排序方式: 共有78条查询结果,搜索用时 171 毫秒
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针对风机叶轮射流尾迹与蜗舌产生的动静干涉流场的特性,研究风机内部动静干涉流场的相互作用机制.以某离心风机为研究对象,通过对传统蜗舌的结构进行改进,在叶轮出口长度对应的蜗舌展向长度范围内开槽,采用数值计算的方法分析开槽结构的槽宽、槽深和间距等参数对离心风机的气动特性和风机内部流场分布的影响规律.计算结果表明:开槽蜗舌有助于改善风机的运行效率,减小尾迹对蜗舌前缘的冲击,延缓蜗舌下游边界层的流动分离,削弱叶轮与蜗舌之间的动静干涉作用,抑制蜗壳壁面的非定常压力脉动. 相似文献
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基于标准k-ε湍流模型,结合Zwart-Gerber-Belamri空化模型,对比转速为69的离心泵进行数值模拟,揭示内射流结构对泵内部空化流动的影响机理,比较射流孔径对泵汽蚀性能的影响,分析内射流引起的空化泡形态分布和演变规律.结果表明:射流孔的存在导致泵叶轮流道在进口抽真空状态下更易发生空化,射流孔径越大,对流道中空化发展的影响越强烈;当射流孔直径为6 mm时,在0.8倍、1.2倍和1.4倍设计工况下,模型泵的临界空化余量分别增加17%、69%和5%.由于内射流的轴向速度较大,在剪切层形成局部低压区,其自身更易发生空化.当有效空化余量降低时,在小流量工况下,叶轮进口轴线附近率先出现螺旋型空化带,并逐渐转化为范围更大的空泡团;在大流量工况下,空化发展缓慢,仅发展出空化带结构. 相似文献
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The benchmark of a simply supported beam with damage and bending fuzzy stiffness consideration is established to be utilized for damage detection. The explicit expression describing the Rotational Angle Influence Lines (RAIL) of the arbitrary section in the benchmark is presented as the nonlinear relation between the moving load and the RAIL appeared, when the moving load is located on the damage area. The damage detection method is derived based on the Difference of the RAIL Curvature (DRAIL-C) prior to and following arbitrarily section damage in a simply supported beam with bending fuzzy stiffness consideration. The results demonstrate that the damage position can be located by the DRAIL-C graph and the damage extent can be calculated by the DRAIL-C curve peak. The simply supported box girder as a one-dimensional model and the simply supported truss bridge as a three-dimensional model with the bending fuzzy stiffness are simulated for the validity of the proposed method to be verified. The measuring point position and noise intensity effects are discussed in the simply supported box girder example. This paper provides a new consideration and technique for the damage detection of a simply supported bridge with bending fuzzy stiffness consideration. 相似文献
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高速公路曲线上简支板桥的平面布设方法 总被引:1,自引:0,他引:1
介绍了郑新高速公路平曲线上简支板桥的几种平面布设方法,重点是弦线拨角法的计算图式、公式推导和适用范围。 相似文献
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马驹立交桥的加固与扩建 总被引:3,自引:0,他引:3
文章提供了位于两条高速公路交汇处的旧桥加固扩建的设计构思、施工方法以及新技术、新工艺和新材料的应用。 相似文献
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Service computing is a new paradigm and has been widely used in many fields. The multi-objective service selection is a basic problem in service computing and it is non-deterministic polynomial (NP)-hard. This paper proposes a novel multi-objective artificial bees colony (n-MOABC) algorithm to solve service selection problem. A composite service instance is a food source in the algorithm. The fitness of a food source is related to the quality of service (QoS) attributes of a composite service instance. The search strategy of the bees are based on dominance. If a food source has not been updated in successive maximum trial (Max Trial) times, it will be abandoned. In experiment phase, a parallel approach is used based on map-reduce framework for n-MOABC algorithm. The performance of the algorithm has been tested on a variety of data sets. The computational results demonstrate the effectiveness of our approach in comparison to a novel bi-ant colony optimization (NBACO) algorithm and co-evolution algorithm. 相似文献