余热回收喷淋塔喷淋优化研究

针对喷淋塔内烟气偏流影响烟气与下落液滴群热质交换的问题,构建并通过试验验证了喷淋塔内气液流动及余热回收理论模型,基于液滴自调整效应,运用CFD技术模拟研究4种喷淋层布置方式下余热回收喷淋塔的性能,获得了最佳喷淋方案及其喷淋参数。结果表明：与常规单层均匀喷淋方式相比,增设半层喷淋能够有效提升塔内烟气流动均匀性,塔内烟气均匀度由1降至0.3左右,喷淋塔全热交换效率最多可提升20%;半层喷淋最佳布置位置在烟气入口中心线上3 m处;综合考虑余热回收效果和运行成本,最佳喷淋液滴直径为0.6～0.8 mm,最佳水气比为5 kg/kg。构建的喷淋塔内烟气余热回收模型与提出的喷淋优化方法可为其特性分析、工艺优化、参数设计及运行提供理论指导。     

新式波形板除雾器气液分离性能评价和流场分析

为了评价实际应用中广泛使用的新式波形板气液分离性能,试验研究了在液滴粒径分布范围为10~200μm的情况下,气速和加液浓度对波形板分离效率和压降的影响,并采用计算流体力学方法对波形板内部流场进行了数值模拟分析。结果表明,与旧式波形板相比,新式波形板具有效率高、压降增长率低、临界气速大以及对小液滴分离效果好等优势;通过波形板的液滴浓度增大,波形板分离效率升高,新式波形板在液滴浓度低时性能较佳;袋式排液结构比钩式排液结构所带来的压降更小,并且能够减小二次夹带的影响;新式波形板更适用于实际应用的复杂工况。     

低压亚超混合层燃油雾化特性数值研究

对内嵌火箭发动机低压条件下的亚超剪切混合层中的燃油雾化特性进行研究,分析总结了环境压力、气液比、韦伯数对燃油雾化性能的影响。研究过程中采用ANSYS软件,使用了可有效捕捉漩涡的RNG k-ε模型并加入了TAB二次破碎模型,在0.01 MPa～0.1 MPa中改变环境压力,并通过改变燃油入口速度改变韦伯数和气液比。研究结果表明,随着环境压力降低,索泰尔平均直径增加,颗粒直径下降速度在接近常压时逐渐放缓,雾化性能下降;随着气液比的增加,索泰尔平均直径减小,颗粒分布更为均匀,提升了雾化性能;提高韦伯数使得气动力增加,索泰尔平均直径几乎呈线性趋势降低,提升了雾化性能。对数值模拟的数据进行分析,在低压条件下得到了索泰尔平均直径的经验计算模型。     

吸入室直径对液气射流泵流场特性影响的数值模拟

为了全面分析液气射流泵内部结构对液气射流泵吸气性能的影响,以提高液气射流泵整体吸气性能。利用Fluent软件对不同吸入室直径下液气射流泵内部流场进行了三维数值模拟,获得了液气射流泵内部压力场和速度场分布以及轴心静压曲线,并拟合出压力比、流量比、效率与不同吸入室直径的关系曲线。对比分析表明,吸入室直径的大小会对液气射流泵内部压力、速度及吸气效率产生很大影响。射流泵其他结构一定时,吸入室直径大小存在最优值或者最优范围,使得液气射流泵的吸气性能最佳。     

喷雾闪蒸过程的数学模型建立

在扩散控制蒸发模型的基础上,运用质量守恒、能量守恒和传热传质等基本定律,建立了喷雾闪蒸的数学模型,使用MATLAB/Simulink进行求解,经计算得出闪蒸过程中液滴温度、直径、质量、蒸发速率和蒸发率的变化规律,使用控制变量法,研究了液滴初始温度、闪蒸环境压力、液滴直径对液滴的温度、直径、质量、蒸发速率和蒸发率随着时间的影响,得出了相应的结论。     

气流式喷雾干燥过程的数值模拟

应用气液两相流理论和计算流体力学方法,结合气流式喷雾干燥的特点,建立了喷雾干燥塔内气液两相湍流流动的CFD模型.采用CFD软件对气流式喷雾干燥过程进行了非稳态数值模拟,对比分析了颗粒液滴喷射前后干燥塔内的温度场和含湿量等参数分布及变化情况,研究了颗粒在塔内的运动轨迹及直径分布.     

