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Wang P.,Beihang University | Li Y.,Beihang University | Li Y.,Beijing Institute of Nearspace Vehicles Systems Engineering | Zou Z.P.,Beihang University | And 2 more authors.
Numerical Heat Transfer; Part A: Applications | Year: 2012

For the conjugate heat transfer simulation, two-equation turbulence models will predict an anomalously large growth of turbulent kinetic energy in high strain rate flows, and then the flow and heat transfer will be unreasonable. The current study improved the low Reynolds number Chien k-two-equation model using the realizability based C μ limiter and the production term P k limiter. This study was conducted based on a developed preconditioned density-based conjugate heat transfer algorithm. Calculations are presented for the flat plate turbulence flow and the conjugate heat transfer of the MarkII cooling turbine blade using the improved model. The results were analyzed and compared with semi-empirical formula and experimental data. Significant improvement in the turbulent kinetic energy anomaly was obtained using both limiters. The prediction accuracy of the Chien k-model for the flow and heat transfer in the conjugate heat transfer simulation was significantly enhanced. The changes in the model are guaranteed to not have unfavorable influence on the simulation of low strain rate flows. © 2012 Copyright Taylor and Francis Group, LLC.

Zhang S.-D.,Harbin Institute of Technology | Xia X.-L.,Harbin Institute of Technology | Dai G.-L.,Harbin Institute of Technology | Yu M.-X.,Beijing Institute of Nearspace Vehicles Systems Engineering | Yan W.-X.,Beijing Institute of Nearspace Vehicles Systems Engineering
Kung Cheng Je Wu Li Hsueh Pao/Journal of Engineering Thermophysics | Year: 2012

An experimental device for measuring spectral transmittance at high-temperature was developed. By measuring, four bands of normal transmittance in visible and near infrared spectra were obtained for the optical quartz specimen at the temperature range of 300 K to 1100 K. The double-thickness method was used to analyze the experimental data to deduce the spectral refractive index and spectral absorption coefficient of the quartz. By the two spectral property parameters obtained previously, the spectral transmittance was theoretically forecasted for another sample. The comparison with the experimental data shows that the errors of predicted values are less than 10%.

Zhong D.F.,Harbin Institute of Technology | Yuan J.B.,Beijing Institute of Nearspace Vehicles Systems Engineering | Shan X.B.,Harbin Institute of Technology | Xie T.,Harbin Institute of Technology
Advanced Materials Research | Year: 2012

A new mathematical model on the stiffness matrix of the bearing was established by using the non-conforming Hertz contact theory. In this model, the case of compound load and the coupling effects was considered. The numerical arithmetic to estimate the displacements under the compound loads is discussed. As a sample, a wire race ball bearing used in a certain type of three-axis aircraft simulating rotary table was provided. The curves of axial stiffness and radial stiffness were obtained in MATLAB. The experimental system for measuring the stiffness was built. The experimental results verify the validity of the theoretical model. © (2012) Trans Tech Publications, Switzerland.

Xie T.,Xi'an Jiaotong University | He Y.-L.,Xi'an Jiaotong University | Tong Z.-X.,Xi'an Jiaotong University | Yan W.-X.,Beijing Institute of Nearspace Vehicles Systems Engineering | Xie X.-Q.,Beijing Institute of Nearspace Vehicles Systems Engineering
International Journal of Heat and Mass Transfer | Year: 2014

In the current work, we present an experimental study to investigate the reaction mechanism of silica aerogel material at high temperature. The experimental study is based on simultaneous thermal analyzer 449F3 as well as Fourier Transform Infrared Spectroscopy (FTIR). The results show that when the material is exposed at high temperature, the mass of material will decrease about 1.98% accompanying with endothermic effect. Via FTIR analysis, it is found that the mass loss of material may be caused by the removal of adsorbed water. Besides the experimental study, a numerical heat transfer model is constructed to study the transient heat transfer characteristic of aerogel material by taking the endothermic reaction into account. The numerical heat transfer model is validated by a classical Stefan problem and a corresponding experimental measurement. Afterwards, a parametric study is conducted to investigate the effect of two parameters, reaction temperature and reaction heat, on transient heat transfer characteristics of aerogel insulating material. The results show that: (1) Before reaching the reaction temperature Treaction, the material that with lower Treaction possesses lower temperature. However, when it exceeds the reaction temperature, the material shows the highest temperature among other materials. (2) With the increase of reaction heat, the increasing trend of temperature is weakened and the emergent of the turning point that separates the temperature platform and temperature-rise period appears later. © 2013 Published by Elsevier Ltd.

