变结构PID算法在电子战飞机液冷子系统设计中的应用

针对电子战飞机雷达与电子战设备液冷精细化控制需求,通过对PID算法的研究,文章提出了基于变结构PID控制算法的冷却液流量控制方法,用于飞机液冷系统流量调节阀门控制,经过仿真与系统联试验证,控制响应快,超调量小,稳态精度高。     

数据中心液冷技术研究

在数据中心电能利用效率管控及“双碳”目标的压力下,液冷技术逐渐成为数据中心绿色、节能、低碳的一种制冷技术。冷却液是液冷技术中最为重要的一种冷却介质,结合液冷技术应用方式,介绍了冷却液种类及对应的物性参数技术要求,通过该研究意在促进液冷技术在信息通信技术中的应用,并提供一些指导建议。     

球形调节阀门流量特性试验研究

本文采用一型液冷调节球阀为研究对象,在不改变其结构设计的前提下,通过试验研究,给出不同阀门开度下的流体阻力特性,通过计算得出流量系数并分析流量能力,为液冷系统工作模式选择提供有效依据,对后期该类型的液冷阀设计提供指导价值。     

微通道液冷冷板散热特性研究

本文研究了3种典型构型微通道冷板的散热特性,分别为冷板盖板与翅片焊接、冷板盖板与翅片不焊接以及翅片双面插排形式.对比了3种不同构型冷板的散热能力并对3种构型冷板的流阻特性进行了研究,发现翅片排布越密集流阻越大,越不利于整个液冷系统的流量分配.研究了冷却液流量对功率芯片温度的影响,发现冷却液流量较小时,流量增加可大幅降低...     

喷墨印刷沉积的PEDOT/PSS薄膜导电性能

利用压电喷墨印刷技术沉积了PEDOT/PSS有机导电薄膜,研究了退火温度和乙二醇掺杂对薄膜导电性能的影响。实验结果表明:未退火和退火温度为120,140,160℃时,薄膜表面平均粗糙度分别为8.15,4.10,3.36,2.66nm;乙二醇掺杂使导电激活能由未掺杂时的0.096eV减小为0.046eV;电导激活能减小表明PEDOT分子链从低电导率的卷曲构象向高电导率的伸展构象转变;此外,乙二醇掺杂促使PSS与PE-DOT/PSS分离,使团聚的PEDOT/PSS颗粒变小从而分散更均匀,降低了表面粗糙度。     

电子设备液冷散热的冷却液热学性能分析

从3个方面对液冷散热器中冷却液的热学性能进行分析对比,包括不同温度下的热物理参数变化、不同流态下的热传导系数和相同功耗下的冷却液温升。以65#冷却液和PAO冷却液为例,对比分析表明在-20~70 ℃区间内65#冷却液在热学性能上较PAO更强,但物理参数的稳定性较PAO差。在同一电子设备系统的液冷散热器中使用这两种不同冷却液介质后,通过实验测量电子设备内各芯片的平衡温度,结果表明,65#冷却液较PAO具有更好的散热效果,芯片温升约可降低10 ℃。     

新型雷达波吸收材料导电聚合物的研究

介绍了新型雷达波吸收材料导电聚合物的研究现状及发展趋势，导电聚合物吸波剂在众多雷达波吸波剂分类中所属类型，导电聚合物的导电机理，提出了在进一步研究中，导电聚合物更好地应用于雷达吸波材料所要考虑的问题．     

基于GaN的S波段固态发射机的设计

介绍了一种基于GaN功率管应用于相控阵雷达的S波段全液冷全固态发射机,利用GaN的高输出功率、高效率特性,对本发射机系统的设计思想、结构组成及工作原理作了详细分析,对采用的模块化设计技术、电磁兼容技术及液冷热设计都给出了重点介绍。实现了在20%占空比、总输出功率不小于32kW和工作效率不低于30%指标要求。     

一种基于接收相参的鸟类目标探测雷达

针对鸟类目标探测技术能有效预防飞鸟对飞机起降带来的危害问题,提出了一种基于接收相参的鸟类目标探测雷达方案。通过对鸟类目标探测雷达系统及鸟类目标实际飞行姿态的分析,研究系统构架及技术途径。并通过工程实践研究接收相参技术在鸟类目标探测雷达中的应用。以试验数据验证了该方案的可行性,对下一步的工程应用具有参考价值。     

