Infrared window in hypersonic missile usually suffers complex aerodynamic force/heat during high-speed flight.A finite element method was adopted to simulate the thermal and stress response of microscale functional fi...Infrared window in hypersonic missile usually suffers complex aerodynamic force/heat during high-speed flight.A finite element method was adopted to simulate the thermal and stress response of microscale functional film for infrared window under different aerodynamic heats/forces conditions.Temperature and stress distribution were obtained with different heat fluxes.There is almost constant stress distribution along the film thickness except a sudden decrease near the substrate.The maximum stresses are located at the points which are 0.3 mm away from the edges.Different film materials result in different stress values.The temperature and stress in ZrN are larger than those in Y2O3.Besides the numerical simulation,an oxygen propane flame jet impingement test was performed to investigate thermal shock failure of the infrared window.Some place of the window surface has spots damage and some place has line crack damage after thermal shock.展开更多
A boundary element method has been developed for analysing heat transport phenomena in solitary wave on falling thin liquid films at high Reynolds numbers. The divergence theorem is applied to the non-linear convectiv...A boundary element method has been developed for analysing heat transport phenomena in solitary wave on falling thin liquid films at high Reynolds numbers. The divergence theorem is applied to the non-linear convective volume integral of the boundary element formulation with the pressure penalty function. Consequently, velocity and temperature gradients are eliminated, and the complete formulation is written in terms of velocity and temperature. This provides considerable reduction in storage and computational requirements while improving accuracy. The non-linear equation systems of boundary element discretization are solved by the quasi-Newton iterative scheme with Broyden's update. The streamline maps and the temperature distributions in solitary wave and wavy film flow have been obtained, and the variations of Nusselt numbers along the wall-liquid interface are also given. There are large cross-flow velocities and S-shape temperature distributions in the recirculating region of solitary wave. This special flow and thermal process can be a mechanism to enhance heat transport.展开更多
为了将PTC（positive temperature coefficient）电子浆料以厚膜电路的形式制备在不锈钢基片上，并把不锈钢本体作为散热器，引出电极利用PTC效应制成可控电热元件．方法：提出基于1Cr18Ni9不锈钢基片的PTC厚膜电路的组成结构，并根据IC...为了将PTC（positive temperature coefficient）电子浆料以厚膜电路的形式制备在不锈钢基片上，并把不锈钢本体作为散热器，引出电极利用PTC效应制成可控电热元件．方法：提出基于1Cr18Ni9不锈钢基片的PTC厚膜电路的组成结构，并根据ICr18Ni9的膨胀系数和电路元件的电气特性实现了厚膜电路PTC电子浆料的应用设计技术．结果显示以PTC厚膜电路材料组成的可控电热元件，其功率密度高达200W／cm^2；其电阻膜层的表面加热速度可达200—300℃／s；其使用寿命达到1万小时以上．可见与传统的电热合金材料、陶瓷基片加热器以及元件组合的加热器相比，本实现技术电路具有功率密度大、响应速度快、加热温度可控等优点。展开更多
Heat transport at the microscale is of vital importance in microtechnology applications. The heat transport equation is different from the traditional heat transport equation since a second order derivative of tempera...Heat transport at the microscale is of vital importance in microtechnology applications. The heat transport equation is different from the traditional heat transport equation since a second order derivative of temperature with respect to time and a third-order mixed derivative of temperature with respect to space and time are introduced. In this study, we develop a hybrid finite element-finite difference (FE-FD) scheme with two levels in time for the three dimensional heat transport equation in a cylindrical thin film with sub-microscale thickness. It is shown that the scheme is unconditionally stable. The scheme is then employed to obtain the temperature rise in a sub-microscale cylindrical gold film. The method can be applied to obtain the temperature rise in any thin films with sub-microscale thickness, where the geometry in the planar direction is arbitrary.展开更多
基金Projects (51222205,51372053) supported by the National Natural Science Foundation of ChinaProject (JC201305) supported by Heilongjiang Provincial Science Fund for Distinguished Young Scholars,ChinaProject (20112302110036) supported by Ph.D. Programs Foundation of Ministry of Education of China
文摘Infrared window in hypersonic missile usually suffers complex aerodynamic force/heat during high-speed flight.A finite element method was adopted to simulate the thermal and stress response of microscale functional film for infrared window under different aerodynamic heats/forces conditions.Temperature and stress distribution were obtained with different heat fluxes.There is almost constant stress distribution along the film thickness except a sudden decrease near the substrate.The maximum stresses are located at the points which are 0.3 mm away from the edges.Different film materials result in different stress values.The temperature and stress in ZrN are larger than those in Y2O3.Besides the numerical simulation,an oxygen propane flame jet impingement test was performed to investigate thermal shock failure of the infrared window.Some place of the window surface has spots damage and some place has line crack damage after thermal shock.
基金This project was financially supported by the National Natural Science Foundation of China
文摘A boundary element method has been developed for analysing heat transport phenomena in solitary wave on falling thin liquid films at high Reynolds numbers. The divergence theorem is applied to the non-linear convective volume integral of the boundary element formulation with the pressure penalty function. Consequently, velocity and temperature gradients are eliminated, and the complete formulation is written in terms of velocity and temperature. This provides considerable reduction in storage and computational requirements while improving accuracy. The non-linear equation systems of boundary element discretization are solved by the quasi-Newton iterative scheme with Broyden's update. The streamline maps and the temperature distributions in solitary wave and wavy film flow have been obtained, and the variations of Nusselt numbers along the wall-liquid interface are also given. There are large cross-flow velocities and S-shape temperature distributions in the recirculating region of solitary wave. This special flow and thermal process can be a mechanism to enhance heat transport.
文摘为了将PTC（positive temperature coefficient）电子浆料以厚膜电路的形式制备在不锈钢基片上，并把不锈钢本体作为散热器，引出电极利用PTC效应制成可控电热元件．方法：提出基于1Cr18Ni9不锈钢基片的PTC厚膜电路的组成结构，并根据ICr18Ni9的膨胀系数和电路元件的电气特性实现了厚膜电路PTC电子浆料的应用设计技术．结果显示以PTC厚膜电路材料组成的可控电热元件，其功率密度高达200W／cm^2；其电阻膜层的表面加热速度可达200—300℃／s；其使用寿命达到1万小时以上．可见与传统的电热合金材料、陶瓷基片加热器以及元件组合的加热器相比，本实现技术电路具有功率密度大、响应速度快、加热温度可控等优点。
文摘Heat transport at the microscale is of vital importance in microtechnology applications. The heat transport equation is different from the traditional heat transport equation since a second order derivative of temperature with respect to time and a third-order mixed derivative of temperature with respect to space and time are introduced. In this study, we develop a hybrid finite element-finite difference (FE-FD) scheme with two levels in time for the three dimensional heat transport equation in a cylindrical thin film with sub-microscale thickness. It is shown that the scheme is unconditionally stable. The scheme is then employed to obtain the temperature rise in a sub-microscale cylindrical gold film. The method can be applied to obtain the temperature rise in any thin films with sub-microscale thickness, where the geometry in the planar direction is arbitrary.
