烧嘴流速对辊道窑烧成带内温度分布影响的数值研究

建立了辊道窑烧成带的三维物理模型,借助计算流体力学(CFD)软件FLUENT6.0模拟烧成带的工况,研究烧嘴流速对烧成带内温度分布的影响,为辊道窑的运行提供了有益的参考,也为烧嘴研制的基础性工作提供理论支持。     

低温明火炉内钢板加热温度的均匀性实验研究

为研究低温回火热处理炉加热的温度均匀性,搭建低温明火炉实验平台,在实验炉内采用高速烧嘴脉冲燃烧加热,获得了实测的炉膛温度分布和炉内钢板表面温度,试验结果表明在合理布置炉内烧嘴和合理的供热方式条件下,不采用循环风机也可满足炉内钢板加热温度均匀性要求。     

干式地板辐射供暖系统实验研究

以干式地板辐射供暖系统为研究对象,通过实验研究的方法,测量系统从开启到关闭后5h的室内温度、地板表面温度、围护结构表面温度等参数,分析系统热工特性和热舒适性。研究结果表明:系统稳定运行时,室内空气温度在水平和竖直方向分布均匀,热稳定性好,辐射换热量占总换热量的60%,运行3h可满足热舒适性要求;同时,也存在相对于湿式地板供暖,系统蓄热性较差、地板表面温度分布均匀性略差问题。     

燃气轮机SCR脱硝喷枪投运方式试验研究

SCR反应过程中,管道内的流场和物质浓度对反应过程有重要影响,文中采用模型试验台实验研究了实际运行中三种负荷喷枪投运的影响,结果表明三种负荷选择不同的喷枪组合均能保证流场均匀性和物质分布均匀性,能够很好地满足实际要求。     

600MW汽轮机排汽通道加装导流装置的数值研究

针对某600 MW汽轮机排汽通道出口流场不均匀所造成的排汽压力偏高、经济性降低的问题,对配备双背压凝汽器的汽轮机排汽通道进行三维数值模拟,分析造成排汽通道出口流场分布不均匀的原因,并给出了一种能够极大改善排汽通道出口流场均匀性的导流装置布置方案.结果表明:汽轮机排汽缸的结构、小汽轮机排汽和低压加热器的存在导致排汽通道出口流场分布极其不均匀;在排汽通道内加装合理的导流装置后,出口流场均匀性得到改善,排汽通道的工作性能得到提高,排汽通道总压损失系数仅增大0.5%~2.5%,而静压恢复系数增大6.4%~8.8%,均匀性系数增大10.4%~13.4%.     

烧结-热等静压炉结构优化与仿真

通过对烧结-热等静压炉石墨发热体的优化设计,改善石墨筒内温度场的均匀性,以解决实际生产中存在的石墨筒内温度分布不均匀、底部空间和靠近两个炉门侧空间温度偏低的问题,并对石墨发热体改进前后石墨筒内温度场分布情况进行了数值仿真。结果显示,改进后石墨筒内及整炉烧结制品表面温度场均匀性得到明显的改善,减少了由于炉门处未布置发热体所带来的影响。     

化学气相沉积石英玻璃工艺数值模拟

为提高某型号立式化学气相沉积炉生产大尺寸高纯度石英玻璃过程中石英玻璃沉积体表面的温度分布均匀性,从而提高其光学性能,对立式沉积炉内石英玻璃的生产过程中温度场和速度场的分布情况进行了数值模拟。通过调整燃烧器的结构,对沉积炉原有模型进行了进一步的改进优化。结果表明改进了的燃烧器型式可以有效地消除偏峰现象,提高表面温度分布的均匀性。     

导流板对霍戈文矩形燃烧器流场均匀性影响的试验和模拟研究

流场均匀性对于提高热风炉风温具有重要意义。针对双导流板结构的热风炉矩形燃烧器,采用试验和数值模拟的方法对其流场均匀性进行了研究,考察了导流板间隙对燃烧器出口流速均匀性的影响。试验和模拟结果都表明随着间隙的增大,空气流速分布的均匀性越来越好;出口截面上靠近左右两侧壁面处的流速相对中间区域较大;出口速度呈波浪状分布。模拟结果表明间隙为180 mm时,均匀性指数为0.975,出口流速均匀性最好。模拟与试验结果的相对误差最大为1.3%吻合度高。     

