Interval finite difference method for steady-state temperature field prediction with interval parameters

A new numerical technique named interval finite difference method is proposed for the steady-state temperature field prediction with uncertainties in both physical parameters and boundary conditions. Interval variables are used to quantitatively describe the uncertain parameters with limited information. Based on different Taylor and Neumann series, two kinds of parameter perturbation methods are presented to approximately yield the ranges of the uncertain temperature field. By comparing the results with traditional Monte Carlo simulation, a numerical example is given to demonstrate the feasibility and effectiveness of the proposed method for solving steady-state heat conduction problem with uncertain-but-bounded parameters.

Mass-Spring-Damper Model with Steady State Parameters for Predicting the Movement of Liquid Column and Temperature Oscillation in Loop Heat Pipe

In order to investigate the mechanism of the temperature oscillation in loop heat pipes,this paper investigated the movement of the phase interface as the changed input power by a mass-spring-damper model.The model was solved with MATLAB and was used to explain the high-frequency and low-amplitude temperature oscillation.Temperature variation with the input power from 20 W to 75 W was investigated based on a LHP prototype in a literature.The model agreed well with the experimental data in the literature.The simulation results suggested that the movement of the liquid column was caused by the fluctuation of pressure difference applied on the liquid column and the stiffness coefficients of the vapor springs increasing with the input power.According to parameter analyses,the temperature oscillation at the outlet of the condenser can be weakened by increasing the mass of the liquid column and keeping the temperature at the outlet of the condenser steady.

Steady State Temperature Study on RF LDMOS with Structure Modification

This paper is devoted to temperature analysis on power RF LDMOS with different feature parameters of die thickness, pitch S length and finger width. The significance of these three parameters is determined from temperature comparison obtained by 3D Silvaco-Atlas device simulator. The first three simulations focus on temperature variation with the three factors at different output power density respectively. The results indicate that both the thinner die thickness and the broaden pitch S length have distinct advantages over the shorter finger width. The device, at the same time, exhibits higher temperature at a larger output power density. Simulations are further carried out on structure with combination of different pitch s length and die thickness at a large 1W/mm output power density and the temperature reduction reaches as high as 55%.

面向数字孪生模型应用的油浸式变压器绕组温度POD-RBFLP降阶计算方法

了解油浸式电力变压器绕组的温度情况是保证其运行稳定性的关键,也是当前针对油浸式变压器数字孪生分析的必然需求。为了快速地获得变压器绕组的稳态温度,该文提出一种基于本征正交分解(proper orthogonal decomposition,POD)和包含线性多项式的径向基函数响应面法(radial basis function response surface method including linear polynomial,RBFLP)的降阶计算模型。首先,讨论POD方法的降阶特性,并设计一种基于留一法交叉验证的自适应获得快照矩阵方法,以提高计算精度及效率;其次,采用响应面方法建立POD模态系数与绕组工况的相关关系,旨在实现通过绕组工况快速获得POD模态系数,从而跳过对降阶模型的复杂非线性计算,进而高效重构绕组温度场。相关算例表明,该方法具有较好的计算精度和效率,在50组测试工况下,与全阶计算相比,误差不超过2.5 K,且总计算时间仅为1.45 s;最后,基于110 kV变压器绕组搭建温升试验平台,试验结果表明,降阶计算结果相较于试验结果,平均计算误差不超过2 K,且单步计算时间仅为0.03 s,相较于同等规模的全阶计算,计算效率有较大幅度地提升。

Evaluation of The Thermal Performance of Multi-Element Doped Graphite under Steady-State High Heat Flux

Multi-element doped graphite, GBST1308 has been developed as a plasma facing material (PFM) for high heat flux components of the HT-7U device. The thermal performance of the material under steady-state (SS) high heat flux was evaluated under actively cooling conditions, the specimens were mechanically joined to copper heat sink with supercarbon sheet as a compliant layer between the interfaces. The experiments have been performed in a facility of ACT (actively cooling test stand) with a 100 kW electron gun in order to test the suitability and the loading limit of such materials. The surface temperature and bulk temperature distribution of the specimens were investigated. The experimental results are very encouraging that when heat flux is not more than 6 MW/m2, the surface temperature of GBST1308 is less than 1000℃, which is the lowest, compared with IG-430U and even with CX-2002U (CFC); The primary results indicate that the mechanically-joined material system by such a proper design as thin tile, super compliant layer, GBST as a PFM and copper-alloy heat sink, can be used as divertor plates for HT-7U in the first phase.

