精密镗床主轴系统温度场与热误差解析建模

为了准确真实地建立反映主轴瞬态温度场与热误差变化的物理解析模型,提出了一种考虑辐射换热以及轴承瞬态生热的主轴热网络模型,分析主轴系统的轴承热-结构相互作用机理及其对生热率的影响,计算了轴承的时变生热率;分析讨论辐射换热对主轴系统温度场与热误差的影响,基于辐射网络提出了主轴系统以辐射换热方式耗散热量的计算方式;提出将辐射换热引入热网络模型的计算方法,建立更完善的主轴温度场与热误差解析模型。为了验证该模型的准确性和泛化能力,进行了不同转速、不同环境温度及不同初始结构温度下主轴系统的热特性实验,结果表明,辐射换热对于主轴温度场与热误差的影响不可忽略,考虑辐射换热的物理解析模型精度更高。

盘式永磁涡流驱动器的电磁-温度耦合解析模型

提出盘式永磁涡流驱动器的电磁-温度耦合解析模型,用于进行电磁场解析计算和温度场分析。首先,基于分离变量法建立三维电磁场解析模型用于计算磁场分布,推导转矩和涡流损耗表达式。然后,将涡流损耗作为热源,基于等效热网络法建立温度分析计算模型。电磁-温度耦合解析模型的计算是考虑材料电磁和温度特性随温度变化,通过温度迭代过程实现的。最后,利用该文提出的电磁-温度耦合解析模型,分析转矩、涡流损耗、永磁体和铜盘温升随负载的变化,并分析结构参数对转矩的影响。将解析模型结果与有限元和实验结果进行对比,证明解析模型的合理性和正确性。

热解析仪温度指示与实际不符引起解析率分析误差

目的提示同仁对新购进的热解析仪或同类型的仪器应重视对计量器具的校对。方法采用热解析法及气象色谱法。结果在使用热解析仪时,因忽略对仪器所采用的数显温控器进行校对,致使显示温度低于实际温度达40%左右,引起解析率分析误差。结论对新购进的热解析仪或同类型的仪器时应重视对计量器具的校对。

CPL冷凝单管液体段瞬态温度场解析解

ＣＰＬ冷凝单管液体段瞬态温度场解析解卢文强（中国科学院研究生院力学与工程热物理教研室北京１０００３９）关键词ＣＰＬ冷凝单管，温度场解析解１导言ＣＰＬ（毛细泵两相流回路）是一种新型的微重力热管，为了确保ＣＰＬ在空间正常运行，一个重要的问题是防止冷凝器中...

超临界CO_2萃取霉酚酸解析过程参数的响应面法优化

采用超临界CO2萃取霉酚酸,通过调节分离釜Ⅰ的压力和温度,增加萃取物的解析选择性,提高分离釜Ⅰ中解析物的霉酚酸纯度.采用2因素5水平的星点设计试验,考察了分离釜Ⅰ的压力和温度对萃取物的霉酚酸含量(CMPA)和霉酚酸萃取回收率(RR)的影响;响应面分析显示,RR与分离釜Ⅰ的压力和温度符合二次模型,压力的一次项和二次项均对RR有极显著影响,温度的一次项也对RR有较显著影响;而CMPA与分离釜Ⅰ的压力和温度符合线性方程,压力对CMPA有极显著影响.根据拟合方程预测分离釜Ⅰ的最佳压力和温度,综合考虑RR和CMPA,确定为14.69 MPa和69.99℃.验证实验中设定分离釜Ⅰ的压力为14.5 MPa、温度为70℃,RR为(91.57±1.31)%,CMPA为(77.50±1.03)%,与预测值90.96%和76.49%接近.

