STUDY OF THE SPECIFIC FEATURES OF PULSED-PLASMA GENERATION IN AIR AT ATMOSPHERIC PRESSURE Ya. A. Chivel’, a O. O. Kuznechik, a D. V. Min’ko, a I. S. Nikonchuk, b A. V. Chumakov, b and K. E. Belyavin c UDC 621.373.826:621.762 The structural scheme and operational characteristics of a pulse-plasma device generating a pulsed plasma in air at atmospheric pressure are presented. The functional scheme and the operation algorithm for a high-volt- age power supply are given. It is shown that the pulsed-plasma device can generate air plasma flows with a frequency of 1–10 Hz and maximum parameters of pressure, temperature, and velocity of 6.5 MPa, 12,000 K, 4 km ⁄ s, and 110 dB A , respectively. Comparative analysis is presented of these quantities with characteristics of the plasma flow generated by the detonation pulsed-plasma device, which uses an air-propane mixture as the plasma-forming substance. It is shown that replacing the air-propane gas mixture with air provides a 70 dB A decrease in the noise level of the pulsed-plasma treatment. Recommendations are given as to using the pulsed-plasma device for surface strengthening of the instrument and parts of the machine. Keywords: pulsed plasma, air pulsed-plasma treatment, high-voltage power-supply unit, pulsed plasma flow, pressure, acoustic noise, temperature. Introduction. Increasing the wear resistance of working surfaces of the instruments and parts of machines by surface strengthening of their material and coatings is a topical problem of machine construction. This problem can be solved using the method of the pulsed-plasma treatment in air at atmospheric pressure, which is implemented [1–3] with the aid of the devices including a facility for preparing and feeding the gas mixture detonation and acceleration chambers, and pulse high-voltage power supply and control. The operational principle of such devices is as follows. Initially, the air-propane gas mixture arrives from the preparation and feeding device at the detonation chamber where, as a result of combustion, a plasma-forming substance is formed, which is admitted to the acceleration chamber under the action of excess pressure. Thereafter, in this chamber, pulsed high-voltage (10 3 V) discharges that are generated by the high-voltage power supply and control unit are transmitted through the plasma-forming substance. The frequency of high-voltage discharges generated by such power supply and control units currently has the limits 0.1–10 Hz. Owing to the struc- ture of the acceleration chamber [1, 4], in pulsed high-voltage discharges a pulsed magnetic field is formed, which can accelerate the pulsed plasma generated from the plasma-forming substance to supersonic (5–6 km ⁄ s) velocities. Here the current density in the pulsed plasma can be as high as 10 3 –10 4 A ⁄ cm 2 , the temperature can increase to 2⋅10 4 K, and the maximum noise can exceed 180 dB A . The use of detonation gas mixtures as the plasma-forming substance and the acoustic noise at the outlet from the acceleration chamber larger than 180 dB A limit the efficiency of technologies of pulsed-plasma treatment at atmos- pheric pressure under the conditions of actual production. These limitations can be removed by designing devices [5–7] in which instead of the detonation air-propane mixture use is made, for example, of air. Such replacement of the plasma-forming substance can be effected by restructuring [5, 8] elements of the pulsed-plasma device, namely, the ac- celeration chamber and the high-voltage power supply and control. In this case, a need arises (which is the aim of the study) for investigating specific features of generation by such a device, the pulsed-plasma flows in air at atmospheric pressure, for performing comparative analysis, and for working out recommendations for the application of the pulsed- Journal of Engineering Physics and Thermophysics, Vol. 84, No. 5, September, 2011 a Institute of Powder Metallurgy, National Academy of Sciences of Belarus, 41 Platonov Str., 220005, Minsk, Belarus; b B. I. Stepanov Institute of Physics, 68 Nezavisimost’ Ave., Minsk, 220072, Belarus; c Belarusian National Technical University, 65 Nezavisimost’ Ave., Minsk, 220013, Belarus. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 84, No. 5, pp. 1028–1033, September–October, 2011. Original article submitted April 21, 2010; revision submitted November 17, 2011. 1062-0125/11/8405-11082011 Springer Science+Business Media, Inc. 1108