The calculation of hydrocarbon-generating temperature——Theory and practice

How to quantitatively evaluate the maturity of crude oils is still an open question. Mango discovered a remarkable compositional invariance of four isoheptane ratios in crude oils, and proposed a steady-state catalytic model for the origin of light hydrocarbons. According to this model, 2,4/2,3 dimethylpentane ratio is a pure temperature parameter. Bement, Mango et al. established the functional equation between the two parameters-light hydrocarbon temperature and burial temperature and applied it to the calculation of hydrocarbon-generating temperature, which provided a new choice for the study of oil maturity. In this paper, the Mango's parameters for hydrocarbons from the Tazhong area were calculated, the average K1 value is 1.06, which is in good consistency with the Mango's proposal that the K1 value is relatively stable. Calculated with the functional formula of hydrocarbon-generating temperature, the hydrocarbon-generating temperatures are with the range of 120-129℃, and the converted vitrinite reflectance (Ro) varies from 0.88% to 0.90%. This is well consistent with the maturity characteristics of neohopanes. The results have verified the reliability of this method.

Fe-30Ni-15Cr-0.6Nb-3Al-2Mo-3.5Cu奥氏体耐热钢高温蠕变行为

研究了一种含铝奥氏体耐热钢在温度为750℃,蠕变应力为120、170、210和250 MPa下的高温蠕变行为,运用扫描电子显微镜、电子背散射衍射技术研究了蠕变试样的微观结构演变。结果表明,蠕变后第二相主要是B2-NiAl相与σ-FeCr相,没有发现Laves-Fe_(2)Nb相的析出;随着蠕变应力从250 MPa下降到120 MPa,最小蠕变速率从5.72×10^(-6)s^(-1)下降到3.11×10^(-7) s^(-1)。在蠕变过程中,B2-NiAl相初期在晶界析出,随后逐渐在晶内析出并有轻微长大现象,B2-NiAl相的析出有助于提高材料的抗蠕变性能。通过包含双曲正弦函数的方程计算得到应力指数n=3.01,确定相关的蠕变变形机制是位错滑移。根据蠕变断口微观形貌与蠕变损伤容限因子表明,确定蠕变失效是由析出相粗化导致的显微组织退化引起的。

Temperature inferential control of a reactive distillation column with double reactive sections

Temperature inferential control (TIC) is studied for a reactive distillation column with double reactive sections (RDC-DRSs) processing a hypothetical two-stage consecutive reversible reaction (A + B■C + D, C + B■E + D with αD > αB > αC > αA > αE). Because of the complicated dynamic behaviors, the controlled stages by sensitivity analysis lead to great steady-state deviations (SSDs) in top and bottom product purities. Since TIC involves considerably reduced settling times in comparison with direct composition control, small SSDs in product qualities correspond generally to small transient deviations (TDs) in product qualities. An objective function that measures SSDs in product qualities is formulated to represent the performance of a TIC system and an iterative procedure is devised to search for the best control configuration. The application of the procedure to the RDC-DRS gives considerably suppressed TDs and SSDs in top and bottom product qualities as compared with the one by sensitivity analysis. The method is simpler in principle and less computationally intensive than the current practice. These striking outcomes show the effectiveness of the proposed principle for the development of TIC systems for complicated reactive distillation columns.

Solid-state synthesis of Sr-and Co-doped LaMnO_3 perovskites

The synthesis process for La 1- x Sr x Mn 1- y Co y O 3- δ ( x = 0.2, 0.3; y = 0.2, 0.8, designated as LSMC below) perovskite oxides prepared by solid state reaction was investigated using DSC/TG, XRD, EPMA and particle size analysis methods. It was found that LSMCs were all of single phase and the synthesis process might be divided into three stages: the decomposition of reactants, the formation of LaMn(Co)O 3 based oxides, and the formation of LSMC solid solution. Typical average and the peak value of particle size, and the specific surface area are 14.65?μm, 16.4?μm and 1.38?m 2/mL, respectively, for mixed reactants and are 23.81?μm, 32.11?μm and 0.5?m 2/mL, respectively, for powder synthesized at 1?200?℃ for 8?h in air.

Temperature and Doping Dependencies of the Transport Properties within GaN and GaAs

Temperature and doping dependencies of the transport properties have been calculated using an ensemble Monte Carlo simulation. We consider the polar optical phonon, acoustic phonons, piezoelectric, intervalley scatterings and Charged impurity scattering model of Ridley;furthermore, a non nonparabolic three-valley model is used. Our simulation results have shown that the electron velocity in GaN is less sensitive to changes in temperature than that associated with GaAs. Also it is found that GaN exhibits high peak drift velocity at room temperature, 2.8 × 105m/s, at doping concentration of 1 × 1020 m–3and the electron drift velocity relaxes to the saturation value of 1.3 × 105 m/s which is much larger than that of GaAs. The weakening of the phonon emission rate at low temperature explains the extremely high low field mobility. Our results suggest that the transport characteristics of GaN are superior to that of GaAs, over a wide range of temperatures, from 100 K to 700 K, and doping concentrations, up to 1 × 1025