直线形单排管冻土帷幕平均温度计算

在人工地层冻结工程中,平均温度是评价冻土帷幕状态,进行冻土帷幕力学性能分析的基本参数,本文研究单排管冻结形成的冻土帷幕的平均温度计算。基于单排管冻结稳态温度场解析解,直接对温度场表达式进行积分运算,运用分部积分法和积分中值定理,得到了单排管冻结平均温度计算公式,根据工程中的实际参数取值进行了公式的简化。考虑到温度场解析解在冻结管区域的不适用,采用相同的积分策略求解冻结管区域对平均温度计算的影响,进行了平均温度计算公式的修正。使用A NSYS进行了单排管冻结的热学稳态数值模拟与平均温度计算公式的结果进行比对,考察管间距l=0. 4,0.6,0.8,1.0,1.2,1.4 m,相对厚度ξ/l=0. 5,0.6,0. 7,0. 8,1.0,1.5共6种冻结发展状态,根据试验报告进行土质参数取值,冻结参数为工程中常用取值。对比计算结果显示,公式计算与数值计算的结果较为吻合。当相对厚度大于0.5时,随着冻土厚度的发展(相对厚度的增大),理论计算结果与数值计算结果的差值迅速减小到0.5以内,当相对厚度大于0.6时,差值小于0.2℃当相对厚度为1及以上时,差值小于0.1℃。通过数值模拟验证了平均温度计算公式的准确性,也说明公式简化和修正的合理性,公式计算的误差满足工程应用的要求。

岩石取芯切削钻进过程温度分析与试验研究

为深入研究取芯钻钻头在钻进过程中的温度变化规律,归纳影响钻头温度的各类参数,建立钻头温度解析计算模型;结合红外热像仪,实现取芯钻工作条件下钻头温度的定性分析。研究结果表明:摩擦热占据取芯钻热功转换的绝大部分,在其他条件不变的情况下,增加进给力能够加大钻头的摩擦热,温度明显增加;增大钻头的尺寸和转速,使钻头发生更剧烈的剪切和摩擦,从而温度增大。钻头的进给力、尺寸和转速与钻头温度呈现明显的正相关特性,而决定剪切热的主切削力则对温度的影响变化不显著。试验中岩石切屑对观测结果有一定影响,但试验结果与理论计算结果基本相符。

基于解析法的黑体空腔传感器测温预估研究

通过对黑体空腔钢水连续测温传感器传热机理的分析,建立了其一维轴对称非稳态传热模型。利用分离变量法和叠加原理,推导了传感器温度解析解。计算分析传感器温度随时间的变化,并与有限元数值模拟对比得出最大偏差为6℃,一致性较好。根据预估补偿的概念,利用所建立的解析模型推导了钢水温度预测式。算例验证:利用钢水预估式可将滞后时间降低至120 s左右。

PD SOI NMOSFET翘曲效应的温度模型

报道了一个部分耗尽 (PD) SOI NMOSFET翘曲效应的温度解析模型 .该模型从 PD SOI NMOSFET器件的物理结构 ,即由顶部的 NMOSFET和底部的寄生 BJT构成这一特点出发 ,以一定温度下 PD SOI NMOSFET体-射结电流与漏 -体结电流的动态平衡为核心 ,采用解析迭代方法求解 ,得出漏 -体结碰撞电离产生的空穴在体区中近源端积累达到饱和时的体 -射结电压 ,及漏 -体结和体 -射结电流的各主要分量 ,进而得到了 PD SOI NMOSFET翘曲效应漏电流的温度解析模型 ,并将一定条件下的模拟结果与实验结果进行了比较 。

矿用光纤测温系统设计及应用技术研究

利用光纤测温技术对煤矿火灾事故进行监测预警是煤矿火灾安全领域的重点发展方向。针对矿用光纤测温系统设计的关键技术问题,该文首先简要介绍了光纤测温基本原理。其次,在分析系统需求的基础上进行硬件功能模块的参数设计,提出了根据已知测点温度解析其他测点温度的实用温度解析方法并进行了温度噪声测试。最后,该文还提出通过始末点进行正段光缆温度标定的标定算法并进行了温度误差测试,研究了综合应用多种温度报警参数的温度预警方法。试验测试数据表明,该文设计的系统常温下的温度噪声小于±1℃,标定后的温度误差小于±2℃。

均匀设计在盾叶薯蓣皂素超临界CO_2萃取中的应用

采用均匀设计方法,以萃取压力、萃取温度、解析压力、解析温度4因素7水平进行实验,研究了盾叶薯蓣皂素超临界CO_2萃取最佳条件为:萃取压力32 MPa,萃取温度56℃;解析压力8 MPa,解析温度62℃。与传统有机溶剂提取法相比,应用超临界CO_2萃取盾叶薯蓣皂素,不仅方法简便、安全、提取周期短,而且提取的选择性与效率高。

