Experimental studies of temperature fields in the engine compartment of a supersonic aircraft


Аuthors

Bykov L. V.1*, Varentsov A. A.2

1. Research Department of Department 204,
2. Russian Aircraft Corporation «MiG», 6, Leningradskoe shosse, Moscow, 125171, Russia

*e-mail: bykovlv@mai.ru

Abstract

This article presents the results of experimental studies of temperature fields in the engine compartment of a prospective supersonic aircraft, conducted to substantiate the choice of a thermal protection system for the avionics compartments.
During the development of prospective supersonic aircraft (Mach number M > 2), the avionics compartments, often located in the interengine zone, are subject to extreme thermal loads from the power plant and aerodynamic heating. Ensuring the avionics' normal operating temperature is only possible with effective thermal protection for the compartment, requiring accurate data on the thermal fields for selecting thermal protection materials.
To measure maximum temperatures, a combined method was used using INTEM disposable thermal indicators (range 40–230 °C) and MS150-12 multi-transition thermal paint (range 355–1200 °C). Preliminary laboratory tests of the thermal paint were conducted on steel samples. The tests included refining the application technology of the thermal paint, visually recording color transitions at various heating temperatures of the test sample, assessing the paint response time for each temperature range, and evaluating the transition time between successive color states.
The experiments were conducted both during ground testing of engines in “Full Afterburner” mode and during full-scale testing at Mach numbers of Mach ≈ 2,5.
1. The high efficiency of the combined method was confirmed: thermal indicators provide accurate recording of threshold temperatures, while the thermal paint allows for mapping fields over large areas and in hard-to-reach zones.
2. It was established that during ground testing in “Full Afterburner” mode, temperatures do not exceed 230 °C. However, during full-scale flights at Mach > 2,5, due to increased engine operating time, temperatures reach critical values – up to 540 °C in the nozzle exit zone.
3. Peculiarities of working with thermal paint were identified: the subjectivity of visual color assessment requires mandatory photographic recording under controlled lighting and the use of reference scales.
The placement of avionics in the interengine zone of a supersonic aircraft makes their normal operation impossible without special protective measures. The obtained experimental data (temperatures up to 540 °C) demonstrate the need for a combined multilayer thermal protection system, including reflective screens, low-thermal-conductivity insulators (aerogels, ceramics), and heat removal systems. The results of this study serve as the basis for thermal strength calculations and the design of thermal management systems for advanced aircraft.
Based on the results, recommendations were formulated for the use of a combined thermal protection system, including reflective screens, thermal insulation materials, and heat removal systems. The proposed measurement method with duplication of results by two independent means ensures the reliability of the data and is recommended for use in the development of thermal protection at various stages of flight tests of promising supersonic systems.

Keywords:

supersonic aircraft, thermal protection, avionics, engine compartment, INTEM thermal indicators, MC150-12 thermal paint, aerodynamic heating, afterburner

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