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有坎缺口式量水槽是结合U形渠道测流提出的一种新型的量水设施.本文通过理论分析得出了这种量水设施的流量系数随收缩比和水深的变化规律.通过试验得出了该设施收缩此的范围和水力计算方法. 相似文献
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根据明渠均匀流理论,推求了U形渠道的水深流量关系和水力最优断面.并通过算例比较证实,U形渠道可以大幅度的节约土地面积. 相似文献
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本文应用等面积系数法提出了圆形和U形断面临界水深的一种直接计算公式。该式概念清楚,形式简单同时又能满足工程精度和范围的要求,适合在水力设计和教学中应用。 相似文献
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由于超声波技术的发展和计算机技术的应用,超声波测流已成为适用于水电站机组流量测量的现代测流技术.本文介绍了超声波测流的基本原理,国内外对超声波测流的理论研究和超声波测流技术的发展状况,以及超声波测流在水电站的应用情况与发展前景. 相似文献
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吴国庆 《电网与水力发电进展》2014,(7):86-91
马蹄形断面几何形状复杂,正常水深和临界水深的计算需求解超越方程,计算比较麻烦。根据明渠均匀流理论和临界水深理论,研究了马蹄形断面正常水深和临界水深的一般计算方法,并引入无量纲参数和优化拟合理论,得到了标准Ⅱ型马蹄形断面正常水深和临界水深的简化计算公式,公式形式简单,计算方便,精度满足工程设计要求。 相似文献
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抛物线形断面渠道均匀流水深的近似计算公式 总被引:3,自引:0,他引:3
针对二次抛物线形断面渠道均匀流水深计算存在的问题,采用优化拟合的方法,通过对二次抛物线形断面渠道均匀流水深计算公式的拟合,得到了表达形式简单、计算过程简捷、实用范围广、便于工程设计人员实际应用的近似计算公式。误差分析及算例计算表明,在工程实用范围内,该公式的无量纲水深最大拟合相对误差为0.257%,均匀流水深计算最大相对误差为0.513%,完全满足实际工程的水力计算及设计精度要求。 相似文献
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水电站机组流量测量技术是原型水轮发电机组效率试验的关键技术。本文对适用于水电站流量测量的五种主要测流方法作了简要介绍,分析了每种测流方法的优缺点及适用场合,并介绍了水电站测流的目前状况及测流技术的最新发展动态。 相似文献
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降雨和径流综合作用下的细沟断面形态分异特征 总被引:3,自引:0,他引:3
为探究特定细沟自身的空间形态差异及其形成机制,采用室内模拟试验,研究了沿程冲刷与溯源侵蚀共同作用条件下细沟断面形态的分异特征。结果表明,沟宽与宽深比沿坡长方向呈先减小后增大的非线性规律,沟深则呈沿程减小的线性规律;沟宽与流量、坡度指数关系中的流量指数、坡度指数沿坡长方向分别由0.95、0.79降至0.47、0.31,沟深关系中流量与坡度指数也呈类似的沿程递减规律,宽深比指数关系中的两个指数在坡面下方均接近于0;沿程冲刷对细沟断面的塑造作用体现为沟宽与沟深的同时增加,作用强度沿坡长方向降低;溯源侵蚀的塑造作用体现为沟宽增大速率大于沟深,断面向宽浅方向发展,作用强度逆坡长方向降低;沿程冲刷与溯源侵蚀在空间上的叠加效应导致了细沟断面形态的分异特征。因此,在沟蚀防治过程中,可在一定汇流范围内布置截排水设施,以避免形成较大股流导致沿程冲刷与溯源侵蚀。 相似文献
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《Journal of power sources》1988,24(3):195-206
The cycle life of a rechargeable cell depends on operating conditions such as the depth of discharge, specific voltage limits during charge and discharFor a rechargeable Li/MoS2 cell, a strong dependence of cycle life on discharge current was found. For discharge rates ranging from 0.5 to 20 h, a 相似文献
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对明流、急流流态的泄洪洞,尤其是采用挑流消能工的明流、急流泄洪洞工程,在水流起挑之前形成洞内的水跃现象;如果所设计工程的起挑流量值过大,洞内形成的水跃高度即跃后水深可能造成隧洞封顶,形成明满流流态。本文介绍了采用挑流式消能工的明流、急流泄洪洞起挑流量的确定方法,供设计人员参考使用,以确保泄洪洞工程流态的单一性。 相似文献
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《Journal of power sources》2002,111(2):304-319
This paper presents the results of an investigation into the initial stage of the discharge voltage response of valve-regulated lead–acid (VRLA) batteries. This region is dominated by the phenomenon known as the coup de fouet which manifests itself as a voltage dip followed by a recovery. The research focuses on two parameters found within the coup de fouet region, namely, the trough and the plateau voltage. It is found that these parameters are influenced by the operating conditions and the sate-state-of health (SoH) of the battery. The operating conditions considered are discharge rate, ambient temperature, depth of previous discharge, charge duration, and float voltage. The coup de fouet parameters corresponding