溶胶凝胶法制造NO2燃料微球的流体力学计算

利用伯努利方程建立了在外胶凝工艺中喷嘴射流速度与压力罐液面高度、喷嘴射流速度与液面压强的关系式,并使用该关系式进行计算,结果表明：管道中整个流动过程是层流;液面高度对射流速度的影响非常小;由液面高度所造成的UO2微球直径的最大偏差远小于微球的控制偏差。     

气动式脉冲液体射流泵性能实验研究

实验研究了喷嘴直径为5 mm,扩散管直径分别为5、7 mm,提升高度为6.7 m的气动式脉冲液体射流泵的性能。结果表明:料桶内的液面高度对气动式脉冲液体射流泵的效率、扬程、输送量影响甚微,而随着操作压力的增加,脉冲液体射流泵的效率、扬程、输送量也增大。证明了在本实验条件下,最佳喷嘴间距与喷嘴直径之比为0.8～2.0范围内,并讨论了不同喷嘴间距所对应的最低操作压力条件。     

稳定蒸汽浸没射流冷凝传热系数评价

为分析稳定蒸汽浸没射流的传热特性,对3类典型冷凝传热系数开展评价。结果表明:平均传热系数实验值精度主要受界面面积计算模型影响,由冷凝驱动势和蒸汽质量流速表征的传统半经验关系式在不同孔径下的预测偏差较大,新增排放孔径为独立拟合变量的纯经验关系式适用范围更广且误差在±30%以内;界面传热系数的预测精度主要受汽羽微观参数取值的影响;由压力振荡主频表征的无量纲传热系数在低池水过冷度下与实验值偏差较大,关系式中纳入汽羽贯穿长度后,预测趋势与实验值类似。      

数值模拟激光辅助凝聚抑制同位素分离中喷嘴构型对超声速射流的影响

激光辅助凝聚抑制同位素分离(CRISLA)方法需要激光选择性激发超声速射流中的同位素分子，装置内的流场会对分离效果产生影响。CRISLA中超声速射流主要受喷嘴构型的影响，本研究利用计算流体力学(CFD)方法研究喷嘴构型参数(喉部直径、扩张段长度、扩张角度)对CRISLA流动的影响。结果表明，喉部直径是影响射流低温区温度的主要因素，喷嘴扩张段长度对喉部直径3～5 mm喷嘴射流低温区温度影响不明显，而对喉部直径<3 mm的喷嘴射流低温区温度影响较大；喉部直径在3～5 mm时，扩张段长度及扩张角度对射流低温区位置影响小，低温区都位于喷嘴外，喉部直径<2 mm时，扩张段长度与扩张角度对射流低温区位置有显著影响，需要优化二者关系才能在喷嘴外获得较理想射流。在保障低温区位于喷嘴外的前提下，适当增大扩张段角度有利于射流径向扩散。研究的几种喷嘴构型能形成较理想射流，可为未来实验研究提供参考。     

胶凝法制造UO_2陶瓷微球时空气区长度的确定

胶凝法是制造高温气冷堆(HTR)燃料元件核芯UO_2陶瓷微球的主要方法。在制造过程中胶液首先从喷嘴喷出,分散成滴并经过一段空气区后液滴球形度达到一定要求,随即进入固化区进行固化成形。液滴从离开喷嘴到进入固化区落下的距离即为空气区长度。为了获得具有较高球形度的UO_2微球,本文建立了一个数学模型,通过理论计算得到了优化的空气区长度,并通过实验验证了计算结果。当球形度E=1.05时,空气区高度为0.22 m,与实际操作相吻合。     

溶胶-凝胶法制造UO2燃料微球振动频率选择

利用射流力学理论建立了最优振动频率关系式,并将它应用到了UO₂燃料微球工艺中,最优频率的计算值与实验值较符合。分析了空气密度、胶液粘度、胶液表面张力和胶液密度对最优振动频率的影响。结果表明,空气密度对频率影响很小,最优振动频率随胶液粘度的增大而减小,随胶液表面张力和胶液密度的增大而增大。     

