低含水油水两相流等效介电常数模型

电容法测油水两相流含水率在油田的地面油水计量及井中的产出剖面分层测试中都得到广泛应用。持水率(水相体积分数)的测量需要建立油水两相流持水率与传感器电容的关系,为此需要建立混相等效介电常数与持水率的理论模型或经验模型。由于油井采出的地层水以及地面实验室标定所用的自来水在低频和中频时均具有良好导电性,因此,单纯考虑介电性而不考虑导电性会对持水率测量的准确性产生显著影响。基于电介质极化的有效电场理论,在低含水且油水状态为精细泡状流条件下,将水视为良导体,建立了油水两相流等效介电常数模型。按此模型,油水两相流的等效介电常数只取决于持水率和油相介电常数,与水相介电常数以及水相电导率无关,初步实验验证了模型正确。该研究对于油为连续相时油水两相流的含水率传感器的设计和现场应用具有重要意义。

感应式含水率传感器响应特征的仿真分析

油水两相流的含水率是油田油井地面油气水计量和油井内产出剖面测井的重要参数。已有油井内多相流含水率测量方法无法适应中国油田油井高含水、低产量、携带固体杂质的复杂情况。感应式含水率传感器具有与流体非接触、无可动部件、全场测量的特点,具有较高的可靠性及良好的应用前景。为了准确评价感应式含水率传感器对水相连续时的油水两相流含水率的响应特征,采用有限元仿真软件建立了感应式含水率传感器的仿真模型,分析了水相电导率、激励频率、线圈匝数及磁屏蔽体磁导率和厚度等参数对传感器响应特征的影响。通过原理解析和仿真数据对比验证了简化后模型的可靠性。实验结果表明,电导率的测量误差小于1.6%,说明该方法测量含水率可行。该方法中仿真设计对参数的研究有助于优化现场含水率传感器的设计参数。

Mechanism of Regional Subseasonal Precipitation in the Strongest and Weakest East Asian Summer Monsoon Subseasonal Variation Years

Using the National Center for Environment Prediction Climate Forecast System Reanalysis coupled dataset during 1979–2010,we selected four subseasonal indexes from the 16 East Asian Summer Monsoon(EASM)indexes to characterize the subseasonal variability of the entire EASM system.The strongest(1996)and weakest(1998)years of the subseasonal variation were revealed based on these subseasonal EASM indexes.Furthermore,three rainfall concentration areas were defined in East Asia,and these areas were dissected by the atmospheric midlatitude jet stream axis and the position of the Western North Pacific Subtropical High(WNPSH).Then,the subseasonal effects of the WNPSH,the South Asian High(SAH),the Mongolian Cyclone(MC),and the Boreal Summer Intraseasonal Oscillation(BSISO)on each rainfall concentration area were studied in the strongest and weakest subseasonal variation years of the EASM.During the summer of 1998,the WNPSH and the SAH were stable in the more southern region,which not only blocked the northward progression of the BSISO but also caused the MC to advance southward.Therefore,the summer of 1998 was the weakest subseasonal variability of the EASM,but with significant subseasonal precipitation episodes in the northern and central rainfall areas.However,in 1996,the BSISO repeatedly spread northward in the south rainfall area because of the weak intensities and northern positions of the WNPSH and the SAH,which caused significant subseasonal precipitation episodes.In addition,MC was blocked to the north of approximately 42°N with a weak subseasonal rainfall.

新型永磁励磁型饱和铁芯故障限流器

应用饱和铁芯故障限流器(saturated-core fault current limiter,SCFCL)是限制系统短路电流的最有效措施,为解决传统SCFCL直流励磁损耗大的难题,提出了一种新型永磁励磁型饱和铁芯故障限流器(permanent-magnet-biased saturated-core fault current limiter,PSFCL)o本文利用等效磁路、等效电路对该新拓扑进行研究分析,并进行相关参数设计,通过搭建基于Maxwell-3D的有限元电磁仿真模型,证明所提新型拓扑可有效限制故障电流,并通过样机试验进一步验证所提结构的有效性与理论的正确性。

耦合蒸汽压缩制冷循环和有机朗肯循环的冷电联供系统参数分析

针对目前空调冷凝余热直接排放导致环境温度升高的问题,采用有机朗肯循环回收蒸汽压缩制冷循环的冷凝热,构建耦合蒸汽压缩制冷循环和有机朗肯循环的冷电联供系统.冷凝剂采用纯工质R134a,有机工质采用混合工质R245fa/R123(0.5/0.5).基于热力学第一定律,构建循环的热力学模型,研究蒸发温度和冷凝温度对吸收全冷凝热和过热部分冷凝热2种工况下冷电联供系统的性能的影响并进行对比.结果表明,随着蒸汽压缩制冷循环冷凝温度增加,有机朗肯循环的净输出功由5.7 kW增加到6.4 kW,发电量由4.9 kW增加到5.5 kW;随着有机朗肯循环蒸发温度增加,净输出功由3.2 kW增加到8.4 kW,净发电量由2.5 kW增加到7.5 kW.随着蒸汽压缩制冷循环蒸发温度和有机朗肯循的冷凝温度的增加而减小.吸收全冷凝热量方式的VCC⁃ORC的性能参数COP增加了17.9%~26.9%.当有机朗肯循环系统工质吸收蒸汽压缩制冷循环系统释放的全冷凝热量时,净输出功和发电量明显优于只吸收过热部分热量的回收方式.