基于实时计算的雷达波形发生器

面对复杂的战场环境,低截获雷达需要发射复杂雷达波形,以防止被敌方截获。传统的雷达波形发生器多采用专用DDS芯片实现,工作频率低且方式不够灵活,无法满足日益增长的波形多样性需求。为解决该问题,提出通用高速DA加FPGA的波形发生器架构。分析了几类常用低截获波形的特性并给出实现方法,采用FPGA实时计算波形参数的方式,可产生线性调频信号、巴克码等雷达波形。经仿真和试验验证其满足使用要求。     

IGBT junction and coolant temperature estimation by thermal model

The capability of IGBT (Insulated Gate Bipolar Transistor) to handle heat is one of its main limitations of high power application. This paper aims to study an IGBT thermal model under flow cooling condition and estimate the IGBT module junction and coolant temperature. Firstly, this paper studies the IGBT module internal sandwich structure and calculates the thermal resistance and thermal capacitor for each layer using a 1D physical model. Then a Cauer electric model is built for the IGBT module to evaluate the thermal constant time of the model. The liquid cooling method is applied in this project for fast cooling and the thermal parameters are studied and measured since this cooling method involves both solid and liquid. In order to estimate the junction temperature, the sensing temperature from NTC (Negative temperature coefficient) resistor inside the module is used as reference temperature. The equivalent thermal models, also named Foster model, from both junction to NTC and NTC to coolant are built, respectively. With these thermal models, the junction and coolant temperature estimation methods are derived. For the purpose of making the estimation accurate, the thermal coupling effect is carefully studied. Finally, the thermal model is verified by inverter application with current steps sweeping; the estimated temperature is compared with thermal camera measurement result which demonstrates good accuracy of the thermal model. The estimated coolant temperature is also well matched with thermocouple measurement result.     

Research on the Compatibility of the Cooling Unit in an Automotive Exhaust-based Thermoelectric Generator and Engine Cooling System

The temperature difference between the hot and cold sides of thermoelectric modules is a key factor affecting the conversion efficiency of an automotive exhaust-based thermoelectric generator (TEG). In the work discussed in this paper the compatibility of TEG cooling unit and engine cooling system was studied on the basis of the heat transfer characteristics of the TEG. A new engine-cooling system in which a TEG cooling unit was inserted was simulated at high power and high vehicle speed, and at high power and low vehicle speed, to obtain temperatures and flow rates of critical inlets and outlets. The results show that coolant temperature exceeds its boiling point at high power and low vehicle speed, so the new system cannot meet cooling requirements under these conditions. Measures for improvement to optimize the cooling system are proposed, and provide a basis for future research.     

半导体激光器非典型宏通道水冷散热系统设计

针对大功率半导体激光器散热系统展开设计研究。首先，对水冷散热系统的流体通道中的冷却液进行了流体分析，结果表明在传统矩形流体通道结构中，冷却液在进液口处和弯度较小处容易产生湍流空洞。湍流空洞不仅会产生空泡腐蚀效应，还会导致靠近热源的上层冷却液填充不充分，降低系统的散热效率；其次，在传统流体通道结构的基础上，提出了一种非典型宏通道结构的优化模型。采用有限元分析软件Fluent分别对散热模型的分布和激光器模块器件的分布进行了数值模拟，流场结果表明优化模型中冷却液流动时没有湍流空洞产生，散热系统可靠性更高，冷却液在流体通道的上层填充效果更好，同时解决了传统模型中流体在局部流道中流速缓慢的问题，使散热系统具备更良好的散热性能。接着又通过温度场仿真结果得出，优化模型搭建的散热系统工作时激光器最高温度可降低2 ℃，且热源1上温度更均匀，热源3上温度降低1.25 ℃；最后，在激光器满功率输出情况下进行的散热实验对比，获得的实验数据与仿真结果基本一致。     

Heat Transfer in Surface-Cooled Objects Subject to Microwave Heating

Several investigators in microwave bioeffects research have exposed biological preparations to intense microwave fields, while at the same time cooling the sample with flowing water. We examine the heat transfer characteristics of this situation, to estimate the maximum temperature increase and thermal time constants that might be encountered in such an experiment. The sample is modeled as a uniform sphere, cylinder, or slab subject to uniform heating, which is located in an unbounded coolant flow. The heat transfer is determined by the Biot and Reynolds numbers (which reflect the geometry, fluid flow, and material thermal properties of the system) the temperature rise is governed by the heat conduction equation coupled with external convection. The results are expressed in terms of nondimensional quantities, from which the thermal response of a heated object of arbitrary size can be determined. At low coolant flow rates, the maximum temperature rise can be biologically significant, even for relatively small objects (of millimeter radius) exposed to moderate levels of microwave energy (with a SAR of ca. 100 mW/g). The results are valid also where the coolant is a gas or a liquid different from water, the only restriction being on the Reynolds number of the flow.     