高气液比工况的管柱式气液分离器分离性能研究

为了提高分离器结构紧凑性与分离稳定性,采用管柱式气液分离器进行高气液比工况下的气液分离操作。基于CFD数值模拟方法,运用雷诺应力模型对管柱式气液分离器内部流场进行模拟,运用离散相模型对液滴进行追踪,得到分离器内部的流场分布情况以及不同结构参数对分离器分离效率的影响。对具体工况下的管柱式气液分离器结构进行优化设计,为管柱式气液分离器在高气液比工况下的设计与应用提供参考。     

带气环旋喷射流流场特征及喷嘴结构正交优化研究

为提高二/三重管法旋喷射流切割土体效率,采用Mixture多相流模型和RNG κ-ε湍流模型,开展了淹没环境下带气环旋喷射流流动模拟研究,获得了射流速度、气液两相体积分布、靶体作用压力等流场特征,并基于L₁₆(4⁵)正交试验设计及误差分析方法,获得了旋喷射流喷嘴关键结构参数对射流速度及其作用靶体压力的影响敏感程度与影响规律。结果表明：带气环旋喷射流能量衰减慢且集中在轴心区域,射流等速核心段长,冲击破坏土体性能好;喷嘴结构参数对射流冲击性能的影响敏感次序为：射流喷嘴出口直径>收敛角>气体喷嘴直径>气液喷嘴间距>射流喷嘴长径比;射流轴心速度及其作用靶体压力随出口直径和气体喷嘴直径的增大呈先快速增加后缓慢增加趋势,随收敛角、长径比、气液喷嘴间距的增大呈先增加后降低趋势。基于此,考虑旋喷射流设备性能,给出了最优结构参数为：射流喷嘴出口直径2.0 mm,收敛角12°或18°,长径比1,气体喷嘴直径0.9 mm,气液喷嘴间距5 mm。     

微引射式防冰腔结构参数对换热性能的影响

采用数值模拟的方法研究了航空发动机微引射式防冰腔结构参数对防冰热效率和发动机蒙皮温度分布的影响.通过改变射流孔直径、射流孔孔距、混合腔长径比和波纹板通道出口高度,建立了不同的微引射式防冰腔模型.在进口热气流量一致的情况下,对不同防冰腔模型进行了数值计算.结果表明:减小射流孔直径和波纹板通道出口截面高度能提高防冰热效率和...     

一种新型离心式气液分离器分离性能的数值模拟与试验研究

为了研究该分离器的分离性能,通过搭建气液两级分离实验台架进行实验测量,同时应用计算流体力学(CFD)方法对分离器内的气液两相流动进行数值模拟.重点研究了流量、气液比、介质粘度、密度、气泡直径及转鼓转速等六个变量对离心式气液分离器分离效率的影响.通过比较数值计算与实验测定结果,验证了数值模拟方法的可行性.分析结果表明,预测的分离效率变化趋势与实测结果在总体上是一致的, CFD可作为离心式气液分离器设计的有效工具.     

Heat transfer of a spray droplet in a PWR pressurizer

Heat transfer rates to spray droplets under conditions corresponding to those of spray transients in a pressurizer of pressurized water reactor (PWR) have been predicted by a simple droplet model with internal thermal resistance and partial internal mixing. In those processes, the temperature distributions in the droplet have been obtained using the integral method, and the physical properties of the saturated steam-hydrogen gas mixture surrounding the droplets are estimated applying the concept of compressibility factor and using appropriate correlations. Results have been provided for the temporal variations of total heat flux with its convection and condensation heat transfer components, dimensionless droplet bulk temperature and droplet flight distance. The effects of ambient pressure, initial droplet size, concentration of hydrogen gas in the mixture, initial injection velocity, and spray angle on the heat transfer of spray droplets have been discussed.     

