摘要：Separate type heat pipe heat exchangers are often used for large-scale heat exchanging. The arrangement of such a heat exchanger conveniently allows heat input to and output from the heat exchanger at remote locations. The traditional method of designing an ordinary HPHE (heat pipe heat exchanger) is commonly applied in the separate type exchanger design, but the calculations have to be carried out separately, which makes it very complicated. In this work, the ε-NTU (effectiveness-Number of Transfer Units) method was applied for optimization analysis of single- or multi-level separate type heat pipe heat exchangers. An optimizing formula for single-level separate type heat pipe heat exchangers was obtained. The optimizing principles of effec- tiveness-NTU and heat transfer rate by the equal distribution method for multi-level separate type heat pipe heat exchanger are presented. The design of separate type heat pipe heat exchangers by the optimizing method is more convenient and faster than by the traditional method.

摘要：The paper presented topology optimization of 2 D and 3 D Nanofluid-Cooled Heat Sink(NCHS). The flow and heat transfer problem in the NCHS was treated as a single-phase nanofluid based convective heat transfer model. The temperature-dependent fluid properties were taken into account in the model due to the strong temperature-dependent features of nanofluids. An average temperature minimum problem was studied subject to the fluid area and energy dissipation constraints by using the density method. In the method, the design variable is updated according to the gradient information obtained by an adjoint based sensitivity analysis process. The effects of the energy dissipation constraint, temperature-dependent fluid properties and nanofluid characteristics on optimal configurations of NCHS were numerically investigated with following ***, branched flow channels in the optimal configuration increased with the rise of the allowed energy dissipation. Secondly, temperature-dependent fluid properties were significant for obtaining the appropriate optimal results with best cooling performance. Thirdly, heat transfer performances of optimal configurations were enhanced by reducing the nanoparticle diameter or increasing the nanoparticle volume fraction. Fourthly, the optimal configuration for nanofluid had better cooling performance than that for its base fluid.

摘要：Biological world always provides inspirations for engineering designs, and insects are important targets to mimic. For the Coleoptera, its flight has been emphasized for long. However, the invisible folding procedure of hind wings, which occurs under the stiff elytra after flight, still remains unknown. In this paper, the wing folding process and the surficial microstructures of elytra, hind wing and abdomen are investigated by video recording and scanning electron microscopy. The results show that there are hooklike protrusions approximately 15 μm in length distributing on the inner side of elytra, and bump-like protrusions on the hind wings. The ＇hooks＇ may anchor the ＇bumps＇ on the main wing to prevent corrugation during folding. The horizontal protrusions observed on the abdomen shape a hairy cuticle, which is conducive to a better wing-abdomen interaction. Thus, the ratcheting mechanism that wing folding facilitated by micro-protrusions on the body surface is revealed. This new finding helps us to further understand the functions of diversely shaped protrusions in the physiology of insects. More importantly, the ratcheting mechanism could serve as a cuticle interaction model and inspire new engineering applications, such as microsystems.

摘要：本文介绍了一种通过调整卡箍使得管道避免发生共振的设计策略.当管道的固有频率在机械设备运作时产生的振动频率范围内,会引发共振现象,给机械设备的正常操作带来严重的灾难.因此,把机械设备操作产生的振动频率范围定义为频带禁区.通常,工程中的管道被简化为多跨输流管道:通过将卡箍简化为线性和扭转刚度,建立了多跨输流管道的整体管道模型.通过采用Galerkin截断方法并应用广义特征值方法,获得了多跨输流管道的固有频率.通过对比不同长度的管道固有频率和频带禁区,定义了管长的安全范围和共振范围分别为频带禁区的外和内,并且通过分析卡箍的影响推导得出了绝对安全长度和绝对共振长度.此外,还确定了卡箍刚度和位置对安全范围的影响.结果表明,通过调整卡箍的线性刚度、扭转刚度和位置,管道的安全范围会发生显著地变化.根据这些结果,提出了一种管道设计策略,从而避免了管道的共振发生,并减少了使用卡箍的数量.最后,以飞机上的一段管道为例进行了设计,结果表明:通过调整卡箍,管道的固有频率成功地远离了频带禁区,因而在飞机的运行过程中不会发生共振.总而言之,通过调整卡箍的刚度或位置,可以获得避免多跨输流管道发生共振的设计策略.

摘要：The nonlinear energy sink(NES)is outstanding in vibration control for the well-known character of energy targeted transmitting and resonance automatically *** enhance the practicability,this paper proposes a ground-limited *** novel design can be encapsulated in a certain ***,as the vibration region of NES is limited,the control efficiency of it must be considered ***,the ground-limited NES is discussed via the analytical method,the simulation method,and especially the experiment in forced *** parameters involved in this study are obtained through the parameter identification based on the experimental *** piecewise nonlinearity is fitted into the continuous nonlinearity by the hyperbolic tangent *** the harmonic balance method(HBM)is used during the analytical processing to promote the accuracy of the *** direct numerical method produces results to verify the analytical method together with the experimental *** discussion on the control parameters shows that a proper limiting spring can effectively reduce the vibration of the NES while the cost of the control efficiency is *** a word,this work provides a simple and reliable approach for restricting the NES,which is beneficial to the design of the NES and broadens the application of the NES in engineering.

