Coherent sound field generated by an airborne power

ultrasonic transducer with rectangular plate radiator for food

dehydration purposes.

Introduction: The use of airborne power ultrasonic transducers (APUT) for food dehydration processes may carry important advantages

regarding energy consumption, processing time and quality of the final product. The high intensity acoustic field generated by the

transducer, and propagated along the processing chamber provokes the desired effects in the samples located strategically in some

points of the near field. Therefore, the main goal when designing an ultrasonic technology is that the system generates a coherent

acoustic field in free field with a directive behavior.

The ultrasonic system considered for this purpose consists of an APUT with rectangular plate radiator working at a flexural mode with

twelve nodal lines (12NL) around 21 kHz, and a set of reflectors to put in phase the ultrasonic waves in order the generate the required

coherent field.

This work presents the acoustical effects provoked by the set of reflectors in terms of ultrasonic field and directivity, obtained by

experimental methods.

Conclusion: This work has proved that the use of a

reflectors system enables the generation of a directive

ultrasonic field with higher acoustic pressure because

the energy of both faces of the radiator is used in a

coherent field, obtaining a most efficient system for food

dehydration processes.

X=38 mm X=1129 mm X=38 mm X=1083 mm X=2612 mm

Acknowledgments: This work has been

supported by the project DPI2012-37466-

C03-01 funded by the Spanish Ministry of

Economy and Competitiveness.

Directivity

Ultrasonic field

Roque R. Andrés, Enrique Riera, Ángel Guinot, Ignacio Martínez, Alberto Pinto

Dpto. Sensores y Sistemas Ultrasónicos, ITEFI, CSIC, Serrano 144, E28006-Madrid, Spain

APUT

12 NL operational mode Ultrasonic system with reflectors

Reflectors

Rectangular radiator

Horizontal (XY) plane

Vertical (XZ) plane

YZ slice. X=38 mm YZ slice. X=1129 mm YZ slice. X=0 mm YZ slice. X=1083 mm YZ slice. X=2612 mm

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