紫花苜蓿挥发性成分萃取条件优化与定性、定量分析

挥发性成分是判断苜蓿干草品质优劣的基本感官指标,苜蓿干草在贮藏过程中受环境变化和微生物的作用,挥发性成分发生明显改变,直接影响苜蓿干草的适口性。目前我国牧草行业内缺乏针对苜蓿干草挥发性成分的分析鉴定方法,为此本研究采用顶空固相微萃取–气相色谱–质谱联用法(HS–SPME–GC–MS)分析紫花苜蓿(Medicago sativa)挥发性成分,结合峰面积归一化法确定各化合物的相对含量。结果表明:萃取温度90℃、萃取时间80 min、解析温度250℃、解析时间3 min为最佳萃取条件。该萃取条件下紫花苜蓿中共检测出52种化合物,包括酮类化合物9种,占总挥发物的37.55%;醇类化合物12种,占总挥发物的21.74%;醛类化合物15种,占总挥发物的19.31%;酯类化合物6种,占总挥发物的9.41%。其中β-紫罗兰酮含量可达到总挥发物的20%左右,苯乙醇、反式-2-己烯醛、2-苯基乙醛、壬醛、癸醛、6-甲基-5-庚烯-2-酮、3,5,5-三甲基环己-2-烯酮、胡薄荷酮等对紫花苜蓿挥发性成分贡献较大。

汽车内饰件挥发性有机化合物释放规律研究

利用热脱附-气相色谱-质谱联用仪研究了不同热解析温度(50、70、90℃)和不同热解析时间(15、30、60 min)下10种汽车内饰件样品挥发性有机化合物苯、甲苯、二甲苯、乙苯、苯乙烯以及总挥发性有机化合物(TVOC)的释放情况。结果表明,热解析温度对挥发性有机化合物释放量的影响要大于热解析时间的影响,热解析温度由50℃升至90℃时,TVOC和苯系物释放量均显著增加;而延长热解析时间,除TVOC有一定增加外,苯系物释放量增加不明显。另外,相同热解析条件下B柱内饰(聚丙烯+聚乙烯,PP+PE)、地毯(聚酯纤维,PET)以及座椅(皮)单位质量TVOC释放量较大;地毯(PET)中甲苯、二甲苯释放量较大;仪表罩(丙烯腈-丁二烯-苯乙烯共聚物,ABS)中乙苯、苯乙烯释放量较大。

Extension of analytical model of solid-state phase transformation

Departing from an analytical phase transformation model, a new analytical approach to deduce transformed fraction for non-isothermal phase transformation was developed. In the new approach, the effect of the initial transformation temperature and the accurate ＂temperature integral＂ approximations are incorporated to obtain an extended analytical model. Numerical approach demonstrated that the extended analytical model prediction for transformed fraction and transformation rate is in good agreement with the exact numerical calculation. The new model can describe more precisely the kinetic behavior than the original analytical model, especially for transformation with relatively high initial transformation temperature. The kinetic parameters obtained from the new model are more accurate and reasonable than those from the original analytical model.

Influence of pyrolysis temperature on ferroelectric properties of La and Mn co-doped BiFeO_3 thin films

Bi0.9La0.1Fe0.95Mn0.05O3 （BLFMO） ferroelectric thin films were fabricated on Pt/Ti/SiO2/Si/ substrates by the sol-gel process at different pyrolysis temperatures. The mass loss of BLFMO powder was investigated by thermo gravimetry analyser （TGA）, and the polycrystalline structure and smooth surface of BLFMO thin films were characterized by X-ray diffraction （XRD） and atomic force microscopy （AFM）, respectively. The remnant polarization （Pr） of the BLFMO films pyrolyzed at 420 ℃ is 21.2 μC/cm2 at the coercive field （Ec） of 99 kV/cm and the leakage current density is 7.1×10-3 A/cm2, which indicates that the BLFMO thin films display relatively good ferroelectric property at this temperature.