导流装置对汽轮机排汽通道流动特性的影响

摘要：采用RNG 模型对某600MW机组低压排汽通道内气动特性进行了三维数值研究,研究了排汽通道内流场分布并提出三种不同的导流方案对排汽通道内的流场进行优化改造。研究结果表明：排汽缸上部通道中气流呈漩涡流动,通道内排汽压力损失增加;在喉部出口截面每1/4区域内都有一个漩涡,相邻的两个漩涡之间流场分布不同;加装导流装置能够有效破坏流场中的漩涡结构,改善通道内的流场分布;在机组变负荷运行时,不同的优化方案同样适用;低负荷运行时,三种不同方案压力损失数值变化不大,方案三中喉部加装四块导流板时喉部出口流场均匀性最好。     

锅炉冷风道的流场仿真及道体结构优化研究

由于锅炉冷风道的道体结构设计不当,造成高能湍流脉动气体在风道内流速分布不均,产生大范围回流的漩涡扰动,导致道体振动。通过流场仿真研究,提出在风道内布置"井"字隔板装置,通过仿真研究,加装"井"字隔板后的风道内气体流速分布均匀程度得到较大改善,认为该方案如在实际工程中实施,可以较好地改善风道内气流分布均匀性和消除道体振动的问题。     

板坯加热炉内常规燃烧与富氧燃烧数值计算对比分析

以某公司热轧厂板坯加热炉为研究对象,建立该加热炉内流动、传热、燃烧和板坯运动吸热过程的三维物理数学模型,运用CFD仿真技术对其进行详细的数值计算,重点对比分析了常规燃烧和富氧燃烧特性,得到了各自的炉内速度场和温度场分布规律、板坯的升温曲线以及板坯温度分布均匀性,计算结果与“黑匣子”实验测量数据吻合良好.总结出的富氧燃烧...     

板坯加热炉内加热特性的数值分析

以某公司热轧厂常规与双蓄热烧嘴组合供热的板坯加热炉为研究对象,建立该加热炉炉内流动、传热、燃烧和板坯运动吸热过程的三维物理数学模型,运用CFD仿真技术对其进行详细的数值计算,得到炉内稳态的速度场和温度场分布规律、板坯的升温曲线以及板坯温度分布均匀性,计算结果与"黑匣子"实验测量数据吻合良好。本文给出的板坯加热特性计算方法为研究加热炉新工艺、优化板坯加热温度制度提供了科学依据。     

中厚板无氧化低温辊底式热处理炉的脉冲控制策略

针对国内某钢铁企业新建中厚板无氧化辊底式热处理炉工程,对辐射管加热系统在低温下的脉冲控制策略进行组合、优化,使无氧化热处理炉在低温下获得了很好的温度均匀性,扩大了该热处理炉产品种类范围,取得很好的效果.     

Numerical analysis of rapid solidification in a single roller process

The rapid solidification in a single roller process has been used to make amorphous ribbons. Because this process occurs rapidly, it is difficult to obtain useful experimental data. Therefore, a numerical analysis has been performed on the rapid solidification in a single roller cooling process. The VOF (volume of fluid) method was adopted as the numerical method used to simulate transient two-dimensional thermal and fluid flow with a liquid-solid phase change and free surfaces. We simulated the behavior of an aluminum alloy. The geometry of the amorphous ribbon, flow and temperature fields, temperature history of alloy particle whose initial location is at the center of the nozzle, and the cooling rate were obtained using as parameters the roll velocity, the nozzle slot breadth, and the gap between nozzle and roller. © 1999 Scripta Technica, Heat Trans Asian Res, 28(1): 34–49, 1999     

Feasibility evaluation of gas-assisted heating for mold surface temperature control during injection molding process

Dynamic mold surface temperature control has the advantage of improving molded part qualities without significant increases in cycle time. In this study, a gas-assisted heating system combined with water cooling and different mold designs to achieve dynamic mold surface temperature control was established. The feasibility of using gas-assisted heating for mold surface temperature control during the injection molding process was then evaluated from experimental results. The effect of mold design as well as heating conditions including hot gas temperature, gas flow capacity, and heating time on the heating efficiency and the distribution uniformity of mold surface temperature were also studied. Results showed that as hot gas temperature and gas flow capacity increased, as well as increasing heating times from 2 s to 4 s, mold surface temperature increased significantly. Fan shaped gas channel design exhibits better mold surface temperature distribution uniformity than tube shaped gas channel design. During gas-assisted heating/cooling, it takes 2 s to increase mold surface temperature from 60 °C to 120 °C and 34 s for mold surface to return to 60 °C. In addition, under specified heating conditions and using the best composite mold designs, the heating rate can reach up to 30 °C/s, a rate well-suited to industrial applications.     

