Determination of aircraft multi-shield skin temperature field with variable materials characteristics
Strength and thermal conditions of flying vehicles
Moscow Aviation Institute (National Research University), 4, Volokolamskoe shosse, Moscow, А-80, GSP-3, 125993, Russia
This article is directed on assessment of variability thermalphysic characteristics of constructional and the heat protection materials on aircraft construction heating.
It is including the materials’ thermalphysic characteristics variability of temperature.
It uses compact, fast-acting calculation procedure.
It is examining heat extension coherently thermal conduction. The task is reducing to calculation about skin one-dimensional heating (along thickness). It supposes that thermalphysic characteristics de-pend on temperature. Therefore the thermal conductivity coefficient of the material is variable along thickness.
The thermal conductivity one-dimensional differential equation writes down as derivative of two functions product. The skin thickness is splitting into several calculation points with defined step. The thermal conductivity differential equation is producing in the difference form by way of central finite differences. This expression use only adjacent points temperature value. Thusly it is creating algebraic equations set with three diagonal coefficients matrix. The fast-acting sweep method is using for the equations set finding . The boundary conditions equations are using for the skin confines points. The supply and divert heat transfer rate balance equation is using for the external and internal surfaces. The heat transfer rate equality as boundary condition equation is using for the different materials meeting surface.
The analysis of constructional and heat protection materials thermalphysic characteristics achieves appreciable relation their value from temperature. Especially it is exhibiting for the heat-resistant materials, which works in wide temperature range. Also it is very considerable the thermalphysic characteristics vari-ation of radome materials and some of the heat-insulating materials.
The calculation results is achieving, that the using of the thermalphysic characteristics value, achieved at room temperature, for greatly heating constructions can give great inaccuracy (to 50%). The disregard of value thermal conductivity coefficient variableness along material thickness can give great inaccuracy too (to 29%).
The suggested determination scheme permits to correctly simulate the heat conduction process in sandwich structure with consideration of thermalphysic characteristics relation to temperature and without additional admissions. It distinguishes suggested determination scheme from «the heat balance equation» method, which used in some methodologies.
Keywords:temperature field, multi-shield skin, aircraft, material characteristics, adequacy, intercomparison
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