水轮机空化空蚀分析软件设计

本文从数据的测试与存储管理、信号数据的分析、空蚀失重量估计等方面介绍了永轮机空化空蚀软件的设计思路和方法.介绍了两种分析空化噪声的有效方法:多维空化分析和叶片通道频率分析;通过修正J.L.Gordon空蚀率估计公式,并结合工况和空化噪声的分析计算,提出了空蚀失重量估计的思路,并在软件上加以实现.     

贯流式水轮机三维定常湍流计算及改型设计

本文完成了福建大干水电站贯流式水轮机转轮的改型设计，同时完成了水轮机原型改型前后的全流道三维定常湍流计算，验证了改型设计的可行性。通过计算获得了各过流部件的流动细节，预估了水轮机的性能，与模型试验结果进行了比较，并从提高流量的角度对水轮机进行了改进，提高了机组的出力。     

EMS数据采集的通信规约转换

0引言江苏省电力局调度所引进了美国CDCEMPROS公司的能量管理系统（EMS）。由于该系统在信息采集方面仅能直接与8890型RTU通信,而省调下属厂、站的运动设备有多种,如C3000型＊＊U,卜4F型＊＊U及国产＊＊Y和MW＊一C3等型号的RTU,故必须进行通信规约转换。这些＊＊U使用的通信规约可分为3类：①卜4F规约;②C3000规约;③国产RTU的部颁规约。其中p4F型和C3000型为Pollinn方式,即问答式;国产＊＊U为＊＊T方式,即循环传送式。以卜4F型为例说明这些RTU与8890型RTU在通信规约方面的差别：（）I／）参数配置方面,p4F型R…     

基于分布式估计扩散机制的协作频谱感知方法

研究网络通信频谱优化问题,在分布式网络中,多节点联合估计未知参数.为了满足实时性要求,提出了一种扩散机制的协作频谱感知算法.算法采用扩散矩阵作为加权因子协作更新目标状态估计值,且以较小的均方误差快速实现对信号能量的最优估计.传统的协作感知方法快速性差.提出的算法不需要融合中心,能很好适应拓扑结构动态变化的随机网络.仿真结果表明,改进算法与分布式平均一致性估计算法相比,能够提高实时性并显著改善认知无线电网络的频谱感知性能.     

叶轮内部流动无粘性-边界层迭代及前缘粘性流动计算

本文用无粘性一边界层迭代算法计算轴流叶轮内部流动。即用流函数有限差分法对S_1和S_2相对流面上的流动进行计算和迭代。在S_1和S_2流面无粘性流动计算同时,引入边界层计算,而得到准三元粘性流动解。在此解基础上,用涡一流函数法计算了叶轮S_1流面前缘部分的层流,以便准确估计前缘流态。全部程序可应用于风机、压气机,水泵和水轮机等大部分叶轮机械。形成较为完整的流动分析软件。     

螺纹车刀牙形角的修正值

车削螺纹时,螺纹车刀刀尖角一般小于螺纹牙形角。前角越大,相差越多。下表为螺纹车刀刀尖角的修正值,供选用。     

高速泵内三维非定常动静干扰流动计算

利用三维Navier-Stokes方程和RNG湍流模型,并在转动部件与静止部件间采用滑移网格技术建立交互界面,对高速泵内多级动静干扰引起的三维非定常湍流进行了计算,得到了旋转叶轮与固定导叶间的流体的紊流特征。     

水泵叶轮中S_1流面的简化湍流计算

本文用流函数有限差分法和K-ε湍流模型计算水泵中S_1相对流面上的简化湍流。所用的湍动能及其耗散率方程考虑了叶轮旋转的影响。文中列举了离心水泵叶轮中S_1流面简化湍流计算结果,并与相应的试验和无粘性流动计算结果进行了比较。     

Three-dimensional large eddy simulation and vorticity analysis of unsteady cavi- taring flow around a twisted hydrofoil

Large Eddy Simulation (LES) was coupled with a mass transfer cavitation model to predict unsteady 3-D turbulent cavitating flows around a twisted hydrofoil. The wall-adapting local eddy-viscosity (WALE) model was used to give the Sub-Grid Scale (SGS) stress term. The predicted 3-D cavitation evolutions, including the cavity growth, break-off and collapse downstream, and the shedding cycle as well as its frequency agree fairly well with experimental results. The mechanism for the interactions between the cavitation and the vortices was discussed based on the analysis of the vorticity transport equation related to the vortex stretching, volumetric expansion/contraction and baroclinic torque terms along the hydrofoil mid-plane. The vortical flow analysis demonstrates that cavitation promotes the vortex production and the flow unsteadiness. In non-cavitation conditions, the streamline smoothly passes along the upper wall of the hydrofoil with no boundary layer separation and the boundary layer is thin and attached to the foil except at the trailing edge. With decreasing cavitation number, the present case has σ= 1.07, and the attached sheet cavitation becomes highly unsteady, with periodic growth and break-off to form the cavitation cloud. The expansion due to cavitation induces boundary layer separation and significantly increases the vorticity magnitude at the cavity interface. A detailed analysis using the vorticity transport equation shows that the cavitation accelerates the vortex stretching and dilatation and increases the baroclinic torque as the major source of vorticity generation. Examination of the flow field shows that the vortex dilatation and baroclinic torque terms increase in the cavitating case to the same magnitude as the vortex stretching term, while for the non-cavitating case these two terms are zero.     

半开式离心泵内部流场的数值模拟研究

采用标准k-epsilon,SST以及DES 3种湍流模型对小流量工况下半开式离心泵的流量-扬程曲线和内部流场进行了数值模拟。为了验证模拟结果,应用二维粒子图像测速技术(PIV)对离心泵的内部流场进行了实验测量。研究证明:对于半开式离心泵流量-扬程曲线的预测,3种数值方法都能比较准确的进行预测;而对于内部流场的预测,标准k-epsilon和SST湍流模型不能得到准确全面的结果,而DES方法则可以较为准确的预测出内部流场细节。