Control of temperature uniformity during the manufacture of stable thin-film photovoltaic devices

The production of stable thin-film photovoltaic cells requires tight control of temperature uniformity within the glass substrates during the vacuum deposition process. Though traditional approaches such as radiation shielding and channeling more power to outer lamps result in substantial improvements in temperature uniformity they fail in meeting the stringent requirement of less than 1 °C variation across the substrate required to guarantee the long-term stability of the devices. The problem becomes especially acute while scaling up to larger commercially-viable panel sizes. To this end, a finite element thermal model of a commercial-scale deposition station has been developed and optimized with the target of achieving the desired temperature uniformity of 1 °C. The effects of improvements such as radiation shielding, addition of radiation spreader, contouring of radiation spreader and optimizing power distribution among the radiation lamps have been studied. A new lamp configuration has been proposed for attaining the desired uniformity levels.     

大型柴油机滚轮内孔线型分析

大型柴油机滚轮内表面磨损,外表面拉毛,极大影响柴油机安全运行。现针对多次发生滚轮破坏事故的柴油机,利用ANSYS有限元软件对滚轮不同的内孔线型进行应力、变形以及接触应力等分析,得出使用内凸形滚轮优于直线型和内凹型的结论,并在工程应用中验证了其有效性。     

Rules‐of‐thumb of implementing short electric band heaters (length to diameter ratio <1.5) for external heating of pipe flows

Short electric band heaters (L/D_i<1.5) are constructed for the ease of implementation in small scale heating applications. They are usually mounted side‐by‐side in series along the external wall of a pipe for heating the fluid within the pipe. There are no rules‐of‐thumb available about designing such a system to achieve good uniformity of the temperature profile at the pipe inner surface beforehand. Non‐uniformity can cause preferential fouling at hotter spots. This study focuses on the axial uniformity of heating along a pipe inside which the heated fluid if flowing. The situation has been simplified a great deal in mathematical terms from the corresponding conventional conjugate problem considered previously due to the small temperature rise in the fluid flow through one section of the pipe which is heated by one band heater. Similarity parameter sets have been deduced and verified by numerical simulations. The worst scenario of non‐uniformity for such short band heaters, that is when L/D_i=1.5, is presented in this paper. This may be used for designing a system to minimize the non‐uniformity in terms of choosing the right pipe material, percentage of heater wire coverage in the band heater, etc. Copyright © 2002 John Wiley & Sons, Ltd.     

NACT滚筒冷渣机工业性能研究

报道第一台NACT(新型灰渣冷却技术)滚筒冷渣机的工业试验结果。工业测试显示,锅炉满负荷运行时NACT滚筒冷渣机的表观传热系数大于95 W/(m~2·K),几乎是现有滚筒冷渣机产品传热系数的2倍。该装置采用扬料板组织灰渣运动,设置迎合抛洒灰渣的对流受热面,将主导热阻由灰渣接触热阻转变为灰渣对流冲刷热阻,大幅度提高了总传热系数。工业测试结果显示:滚筒转速对NACT滚筒冷渣机性能影响巨大。随着滚筒转速提高,灰渣处理量直线升高,但不同转速下的排渣温度升高速率不同;滚筒转速增加,表观传热系数升高,有利于传热过程。增加滚筒对流传热份额,延长灰渣在滚筒内停留时间,是滚筒设计的关键。     

Key parameters and optimal design of a single-layered induction coil for external rapid mold surface heating

Setting high mold temperatures for injection-molding plastics facilitates favorable flow conditions for filling cavities with melted materials and provides an esthetically pleasing surface as well as a high replication rate of high-quality products; however, the cooling times are typically prolonged. Electromagnetic induction heating incorporating surface heating instead of conventional volume heating for mold-heating processes is advantageous because it provides a rapid heating time and a reduced cooling time, is environmentally friendly, and saves energy; therefore, it has been adopted in various variotherm injection-molding systems. Although previous studies have discussed how induction heating is influenced by major factors, such as the number of coil turns, working frequency, and heating distance, few studies have investigated other crucial factors, such as the thickness of the heated target and the position of the induction coil. In this study, the effects of the thickness of a heated target, pitch of coil turns, heating distance, position of the induction coil, working frequency, and waiting time on the heating rate and temperature uniformity of induction heating on a mold surface by using a single-layered coil were analyzed. In addition, the Taguchi method and principal component analysis were applied to determine the optimal combination of control factors for achieving a high heating rate and low temperature deviation. Both simulation and experimental results indicated that the thickness of a heated target plays a crucial role in affecting the heating rate; specifically, a thicker workpiece slows the heating process and generates rapid heat dissipation after induction heating. Moreover, the position of the induction coil exerts the most notable effect on heating uniformity.