Journal: Volume 21, No. 3, 2016
Pages: 95 – 102
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Determination of thermal shock external influences on IR-devices at their operation

І. Yatsenko, Valentyn Gordienko, Oksana Kyrychenko, Vyacheslav Vaschenko, Valentin Tsybulin

Abstract

To improve the reliability of IR-devices in the conditions of high temperature supersonic gas flows it is necessary at the design stage to predict the most dangerous areas on fairings surface, within which there are maximum external thermal influences that lead to the destruction of IR-devices. By this time the processes of heating of optical ceramics fairings in the form of hemispherical shells by oncoming supersonic airflow for different flow regimes are insufficiently investigated. The aim of this work is to simulate thermal effect of supersonic airflow on the surface of optical fairings of IR-devices and to find the locations in which there are maximum external thermal influences, leading to their destruction and IR-devices failure. The results of experimental and theoretical investigations of the process of thermal influence of supersonic gas flow in hemispherical fairings on optical ceramics of IR-devices are presented. Analytical expressions for the distributions of heat flux from boundary layer along the surface of the fairing are received and the location of its sites subjected to a maximum external thermal influences is installed. The location of the maximum values of heat flux (q w max) on the surface of the fairing depends on the flow regime: for laminar flow the values (q w max) are close to the front of critical point (θ = 0) fairing; for turbulent flow the values (q w max) have already shifted from θ = 0 to θ max = 19...23. Heat flux in the zones of maximum external thermal impact on the surface of the fairing substantially depends on the velocity of blowing airflow (for u = 7102...2103 m/s values (q w max) increase from 0.3106 W/m2 to 2.3106 W/m2 (turbulent flow regime) and from 0.2106 W/m2 to 1.3106 W/m2 (laminar flow regime)

Keywords

external thermal influences, optical fairings, optical ceramics

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Suggested citation

Yatsenko, I., Gordienko, V., Kyrychenko, O., Vaschenko, V., & Tsybulin, V. (2016). Determination of thermal shock external influences on IR-devices at their operation. Bulletin of Cherkasy State Technological University, 21(3), 95-102.