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颜锦文 《中国农村水利水电》1988,(5)
在多泥沙泵站中,由于泥沙磨损作用,使水泵部件受到严重损害,导致水泵效率下降,检修频繁。如山西省夹马口抽黄泵站每年处于维修而不能运行的泵站占1/4:陕西东雷抽黄工程的黄河型水泵,运行300小时一小修,700小时一大修。叶轮使用年限1～2年,其它易损部件如口环、止推轴承等使用年限更短。 相似文献
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我国泵站工程建设,就其规模和数量来看,均居世界各国前列.长期以来,水泵过流部件泥沙磨损、汽蚀损害问题持续困扰着广大泵站运行管理部门,尤其是在我国黄河流域以黄河水为水源的高扬程提灌泵站的水泵泥沙磨损问题更为为突出.针对这一问题,阐述了我国沿黄高扬程提灌泵站水泵磨蚀状况及危害,分析了现有水泵抗磨蚀技术,推荐了几种解决水泵磨蚀问题的方案. 相似文献
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多泥沙水源泵站的布置当水泵从多泥沙水源抽水时，水泵效率下降，零部件损失加快，气蚀现象加重。为提高水泵效率，可采用如下措施。一、引水口向下游布置、这样既可防止水草等杂物堵塞管道，泥沙含量也明显降低。二、少用弯管。因为水流携沙在管弯处水头损失加大。流速降... 相似文献
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从清水泵入手，提出了两相流泵的概念，简要分析了水泵失效的原因，创建水泵磨蚀过程的“车削”模拟。根据水泵车削调节公式，推导出叶轮临界标志的电动机瞬时功率值，并从电动机效率和叶轮效率两方面进行校验，进一步提出叶轮更换应考虑的因素和延缓叶轮更换的措施，为多泥沙泵站的运行提供了一种简便易行的方法。 相似文献
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黄河多泥沙水源离心泵站水泵磨蚀成因及防治对策 总被引：1，自引：0，他引：1
针对段家塬三、四级泵站水泵磨蚀严重的问题,系统地分析了泵站设计运行存在的问题和水泵磨蚀的特点,指出了扬程较高的黄河多泥沙水源离心泵站水泵磨蚀的成因和机理,在此基础上提出了水泵磨蚀防治的5项对策,对高扬程黄河多泥沙水源离心泵站的安全、经济运行有很好的指导作用. 相似文献
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为了探明滴灌加压泵站调速运行条件,分析了滴灌泵站运行特点,并在叶片泵基本方程基础上分析了滴灌泵站装置运行工况与离心泵调速运行工况之间的关系,以及影响调速工况等效性的因素。结果表明,虽然在理论上滴灌泵站调速运行中离心泵运行工况可以无条件等效,但是,实践中滴灌系统过滤装置水头损失升高,使系统装置特性曲线斜率增大,并且还随着水泵调速幅度的增加而增大,不仅使得水泵调速前、后工况效率不相等,还将导致滴灌系统不能正常工作。所以滴灌泵站的调速范围应小于允许的单泵调速运行范围。另外,水泵降速超过一定范围后造成叶轮内速度三角形夹角α2（叶轮出口处叶片的牵连速度与流体绝对速度之间的夹角）增大,叶轮水力条件不再相似,水泵调速前、后的运行工况的效率不再相等。本研究对完善滴灌泵站管理理论有帮助。 相似文献
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《中国农村水利水电》2016,(8)
采用欧拉-拉格朗日多相流模型对双吸式离心泵内的水流和泥沙颗粒运动进行了模拟,运用离散相冲击模型对叶片及轮毂的磨损情况进行了预测,分析了变速调节对离心泵泥沙磨损的影响。结果表明:设计工况下,叶轮磨损严重的位置主要集中在叶片头部以及轮毂面上靠近叶片吸力面的区域,叶片吸力面磨损强度大于压力面,数值模拟结果与现场观测结果相吻合;提高水泵转速后,叶轮流道中的相对流速分布变均匀,叶片和轮毂面的磨损明显改善,高强度磨损面积减小,磨损区域变分散。 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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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
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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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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