基于Wagner函数的卷弧翼非定常气动力分析

为研究卷弧式尾翼的气弹特性,基于Wagner函数,建立了卷弧尾翼在非定常气动条件下的升力及滚转力矩模型。以此为基础,针对在特定振荡频率的攻角激励作用下,不同张开角度、弦长及分布数量翼片的升力,不同安装及滚转方向翼片的滚转力矩,进行了数值仿真分析,并利用fluent仿真软件进行了建模仿真验证。结果表明升力响应幅值随着张开角及弦长的增大单调递增,不同分布数量尾翼的升力近似相等,反装反旋安装方式有效降低了尾翼滚转力矩。对于卷弧尾翼弹箭的优化设计,颤振特性分析以及锥形运动的抑制等问题具有积极意义。     

角度传感器的使用

你想不想知道植物是在白天长得快,还是在夜里长得快?单摆的周期与哪些因素有关?阻尼振动的情况是怎样的?这些问题都可以用角度传感器来测量。角度传感器是用低力矩电位器制成的,能测量0°～340°角的变化,标准度为正负0.2,最大负载为50克,转动力矩最大为0.25oz。使用时,用细线或细金属丝穿过转轴上的小孔,当细线或金属丝转动时就会带着转轴一起转动,角度传感器就会记录下转轴旋转的角度(图1)。当转轴     

节能型蒸汽计量技术分析

鉴于常用孔板测量蒸汽流量时会造成较大的压力损失,提出采用Verabar型流量传感器取代孔板,可取得明显的节能效果。     

GYG-1光纤压力传感器应变体力学模型设计

根据膜片式压力传感器的结构和特点,利用材料力学相关知识对其弹性体进行设计,并建立力学模型;根据膜片式压力传感器灵敏度要求,运用有限元分析方法进行分析,建立了既符合实际又简化的有限元模型;研究了弹性体的结构参数、温度、载荷等因素对传感器灵敏度的影响,为光纤光栅膜片式压力传感器的优化设计提供依据。     

动力伞伞翼阵风响应的数值模拟

采用有限体积法求解非定常Euler方程,并通过引入动态网格方法模拟阵风条件,对不同风速下水平和垂直阵风的伞翼气动力响应进行动态模拟与计算,针对动力伞伞翼柔性结构和飞行速度慢的特点,运用动态仿真方法求解阵风响应的附加气动力与力矩。结果表明:遇水平阵风时,伞翼气动力表现为多周期不同幅度的主动颤振运动;遇垂直阵风时,气动力响应基本与阵风速度变化趋势保持一致,最终稳定后气动力相对于阵风加载前变化不大。     

动力翼伞非线性动力学建模与仿真

关于空运翼伞控制问题建立合理的动力学模型,是实现动力翼伞飞行控制的前提条件之一.传统方法翼伞建模多数是针对不带动力情况下的翼伞建模,不能适应动力翼伞的飞行控制.假设翼伞承载物和软翼之间具有俯仰和偏航2个自由度,通过对承载物和软翼所受作用力和作用力矩进行分析,分别建立软翼和承载物体坐标系下的作用力和力矩的平衡方程,通过体坐标系转换和消除翼伞内部状态量,得到有利于实现动力翼伞控制的8自由度非线性动力学状态方程.仿真结果表明这种动力学模型正确有效,更有助于实现动力翼伞的飞行控制.     

复杂环境翼伞气动性能建模仿真研究北大核心CSCD

翼伞飞行环境复杂多变,常存在阵风与降雨干扰,对翼伞气动性能产生动态影响,造成系统失衡。传统模型忽视翼伞力矩失衡产生的俯仰运动,分析结果误差较大。针对时刻变化的流场环境与翼伞姿态,可借助CFD软件,通过网格速度模拟阵风、离散相模拟降雨、动网格模拟俯仰运动,对非定常Euler方程空间离散求解,得到阵风与降雨对翼伞气动性能的单独影响与耦合影响。利用修正后的翼伞模型进行仿真,结果表明,上述模型能较好描述翼伞气动性能在复杂环境中的变化规律,为翼伞精确建模与归航优化控制提供了参考。     

基于滑移网格海龟扑翼推进数值仿真研究

为了探讨海龟翼摆动时产生的流体推进力与摆动频率、幅度以及来流速度之间的关系,对海龟翼在不同工况下进行了数值仿真计算.针对海龟翼在粘性介质中运动,采用滑移网格技术,结合扑翼运动规律,建立扑翼推进数值计算模型,模拟海龟二维剖面翼以特定规律运动时的流体动力特性.通过数值仿真,得出扑翼推进力与摆动频率、摆动幅度以及来流速度之间的关系.经实践证明:翼静水中摆动平均推力随着摆动频率、幅度的增加而增大,且频率较大时随频率增大得更为明显,为下一步扑翼驱动机构设计打下基础,具有一定的实践指导意义.     

