共查询到20条相似文献,搜索用时 62 毫秒
1.
轴流泵的气蚀主要以叶片气蚀和间隙气蚀最为常见,这种现象严重影响轴流泵装置系统的安全正常运行,甚至是不可避免的.运用两相流混合模型对典型立式轴流泵装置全流道流动条件下的叶片气蚀进行数值模拟.初步分析了叶片气蚀的初生、位置及内流特性等.也为相关深入的机理研究提供了基础和参考. 相似文献
2.
轴流泵水力模型选择专用软件的开发 总被引:1,自引:0,他引:1
为选择到合适的轴流泵水力模型,基于轴流泵段性能与泵装置性能之间的关系,确定水力模型选择的方法与步骤,提高泵段模型与进、出水流道组成的泵装置效率。以南水北调工程水泵模型同台测试成果为主要的数据资料,采用Manab结合Visual C++语言开发了选择轴流泵水力模型的专用软件,通过输入泵站扬程、流量数据,计算出满足基本要求的水力模型、原型泵的转速与叶轮直径以及原型泵的综合特性曲线。计算结果表明,该专用软件为比选水力模型建立了优秀的平台,在轴流泵站设计水泵选型中具有较高的应用价值。 相似文献
3.
4.
随着河水等水位的不断下降,高吸程喷射泵得到越来越多的应用。当射流泵内压力低于流体的汽化压力时,就会发生气蚀,不仅对进入喉管的流体有节流的作用,减小流量,还会剥蚀射流泵部件壁面,产生噪声,降低泵效。为了避免气蚀的发生,就要控制高吸程喷射泵的气蚀临界沉没度。本文推导出了气蚀临界沉没度的计算公式,通过已知的高吸程喷射泵产品性能参数及下泵深度求得气蚀临界沉没度。通过试验,间接测量了两组扬程分别为44m及34m的高吸程喷射泵正常工作时的最大吸程,验证了理论计算结果。通过对计算所得气蚀临界沉没度和试验测得的最大吸程比较分析,发现高吸程喷射泵射流泵无法正常工作的原因是发生了气蚀或工作压力太小,可以采取调节下泵深度或增加工作泵扬程等措施以满足使用需要。 相似文献
5.
自润滑轴承由外套、丁晴橡胶和聚四氟乙烯三层不同材料组成,利用聚四氟乙烯的高度化学稳定性和优良的润滑性与低静摩擦系数等特性,使该轴承应用于轴流泵时,能改善泵的起动性能和提高运行可靠性;特别是泵起动时不需注入润滑水,简化了轴流泵的配套装置。 相似文献
6.
为了提高轴流泵抗空化性能,采用泵的三元设计理论与数值试验相结合的方法,研究了汽蚀比转数为1 290的轴流泵抗空化性能.在相同的流量、扬程、转速等设计指标下,采用泵的三元设计理论对具有不同叶片数和过流通道形状的轴流泵模型分别进行了设计;并采用数值试验手段对所设计轴流泵模型性能进行计算和分析,得到了适合于该轴流泵的过流通道形状和最佳叶片数.运用相同的方法对不同叶片负载分布规律的轴流泵叶轮分别进行了设计,并采用数值试验手段计算了各水力模型的扬程、功率和效率特性曲线,对比和分析了不同负载分布规律对泵效率和抗空化性能的影响,得到了有利于轴流泵空化性能提高的负载分布规律.最后,根据数值计算结果,对如何有效提高轴流泵抗空化性能提出了建议:叶轮叶片后部重载光顺无阻塞的过流通道、适当增加叶片数将有利于轴流泵抗空化性能的提高. 相似文献
7.
冯永祥 《中国农村水利水电》1988,(7)
扬州市现有排灌设施大都采用混流泵、轴流泵和圬工泵,但圬工泵效率低,原混流泵和轴流泵的扬程一般在4米以上,缺乏更低扬程的泵型,致使泵站的装置效率很低。针对这种情况,闸门式贯流泵应运而生。本文叙述了三种贯流泵的安装形式和前置式贯流泵的性能,强调了贯流泵在安装中的注意事项。 相似文献
8.
9.
10.
11.
12.
13.
14.
15.
《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
16.
17.
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
18.
19.
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
20.
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