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一种“两相流”离心泵叶轮的水力设计方法
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作者 于京诺 朱天博 +1 位作者 王亮申 张永利 《流体机械》 CSCD 北大核心 2008年第3期33-38,共6页
基于普朗特的边界层思想,在二维离心场内给出了叶片近壁表面固液两相流体的边界层方程及其解的表达式和边界层厚度的有限次逼近算法。并以所得到的边界层参数为依据进行叶轮的水力设计以确定叶片型线及叶轮出口参数。通过对比实验的比较... 基于普朗特的边界层思想,在二维离心场内给出了叶片近壁表面固液两相流体的边界层方程及其解的表达式和边界层厚度的有限次逼近算法。并以所得到的边界层参数为依据进行叶轮的水力设计以确定叶片型线及叶轮出口参数。通过对比实验的比较,验证了设计结果的合理性,同时也验证了采用该理论进行设计所得到的产品,能够避免或减少由边界层分离所造成的脱流损失,改善了主流区的压力分布,使得水力效率相对提高,振动和噪音相对降低。不仅如此,通过实例设计的结果可以看出,该计算方法,能够在工程设计中实现计算边界层参数的要求。最后指出所给方法可以指导离心式固液两相流泵的工程设计。 展开更多
关键词 离心式固液两相流泵 边界层分离 边界层设计 对比试验
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永磁同步电机无传感器控制的软开关滑模观测器 被引量:85
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作者 陆婋泉 林鹤云 +1 位作者 冯奕 韩俊林 《电工技术学报》 EI CSCD 北大核心 2015年第2期106-113,共8页
针对滑模观测器估计中存在的抖振问题,采用边界层可变的正弦型饱和函数替代传统开关函数,提出了一种用于永磁同步电机无传感器控制的软开关滑模观测器。为了确定不同饱和函数的收敛速度,定义等效收敛区间,通过正弦型饱和函数边界层内的... 针对滑模观测器估计中存在的抖振问题,采用边界层可变的正弦型饱和函数替代传统开关函数,提出了一种用于永磁同步电机无传感器控制的软开关滑模观测器。为了确定不同饱和函数的收敛速度,定义等效收敛区间,通过正弦型饱和函数边界层内的滑模状态表达式推导其等效收敛时间,并与现有初等、终端滑模型和双曲正切型饱和函数进行了对比。为扩大滑模观测器的速度适用范围,确定了开关增益的转速自适应律。利用锁相环方法提取转子位置与速度信息,解决由滤波器引起的相位误差。通过仿真分别分析了饱和函数类型和开关增益、等效收敛系数及边界层厚度等系数对估计精度与收敛时间的影响,验证了正弦型饱和函数的有效性。实验结果表明,正弦型软开关滑模观测器能够准确地观测出转子速度和位置,并很好地消除了估计结果的抖振。 展开更多
关键词 永磁同步电机 滑模观测器 边界层设计 等效时间收敛
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Boundary Layer Development on a Concave Surface: Flow Visualization and Hot Wire Velocity Measurements
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作者 Farouk Hachem Mahmoud Khaled Mohamad Ramadan Charbel Habchi 《Journal of Energy and Power Engineering》 2014年第7期1177-1182,共6页
Gortler vortices are key issues in the design of gas turbine blades. The present study deals with flow visualization over concave surface for gas turbine applications. The aim is to comprehend qualitatively the flow t... Gortler vortices are key issues in the design of gas turbine blades. The present study deals with flow visualization over concave surface for gas turbine applications. The aim is to comprehend qualitatively the flow trends, particularly the Gortler vortices formation and development. Gortler vortices have the shape of mushroom-like vortices regularly spaced at 25 mm. These vortices grow and increase in strength more rapidly along the surface in the case of the same grid of turbulence applied to the measuring section. The curvature radius of the studied blade is 0.5 m and the stream turbulence intensity level is 2.6%. The velocity field is measured by hot wire anemometer in the streamwise direction. The velocity profile is found to be highly distorted by the momentum transfer associated with Gortler vortices. The results are compared to Blasius flow and to literature data for a blade with curvature radius equal to 2 m. 展开更多
关键词 Gortler vortices concave surface flow visualization velocity profile gas turbine.
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Numerical simulation of gurney flaps lift-enhancement on a low reynolds number airfoil 被引量:4
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作者 HE Xi WANG JinJun +3 位作者 YANG MuQing MA DongLi YAN Chao LIU PeiQing 《Science China(Technological Sciences)》 SCIE EI CAS CSCD 2017年第10期1548-1559,共12页
Two-dimensional steady Reynolds-averaged Navier-Stokes (RANS) equations with transition shear stress transport (SST) model were solved to investigate the effects of Gumey flaps on the aerodynamic performance of a ... Two-dimensional steady Reynolds-averaged Navier-Stokes (RANS) equations with transition shear stress transport (SST) model were solved to investigate the effects of Gumey flaps on the aerodynamic performance of a low Reynolds number airfoil. This airfoil was designed for flight vehicles operating at 20 km altitude with freestream velocity of 25 rn/s. The chord length (C) of this airfoil is 5 m and the corresponding Reynolds number is 7.76× 10^5. Gurney flaps with the heights ranging from 0.25%C to 3%C were investigated. It has been shown that Gurney flaps can enhance not only the prestall lift but also lift-to-drag ratio in a certain range of angles of attack. Specially, at cruise angle of attack (3°), Gurney flap with the height of 0.5%C can increase lift-to-drag ratio and lift coefficient by 1.6% and 12.8%, respectively. Furthermore, the mechanisms of Gumey flaps to improve the aerodynamic performance were illustrated by analyzing the surface pressure distribution, streamlines and trailing-edge flow structure for this low Reynolds number airfoil. Specially, distinguished from some other numerical researches, the flow details such as the laminar separation bubble and transition phenomena for low Reynolds number airfoil with Gumey flaps were investigated and it was found that Gurney flaps can delay the transition onset position at small angles of attack (≤2°). However, with the increase of angles of attack, Gurney flaps will promote the boundary layer transition. 展开更多
关键词 gurney flaps lift-enhancement low reynolds number numerical simulation
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