一种主振放大链式发射机冷却系统的热力学研究

以某雷达主振放大链式发射机液体冷却系统为基础,建立了液冷系统的热力学模型,并重点对该模型进行热交换器的热力学分析,推导出理论上所需冷却系统的散热功率。对该雷达冷却系统的测试表明,被冷却器件实际的发热功率低于理论推导功率,即该冷却系统能满足电子器件冷却的要求。     

高功率LED热管理方法研究最新进展

LED芯片结温的高低直接影响其出光效率、工作寿命和可靠性。在分析系统各个环节热阻的基础上,详细评述了高功率LED产品从芯片到系统级的热管理研究新动向,包括:自然对流冷却,采用压电风扇、电离方法所进行的强迫空气对流冷却,采用水、液态金属作为冷却工质的液冷方法,采用热管实现的相变冷却,采用热电片进行的固态冷却方案以及利用热电片对余热进行回收利用的热管热回收方案和液体金属冷却方法。并在上述基础上提出了发展更高功率密度LED热管理方法的关键科学问题。     

Design and Optimization of Single-Phase Liquid Cooled Microchannel Heat Sink

Semiconductor devices for demanding automotive applications generate a large amount of heat $({≫}{rm 100}~{rm W}/{rm cm}^{2})$. These high power devices can be cooled off very effectively by liquid coolant flowing through the microchannel heat sink. Microchannel heat sinks are very attractive because of their compactness, light weight, and large surface-to-volume ratio. Higher surface-to-volume ratio results in enhanced cooling performance. In this paper, a systematic robust analytical method is presented for design and optimization of single-phase liquid cooled microchannel heat sink. Effects of various design parameters such as eccentricity and footprint of heat source or device, thickness of the heat sink base, channel aspect ratio, number of microchannels or fins, coolant flow rate, and thermal conductivity of heat sink material on heat sink thermal resistances and pressure drop are delineated. Finally, analytical results are compared with experimental data and good agreement is obtained. The analytical method helps to reduce the design cycle time and time-to-market significantly.      

High-performance heat sinking for VLSI

The problem of achieving compact, high-performance forced liquid cooling of planar integrated circuits has been investigated. The convective heat-transfer coefficient h between the substrate and the coolant was found to be the primary impediment to achieving low thermal resistance. For laminar flow in confined channels, h scales inversely with channel width, making microscopic channels desirable. The coolant viscosity determines the minimum practical channel width. The use of high-aspect ratio channels to increase surface area will, to an extent, further reduce thermal resistance. Based on these considerations, a new, very compact, water-cooled integral heat sink for silicon integrated circuits has been designed and tested. At a power density of 790 W/cm², a maximum substrate temperature rise of 71°C above the input water temperature was measured, in good agreement with theory. By allowing such high power densities, the heat sink may greatly enhance the feasibility of ultrahigh-speed VLSI circuits.     

激光预热/流体冷却辅助激光金属沉积AlSi10Mg成形

铝合金导热率高、激光吸收率低、热累积效应显著,难以稳定形成激光金属沉积（LMD）。为实现自动精确预热、消除热累积、分析预热影响并提升AlSi10Mg铝合金LMD成形能力,采用“光内送粉”Ar送气保护式激光金属沉积技术,设计激光预热与流体冷却温控系统并建立预热与冷却温控模型,进行AlSi10Mg 铝合金LMD成形实验研究,系统分析预热对激光吸收率、表面质量、截面形貌、温度场和材料组织性能的影响。结果表明:激光预热与流体冷却温控系统可实现精确预热并消除热累积,获得表面粗糙度Ra为2.6 μm的单熔道,实现AlSi10Mg搭接、块体和薄壁的高精高效稳定LMD成形。预热提高激光吸收率,使熔道扁平化,增大了晶粒尺寸。该辅助系统和方法能够有效解决铝合金LMD成形稳定性差的难题,为成形质量控制与熔池温控提供了新思路新工艺。