车辆稳态回转对轮胎热-力耦合响应的影响研究

研究车辆稳态回转对轮胎热-力耦合响应的影响。结果表明:车辆操纵稳定性测试前采用稳态回转暖胎时,定回转半径、不定车身侧向加速度工况下较定车身侧向加速度、不定回转半径工况下的轮胎整体温升梯度和幅值波动大;车辆稳态回转时,轮胎温度变化对车身侧向加速度波动非常敏感,左转向车辆车身侧向加速度增大与右侧轮胎分配负荷呈正相关变化,在复合侧偏侧倾作用下,能够加剧轮胎温升;暖胎引起轮胎温度的变化改变轮胎侧偏和纵滑等力学特性响应,造成非线性滑移区滞回幅值不稳定,易导致车辆操纵稳定性测试数据的重复性变差,进而对车辆动力学仿真验证和模型调整带来困难。本研究结果可为整车测试提供指导。

不同稳态工况对同步调相机单相短路后暂态温升的影响

同步调相机可在系统故障时为特高压直流换流站提供暂态无功支持,以保持系统电压稳定,防止直流换相失败,但调相机的高无功输出也会导致其温升增加,运行能力受限。系统故障前同步调相机的初始工况是影响其暂态温升和运行能力的一个重要因素,为研究系统低电压时调相机暂态温升与初始工况之间的关系,该文将调相机的电磁场、温度场与电网模型耦合,计算调相机不同稳态工况下的定转子损耗和温度分布;以线路单相短路故障引起的系统低电压为例,研究调相机初始工况对暂态温升的影响。在考虑各结构件最大容许温度的条件下,揭示调相机单相短路持续时间随初始工况的变化规律。研究结果为提升调相机在系统低电压下的暂态运行能力提供技术支持。

基于压力衰减法的低渗透储层高温敏感性评价实验

低渗透油气藏在钻完井过程中易受到损害且难以解除,而利用传统的稳态驱替法评价低渗透储层损害存在适用性差及实验效率低等技术局限。为此,基于压力脉冲衰减法基本原理,分析了上游压力衰减规律及其与岩心渗透率的关系,以岩心损害前后压力脉冲衰减时间为评价指标,建立了适用于低渗透储层损害评价的实验设备与方法,并利用渤海湾盆地渤中凹陷深部低渗透砂岩岩心,开展了室温和150℃高温条件下的敏感性实验。研究结果表明:(1)当实验条件一定时,压力衰减时间仅与岩心的渗透率有关,压力脉冲衰减法可在无需计算渗透率的情况下对低渗透岩心的损害程度进行评价;(2)实验设备组成简单且操作便捷,避免了复杂的渗透率计算及其带来的误差,实验所需时间远低于常规的稳态法且可重复性良好,在低渗透气藏、特低渗透及超低渗透油藏具有很好的适用性;(3)高温环境明显加剧了储层的敏感性损害,深部高温储层损害特征及技术对策研究需要充分考虑高温的影响。结论认为,该认识解决了传统低渗透储层敏感性评价方法适用性差的难题,为高温低渗透储层保护技术对策研究提供了实验方法支撑和理论依据。

Analytical Solution to Steady-State Temperature Field of Two Freezing Pipes with Diferent Temperatures

The existing analytical formulas to calculate the temperature field distribution of artificial frozen soil walls are all based on the conditions that the surface temperatures of all freezing pipes are equivalent. In this paper, analytical solution of steady state temperature field of two freezing pipes with diferent temperatures is deduced based on thermal potential superposition method. The correctness of the analytical formulas is verified by comparing the temperature field distributions of the analytical formulas and those of the numerical simulations in the same conditions. And discussions are made to analyze the influence of some parameters on temperature field distribution of this condition.

Mathematical models of steady-state temperature fields produced by multi-piped freezing

题目：少量管冻结稳态温度场数学模型目的：少量任意布置冻结管冻结的稳态温度场无解析解。建立任意布置少量管冻结稳态温度场模型，获得解析解，解决人工冻结温度场理论问题。创新点：1．基于势函数叠加原理，确立人工地层冻结中少量管冻结稳态温度场的通用求解方法；2．建立任意布置的3根和4根非等温冻结管下冻结稳态温度场数学模型，获得其解析解通解及特解。方法：1．通过理论分析，将冻结管简化为热汇点源，确定人工地层冻结热势的拉普拉斯方程表述；2．应用势函数叠加原理建立少量管冻结稳态温度场的通用求解方法；3．建立少量管冻结稳态温度场的数学模型，通过理论推导获得温度场解析解；4．通过数值模拟，验证所提方法、数学模型和解析解的正确性和准确性。结论：1．将冻结管简化为点源（热汇），其冻结形成的热势场服从拉普拉斯方程，其解即为热势函数；2．多根冻结管冻结时，将单根冻结管的热势函数叠加，由冻结管的位置决定每根冻结管的热流，再根据边界条件定解。这一方法（即势函数叠加法）可以用于任意布置冻结管冻结稳态温度场解析解的求解：3．将冻结管简化为点源导致获得的解析解存在一定的误差，但误差仅发生在冻结管附近极小的范围内，并且误差微小，完全满足工程上的精度要求。

