scholarly journals Research on Thermal Insulation Performance of Lightweight Thermal Protection Materials for High Speed Aircraft under Different Boundary Conditions

2018 ◽  
Vol 179 ◽  
pp. 02001
Author(s):  
Feng Wang ◽  
Dafang Wu ◽  
Haoyuan Ren
Keyword(s):  
Boundary Conditions ◽  
Thermal Insulation ◽  
High Speed ◽  
Thermal Protection ◽  
Different Boundary Conditions ◽  
Flight Vehicles ◽  
Calculation Results ◽  
Different Temperatures ◽  
Insulation Performance

The determination of thermal insulation performance of thermal protection materials or structures is an indispensable and important step in the safety design of high speed flight vehicles. To obtain the temperature difference of the radiating surface for plate specimens under three different boundary conditions in heat insulation experiments (the specimens were placed either vertically or horizontally with the radiating surface facing down or horizontally with the radiating surface facing up), three thermal test setups were established to test the thermal insulation performance of light-weight ceramic specimens at different temperatures. The results show that the radiating surface temperature was the highest when the specimen was placed horizontally with the radiating surface facing down, while it was the lowest when the specimen was placed horizontally with the radiating surface facing up.The numerical calculation results agreed very well with the experimental ones, confirming the credibility and accuracy of the experimental results. The different thermal insulation performances of the plate specimens obtained under three different boundary conditions will provide important guidance for designers in the design of thermal protection systems for large cabins of high speed flight vehicles.

scholarly journals Determining the Geometrical Sizes of Plates with Internal Hinges by Using Additional Conditions

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Vildan Yazıcı ◽  
Zahir Muradoğlu
Keyword(s):  
Finite Difference ◽  
Boundary Conditions ◽  
Difference Equations ◽  
Transmission Conditions ◽  
Elastic Plates ◽  
Different Boundary Conditions ◽  
Mechanical Constraints ◽  
Finite Difference Equations ◽  
The Common

For a system obtained by placing more than two elastic plates side by side, the transmission conditions are obtained at the common boundaries. Finite difference equations are developed for the problem of plates with internal hinges and applied for determination of the response of a system assembled from three different plates with different mechanical constraints between adjacent plates in this study. An algorithm is written to find out how long the size of the plates should be in order to obtain the desired amount of bending against the force affecting the system under different boundary conditions. The bisection and multigrid methods are used for this. These two methods are compared based on the obtained data.

scholarly journals Effect of Torsional Element towards High-Speed Rotating Shaft’s Critical Speed at Different Boundary Conditions

2019 ◽  
Vol 8 (4) ◽  
pp. 6787-6792
Keyword(s):  
Finite Element ◽  
Boundary Conditions ◽  
High Speed ◽  
Critical Speed ◽  
Element Model ◽  
Accurate Estimation ◽  
Fe Model ◽  
Rotating Shaft ◽  
Different Boundary Conditions ◽  
The Difference

Efficiency improvement that can be provided by the high-speed rotating equipment becomes a concern for designers nowadays. Since the high-speed rotating machinery was capable of rotating at very near to critical speed, the accurate estimation of critical speed needs to be considered. This paper investigated the effect of torsional element towards critical speed of high-speed rotating shaft system for pinned-pinned (P-P), clamped-free (C-F) and clamped-free (C-F) boundaries condition. The Nelson’s finite element model that considers the torsional effect was developed for formulating the finite element (FE) model. This FE model was used to derive Mathieu-Hill’s equation and then solved by applying the Bolotin’s theory. From the solution, the Campbell’s diagram of the high-speed shaft was plotted. It was found that torsional motion has significant effect on the critical speed for different boundary conditions. The difference between critical speed of 4DOF and 5DOF models can be as high as 6.91 %.

Calculation and Experimental Evaluation of the Thermal Resistance of a Structure with Reflective Insulation

2014 ◽  
Vol 899 ◽  
pp. 374-380 ◽  
Author(s):  
Jiří Kalánek ◽  
Libor Šteffek ◽  
Milan Ostrý
Keyword(s):  
Thermal Properties ◽  
Thermal Resistance ◽  
Thermal Insulation ◽  
Experimental Methods ◽  
Test Element ◽  
Normative Requirements ◽  
Box Method ◽  
Insulation Performance ◽  
Heat Transfer By Radiation

As reason of increasing requirements of thermal insulation properties of the exposed envelope, reflective insulation are among kind of modern thermal insulation materials ones, which can significantly increased thermal insulation performance if their application is correct. Thermal insulation performance is caused by reduction of the heat transfer by radiation. Conjunction of low-emissivity surface of the reflective insulation and air layer is important to account. This article is focused on the determination of thermal properties of reflective insulation and the results of measured values thermal resistance of determination by hot box method using heat flow meter are presented here. As part of determination of thermal properties of reflective insulation by experimental methods, the test element used to measure the thermal resistance of an insulated air cavity had to be created for concordance with the normative requirements. The part of this article is determination of the thermal resistance by the calculation of derived physical relations and comparison with values of the laboratory measurement.

scholarly journals Impact of Building Walls of Historic Objects from Half-Timbered Wall in their State of Thermal Protection / Wpływ Budowy Ścian Historycznych Budynków z Muru Pruskiego Na Ich Stan Ochrony Cieplnej