气-液喷射器内两相流流型分析

对水平安装气-液喷射器内两相流流型进行了分析研究。根据圆管内气-液两相流流型转变的经验准则式,结合气-液喷射器性能方程,得出了气-液喷射器内环状流和雾状流的流型区间。以空气-水喷射器为例,给出了喷嘴出口当地最大马赫数与引射流体入口／出口压比的关系式,证明了当工作气体（空气）在喷嘴中作超临界膨胀时,喷射器内流型至少为环状流。     

陶瓷UO_2微球尺寸与球度的控制方法

陶瓷ＵＯ２微球尺寸与球度的控制问题，不仅是溶胶－凝胶工艺研究中的重要课题，也是高温气冷堆燃料元件生产中的重要课题。因此，近几年来通过批量试验对全胶凝工艺控制包覆芯核尺寸与球度的方法进行了研究，并取得了阶段性进展，为１０ＭＷ高温堆燃料芯核的生产奠定了基础。结果表明：ＵＯ２芯核尺寸与球度的控制主要是通过控制溶胶分散参数来实现的。对单一振动喷嘴而言，其分散参数应当同时满足均匀分散流量方程和振动频率方程的要求；另一方面为了控制芯核的球度，还必须对喷嘴的振动加速度、３区高度及气相氨的分布进行控制。     

喷洒器蒸汽浸没射流汽羽长度实验研究

以孔径分别为4、10、16 mm的侧开孔I型喷洒器为实验件,对质量流速为300~1100 kg·m?2·s?1的饱和蒸汽浸没在温度为35~65℃的过冷水中的直接接触式冷凝开展实验研究。结果表明:孔径不变时,汽羽贯穿长度基本随蒸汽质量流速和池水温度的升高而增大;大孔径喷洒器的汽羽长度与直管式喷嘴的汽羽长度接近,拟合值与实验值的偏差在±15%以内;小孔径喷洒器的汽羽长度明显低于直管式喷嘴,拟合值与实验值的偏差最高达80%;采用收缩喷管流量公式对蒸汽质量流速进行修正,拟合值与实验值的偏差在±20%以内,由实验值拟合的新关系式的预测误差在±10%以内。      

气泡破裂及其诱发射流液滴释放过程的实验研究

本文基于实验方法,通过高速摄像的方法捕捉不同直径下的气泡破裂过程及射流液滴的释放过程,获得了气泡破裂后气泡空腔的演变过程,捕捉了射流液滴的速度,探究了气泡直径和气泡表面寿命对射流液滴释放过程的影响规律。实验结果表明,气泡表面寿命对气泡破裂产生射流液滴的过程有着重要影响。随气泡表面寿命的增加,破裂气泡产生的射流液滴的速度也随之增加。当气泡直径较小时,气泡表面寿命呈现Rayleigh分布的特征,射流液滴的释放概率也较高。随气泡直径的增加,气泡表面寿命逐渐转变为指数衰减分布的特征,射流液滴的释放概率也随之下降。基于现有实验数据给出了一个精度更高的射流液滴速度与气泡直径关系式。     

Experimental study on a steam-driven turbulent jet in subcooled water

This study was designed to investigate the behaviour of a steam-driven turbulent jet in subcooled water. The total pressures along the axis of the jet were measured under various steam mass fluxes, water temperatures and nozzle sizes. The results indicated that the lifting-pressure coefficient decreased with inlet steam pressure and water temperature, and an optimal lifting-pressure coefficient could be obtained at pressure ratio 0.228. Then an empirical correlation based on the influencing factors was given to fit the position of the maximum pressure. Moreover, the velocity profiles in the turbulent jet region were obtained, and the results showed the self-similarity property of the velocity profiles. An empirical correlation was suggested to correlate the jet half width obtained from the velocity profiles.     

Experimental study on an impingement high-pressure steam jet

An experimental study on impingement high-pressure steam jet was performed as one of the efforts to establish evaluation methods for effects caused by a jet under the postulated pipe rupture accident in a nuclear power plant.An ejected steam jet from a nozzle into the atmosphere is impinged vertically on the flat plate. Nozzle reaction, jet impingement force and impingement pressure distribution were measured over a wide range of impingement distances. Employed nozzles are circles and ellipses. The steam is supplied under steady state and dry saturated, and the pressure is approximately 4.56 MPa.From the data of nozzle reaction and impingement force, these are mutually equal and are proportional to the stagnant pressure upstream of the nozzle; and from this data, the thrust coefficient for each nozzle was calculated. Based on the data of impingement pressure distribution, the jet is roughly divided into three regions on the axis according to the characteristics of distribution in both circular an elliptical nozzles. In addition, in the case of a circular nozzle, locations where the characteristics of distribution distinctly change depend on the location of Mach disk. In the case of an elliptical nozzle, expansion on the minor axis is remarkably higher than on the major axis, particularly near the nozzle exit.     