Xie T.,Xi'an Jiaotong University | He Y.-L.,Xi'an Jiaotong University | Tong Z.-X.,Xi'an Jiaotong University | Yan W.-X.,Beijing Institute of Nearspace Vehicles Systems Engineering | Xie X.-Q.,Beijing Institute of Nearspace Vehicles Systems Engineering
Applied Thermal Engineering | Year: 2015

Silica aerogel is a kind of highly nano-porous material with excellent performance in heat insulation. Some researches showed that during the heating process, some kind of reactions happened inside the material accompanying with endothermic/exothermic phenomenon, such as evaporation of water or residual solvent. These reactions will greatly change the properties of the material as well as affect its insulation performance at high temperatures. Therefore, it is crucial for silica aerogel insulating material to understand its transient heat transfer characteristics and to identify the thermal properties as well as some other key parameters. In this study, a numerical heat transfer model is constructed to study the transient heat transfer characteristics of the aerogel material in which the reaction effect is taken into account. Finite volume method combined with Enthalpy method are used to numerically solve the heat transfer problem. In order to determine the key parameters of the heat transfer model, an inverse analysis is conducted based on the Levenberg-Marquardt method. Through the inverse analysis technique, parameters such as thermal conductivities before and after the reaction, λvirgin and λreacted, reaction temperature Treaction and reaction heat L, can be estimated by using a group of experimentally measured temperature history curves. Besides, sensitivity analysis as well as the influence of measurement errors are also discussed. The results show that (1) The optimum values for these parameters which are consistent with the actual situation are Xu0 = (λvirgin, λreacted, Treaction, L) = (0.1380 W/(m·K), 0.0535 W/(m·K), 355.45 K, 230,670 (J/kg)); (2) The accompanying thermal effect of the reaction heat is small and can be neglected. The main effect of reaction on the heat transfer characteristics is due to the change of the component of the material. The component change of material will then lead to the variation of thermal properties which greatly affect the heat transfer process. © 2015 Elsevier Ltd. All rights reserved.

Cui M.,Dalian University of Technology | Yang K.,Dalian University of Technology | Xu X.-L.,Beijing Institute of Nearspace Vehicles Systems Engineering | Wang S.-D.,Dalian University of Technology | Gao X.-W.,Dalian University of Technology
International Journal of Heat and Mass Transfer | Year: 2016

Despite numerous studies of Levenberg-Marquardt (LM) algorithms for solving inverse heat conduction problems, sensitivity coefficients are mainly evaluated by numerical differentiation methods. However, sensitivity coefficients are difficult to be precisely calculated by numerical differentiation methods, if multi-dimensions, transient states and nonlinearities are involved. To the best knowledge of the authors, there has not been a general method for accurately calculating sensitivity coefficients for a LM algorithm, except numerical differentiation methods. In this study, a modified LM algorithm is presented by introducing the complex-variable-differentiation method for sensitivity analysis, and multi-parameters of boundary heat flux are simultaneously recovered by solving transient nonlinear inverse heat conduction problems. The results show that the modified LM algorithm has the advantages of the conventional LM algorithm, that are effective, accurate and robust for simultaneous estimation of multi-parameters of boundary heat flux. Meanwhile, the efficiency and the convergence stability of the modified LM algorithm are improved, which are attributed to accurate evaluation of sensitivity coefficients, compared with the conventional LM algorithm. © 2016 Elsevier Ltd. All rights reserved.