摘要：Methods for the analysis of heat exchangers with various flow arrangements modeling,design,and performance are essential for heat transfer system modeling and its integration with other energy system *** paper proposes the use of the linear-transfer law for the heat exchanger design and performance analysis as a function of the thermal resistance related to the ratio of a linear temperature difference to the total heat transfer ***,we derived a correction factor that represents the influence of the flow arrangement on the heat transfer performance by the effective thermal conductance,as a function of correction factor,heat transfer coefficient,and surface *** on the effective thermal conductance,we propose the hot-end NTU and cold-end NTU for deriving a standardized and general thermal resistance formula for different types of heat exchangers by the combination of the correction factor with linear-transfer ***,for parallel-flow,cross-flow,and 1-2 Tubular Exchanger Manufacturers Association(TEMA)E shell-and-tube heat exchangers,we derived and obtained alternative correction factor expressions without introducing any *** cases about heat exchanger design and performance analysis show that the calculation processes using the correction factor-based general thermal resistance are straightforward without any iteration and the calculation results are ***,the experimental validation shows that the general thermal resistance formula is appropriate for analyzing the heat transfer *** is,the correction factor-based general thermal resistance formula provides a standardized model for heat exchanger analysis and heat transfer/integrated energy system modeling using the heat current method.

摘要：A novel vibration isolation device called the nonlinear energy sink(NES)with NiTiNOL-steel wire ropes(NiTi-ST)is applied to a whole-spacecraft *** NiTi-ST is used to describe the damping of the NES,which is coupled with the modified Bouc-Wen model of *** NES with NiTi-ST vibration reduction principle uses the irreversibility of targeted energy transfer(TET)to concentrate the energy locally on the nonlinear oscillator,and then dissipates it through damping in the NES with *** generalized vibration transmissibility,obtained by the root mean square treatment of the harmonic response of the nonlinear output frequency response functions(NOFRFs),is first used as the evaluation index to analyze the whole-spacecraft system in the *** optimization analysis of the impact of system responses is performed using different parameters of NES with NiTi-ST based on the transmissibility of ***,the effects of vibration suppression by varying the parameters of NiTi-ST are analyzed from the perspective of energy *** results indicate that NES with NiTi-ST can reduce excessive vibration of the whole-spacecraft system,without changing its natural ***,the NES with NiTi-ST can be directly used in practical engineering applications.

摘要：目的:探讨作用于大跨度曲面屋盖非定常气动力的特性,为考虑非定常气动力影响的大跨度曲面屋盖抗风设计提供理论参考。创新点:1.采用强迫振动试验;2.采用大涡模拟(LES)流入脉动风的生成方法;3.研究大跨度曲面屋盖非定常气动力特性。方法:1.通过强迫振动风洞试验方法探讨风速、强迫振动振幅、屋盖的矢跨比和缩减频率对非定常气动力的影响;2.采用计算流体力学数值模拟重现风洞试验,从而在更宽的缩减频率范围内分析非定常气动力的特性,并且通过可视化流场的分析探讨风与屋盖相互作用的机理。结论:1.屋盖的振动对屋盖表面的风压分布影响较大。2.屋盖的振动可能抑制屋盖背风面漩涡的脱落。3.根据风洞试验和数值模拟的结果分析得到的矢跨比、风速和振动振幅对气动阻尼系数和气动刚度系数的影响较小;气动阻尼系数和气动刚度系数主要随着缩减频率的变化而变化。4.气动刚度系数为正值,使得结构的总刚度减小,从而减小结构的固有频率;气动阻尼系数为负值,使得结构总阻尼增加。5.风洞试验和LES模拟结果的一致性可以说明,LES是一个能够有效研究非定常气动力特性的数值模拟方法。

摘要：Piezoelectric ceramic is hard to be integrated with the normal spring *** address the above problem,this paper proposed a new geometry of a clip‑like spring which is very similar to binder clip in our daily *** equivalent stiffness of the designed piezoelectric clip‑like spring is thoroughly researched and discussed through the theoretical model,the finite element simulation and the experimental *** results confirm the possibility of designing a compact piezoelectric clip‑like spring,and the equivalent stiffness can be tuned through the several key geometric ***,theoretical predictions confirmed by experimental results show that the equivalent stiffness of the spring structure is as function of the instantaneous angle of the clip,this stiffness variation caused by the geometric nonlinearity can be ignored in some practical engineering applications,which means it is possible to linearize the clip‑like spring and simplify the following dynamic model of the corresponding piezoelectric oscillators.

摘要：认识剪切型岩爆的触发机理对地下工程科学设计与安全施工具有重要意义。为揭示隧道围岩(DTR)的剪切触发型岩爆机理,进行了砂岩的双矩形隧道和双圆形隧道物理模型剪切试验。在剪切试验过程中,利用高速摄像机和声发射监测仪对DTR的岩爆过程进行监测和记录,揭示了压剪下DTR的宏观和细观断裂特征;进而建立了5种隧道间距数值模型,分析了压剪下含隧洞试样连续-非连续剪切过程及其触发的岩爆机理;提出了一种新的能量冲击指数(S)来评价剪切型岩爆倾向性。试验结果表明,在剪切试验中,DTR的实时剪切特征、内外破裂特征和微裂纹数演化特征可划分为4个典型阶段:整体剪切压缩阶段(Ⅰ阶段)、以裂纹萌生为主的弹性阶段(Ⅱ阶段)、以裂纹扩展-贯通和剪切岩爆为主的剪切破裂阶段(Ⅲ阶段)和剪切摩擦阶段(Ⅳ阶段)。此外,试验结果还表明DTR在剪切型岩爆发生后可形成对称猫耳形缺口;微裂纹演化过程中DTR经历了裂纹预备阶段(Ⅰ阶段)、裂纹初始增长阶段(Ⅱ阶段)、裂纹快速增长阶段(Ⅲ阶段)和裂纹稳定阶段(Ⅳ阶段)。更重要的是,综合分析发现,双矩形隧道和双圆形隧道触发剪切型岩爆机制存在差别的本质是截面形状导致的结构效应,即双矩形隧道和双圆形隧道应力场分布差异导致断裂行为不同。研究结果有利于加深对剪切型岩爆机理的认识,为岩土工程防治提供理论依据。