补水箱内的直接接触冷凝模型研究

补水箱是核反应堆安全系统中的重要设备。事故工况下补水箱内可发生剧烈的直接接触冷凝过程,导致补水箱内压力的迅速降低乃至振荡,影响补水箱的安全注入功能。为提高对补水箱安注行为预测的准确性,本文基于射流速度分布理论和假想管嘴分析方法,考虑液相的温度分层对传热温差的影响,结合补水箱内直接接触冷凝的一般过程,建立了针对性的冷凝传热计算方法。利用该模型对现有实验数据进行了预测,符合良好,初步验证了模型的有效性。相关研究有助于提高补水箱安注过程和相关事故安全分析的准确性。     

Experimental study on the direct contact condensation of steam jet in the passive safety injection tank

The direct contact condensation and subsequent thermal mixing by the injected steam jet onto a quiescent coolant inside a tank were examined experimentally to simulate the phenomena in passive safety injection systems. Specifically, the influence of the steam injection velocity was studied. Even though the total flow rate of injected steam was unchanged, the pressure inside the tank increased quickly at the larger nozzle diameter. Additionally, at a larger nozzle diameter, the thickness of the thermal mixing zone decreased because the amount of direct contact condensation decreased. For the in-depth study on the role of the nozzle size for the thermal mixing, the particle image velocimetry method was used to understand the flow field of water inside the tank. The visualization results demonstrated the formation of a flow field in the coolant due to the expansion and contraction of the steam–air mixture boundary. Furthermore, the thermal mixing zone was found to be closely related to the penetration depth. Finally, a variety of penetration models were examined and compared against the experimental observation. The correlations based on the steam condensation approach under-predicted the penetration depth, whereas the approach that considers the momentum of non-condensable gas gave the reasonable prediction capability.     

含不凝性气体蒸汽浸没射流冷凝压力振荡实验研究

实验研究了不凝性气体（空气）含量、水温和蒸汽质量流速对蒸汽浸没射流冷凝压力振荡特性的影响,实验工况横跨冷凝振荡（CO）区和稳定冷凝（SC）区。结果表明：对于纯蒸汽射流,压力振荡主频随水温的升高而降低,振荡强度随水温的升高而升高;在CO区,振荡主频和振荡强度均随蒸汽质量流速的升高而升高;在SC区,振荡主频随蒸汽质量流速的升高而降低,振荡强度基本上不随蒸汽质量流速的变化而发生改变;对于含空气射流,随空气质量分数的增加,振荡主频总体呈下降趋势,振荡强度先迅速下降后小幅上升,在空气质量分数为0.05～0.1区域内振荡主频和振荡强度均存在极小值。     

接管布置方式对UTSG倒流现象的影响分析

蒸汽发生器进出口腔室的流场结构对倒流现象有重要影响,而进出口接管布置方式能改变其腔室流场结构。本文建立了两种不同接管布置方式蒸汽发生器三维模型,采用CFD方法模拟了其在低流量条件下的流动换热和流场结构,分析了接管布置方式对倒流现象的影响。研究结果表明:接管布置方式对腔室流动速度场产生显著影响,进而影响到U型管进出口压降和流量分配。适当改变接管布置方式可使流量分配不均匀性降低、U型管进出口负压降升高,从而使蒸汽发生器倒流发生的临界流量和倒流总流量降低。     

Development of Transuranium Element Recovery from High-Level Radioactive Liquid Waste

In the present study, the jet breakup characteristics of molten material is experimentally investigated in nonboiling condition using Wood's metal to isolate the key features of jet breakup phenomenon from the conjugated nature of melt breakup and steam generation. The experimental apparatus consists mainly of melt generating furnace and melt crucible equipped with variable nozzle diameter, a rectangular water tank of 350×350×800mm equipped with temperature controlling heater and thermocouples. The jet diameters were 10 and 20 mm and the jet velocity was varied by pressurizing the melt container. Wood's metal of 70°C melting temperature was used. Visualization of jet breakup provided characteristics of jet breakup in water. The range of jet velocity was 2.2–5.5 m/s. The debris were collected and sieved and it was shown that the debris sizes of 1.0–2.8 mm had the largest mass fraction, up to 50%. In the present experimental conditions, the Kelvin-Helmholtz instability is considered the most probable cause of jet breakup.     

