反应堆主泵压水室出口收缩角对水力性能的影响

针对国内某百万千瓦核反应堆主泵的水力性能要求,完成主泵叶轮和导叶的设计;为研究出口收缩角对水力性能的影响,设计了13种压水室出口收缩角,采用三维软件Pro/E完成了三维造型;利用计算流体力学(CFD)软件Fluent进行定常与非定常三维数值模拟,得到内部流场特性及计算点的压力脉动情况,并对其进行分析。结果表明:收缩角对压水室与出口交接处的前后区域影响显著,收缩角在12°~16°范围内,主泵效率均在70%以上,=15°时效率达最大值74.2%;在=15°且其他结构参数不变的情况下,随着流量的降低,主泵叶轮进口前和导叶出口处回流区域逐渐扩大;随着流量的增加,叶轮进口前回流区域逐渐向叶轮进口偏移;回流是引起压水室与出口交接处压力脉动的主要原因;偏离工况越大,压水室出口处的压力脉动波动越严重。     

NRI Řež solution of Exercise 3 of VVER-1000 Coolant Transient Benchmark – Phase 1 with coupled codes DYN3D–ATHLET

The paper presents a solution of VVER-1000 Coolant Transient Benchmark – Phase 1 (V1000CT-1) of Exercise 3 performed with the coupled reactor dynamic code DYN3D and system code ATHLET at NRI Řež. The first part of the paper contains brief characteristics of VVER-1000 NPP input deck and describes also the applied reactor core model. The second part introduces the steady-state results and important time dependencies, compared with experimental values. The calculation results show that such type of transient can be realistically described by the coupled codes DYN3D–ATHLET.     

Effects of reactants/coolant non-uniform inflow on the cold start performance of PEMFC stack

The failure at equally distributing reactants among different channels within the stack leads to uneven reaction and gas concentration distribution in the catalyst layers, which consequently impacts the performance and durability of proton exchange membrane fuel cell stacks (PEMFCs). A three-dimensional, transient, non-isothermal cold start model for PEMFCs with parallel flow-field configuration and coolant circulation is developed in this work to investigate the effects of non-uniform distribution of reactants/coolant inflow rates on the cold start process. The results show that the effect of non-uniform inflow on ice formation amount is obvious and that on the distribution uniformity of current density is apparent over the cold start survival time. Additionally, the simulation predictions show that the non-uniform initial membrane water content distribution due to the purge procedure can significantly increase the rate of ice growth and deteriorate the uniformity of current density distribution in the membrane. It is found that high stoichiometry operating condition is favorable to cold startup, but may result in drying in the membrane at regions close to the channel inlet side. As non-uniform inflow rates issue is inevitable in actual PEMFC stack operation conditions, our results demonstrate that the initial membrane water content and cathode stoichiometry ratio need to be identified to moderate the effects of reactants/coolant inflow maldistribution and to maintain a stable cold start performance for the PEMFC stack.     

冷却液温度对柴油机起动首循环燃烧的影响

冷却液温度是柴油机起动过程中影响失火与燃烧不稳定性的重要因素。喷油首循环的燃烧对后续工作循环着火有较大影响。为了分析冷却液温度对柴油机起动首循环燃烧和排放的影响规律,利用基于循环控制的柴油机起动过程燃烧、排放测控系统,在一台单缸直喷式柴油机上进行了试验研究。试验结果表明冷却液温度对柴油机起动首循环燃烧的稳定性有较大影响。提高冷却液温度对于消除起动过程首循环燃烧状态的不稳定性具有较明显的作用。冷却液温度较低时,使着火滞后期增长,很容易导致失火或不完全燃烧现象,生成较高HC排放。试验也验证了所建立的测控系统为研究柴油机起动过程提供了一种有效的测试手段。     

Numerical study to examine the performance of multi-pass serpentine flow-fields for cooling plates in polymer electrolyte membrane fuel cells

Temperature is an important factor that impacts the performance of polymer electrolyte membrane fuel cells (PEMFCs). Proper cooling systems are indispensable for heat management. Cooling plates with coolant flow channels are mainly used to release the reaction heat in PEMFCs and thus control their operating temperature. In this study, several multi-pass serpentine flow-field (MPSFF) designs are studied in order to achieve better heat management by using cooling plates. Based on computational fluid dynamics (CFD) simulations of fluid flow and heat transfer in the cooling plates, the cooling performance of the six serpentine channel designs is evaluated. The results demonstrate that MPSFFs lead to better cooling performance compared with a conventional serpentine flow-field, in terms of both the maximum temperature and temperature uniformity. The effect of the Reynolds number and heat flux on the cooling performance exhibited by the six designs is also investigated.     

熔融液滴与冷却剂相互作用实验中液滴释放控制机构的研制

在高温熔融液滴与冷却剂相互作用的实验中,熔融液滴的释放控制对整个实验起至关重要的作用.本文在以往实验机械控制装置的基础上,自主设计一个自动控制电路来代替人工机械操作,利用控制电路给电磁铁提供瞬时脉冲来控制液滴瞬时释放下落,简化实验的可持续性操作,提高实验的重复性、精确性和操作方便性.     

高温小球在冷却剂中运动阻力特性的研究

通过实验．研究了高温小球在冷却剂中的运动阻力特性,揭示出高温难挥发的熔融物与低温易挥发的冷却剂相互作用的粗混合阶段具有特殊结构高温熔融金属液滴在冷却剂中的运动规律。研究结果对于开发多成分多相分析程序和研究核电站严重事故中燃料与冷却剂的相互作用具有重要意义一     

核供热堆小破口事故实验研究

通过不同功率、不同破口尺寸核供热堆小破口汽相事故排放的实验,研究了自然循环中断过程中系统的安全性和循环流量的波动现象;实验结果对核供热堆的安全运行及验证小破口事故安全分析程序有重要意义.     

Effects of Cooling and Dressing Methods on Grinding of Glass

Experiments were designed and conducted to evaluate the effects of cooling and dressing methods and five other factors on the grinding of glass. Surface roughness of the ground samples was measured and microscopic studies of the ground glass surfaces were performed. The column effect method and plotting method were applied to analyze and interpret the experimental results. The results showed that the average surface roughness heights of ground glass were improved by 5-36% and 42-52%, respectively, when an improved coolant system and dressing device were employed. The average surface roughness heights decreased by 52-58% and 30-37%, when smaller grit sizes and a resin-bond grinding wheel rather than a metal-bond grinding wheel were used, respectively. In addition, the surface roughness averages decreased by 18-23% and 13-18% when a smaller table-feed rate was used and truing of grinding wheels was performed, respectively. Moreover, compared with the surface roughness heights of the sample that was ground using the existing coolant system and manual dressing method, the surface roughness heights of the sample ground using both the improved coolant system and device-dressing method were improved by 46-70%, because of the positive interaction of these two factors.     

屏蔽式冷却剂泵的减振降噪测试分析

对核动力装置屏蔽式冷却剂泵的减振降噪进行了测试与分析。通过现场测试和数据处理分析，不仅识别出各部件的振动频率，获得了各部件振动测量面上平均速度有效值的平方占全部振动有效值的平方和的百分比(能量比)，同时发现了轴承部件的故障，还进行了温度和流量对辐射噪声影响的研究。