to high rate discharges, as well as discharges conducted at low temperatures, have reduced magnitudes compared with those conducted at lower rates or higher temperatures. This behaviour mirrors the availability of capacity when the battery is discharged under the same operating conditions. The float voltage is found to have a direct relationship with the trough and plateau voltages, whereas an indirect relationship between charge duration and the trough and plateau voltages is observed. The influence of variations in discharge depth on the coup de fouet is more complex. For consecutive discharge depths below approximately 10% of rated capacity, the coup de fouet becomes distorted and exhibits a second voltage dip. For consecutive discharges of greater depth, this does not occur. The influence of the degradation in battery SoH due to accelerated thermal ageing, water replenishment post-accelerated thermal ageing, and field ageing is investigated. The coup de fouet parameters associated with the discharge of batteries with low SoH have a reduced magnitude compared with those associated with the discharge of batteries with a high SoH. 相似文献
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鉴于研究水库溃坝时溃坝波传播过程及流量变化规律对大坝安全管理具有十分重要的意义,特做了30组工况下的平底无阻力矩形水槽瞬时溃坝模型试验。结果表明,瞬时溃坝后下游无水时的溃坝波呈反"S"型向下游演进,下游有水时会有相对稳定的激波区产生;渐进流区水力特性仅受初始上游水深影响,而激波区水力特性除受上游水深影响外,还受初始下游水深比的影响,随着下游水深的增大,所涌起的激波区范围越广水深越大,但溃坝流量越小。研究结果为大坝或水闸设计及其安全管理提供了参考依据。 相似文献
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针对软包锂离子电池放电过程中温度变化过程进行研究,依据电池产热基本理论,通过内阻实验及0.5 C放电倍率下的温升实验计算出瞬态生热率曲线,得出电池熵热系数,建立生热速率随放电深度不断变化的瞬态生热模型,基于该模型进行不同放电倍率的温度仿真模拟,并与实验进行对比。结果表明,温度变化模拟结果与实验相吻合,生热率变化模拟结果与实验计算值相符合,模型可以很好地模拟电池在不同放电倍率下的温度变化,对电池温升过程分析及电池热管理过程控制具有指导意义。 相似文献
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Kazuma Kumai Tomohiko Ikeya Kaoru Ishihara Toru Iwahori Nobuyuki Imanishi Yasuo Takeda Osamu Yamamoto 《Journal of power sources》1998,70(2):235-239
The degradation mechanism due to the decomposition of organic electrolytes during charge and discharge cycling of Li/MoS2 cells has been investigated. The gas products of the electrolyte decomposition during long cycling were measured by gas chromatography (GC), and the changes of electrolyte composition was measured by gas chromatography/mass spectrometry (GC/MS). The gases were produced through two types of electrolyte decomposition: the electrochemical reaction, which was dependent on the charge and discharge voltage, and the chemical reaction, which was independent of the discharge voltage. This decomposition of electrolytes occurred under a discharge voltage lower than 1.4 V. The operating conditions with a lower discharge rate and a deeper depth of discharge (D.O.D.) accelerated the electrochemical decomposition. The rate of gas production by chemical decomposition, which is independent of the discharge condition, was estimated to be about 0.1 ml/h. 相似文献
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针对岸边溢洪道从侧面挑入与其平行布置的已有消力池来消能的布置形式,采用数值模拟方法研究了高程和流量对挑坎(а=45°)及消力池水力特性的影响。结果表明,随着泄流量逐渐增大,挑坎内最大水深、最大压力及消力池最大压力均逐渐增大,挑流水舌入水长度与纵向入水长度均逐渐增大;随着挑坎与消力池高差的减小,挑坎最大水深和最大压力均逐渐增大,而消力池最大压力变化较小。拟合得挑坎最大水深和最大压力的定量计算公式,从而为该型岸边挑坎的工程设计提供了参考。 相似文献