2] Malcolm J. W. Povey, T. J. Mason Ultrasound in Food

Processing, USA, Springer, 1998, p.282. [3] Vladimir N. Khmelev, Roman V. Barsukov, Dmitry V.

Genne, Maxim V. Khmelev. Ultrasonic Device for Foam Destruction. // International Workshops and Tuto-rials on Electron Devices and Materials EDM'2007: Workshop Proceedings. - Novosibirsk: NSTU, 2007.

[4] V.N. Khmelev, I.I. Savin, D.S. Abramenko, S.N. Tsy-ganok, R.V. Barsukov, A.N. Lebedev. Research the Acoustic Cloth Drying Process in Mock-Up of Drum-Type Washing Machine. // International Workshops and Tutorials on Electron Devices and Materials EDM'2006: Workshop Proceedings. - Novosibirsk: NSTU, 2006.

[5] J.A.Gallego-Juarez. New technologies in high-power ultrasonic industrial applications // Ultrasonic sympo-sium. - New York, IEEE, 1994. p.1343-1352.

[6] Vladimir N. Khmelev, Levin S.V., Sergey N. Tsyganok, Andrey N. Lebedev. High Power Ultrasonic Oscillatory Systems. // International Workshops and Tutorials on Electron Devices and Materials EDM'2007: Workshop Proceedings. - Novosibirsk: NSTU, 2007.

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Andrey N. Lebedev (S'03) was born in Kiselevsk, Russia in 1983. He received degree on information measuring engi-neering and technologies from Biysk Technological Institute of AltSTU. He is post-graduate student of Biysk Technol-ogical Institute. His research interests is finite-element modeling.

Andrey V. Shalunov was born in Bi-ysk, Russia, 1980. He is Ph.D (Machi-nery), he received degree on informa-tion measuring engineering and tech-nologies from Biysk Technological Institute of AltSTU. Laureate of Rus-sian Government premium for achievements in

science and engineering. His main research interest is devel-opment software for ultrasonic technological devices.

Sergey S. Khmelev was born in Proko-pievsk, Russia, 1985. He is post-graduate student of Biysk Technological Institute.. His research interests is de-sign and construction ultrasonic oscilla-tion system.