异步起动表面-内置式永磁转子同步电机特性分析及优化

提出一种异步起动表面-内置式永磁转子同步电机(LSSIPMSM),LSSIPMSM通过定子旋转磁场和转子起动铜层间的相互作用产生异步起动转矩。采用解析和有限元法相结合的方法对LSSIPMSM进行性能分析及关键参数优化,研究了起动铜层厚度、永磁体厚度等参数对起动性能和同步运行性能的影响,从而确定最优的铜层厚度和永磁体厚度。建立LSSIPMSM的电磁场有限元模型,分析LSSIPMSM在永磁体不同退磁状况下的起动性能和同步运行性能,并通过三维温度场有限元模型分析了不同退磁状况下的温度场分布。通过仿真结果的对比分析,验证了LSSIPMSM具有较好的动态性能和稳态性能。

国产Q345钢在不同热-力路径下的材料性能对比和材料模型应用

为评估和分析钢结构的耐火性能,以我国10个钢厂生产的Q345钢的424次恒载升温试验和152次恒温加载试验结果为依据,对钢材强度和应变以及不同的热-力作用路径下的力学性能进行对比研究。结果表明,在所有热-力作用路径下,恒载升温试验的强度最小,应变最大,临界温度最低;恒温加载试验的强度最大,应变最小,临界温度最高。随温度升高,热-力作用路径对钢材的力学性能影响增大:在450℃以下影响较小,在500℃以上时影响显著。如果规范采用恒温加载试验强度,是不可靠的。恒载升温条件下的ε-T-k材料模型和恒温加载条件下的ε-k-T材料模型均不能单独用于超静定钢结构的性能分析。超静定钢结构的性能分析可把火灾过程离散为若干时段,把每个时段分解为两个独立的应变-温度过程和应变-应力过程,分别应用恒载升温条件下的ε-T-k和恒温加载条件下的ε-k-T材料模型进行分析,然后迭加计算以得出最后的应变。

大容量抽水蓄能发电机断路器发热特性仿真与散热优化方法

过高的温升会加速真空断路器结构老化、降低机械强度,基于温升仿真分析的断路器散热优化设计对断路器性能提升具有重要意义。为此通过建立大容量抽水蓄能发电机断路器电磁仿真模型,计算不同通流情况下的电磁损耗,并基于各端面接触电阻损耗,获得总发热损耗参数。在此基础上,建立包含对流、传导、辐射热传递模式的断路器自然对流仿真模型,从增强自然对流、辐射两方面对断路器散热结构进行优化设计。研究结果表明,在通流12.5 kA情况下,断路器监测点最高温升为133.7 K,辐射功率占比约23%。通过增加散热片及热管,最高温升能够降低至109.5 K。增大断路器部件表面发射率能够低成本实现辐射功率提升,从而将最高温升进一步降低至96.9 K。通过断路器稳态通流温升实验,验证了仿真可靠性,监测点温升的仿真与实验平均误差小于2.1 K。

高温输气管道热-结构耦合数值仿真分析

针对高温输气管道的结构特点和输送的介质特征,考虑到静压和温度的耦合作用,根据有限元理论,构建了基于稳态热传导的输气管道热-结构耦合模型,提出了数值求解该问题的方法和具体实施步骤,并以某干气压缩机的输气管道为研究对象进行了数值建模和仿真模拟,分析并揭示了内外管壁温度不同条件下结构性能的变化规律.结果表明:应用该方法可以实现高温输气管道热-结构耦合的数值模拟和仿真分析,为管道的现场施工、实时监测和安全性分析提供有价值的参考意见.

RV减速器摆线轮齿廓修形对温度的影响

为分析摆线轮啮合过程中的温度特性,研究不同修形方式对摆线轮温度的影响规律,考虑摆线齿轮常用的3种组合修形方式,以相同的径向间隙为前提,对比分析摆线轮修形前后的接触应力与摩擦热量在轮齿上的分布情况。利用有限元分析,计算出修形前后温度场中的温度分布情况。结果表明:对摆线齿轮进行齿廓修形可以有效降低齿轮的稳态温度,组合修形中降温效果最佳的修形方式为正等距+正移距修形;单齿上温度梯度的密集程度随着啮合范围的减小而增大;摆线轮修形前后瞬时摩擦热量的最大值不受影响,峰值所处的位置会发生变化,而周期摩擦热量的峰值位于轮齿的同一啮合相位角上,但数值会随着轮齿受到的压力的增大而增大。