2016 ◽  
Vol 20 (1) ◽  
pp. 171-178 ◽  
Author(s):  
Agnieszka Szymanowska-Gwiżdż ◽  
Tomasz Steidl
Keyword(s):  
Thermal Insulation ◽  
Thermal Protection ◽  
Utility Functions ◽  
Thermal Parameters ◽  
Upper Silesia ◽  
Industrial Plants ◽  
Correct Determination ◽  
Building Walls

Abstract The paper presents the problems connected with preserved examples of buildings in Upper Silesia that contain the elements of half-timbered walls. This type of construction currently characterizes houses of various utility functions. Often, their formation was related to the construction of patron settlements, accompanied by the development of industrial plants. Today, there is a problem of insufficient thermal insulation of barriers in half-timbered houses and numerous attempts to improve their thermal parameters are observed. In this type of projects, the correct determination of the existing state in terms of construction of the barrier and thermal protection seems to be important, as the starting points for further analysis. The study determines the insulation of frame walls with ceramic fill, with a variety of material and construction solutions. Literature examples and in situ measurements results were used for the research.

scholarly journals Numerical Study of the Influence of Coupling Interface Emissivity on Aerogel Metal Thermal Protection Performance

Gels ◽  
2021 ◽  
Vol 7 (4) ◽  
pp. 250
Author(s):  
Fengfei Lou ◽  
Sujun Dong ◽  
Yinwei Ma ◽  
Bin Qi ◽  
Keyong Zhu
Keyword(s):  
Thermal Insulation ◽  
Radiative Heat ◽  
Thermal Protection ◽  
Numerical Study ◽  
Good Effect ◽  
Research Focus ◽  
Extinction Coefficients ◽  
Volume Method ◽  
Insulation Performance ◽  
Reduction Percentage

For aerogels in metal thermal protection system (MTPS), radiative heat transfer will participate in the thermal transport process. Therefore, the influence of the emissivity of the coupling interface between metal and aerogels on thermal insulation performance is considered an important research focus. In this paper, CFD numerical simulation is performed to study the influence of emissivity on the performance with different extinction coefficients at different boundary temperatures. The finite volume method and the discrete ordinate method are used to solve the govern equations. The results show that when the boundary temperatures are 600 K and 2100 K, the extinction coefficient is 50 m−1, and the reduction percentage of the effective thermal conductivity with an emissivity of 0.2 can be up to 47.5% and 69.8%, compared to the system with an emissivity of 1. Thus, the reduction in emissivity has a good effect on the thermal insulation performance of the MTPS at a higher boundary temperature for materials with small extinction coefficients.

scholarly journals Lateral-distortional buckling of continuous steel-concrete composite beam

2018 ◽  
Vol 11 (4) ◽  
pp. 719-756 ◽  
Author(s):  
T. V. AMARAL ◽  
J. P. S. OLIVEIRA ◽  
A. F. G. CALENZANI ◽  
F.B. TEIXEIRA
Keyword(s):  
Boundary Conditions ◽  
Composite Beam ◽  
Bending Moment ◽  
Composite Beams ◽  
Simplified Model ◽  
Continuous Steel ◽  
Distortional Buckling ◽  
Different Boundary Conditions ◽  
Simply Supported

Abstract In hogging bending moment regions of continuous composite beams the collapse by lateral-distortional buckling (LDB) can occur. The design against LDB according to ABNT NBR 8800:2008 begins with the determination of the elastic critical moment, which depends, among other factors, of the distribution of the bending moment in the analyzed span, taken into account in the formulation through the modification parameter Cdist. To assess the analytical formulations prescribed by ABNT NBR 8800:2008, numerical FE models that simulate the LDB behavior of continuous steel-concrete composite beams were developed in this paper. The different boundary conditions presented in ABNT NBR 8800:2008 were checked using two different models: a simplified model, with a single simply supported span; and models with multiple internal supports and more than one span. It was observed that the Cdist values prescribed by ABNT NBR 8800:2008 can be unsafe, and therefore new values for Cdist are proposed in this paper.

scholarly journals Impact Of The Pulse Width Modulation On The Temperature Distribution In The Armature Of A Solenoid Valve

2015 ◽  
Vol 20 (4) ◽  
pp. 773-786 ◽  
Author(s):  
R. Goraj
Keyword(s):  
Temperature Distribution ◽  
Boundary Conditions ◽  
Pulse Width ◽  
High Speed ◽  
Pulse Width Modulation ◽  
Solenoid Valve ◽  
Thermal Calculation ◽  
Different Boundary Conditions ◽  
Power Set ◽  
Inductive Power

Abstract In order to estimate the inductive power set in the armature of the high-speed solenoid valve (HSV) during the open loop control (OLC) using pulse width modulation (PWM) an analytical explicit formula has been derived. The simplifications taken both in the geometry and in the physical behavior of the HSV were described. The inductive power was calculated for different boundary conditions and shown as a function of the frequency of the coil current. The power set in the armature was used as an input to the thermal calculation. The thermal calculation had an objective to estimate the time dependent temperature distribution in the armature of the HSV. All the derivation steps were presented and the influence of different boundary conditions was shown and discussed. The increase of the temperature during the heating with inductive power has been evaluated both in the core and on the side surface of the HSV.

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