Research of acoustic characteristics by vilga-35a light propeller aircraft on level flight conditions

Аuthors

Samokhin V. F.^1*, Moshkov P. A.^2**

1. Central Aerohydrodynamic Institute named after N.E. Zhukovsky (TsAGI), 1, Zhukovsky str., Zhukovsky, Moscow Region, 140180, Russia
2. Yakovlev Corporation Regional Aircraft Branch, 26, Leninskaya Sloboda str., Moscow, 115280, Russia

*e-mail: samohin_vf@mail.ru
**e-mail: moshkov89@bk.ru, p_moshkov@ssj.irkut.com

Abstract

This work is devoted to the noise problem of light propeller aircrafts. In the article the experimental obtained basic results of acoustical characteristics by light propeller aircraft (LPA) of Vilga-35A in flying conditions are presented. Spectral and power characteristics of LPA power plant (PP), acoustical radiation and also directional characteristics are recorded.
The problem due to decrease noise of PP is rather actual for a general aviation LPA, whereas ICAO norms act on maximum permissible noise levels of such planes [1]. The given work follows of author previous researches [2] about acoustic characteristics of LPA power plants.
Measurements of LPA Vilga-35A acoustic characteristics have been carried out. The plane PP involves a piston engine (ICE) AI-14RA with 2-bladed propeller of variable pitches US-122000. Measurements of acoustic characteristics were conducted at various level flight conditions, which correspond to five power modes.
It was obtained that the acoustic field of a power plant of a LAN is determined by acoustic radiation of a propeller. The regression equations establishing the relation of aircraft noise levels on the ground from power of a PP and Mach number of relative flow velocity in tip section by propeller blade are received. It is find out that acoustical efficiency of Vilga-35A light propeller aircraft power plant on maximum power operation is 0,123 %.
Broadband radiation in the field of 1600-3000 Hz has an aerodynamic origin, and its dominating source is the turbulent wake behind propeller blades. The peak of broadband radiation in the field of 5000-8000 Hz most probably caused by radiation of a mechanical origin from planetary gearbox of the engine.
The complex approach consisting in decrease of power plant noise, i.e. the noise radiated by a propeller and the piston engine is necessary for essential decrease in noise level of LPA with ICE on the ground. Decrease of a propeller noise is enough challenge. The solution of this problem is based on optimization of geometrical, aerodynamic and acoustic characteristics of propeller. Intensity of propeller acoustical radiation under condition of conservation of constant thrust can be reduced by means of optimization ratio between number of blades, propeller diameter and circular velocity by criterion of the minimum acoustical radiation power. For decrease in the noise radiated by the piston engine, it is necessary to apply ICE exhaust silencer.

Keywords:

a propeller, propeller noise, piston power plant noise, light propeller aircrafts noise

References

1. ICAO— International Standards and Recommended Practices— Environmental Protection Annex 16tothe Convention onInternational Civil Aviation— Aircraft Noise, vol. I, 2011, 227p.
2. Samokhin V.F., Moshkov P.A. Elektronnyi zhurnal «Trudy MAI», 2012, no.57, availableat: http:// www.mai.ru/science/trudy/published.php?ID=30715 (accessed 30.06.2012).
   
3. Samokhin V.F., Ostroukhov S.P., Moshkov P.A. Elektronnyi zhurnal «Trudy MAI», 2013, no.70, availableat: http://www.mai.ru/science/trudy/published.php?ID= 44459 (accessed 25.11.2013).
   
4. Zarembo L.K., Krasilnikov V.A. Vvedenie vnelineinuyu akustiku (Introduction innon-linear acoustics), Moscow, Nauka, 1966, 520p.
5. Samokhin V.F. Trudy TSAGI, 1988, no.2355, pp. 65- 75.
   
6. Badyagin A.A., Mukhametov T.A. Proektirovanie legkikh vintovykh samoletov (Designing oflight propeller aircraft), Moscow, Mashinostroenie, 1978, 208p.
7. Hanson D.B., Parzych D.J. Theory for noise ofpropellers inangular inflow with parametric studies and experimental verification, NASA CR, 1993, no.4499, p.108.
   
8. Bazhenova L.A., Semenov A.G. Akusticheskii zhurnal, 2013, vol.59, no.5, pp. 586-595.
   
9. EtkinV., Korbacher G.K., Keefe N.T. Acoustic radiation from astationary cylinder inafluid stream (Aeolian tones), J.Acoust. Soc. Amer., 1957, vol.29, no.1. pp. 30-36.
   
10. Gerrard J.H. Anexperimental investigation ofthe oscillation lift and drag ofacircular cylinder shedding turbulent vortices, J.Fluid Mech, 1961, vol.11, no.2, pp. 244-256.