用于压缩空气储能的微米级水雾冷却等温压缩实验研究

压缩空气储能(CAES)是一种大规模储能技术,可以用于调节城市电力供需,缓解用电高峰电力短缺,减少电网容量建设。目前,储能技术逐渐开始应用于城市,当电价下降时,采用电池储存电力,价格上升时,释放电力,利用峰谷电价差实现盈利。与电池相比,CAES容量大(100 MWh,电池小于10 MWh)、环保(无重金属污染),使用寿命长。但由于储能效率过低,通过电价差盈利空间小,投资回收期长是限制其商业应用的重要因素之一。目前,多数压缩空气储能系统都基于绝热压缩,大约有一半的电力被转化成了热量并耗散。由于压缩时空气的温度上升,导致压缩功增加,并转化得到更多的热。许多研究聚焦在增强压缩空气的散热来达到等温压缩。本研究提出将微米级(10~100 μm)水雾喷入压缩空气与之混合,吸收压缩热,降低压缩空气温度,以实现等温。通过实验对压缩空气压力,体积和温度的变化特性进行了分析。对于总体积为0.94 L的压缩腔,当压缩比为2时,水雾冷却后,压缩功从177.9 J/循环(绝热)下降到121.2 J/循环,且效率达到88.7%(绝热61.6%)。     

铜翅片管热水器的特性研究

以铜翅片管换热器为研究对象,通过合理的简化模型,以相邻2片换热片(取半片)及其之间的烟气通道作为计算区域,利用流体力学软件CFX对烟气通道的流动状况和换热情况进行了数值模拟。研究了管径、翅片厚度和翅片间距对排烟温度的影响,结果表明随着管径和翅片间距的增大排烟温度升高,随着翅片厚度增大排烟温度降低,排烟温度的升高或降低将影响排烟损失的大小,从而影响热效率。该数值模拟结果对改进翅片结构以提高热效率有一定指导意义。     

An investigation of descaling spray on microstructural evolution in hot rolling

High pressure water spray is used to remove oxide scales in hot rolling of steel plate. This would reduce the temperature temporarily on the workpiece surface. To investigate the effect of temperature variation due to the descaling spray on the microstructural evolution, a thermal-mechanical coupled FE model has been established. The heat loss due to the spray is experimentally measured and modelled using the established FE model. The heat transfer coefficient is determined using an inverse engineering method. A set of unified viscoplastic constitutive equations is implemented into the commercial FE solver MARC through the user-defined subroutine CRPLAW. The effect of descaling water spray on the surface temperature variation is numerically studied. Furthermore, the effect of surface temperature variation on the evolution of dislocation density, recrystallisation and grain growth is investigated for various hot rolling conditions.     

An investigation on effect of geometrical parameters on spray cone angle and droplet size distribution of a two-fluid atomizer

A visual study is conducted to determine the effect of geometrical parameters of a two-fluid atomizer on its spray cone angle. The liquid (water) jets exit from six peripheral inclined orifices and are introduced to a high speed gas (air) stream in the gravitational direction. Using a high speed imaging system, the spray cone angle has been determined in constant operational conditions, i.e., Reynolds and Weber numbers for different nozzle geometries. Also, the droplet sizes (Sauter mean diameter) and their distributions have been determined using Malvern Master Sizer x. The investigated geometrical parameters are the liquid jet diameter, liquid port angle and the length of the gas-liquid mixing chamber. The results show that among these parameters, the liquid jet diameter has a significant effect on spray cone angle. In addition, an empirical correlation has been obtained to predict the spray cone angle of the present two-fluid atomizer in terms of nozzle geometries.     

