250 10 th INTERNATIONAL CONFERENCE AND SEMINAR EDM’2009, SECTION IV, JULY 1-6, ERLAGOL 978-1-4244-4572-1/09/$25.00 © IEEE Multifrequency Ultrasonic Transducer with Stepped-Plate Disk Vladimir N. Khmelev, Senior Member, IEEE, Andrey N. Lebedev, Student Member, IEEE, Sergey N. Tsyganok, Andrey V. Shalunov, Anton N. Galahov, Ksenia V. Shalunova, Student Member, IEEE Biysk Technological Institute (branch) Altai State Technical University after I.I. Polzunov, Biysk, Russia Abstract – In article are suggest multifrequency ultra- sonic transducer with stepped-plate disk. This device is mean for coagulation aerosols with 0.4 µm particle size. Also present method of engineering calculation stepped-plate radiator. Index Terms – Coagulation, multifrequency, stepped- plate disk, ultrasonic transducer. I. INTRODUCTION T PRESENT, there is a possibility of getting chemical and biological weapons in the hands terrorists. It confirms cases when toxic gases were sprayed in the buildings. The most terrible case took place in 19 th of March, 1995. In the Tokyo's metro toxic gas was sprayed, as a result 12 people died and more than 5000 were suffered. That is why, it is necessary to provide protection of many groups of people against chemical and biological weapons. To choose protection method it is necessary to understand mechanism of the potential actions. As it is well known, basic conditions of toxic chemical substances are: • vapour (molecular state); • non settling fine-disperse aerosol (particle size no more 30 µm); • settling disperse aerosol (particle size 30- 5000 µm); • drops (particle size is more than 500 µm) [1]. The most probable candidates for using as biological weapons are: anthrax, botulism, plague, smallpox, tularemia and different sorts of virus haemorrhage's fever. Bacterium can be in diameter from 0.3 to 35 µm, viruses are from 0.01 to 0.3 µm [2]. Contamination can occur by spraying agent in near people or throgh the ventilation system. The last case is very dangerous, because infected air propagates with maximal speed. Vacuum blast is represented the grave dangers in a mine and places with a large quantity of suspended dust, such as milling factory. Many researches show, that degree of dispersion is the main factor of explosibility of dust. Particle sizes no less than 1000 µm participate in the blast. The dust explosibility increases with dispersions growth. The most dangerous is dust with particle size from 10 to 200 µm. From previously said it can be concluded that it is necessary to apply methods and tools, which are able to prevent propagation of particles with size of 0.01- 30 µm. II. PROBLEM STATEMENT Most efficient filters using for cleaning of air are HEPA-filters (High-Efficiency Particulate Filter). These filters guarantee interception of particles with size 0.3 µm with efficiency 99.7%. But these filters have some disadvantages, such as: • The filters cannot be applyed for clearing of air on the open space. • They create resistance to air flow. • They demand regular cleaning and chang- ing. The solution of the problem of cleaning conta- minated air can be coagulation of toxic agent par- ticles or dust to agglomerate and increase collapsing. One way for solving this problem is acoustic coagulation. But now in practice there are not tech- nological devices for acoustic aerosol coagulation. Main requirement for realization of this process is a need of using ultrasonic vibrations, i.e. higher limits than human audibility and therefore the device should not influence on human organism. III. THEORY If aerosol has a polydisperse distribution of par- ticles, and relative speed of particle coagulation in the acoustic field depends on concentration, diame- ter, frequency and intensity of radiation, then para- meters of the acoustic field must be determined by particles parameters. As for the intensity of radiation the better intensity sound is the higher is relative speed of flow of aerosol particles. The important parameter of radiator, which characterises efficiency coagulation, is radiation frequency. According to [4] A