Thermal State of an Aircraft Aerofoil in a High-Velocity Air Flow

Author(s):  
Az.A. Aliev ◽  
A.S. Burkov ◽  
V.A. Tovstonog ◽  
V.I. Tomak ◽  
D.A. Yagodnikov

One of the features of high-velocity atmospheric aircraft is the presence of thin aerofoils with edges characterised by a small blunt radius, subjected to high-temperature aerodynamic heating at temperatures of up to 2000 -- 2500 °C. In order to ensure correct operation of both the power plant producing thrust in such vehicles, assumed to be a supersonic combustion ramjet, and respective aerodynamic controls, the components subjected to high-velocity air flows must retain their geometric stability. A way to ensure their performance is to use methods and means of thermal protection, as well as materials that are resistant to high temperatures in an oxidising atmosphere, while one of the promising trends is employing refractory oxide materials such as oxides of aluminium, zirconium and hafnium. Since this class of materials has low thermal conductivity, large temperature gradients develop in the vicinity of the surface being heated, resulting in temperature stresses, all of which designers should take into account. We analysed the temperature state in a model of an acute zirconium oxide wedge featuring a small blunt radius, subjected to a high-velocity air flow. To reduce the edge temperature and temperature gradients, we propose a design solution implemented as a thermally conductive core lined with a thin layer of zirconium oxide. We consider using aluminium oxide and hafnium boride as core materials

2013 ◽  
Vol 444-445 ◽  
pp. 1400-1406 ◽  
Author(s):  
Hao Liu ◽  
Xia Sheng Sun ◽  
Xiao Dong Li

The severe aerodynamic heating on the surface of modern hypersonic flight vehicle, that can bring high temperature and large temperature gradients in the structure of the vehicle, will be a challenge for the vehicles design and multidisciplinary optimization. The transient thermal environment consists of high temperature and large temperature gradients will generate two important problems related to vehicle structure, namely: 1) the material property, such as elastic modulus, will be degraded at elevated temperature, and 2) the non-uniform thermal stress cased by large temperature gradients will change the stiffness distribution of wing structure, which can make the modal frequencies and shapes of structure changed remarkably. Firstly, the theory and methodology of structure modal analysis in transient thermal environment is outlined. Subsequently, the transient temperature field of structure considering aerodynamic heating is obtained by employing computational technology of aerodynamic heating/structure heat transfer coupling program. Finally, the modal frequencies and shapes of vehicle structure under transient temperature field is calculated based on finite element method (FEM). Based on the analysis and investigation of the simulation results, the influence of the transient thermal environment on structure modal frequency and shape is determined. Furthermore, the investigation of wing structure modal analysis considering aerodynamic heating is an important basis of aerothermoelastic simulation.


1980 ◽  
Vol 6 (3-4) ◽  
pp. 227-229
Author(s):  
Carl R. Zimmer

A modified version of the computer programme SINC-S is described which permits the user to specify independently up to 30 different device temperatures in a given problem when the proper control statement is included. An additional option is an algorithm for the steady-state solution of a non-linear network with periodic inputs, so that realistic system operation may be simulated. The programme may be used to provide more accurate simulation of circuits where large temperature gradients are present, and to furnish input data for other thermal analysis programmes


Author(s):  
Magdalena Nakielska ◽  
Krzysztof Pawłowski

Nowadays, people are looking for solutions related to ventilation, cooling or heat demand systems, which would be energy efficient and, at the same time, would not cause the degradation of the surrounding environment. As far as ventilation is concerned, an good solution is a natural ventilation, which improves thermal comfort rooms without increasing the consumption of electrical energy in the building. In order to improve the mode of action of the natural ventilation in the building, one can mount various elements supporting the air flow. One of them is a solar chimney. In order to check the correct operation of a gravity ventilation installation in Poland’s climatic conditions, the measurements was carried out on a test stand on the 3.1 building of UTP University of Science and Technology in Bydgoszcz. The received results show the intensification of the air flow through the room the value between 50% and 150%, depending on a measuring hour (Chen et al. 2003). These research results were compared with the research results received before the installation of the solar chimney on the ducts of the gravity ventilation.


Author(s):  
John Miller ◽  
Wanyoung Jang ◽  
Chris Dames

In analogy to the asymmetric transport of electricity in a familiar electrical diode, a thermal rectifier transports heat more favorably in one direction than in the reverse direction. One approach to thermal rectification is asymmetric scattering of phonons and/or electrons, similar to suggestions in the literature for a sawtooth nanowire [1] or 2-dimensional electron gas with triangular scatterers [2]. To model the asymmetric heat transport in such nanostructures, we have used phonon ray-tracing, focusing on characteristic lengths that are small compared to the mean free path of phonons in bulk. To calculate the heat transfer we use a transmission-based (Landauer-Buttiker) method. The system geometry is described by a four-dimensional transfer function that depends on the position and angle of phonon emission and absorption from each of two contacts. At small temperature gradients, the phonon distribution function is very close to the usual isotropic equilibrium (Bose-Einstein) distribution, and there is no thermal rectification. In contrast, at large temperature gradients, the anisotropy in the phonon distribution function becomes significant, and the resulting heat flux vs. temperature curve (analogous to I-V curve of a diode) reveals large thermal rectification.


Author(s):  
Susanne-Marie Kirsch ◽  
Felix Welsch ◽  
Lukas Ehl ◽  
Nicolas Michaelis ◽  
Paul Motzki ◽  
...  

Abstract Elastocaloric cooling uses solid-state NiTi-based shape memory alloy (SMA) as a non-volatile cooling medium and enables a novel environment-friendly cooling technology without global warming potential. Due to the high specific latent heats activated by mechanical loading/unloading, large temperature changes can be generated in the material. Accompanied by a small required work input, a high coefficient of performance is achievable. Recently, a fully-functional and illustrative continuous operating elastocaloric fluid cooling system based on SMA is developed and realized, using a novel mechanical concept for individual loading and unloading of multiple SMA wire bundles. The fluid-based heat transfer system is designed for efficient heat exchange between the stationary heat source/sink and the SMA elements, operates without any additional heat transfer medium. Rotation frequency and fluid flow-rate are adjustable during operation, which allows adapting the operation point to power- or efficiency-optimized demands. The versatile placement of the in- and outlets allows different duct lengths and counter-flow or parallel-flow experiments. To investigate the air flow parameters at the in- and outlets, as well as the crossflow between the hot and cold side, a measurement system is developed and integrated. In this contribution, the first measurement results of the output temperatures for inlet air flow variation in combination with different rotation frequencies are presented.


1975 ◽  
Vol 97 (1) ◽  
pp. 64-71 ◽  
Author(s):  
B. Lakshminarayana

An analysis is carried out to predict the nature and magnitude of secondary flows induced by temperature gradients in turbomachinery stator and rotor. The effect of this thermal driven secondary flow is severe in gas turbines, due to large temperature gradients that exist at the outlet of the combustion chamber. Secondary flows change the temperature profiles at the exit of the blade row and generate thermal wakes. A method of incorporating these effects into the calculation of gas, blade and casing temperatures in a turbine is demonstrated through an example.


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