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根据调研。谏壁泵站的流量由设计的120m^2/s增容到160m^2/s,因此需要对现有的流道进行计算。为此。应用时均N—S方程和k-ε湍流模型方程对泵站进水流道的流动进行了计算分析,并以流速分布均匀度和速度加权平均角度为优化目标对流道方案进行了评估。结果表明,谏壁泵站原有的进水流道完全满足增容改造以后的要求。 相似文献
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针对谏壁泵站增容量较大而进出水流道尺寸并不富裕的问题,试图对流道进行适当的改造来提高泵站效率.经过对进出水流道多种改造方案的装置试验研究,得出流道小改小动对提高泵站效率作用不大的结论,最后通过选择合适的水力模型达到了增容40m^3/s的目的,取得了显著的经济和社会效益. 相似文献
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为了提高引黄济青工程宋庄泵站的单泵流量,满足梯级泵站联合运行流量调节的要求,通过对宋庄泵站供水能力不足原因的分析和进、出水流道水力条件的分析,提出了在不改变原有水工结构的前提下,采用混流泵替换现有轴流泵的改造方案。 相似文献
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大型泵站钟形进水流道三维紊流数 总被引:1,自引:0,他引:1
结合无锡市城市防洪工程中的仙蠡桥泵站钟形进水流道,采用雷诺平均N-S方程和标准k-ε湍流模型,运用SIMPLEC算法,对几种不同流量工况下的流道内流动进行了数值模拟,揭示了钟形进水流道内流场特征断面的速度分布及水力损失规律。研究结果表明:此进水流道在流量变化很大的情况下,能保持稳定的流态,从而较好地适应各种运行条件。此外,此流道的出水存在一定程度的偏流现象,可作进一步的水力优化。 相似文献
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在泵站更新改造中,利用已有的条件对机组进行增容改造,以提高泵站的排涝标准,这种做法确实起到了事半功倍的效果,因而各地都在推广和采用。根据这些年来泵站机组增容改造的经验,系统地阐述了下列问题:(1)泵站在什么情况下需要进行增容改造;(2)国内外泵站机组增容改造简况;(3)机组增容改造在技术上的主要措施;(4)关于大型同步电动机的变极调速;(5)泵站机组增容改造应注意的问题。其内容可供大型泵站机组增容改造时参考。 相似文献
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感官检验棉花的品级,这是农村常见的一种检测手段.它的一个主要特点就是存在不确定性.这是由于检验员的品级检验水平存在一定的差异,其中有很多因素制约着检验的结果.文章对影响感官检验结果的因素进行了系统的分析. 相似文献
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《Journal of Agricultural Engineering Research》1998,69(3):249-254
A model to represent the discolouration of dried powder of carrots as a function of temperature was developed. Two types of carrots, Asian and European, containing large amount of lycopene and β-carotene, respectively, were tested. The dried powder was stored under an atmosphere with O2and at three different temperatures, 5,20 and 35°C. The surface colour of the powder was monitored during storage by a Hunter colour ratioa/b. In the proposed model, the rate of oxidation was assumed to be represented by the product of the fraction of concentration of oxidized pigment at arbitrary time and a specific rate of oxidation of pigment. The rate parameters in the proposed model were calculated by fitting the experimental data with smooth curves by trial and error at the end of the induction period but before discolouration took place. The frequency constant and activation energy, expressing the temperature dependence of the rate parameters, were expressed by the Arrhenius relation. The simulation results of a Hunter colour ratioa/bof dried powder at 25°C showed good agreement with the experimental data, suggesting that the proposed model was effective for the prediction of discolouration of dried powder of both types of carrot. The use of the induction period in the manner described may enable the shelf life of dried powder to be predicted. 相似文献
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从灾害经济学的角度探讨了城镇供水优化调度的必要性和可能性,认为在缺水不可避免的情况下,对供水进行优化调度可以减小缺水带来的损失,产生较好的减灾效益,特别是可以大大减小严重干旱的灾害效应。并根据水资源的特性,提出了缺水损失的计算模式以及优化调度的原则和方法。 相似文献
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The fractional outflow rate of water from the rumen, measured as the rate of disappearance of the chromium complex of ethylenediamine tetra-acetic acid, was related to a number of dietary factors. A multiple regression equation was derived which expressed fractional outflow rate as a function of the intakes of dry matter, ash, acid-detergent fibre and crude protein.The data analysed consisted of 243 observations for sheep on 59 diets, including forage, concentrate and mixed diets. The ranges covered by the data were: fractional outflow rate 0.7–3.6 day?1; dry matter intake 560–1400g/day; ash 4–30%, acid-detergent fibre 7–41%, crude protein 5–26 % of dry matter; there were no observations for sheep of less than 34 kg liveweight.The equation accounted for 56·3 % of the total variance. Between-sheep variance could not be calculated for the whole of the data but was undoubtedly substantial since, for a sixth of the data, it was known to account for 38 % of the total variance. 相似文献