共查询到20条相似文献,搜索用时 78 毫秒
1.
为准确预估二次再热汽轮机转子在启动、停机过程中的热应力,推导了轴对称结构热固双向耦合计算模型。采用热固单、双向耦合模型和有限元法,计算了二次再热超超临界660 MW汽轮机超高压转子在冷态启动过程中的瞬态温度场和热应力场,对启动曲线进行了优化。研究表明,在冷态启动时双向耦合模型最大热应力值比单向模型计算值小4%,热冲击越大,两者计算值相差也越大,热固双向耦合模型比单向模型计算精度高,但计算时间长。采用优化后的启动曲线,转子最大热应力比原最大值降低了27%,实际机组运行也表明采用优化启动曲线,机组运转良好。 相似文献
2.
3.
采用有限元法建立了基于某电厂汽轮机转子温度场和热应力场的数学模型。在对汽轮机的冷态启动、温态启动、热态启动以及滑参数停机4个工况下的瞬态温度场以及热应力场进行模拟分析基础上,确定转子最大热应力点作为监测点,对监测部位的温度与热应力进行了疲劳损耗仿真计算。根据最小二乘法获得转子钢材料的疲劳特性曲线,利用MATLAB进行多项式拟合,获得转子应变与疲劳寿命损耗的函数关系式,求得汽轮机转子启停下的低周疲劳寿命。研究结果表明:该机组累积十年运行条件下形成的疲劳损耗为2. 506%。机组冷态启动过程中,转子承受最大温差与热应力,最大热应力值445 MPa;当温升率由3℃/min提高到4℃/min时,转子的低周疲劳寿命损耗由0. 040%上升到0. 103%,寿命损耗明显增大。 相似文献
4.
5.
6.
7.
在燃气-蒸汽联合循环机组中,燃气轮机在不同工况下的排烟温度不同,使得整个燃气轮机联合循环 机组启动过程主蒸汽温度波动频繁,从而引起汽轮机启动过程中各金属部件温差增大,热应力和热变形也随 着增加。GE公司的6503燃气轮机的温度匹配功能和汽轮机热应力计算监控模块相结合,可以通过实时控 制主蒸汽温度实现对汽轮机转子热应力的有效监视和控制,减少设备损坏。 相似文献
8.
介绍了基于一阶惯性环节的高压转子温度场的计算原理和方法,推导了在控制系统中使用的简化迭代计算公式.针对1 000 MW超超临界汽轮机,利用有限元法对其温度场进行了计算,验证了在热应力监控中使用高压内缸内壁温度等效代替高压转子外表面温度的合理性.采用一阶惯性环节法、差分法和有限元法等3种方法,对汽轮机高压转子冷态启动、温态启动、热态启动、极热态启动和滑参数停机过程的体积平均温度和转子中心温度进行了计算,并对比分析了3种方法的转子表面温差和转子中心温差的计算精度.结果表明:一阶惯性环节法的计算精度高且方便易用,可作为一种监控汽轮机转子温度场的有效方法. 相似文献
9.
10.
11.
Sverine Gomes Nathalie Trannoy Philippe Grossel Franoise Depasse Claudine Bainier Daniel Charraut 《International Journal of Thermal Sciences》2001,40(11):1794
The used Scanning Thermal Microscopy (SThM) probe is a thin Pt resistance wire acting as a heat source and as a detector simultaneously. Its energetic balance is investigated by the study of the temperature profile along the probe. A theoretical approach of the measurement, based on this investigation, is then proposed. Simulations with this modelling are shown to predict how the heat, electrically produced in the probe, is dissipated in the probe-sample system. In particular, it is shown that the steady-state of conduction losses to the thermal element support varies versus the thermal conductivity of the sample and can lead to bad interpretations of the measurement. 相似文献
12.
For optimum design of borehole thermal energy storage (BTES) and ground sources heat pump (GSHP) applications, determination of underground thermal properties is required. The design and economic feasibility (number and depth of boreholes) of these systems need thermal conductivity of geological structure, λ (W m?1 K?1), and thermal resistance of ground heat exchanger, R (K W?1 m). Thermal properties measured in laboratory experiments do not coincide with data of in situ conditions. Therefore, in situ thermal response test equipment has been developed and used in Canada, England, Germany, Norway, U.K., U.S.A. and Sweden to ensure precise designing of BTES systems. This paper describes the results and evaluations of the Adana continual thermal response test measurements. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
13.
14.
15.
