Entropy production analysis for hump characteristics of a pump turbine model

The hump characteristic is one of the main problems for the stable operation of pump turbines in pump mode.However,traditional methods cannot reflect directly the energy dissipation in the hump region.In this paper,3D simulations are carried out using the SST k-ω turbulence model in pump mode under different guide vane openings.The numerical results agree with the experimental data.The entropy production theory is introduced to determine the flow losses in the whole passage,based on the numerical simulation.The variation of entropy production under different guide vane openings is presented.The results show that entropy production appears to be a wave,with peaks under different guide vane openings,which correspond to wave troughs in the external characteristic curves.Entropy production mainly happens in the runner,guide vanes and stay vanes for a pump turbine in pump mode.Finally,entropy production rate distribution in the runner,guide vanes and stay vanes is analyzed for four points under the 18 mm guide vane opening in the hump region.The analysis indicates that the losses of the runner and guide vanes lead to hump characteristics.In addition,the losses mainly occur in the runner inlet near the band and on the suction surface of the blades.In the guide vanes and stay vanes,the losses come from pressure surface of the guide vanes and the wake effects of the vanes.A new insight-entropy production analysis is carried out in this paper in order to find the causes of hump characteristics in a pump turbine,and it could provide some basic theoretical guidance for the loss analysis of hydraulic machinery.     

Analysis of vorticity dynamics for hump characteristics of a pump turbine model

Conventional parameters based on CFD methodology for the investigation on hump characteristics of a pump turbine cannot reflect the dynamic interaction mechanism between the runner and the fluid. This research presents a dynamic interaction mechanism of a pump turbine operating in the hump region. First, vorticity dynamic parameters were obtained based on the theory of vorticity dynamics. Second, 3-D unsteady flow simulations were performed in a full pump turbine model using the SST k-ω turbulence model, and numerical results have a good agreement with the experiments. Then, analysis was carried out to determine the relation between the vorticity dynamic parameters and hump characteristics. The results indicate that the theory of vorticity dynamics has an advantage in evaluating the dynamic performance of a pump turbine. The energy transfer between the runner and the fluid is through vorticity dynamic parameters-pressure and friction terms, in which the pressure term accounts for the most. Furthermore, vortex generation mainly results from the skin friction. Combining vorticity dynamic analysis with the method of Q-criterion indicates that hump characteristics are related to the reduction of the surface normal pressure work and vortex motion on the suction surfaces close to the leading edges in the runner, and the increase of skin friction work in the stay-guide vanes.

     

Development of a water droplet erosion model for large steam turbine blades

Water droplet erosion is one of major concerns in the design of modern large fossil steam turbines because it causes serious operational problems such as performance degradation and reduction of service life. A new erosion model has been developed in the present study for the prediction of water droplet erosion of rotor blades operated in wet steam conditions. The major four erosion parameter ; impact velocity, impacting droplet flow rate, droplet size and hardness of target are involved in the model so that it can also be used for engineering purpose at the design stage of rotor blades. Comparison of the predicted erosion rate with the measured data obtained from the practical steam turbine operated for more than 90.000 hours shows good agreement.     

LY3ZB型液压传动三缸柱塞泵的研制

介绍了ＬＹ３ＺＢ型液压传动三缸柱塞泵的结构方案,液压系统工作原理及其性能实验结果。该泵以长丫程,低冲次的工作方式适合于输送各种介质,特别是黏稠性介质。     

汽轮机复水泵国产化改型

乙烯装置裂解气压缩机组是乙烯行业最核心的设备,其汽轮机复水器凝渡泵对抗汽蚀能力要求很高。目前乙烯行业基本采用热井泵,由于结构缺陷和工艺波动的影响,故障偏多.中原乙烯装置裂解气压缩机组GB／T201凝液泵为热井泵,该设备的不稳定性长期困扰生产。经过充分技术分析与论证,从经济性和稳定性出发,将超汽蚀叶形的诱导轮技术应用于单级离心泵,进行设备改型.经与北京巡航高科技有限公司合作,按照满足GB3215—82和API两个标准的要求,对设备结构、材料、密封等进行设计、制造,确定了工艺性能,并对现场工艺流程进行了重新布局。该泵于2003年12月单机试运完毕后成为备用泵,至今已间断运行四个阶段,累计165天。从运行统计数据分析,此泵的机械状态和工艺性能良好,完全能够满足生产需要。对比两种型式复水泵的运行情况,可以得出结论：新增卧式复水泵的稳定性要远好于热井泵因此,此次复水泵国产化改型是成功的,消除了生产隐患,为装置长周期运行打下了良好的基础,同时也为今后新建乙烯裂解装置复水泵的选型提供了新路.     

转臂式灭火机器人灭火技术研究与实现

为有效地应对目前日益复杂的灭火环境,减少不必要的人员伤亡,根据火灾现场实际环境,针对现有灭火机器人研究所存在的问题,对机器人灭火技术进行研究并自主研发了基于ATMega单片机技术的灭火机器人系统,该系统设计了独特的转臂灭火机构和喷水灭火装置。经灭火实验验证,该系统可有效地提高灭火质量和效率,为灭火机器人的实际应用和推广提供支持。     

主液压泵跳闸导致汽轮机停机原因分析及改进措施

通过核算,指出蓄能器选型过小是导致主液压泵跳闸时油压不稳、汽轮机停机的主要原因,提出了改进措施。     

GF50-3型单螺杆泵研制及维护使用事项

介绍杭州水泵总厂开发研制的新产品GF50-3型单螺杆泵，包括泵的结构和工作原理、设计、关键加工技术、使用规则和维护事项等。     

高速汽轮机泵推力轴承的设计与功耗问题

以推力可倾瓦轴承为例。在各种参数下，计算了轴承的最高油温、最小油膜厚度以及轴承的功耗。从分析结果可知，无论怎样改变轴承外径do,支点位置半径rp和位置角β都难以有效地降低轴承的功耗。当轴承的瓦块数量减少时，轴承的功耗才能得到有效的降低。