Elasticity solution of laminated beams with temperature-dependent material properties under a combination of uniform thermo-load and mechanical loads

An exact solution for simply-supported laminated beams with material properties variable with temperature under a combination of uniform thermo-load and mechanical loads was investigated,based on the two-dimensional(2-D)thermo-elasticity theory.Firstly,the beam was divided into a series of layers with uniform material properties along the interfaces of the beam.The uniform thermo-load acted on each layer was transformed into a combination of the normal surface forces acted at the two ends and the transverse thermo-load.Secondly,the state space method was employed to obtain the general solutions of displacements and stresses in an arbitrary layer.Thirdly,based on the interfacial continuity conditions between adjacent layers,the relations of displacement and stress components between the top and bottom layers of the beam were recursively derived by use of the transfer-matrix method.The unknowns in the solutions can be solved by the mechanical loads acted on the top and bottom surfaces.The convergence of the present solutions was checked.The comparative study of the present solutions with the Timoshenko’s solutions and the finite element(FE)solutions was carried out.The effects of material properties variable with temperature on the thermo-elastic behavior of laminated beams were discussed in detail.

CHARACTERISTICS AND FORMATION CAUSES OF QINGDAO COLD WATER MASS

In this work, the main characteristics of the Qingdao Cold Water Mass were studied by using "the comparison analysis method" based on 1980 temperature,salinity and dissolved oxygen data on the western South Yellow Sea. The formation cause of the water mass was analyzed based on February of 1959 temperature and salinity data for this area and on some other authors’ studies. The results showed that the Qingdao Cold Water Mass has growing and vanishing processes: appears in the last ten days of March; has stable pattern in April; is biggest in its area in May; becomes small in its area in June; vanishes in July. It comes from the northern Shandong Coastal Water and is characterized by low temperature and salinity and high dissolved oxygen. The mass is formed under the joint effects of anticyclonic circulation and solar radiation.

Similarity Solutions of Marangoni Convection Boundary Layer Flow with Gravity and External Pressure

This study is focused on a steady dissipative layer, which is generated by Marangoni convection flow over the surface resulted from an imposed temperature gradient, coupled with buoyancy effects due to gravity and external pressure. A model is proposed with Marangoni condition in the boundary conditions at the interface. The similarity equations are determined and approximate analytical solutions are obtained by an efficient transformation, asymptotic expansion and Pade approximant technique. For the cases that buoyancy force is favorable or unfavor-able to Marangoni flow, the features of flow and temperature fields are investigated in terms of Marangoni mixed convection parameter and Prantl number.

Study on the pyrolysis behavior of Shendong Shangwan coal and its macerals concentrate

The pyrolysis characteristics of Shendong Shangwan coal and its macerals concentrate were investigated using thermogravimetry （TG） coupled with mass spectrometry （MS）. The evolved gases were analyzed online by MS spectroscopy. The results of TG/DTG （derivative thermogravimetry） show ths vitrinite concentrate has greater weight loss rate and higher volatile yield than the other two samples. More light hydrocarbons C1-C5 are released from the vitfinite concentrate than from the Shendong Shangwan coal and inertinite concentrated in the process of pyrolysis. Three samples have similar shape curves of evolved gases of C2~C5 with different intensities. When the pyrolysis temperature was lower than 418℃, the amount of C6H6 evolved in the process of pyrolysis of inertinite concentrated was higher than that of raw coal and vitrinite concentrate. As the temperature rising, the production rate of C6H6 increased. Below 672℃, C6H6 evolution rate of vitrinite concentrate was far greater than the other two samples; the main evolution temperature range of C7H8 was 400℃ to 700℃ for the three samples. The amount of HE and H20 released first increased and then decreased with the temperature increase while more H2 released for pyrolysis of inertinite concentrated and more H20 released for the pyrolysis of vitrinite concentrate.

Pyrolysis and co-pyrolysis of lignite and plastic

The study firstly discusses the pyrolysis characteristics and kinetics by thermogravimetric analysis （TGA）, and then investigates the pyrolysis of lignite and co-pyrolysis with plastic （polyethylene or polypropyl- ene） in tube furnace. Meanwhile, the research focuses on the co-pyrolysis products under different mix- ing ratios as well as pyrolysis products at different testing temperatures and heating rates. The results show that higher final testing temperature and lower heating rate contribute to bond fission in lignite pyrolysis, resulting in less char product. In co-pyrolysis, lignite acts as hydrogen donor, and the yields of char and water rise with increasing amount of plastic in the mixture, while the yields of gas and tar decrease; and a little admixture of plastic will promote the production of gas and tar. Kinetic studies indi- cate that in temperature range of 530-600℃, activation energies of lignite are higher than those of lig- nite/plastic blends, and as plastic mass ratio increases from 0% to 10%, samples need less energy to be decomposed during co-pyrolysis.