After turning on a room heating system (e.g. central heating) a thermal transient phenomenon takes place on the wall–room system, until it reaches a final thermal equilibrium state. The temperature profiles on the wall cross‐section, starting from an initial profile, corresponding to the initial thermal equilibrium state, come gradually through successive intermediate temperature profiles, to a final temperature profile corresponding to the final thermal equilibrium state. These intermediate, nonlinear and time‐dependent temperature profiles characterize the wall thermal transient state and describe the dynamic thermal behaviour of the wall–room system. The mass of the air in the room is negligible, compared to the mass of the surrounding walls, so the dynamic behaviour of the room–wall system is imposed by the corresponding thermal dynamic behaviour of the walls. The influence of this thermal transient state is important for the room heating behaviour because it acts as a thermal flywheel attenuating and smoothing the room temperature variations. In the present work, using the integral method, analytical expressions yielding the temperature profiles, and the duration of the transient state as a function of thermal and structural characteristics have been developed. Conclusions were drawn on the dynamic thermal behaviour of the room–wall system. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
16.
随着新能源汽车的广泛使用,动力锂离子电池的热安全性问题日益突出。本文以Bernardi生热机理为基础,耦合不同物理量,分别从电化学-热耦合模型、电-热耦合模型和热滥用模型来介绍单体电池的热特性。由于电池能量密度的增加与行驶工况复杂程度的提高,动力锂离子电池容易发生热量堆积,甚至造成热失控,对此,文中梳理了商用动力电池包的常用冷却方式。最后,根据对影响电池模组安全性的热失控蔓延机理及实测结果,介绍了阻断单体及基本模块热失控传播的有效方法。 相似文献
17.
A mobile thermal battery resembling a solar receiver: Innovative design and performance assessment 下载免费PDF全文
An innovative design of a mobile thermal battery resembling the solar receiver is presented. A ternary salt mixture consisting of 52% KNO3, 18% NaNO3, and 30% LiNO3 by wt% is used as the thermal energy storing medium inside the thermal battery. Since the thermal conductivity of the ternary salt mixture is low, aluminum meshes are introduced to create a thermal conduction tree inside the thermal energy storing medium. The actual field data are used in the simulations to resemble the solar irradiation emanating from the parabolic trough and focusing onto the thermal battery outer surface. To improve the uniform heating at the outer surface, the thermal battery rotation along the centerline of the trough is considered. The temperature parameter is introduced to assess the uniform‐like temperature distribution inside the ternary salt mixture. It is found that the use of aluminum meshes improves the heat diffusion in the phase change material of the ternary salt mixture; in which case, it acts like a thermal conduction tree inside the thermal battery. The rotation of the thermal battery results in uniform‐like temperature distribution across the thermal battery cross section and suppresses the excessive temperature rise because of the local heating in the close region of the thermal battery outer surface. 相似文献
18.
A model study for cyclic thermal loading and thermal performance of a thermoelectric generator 下载免费PDF全文
Thermal cyclic loading influences the life cycle of the thermoelectric device pins because of the thermal stress developed in the pins. Although thermal efficiency improves for different geometric configurations of the device pins, development of thermal stresses limit the selection of pin geometry in practical applications, particularly under cyclic thermal loading. Consequently, in the present study, thermal stress analysis of thermoelectric pins under cyclic thermal loading is carried out. The influence of thermoelectric pin geometry on the stress levels is examined when the device is subjected to the thermal cyclic loading. The predictions of thermal stress distribution are validated with the data presented in the open literature. It is found that pin geometric configuration has a significant effect on the stress levels developed in the pin when subjected to cyclic thermal loading. The pin configuration RA = 1 (parallel pins) results in the minimum value of the maximum von Mises stress in the pins as compared to that corresponding to other configurations. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
19.
Rayleigh waves in a half-space exhibiting generalized thermoelastic properties based on Green-Lindsay (G-L), Lord-Shulman (L-S), and classical dynamical coupled (C-D) theories are discussed. The phase velocity of Rayleigh waves in the previous three different theories has been obtained. A comparison is carried out between the phase velocities of Rayleigh waves, displacements, stresses, and temperature as calculated from the different theories of generalized thermoelasticity. The C-D theory is recovered as a special case. It appears, in particular, that the results obtained from G-L theory tend to those of L-S theory as the values of the two relaxation times become closer to each other. The second relaxation time is well pronounced when it becomes larger than the first one. Furthermore, it is found that the thermal relaxation times decrease the speed of the elastic waves and modify the phase velocities of the Rayleigh waves. The results obtained and the conclusions drawn are discussed numerically and illustrated graphically. Relevant results of previous investigations are deduced as special cases. 相似文献