Ma K.,China Aerospace Science and Technology Corporation | Jin J.,China Aerospace Science and Technology Corporation | Li W.,Beijing Institute of Nearspace Vehicles Systems Engineering | Zhang P.,Northwest Regional Air Traffic Management Bureau of CAAC
Proceedings of the International Conference on Anti-Counterfeiting, Security and Identification, ASID | Year: 2016

In this paper, a two-staged decoding strategy which can be used for the Weighted Bit Flipping (WBF) based decoding algorithm for LDPC codes is presented. At the two stages, a parallel WBF and bit-flipping (BF) algorithms are adopted separately. Correspondingly, by the study of the iterative decoding process of the PWBF algorithm, a simple function is introduced to dynamically implement the switch of two decoding stages. The proposed algorithm can noticeably lower the error floor of PWBF algorithm with a modest increase in computation complexity and hardware cost. The validation of the proposed algorithm is verified by simulation. © 2015 IEEE.

Yin Y.-Y.,Beijing Institute of Nearspace Vehicles Systems Engineering
Yuhang Xuebao/Journal of Astronautics | Year: 2010

The displacement of the solid rocket is obtained by the integration of the low-frequency vibration during free flight state. Then by the modal superimposition method, a method for identifying the transverse load of solid rocket is introduced. Based on an example of solid rocket remoting data, the results of transverse bending moments are given. Identified result and measured cross section bending moment are approximate, proving that such a method is practical in load identification for similar problems and much useful in engineering.

Zhang Y.,China Aerodynamics Research And Development Center | Lei J.,Beijing Institute of Nearspace Vehicles Systems Engineering | Mao M.,China Aerodynamics Research And Development Center | Chen J.,China Aerodynamics Research And Development Center
Kongqi Donglixue Xuebao/Acta Aerodynamica Sinica | Year: 2015

Based on CARDC hypersonic numerical simulation platform Chant-2.0, applications of γ-Reθ model to hypersonic boundary layer transition are investigated preliminarily. The transition onset and length are predicted by solving two transport equations for turbulence intermittency factor and momentum thickness Reynolds number. Firstly, γ-Reθ transition model using local correlation functions is calibrated through four cases of low speed flat flows, and in the process freestream turbulence intensities have a wide range from low level natural transition to high level bypass transition. Then, taking account of flow properties of hypersonic boundary layer, the pressure gradient function used in the transition model's Reθt correlation is properly modified for high Mach number flows. Finally, by adopting the new model functions, hypersonic boundary layer transitions of flat and sharp cone are calculated and compared with referrence data. The simulation results indicate that the specially calibrated correlations for hypersonic platform software can accurately predict the onset and length of transition region in low speed cases, and high Mach number correction shows good performance in hypersonic simulations. ©, 2015, Editorial Board of ACTA AERODYNAMICA SINICA. All right reserved.

Xu C.,Nanjing University of Aeronautics and Astronautics | Xu C.,Beijing Institute of Nearspace Vehicles Systems Engineering | Wang X.,Nanjing University of Aeronautics and Astronautics
Transactions of Nanjing University of Aeronautics and Astronautics | Year: 2012

Impact dynamics of flexible solids is important in engineering practice. Obtaining its dynamic response is a challenging task and usually achieved by numerical methods. The objectives of the study are twofold. Firstly, the discrete singular convolution (DSC) is used for the first time to analyze the impact dynamics. Secondly, the efficiency of various numerical methods for dynamic analysis is explored via an example of a flexible rod hit by a rigid ball. Three numerical methods, including the conventional finite element (FE) method, the DSC algorithm, and the spectral finite element (SFE) method, and one proposed modeling strategy, the improved spectral finite element (ISFE) method, are involved. Numerical results are compared with the known analytical solutions to show their efficiency. It is demonstrated that the proposed ISFE modeling strategy with a proper length of conventional FE yields the most accurate contact stress among the four investigated models. It is also found that the DSC algorithm is an alternative method for collision problems.

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