Flow structure of steam–water mixed spray

In this study, the flow structure of a steam–water mixed spray is studied both numerically and experimentally. The velocity and pressure profiles of single-phase flow are calculated using numerical methods. On the basis of the calculated flow fields, the droplet behavior is predicted by a one-way interaction model. This numerical analysis reveals that the droplets are accelerated even after they are sprayed from the nozzle. Experimentally, the mixed spray is observed using an ultra-high-speed video camera, and the velocity field is measured by using the oarticle image velocimetry (PIV) technique. Along with this PIV velocity field measurement, the velocities and diameters of droplets are measured by phase Doppler anemometry. Furthermore, the mixing process of steam and water and the atomization process of a liquid film are observed using a transparent nozzle. High-speed photography observations reveal that the flow inside the nozzle is annular flow and that most of the liquid film is atomized at the nozzle throat and nozzle outlet. Finally, the optimum mixing method for steam and water is determined.     

System Code Calculation and Experimental Verification for Double-hole Steam Jet Condensation Heat Transfer Process Based on ADS1 3 Scaled Model

The steam direct contact condensation of high-temperature steam in sub-cooled water is an important way to reduce the temperature and pressure in the primary circuit in the third generation of advanced pressurized water reactors such as AP1000 and CAP1400 in the event of accidental overpressure. Based on the system codes of RELAP5 and COSINE, the process of saturated steam injecting into large volume sub-cooled water through a double-hole nozzle was modeled, calculated and analyzed. The temperature distributions along the axial direction of the high-temperature steam ejected from the nozzle were obtained. At the same time, the visual experiments of steam jet condensation were performed. The thermocouple matrix and high-speed camera were used to measure the key thermal-hydraulic parameters to obtain the temperature distributions along the steam plume and the flow patterns of the steam jet, which were used to verify the accuracy of the system code to simulate the process of steam spraying and condensation. The results show that the system code RELAP5 can basically simulate the general trend of ADS steam condensation process under the simplified model. The average error of the simulation results is 2.97% compared with the experimental results. In addition, the COSINE code was used to further modify and improve the model of the spraying condensation process. Considering the influence of the overall flow in the water tank on the condensation characteristics, the simulation results fit well with the experimental results, with an average error of 1.89%. However, the actual double-hole spraying process is complex and has obvious three-dimensional characteristics, so the relevant condensation heat transfer model in the system code still needs to be further improved to simulate its local condensation characteristics more accurately.     

基于ADS1～3缩比模型的双孔蒸汽喷放冷凝传热系统程序计算与实验验证

高温蒸汽在过冷水中喷放直接接触式冷凝是AP1000、CAP1400等三代先进压水堆一回路在事故超压情况下重要的降温降压途径。本文基于系统程序RELAP5、COSINE对饱和蒸汽通过双孔喷洒器喷入大容积过冷水中进行直接接触冷凝这一过程进行建模、计算、分析,获得高温蒸汽从喷口喷出后沿轴向的温度分布。同时开展蒸汽喷放冷凝可视化实验,采用热电偶矩阵和高速摄像机等对关键热工参数进行测量,以获得蒸汽汽羽的温度分布和喷放流型等,用于验证系统程序对蒸汽喷放冷凝过程模拟的准确性。结果表明,采用RELAP5程序基本能模拟简化条件下的ADS蒸汽喷放冷凝总体变化规律,模拟结果与实验结果相比平均误差为2.97%。此外,采用COSINE程序对喷放冷凝过程模型进行了进一步修正和改进,考虑水箱内整体流动对喷放特性的影响,模拟结果与实验结果吻合较好,平均误差为1.89%。但由于实际双孔喷放过程较为复杂,并且存在明显的三维特性,所以仍需对系统程序中相关冷凝传热模型进行完善,以更精确地模拟其局部冷凝特征。