喷水推进混流泵叶轮三元可控速度矩设计

本文介绍了混流泵叶轮叶片一种准三元设计法。以速度矩Vur为控制变量,通过正反问题迭代计算从而构制出叶片,力求使叶轮叶片形状与叶轮内实际流态相吻合,从而得到性能优异的混流泵。     

发动机排气消声系统与催化装置的匹配研究

应用GT-Power软件建立某摩托车发动机工作过程的仿真模型,并通过与消声器模型的耦合仿真,得到改进前后消声器的插入损失和压力损失。仿真结果表明,改进后的消声器在压力损失变化不大的前提下,使得插入损失增加了5~9dB(A)。计算结果可为排气消声器的设计和性能的改善提供指导。     

PD雷达解速度模糊中冗余量的选择分析

分析了PD雷达解速度模糊中存在的冗余量选择问题。对比了相控阵雷达利用数字波束形成(DBF)搜索方位和PD雷达频率估计的相似性,提出一种减小冗余量的方法。通过大量的数据仿真,验证了该方法能有效降低解模糊的冗余量,提高PD雷达的估计频率并保证解模糊的准确度。     

采用高阶边界元法的楔形体变速度入水数值模拟(英文)

A high order boundary element method was developed for the complex velocity potential problem. The method ensures not only the continuity of the potential at the nodes of each element but also the velocity. It can be applied to a variety of velocity potential problems. The present paper, however, focused on its application to the problem of water entry of a wedge with varying speed. The continuity of the velocity achieved herein is particularly important for this kind of nonlinear free surface flow problem, because when the time stepping method is used, the free surface is updated through the velocity obtained at each node and the accuracy of the velocity is therefore crucial. Calculation was made for a case when the distance S that the wedge has travelled and time t follow the relationship s=Dtα, where D and α are constants, which is found to lead to a self similar flow field when the effect due to gravity is ignored.     

应用RANS(雷诺平均的纳维尔一斯托克斯方程)和动量理论进行螺旋桨诱导速度的计算研究(英文)

In order to provide instructions for the calculation of the propeller induced velocity in the study of the hull-propeller interaction using the body force approach,three methods were used to calculate the propeller induced velocity:1) Reynolds-Averaged Navier-Stokes(RANS) simulation of the self-propulsion test,2) RANS simulation of the propeller open water test,and 3) momentum theory of the propeller.The results from the first two methods were validated against experimental data to assess the accuracy of the computed flow field.The thrust identity method was adopted to obtain the advance velocity,which was then used to derive the propeller induced velocity from the total velocity field.The results computed by the first two approaches were close,while those from the momentum theory were significantly overestimated.The presented results could prove to be useful for further calculations of self-propulsion using the body force approach.     

基于扰动压力与速度测量水中目标航向与航速的新方法

从不可压理想定常流动的伯努利方程出发,依据水中航行体对水中某点的扰动压力与扰动速度的相关性,提出了基于水中航行体对水中一点的扰动压力与扰动速度测量该航行体的航行速度与航向的新方法。船模实验表明,该方法能较准确地测量出水中航行体的航向与运动速度,航向测量误差在5%以内,速度测量误差在20%以内,说明该方法具有实际应用前景。     

船舶机舱通风数值模拟分析

利用CFD技术对某船舶机舱通风系统进行数值模拟,提出机舱气流组织改进措施.选取舱内典型截面进行分析,指出可以通过安装隔屏来消除舱内大漩涡,同时调节机械抽风口数量和位置,可使舱内气流组织得到改善;对舱内人员活动区域进行分析,表明活动区域环境速度、温度均符合设计要求,而且风机开度与舱内温度密切相关,根据舱内不同温度要求合理选择开度可节省资源.模拟结果证明CFD技术有利于机舱通风设计,为通风系统的改进提供了有力工具.     

双向自增力式制动器摩擦模型的研究

为了科学准确地描述双向自增力式制动器的摩擦系数和速度温度等因素间的关系。综合考虑静摩擦到动摩擦非线性阶段,动摩擦速度稳态阶段以及动摩擦随温度变化阶段,建立了制动器制动过程的摩擦模型,并用仿真曲线与制动过程曲线对比,验证了摩擦模型。     

提高路基压实质量监测密度的途径与方法

路基施工质量检测技术落后和检测密度过低是导致路 基工后沉降过大及产生路基病害的主导因素,在指出目前检测 技术不足的基础上,提出解决检测技术落后和检测密度低的技 术途径,论述了面波测试技术用于路基施工质量检测的技术原 理,并进行了相应的可行性分析。     

光纤式转速测量系统的研究

介绍了用光纤作为转速传感探头的转速测量原理，分析了探头作用距离与探头参数之间的关系，给出了一些解决干扰问题的方法，对电路部分作了必要的说明，本系统探头体积小，易于安装，无电火花，抗电磁辐射，具有传统测量方法所不具备的优点。