优能120纳米冷却液对油-电混动车运行热效率的影响

采用台架试验方法评估了在改变发动机进口温度、功率及转速条件下,优能120纳米冷却液对油电混动车运行热效率的影响。结果表明:温度由90℃切换至95℃时,发动机的出口温度为108℃,比参比防冻液要高9.29℃,此时平均油耗下降11.85%,最大油耗下降18.1%,发电效率提高0.52%,并且入口温度提高后其增加的油耗量仅占防冻液的20%。热机效率的提高是纳米冷却液提升了气缸工作温度,高沸点与高换热率降低了流体由于汽化产生气阻与热损失,及"发动机高温燃烧→水箱快速散热→发动机高温燃烧"周期性循环热平衡运行机制三者共同作用的结果。试验出现过热停机现象是由于发动机进口温度被恒定至设定值,故流经水箱的纳米流体的快速降温作用无法体现所致。     

一种新型热管间接蒸发冷却器的分析

简述了热管技术发展情况及技术特点，介绍了热管在空调热回收、房间空调器、供暖系统中的应用。提出了一种新型热管间接蒸发冷却器，即在热管冷凝段包覆吸水材料，并设置喷淋装置，由此提高了蒸发速度及换热效率，加大了对新风侧的干冷却效果。分析了这一装置的结构形式及其工作原理，并与其它换热器进行了对比，指出了这种新型热管间接蒸发冷却器的优势。     

基于ANSYS的高压机械密封温度场理论研究

根据热平衡方程推导出高压机械密封中的温升计算公式,并建立了机械密封件温度场的有限元模型,利用ANSYS分析软件求解密封环内部各节点的温度。根据温度场分布图,对影响密封环热影响的主要因素进行了讨论。结果表明:密封端面温度最高且靠近内径方向,应通过改善散热和加强冷却防止因摩擦热使正常压力下的液膜流体达到沸点并汽化;密封介质压力、密封端面的平均直径和转速的增加都会使摩擦热增加,从而使密封端面温度升高;不同密封介质的摩擦因数和传热系数会造成不同的温升;导热率越高扩散热量也就越多,选择导热率高的密封材料能有效地降低密封环温度。     

Application of dfb diode laser sensor to reacting flow (II) —liquid-gas 2-phase reacting flow—

Diode laser sensor is conducted to measure the gas temperature in the liquid-gas 2-phase counter flow flame. C₁₀H₂₂ and city gas were used as liquid fuel and gas fuel, respectively. Two vibrational overtones of H₂O were selected and measurements were carried out in the spray flame region stabilized the above gaseous premixed flame. The path-averaged temperature measurement using diode laser absorption method succeeded in the liquid fuel combustion environment regardless of droplets of wide range diameter. The path-averaged temperature measured in the post flame of liquid-gas 2-phase counter flow flame showed qualitative reliable results. The successful demonstration of time series temperature measurement in the liquid-gas 2-phase counter flow flame gave us motivation of trying to establish the effective control system in practical combustion system. These results demonstrated the ability of real-time feedback from combustor inside using the non-intrusive measurement as well as the possibility of application to practical combustion system. Failure case due to influence of spray flame was also discussed.     

Cooling of a heated surface with an impinging water spray

Several important parameters, such as liquid mass flux, droplet size distribution, droplet velocity, and heating target conditions (roughness and surface temperature) are involved in the industrial spray cooling heat transfer process. In this study, we investigated the effect of liquid mass flux, heating target roughness, and the droplet size on the droplet wall direct contact heat transfer in spray cooling phenomena. Three different conditions of surface roughness were investigated. The measurement of test surface temperature was performed using a non-intrusive method, i. e., using an infrared thermometer. The droplet size distribution of water spray was measured with Malvern 2600. The results indicated that the most influential parameters were the liquid mass flux and the surface roughness. The droplet size and the velocity played a less important role in the direct contact heat transfer because the interactions between droplets were very strong in a dense spray. The smooth surface showed the highest heat transfer among the surfaces tested. At high air pressure ([7] kPa), however, the degree of roughness did not affect much the heat transfer rate.