The problem of reducing the thermal signature of an aircraft engine

Аuthors

Nikolaenko V. S., Filippov G. S.^1*, Yashchenko B. Y.²

1. Moscow Aviation Institute (National Research University), 4, Volokolamskoe shosse, Moscow, А-80, GSP-3, 125993, Russia
2. Lavochkin Research and Production Association, NPO Lavochkin, 24, Leningradskay str., Khimki, Moscow region, 141400, Russia

*e-mail: Filippov.Gleb@gmail.com

Abstract

For calculating the indicatrix of infrared radiation (IR) signature propulsion aircraft developed. A new technique based on the Monte Carlo method for calculating the signature of infrared radiation produced by an aircraft propulsion system is developed. This method is used for solving problems by simulating random variables. Calculations are performed by example of AL-31F engine.

The turbulent gas flow inside the nozzle is simulated by solving Navier-Stokes equations. For calculating the heat transfer in the wall of the nozzle the grid and geometry of the nozzle are generated. The temperature distribution inside the aircraft engine result is obtained. During simulation the inner surface of the propulsion system is modeled cones, cylinders, hyperbole, turbine ring, the central body ellipsoid. Infrared radiation are varied in a wide range of angles. In order to reduce this level, we offered to implement a special screen, which is a cylindrical surface extending over the nozzle exit. The screen diameter is large than the diameter of the nozzle and can significantly reduce infrared radiation in the range of angles from 10 ° to 90 ° depending on its configuration. The results of calculations for the

screening element with a different radius r, the length h and the distance to the nozzle exit plane H is shown in figure.

But the usage of such screens is difficult in existing aircrafts. Its overall efficiency is increased slightly with screen size increasing (since the length of 0.85 m). By using a special screen design there is a significant (98%) reduction of infrared radiation in the radial direction. But the level of radiation along the axis is increased. In this screen geometry (length and diameter) are important parameters. The choice of screen geometry defines by designers of airplanes. For the terrestrial infrared equipment matters most radiation in the radial direction and using of such device may be effective.

Keywords:

AL-31F, reflector, IR radiation signature

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