仿鸟扑翼飞行器仿真研究

针对仿鸟扑翼飞行器的柔性翼动力学仿真需要,在非定常空气动力学原理下,用修正的准定常气动力计算模型估算出了扑翼的动力学模型,并建立了其相应的状态空间方程,进而分析研究了在Matlab语言和Simulink环境下,对其仿真系统设计得需求和要求。     

液体自校正涡轮流量传感器的性能试验

从分析自校正涡轮流量传感器与传统涡轮流量传感器的不同出发,介绍了自校正涡轮流量传感器的三个仪表常数及性能评定,给出了样机在正常条件、阻力矩变化、上游旋转流动以及压力损失特性的试验结果。     

A pressure-correction method and its applications on an unstructured Chimera grid

In this paper, an unstructured Chimera mesh method is used to compute incompressible flow around a rotating body. To implement the pressure correction algorithm on unstructured overlapping sub-grids, a novel interpolation scheme for pressure correction is proposed. This indirect interpolation scheme can ensure a tight coupling of pressure between sub-domains. A moving-mesh finite volume approach is used to treat the rotating sub-domain and the governing equations are formulated in an inertial reference frame. Since the mesh that surrounds the rotating body undergoes only solid body rotation and the background mesh remains stationary, no mesh deformation is encountered in the computation. As a benefit from the utilization of an inertial frame, tensorial transformation for velocity is not needed. Three numerical simulations are successfully performed. They include flow over a fixed circular cylinder, flow over a rotating circular cylinder and flow over a rotating elliptic cylinder. These numerical examples demonstrate the capability of the current scheme in handling moving boundaries. The numerical results are in good agreement with experimental and computational data in literature.     

空气质量流量传感器的内部流道建模与设计

对于空气质量传感器中的热电阻表面流场分布,需要设计一种合适的内部小流道,能使得热电阻表面的流场分布合理.选择流场湍流模型,仿真分析了直线形壁面和几种圆弧形壁面的内部小流道的流场分布,研究了它们的流场分布特性,确定了热电阻的安装位置.仿真结果表明:与直线形流道相比,圆弧形流道具有较好的同一水平方向的速度一致性和较小的垂直...     

一种新型磁电感应式转矩传感器的研制

旋转机械设备转矩的准确测量对实现设备的状态监测和故障诊断有重要的作用,为此,设计了一种基于电磁感应原理的新结构转矩传感器。方法是将负载转矩产生的扭角信号转化成传感器励磁绕组和输出绕组的角位移,励磁绕组建立脉振磁通,经过电磁耦合输出绕组会产生与该角位移成正比的感生电动势。推导了传感器的输出特性,构建了传感器的数学模型,包括传递函数和状态空间描述。分析了传感器工作时的能控性和能观性,根据李雅普诺夫稳定判据,证明了传感器工作时的渐进稳定性。最后对传感器进行了标定,实验结果是传感器的灵敏度约为2.8 mV/(N·m),最大重复性误差约为1.24%,最大非线性误差约为0.78%,最大迟滞误差约为0.79%。     

A static turbine flow meter with a micromachined silicon torque sensor

A new class of flow sensors is introduced where a static turbine converts the volume flow into a torque. The structure consists of a turbine fixed to a torque sensor, which in turn is connected to the pipe wall giving a perfectly symmetric, bidirectional flowmeter. In contrast to conventional turbine flowmeters, the wheel does not rotate and consequently it is insensitive to bearing friction and wear that conventional, rotating turbines experience. Furthermore, the flow passing the wheel is distributed over the circumference of the wheel and levels out nonuniform flow profiles leading to profile independent volumetric flow measurement. The torque-sensing element is a 300-/spl mu/m-thick silicon cantilever, 2 mm wide and 16 mm long. The stiffness of the torque sensor, and thereby the sensitivity, is mainly determined by lateral dimensions of specially designed stiffness reduction parts defined by photolithography, thus giving good control of the sensitivity. Two polysilicon strain gauges are placed on each side of the cantilever, measuring the bending moment from the turbine wheel. The torque sensor has been evaluated for different geometries and together with the turbine to evaluate the flow sensing performance. A turbine with a blade length of 2.7 mm and a blade angle of 30/spl deg/ has a sensitivity of 4.0 /spl mu/V/V/(1/min)/sup 2/ when measured using the silicon torque sensor. The output signal shows good symmetry between different flow directions.     

Output Feedback Control of Surge and Rotating Stall in Axial Compressors

Active control has been widely studied to expand the stable operating range of axial flow compressors in aero‐engines.In this paper, a nonlinear active state feedback controller is proposed first based on bifurcation analysis results of MG model.Then by taking pressure ratio as output parameter, a state observer is designed to estimate the compressor's flow coefficient. An output feedback controller is thus established by combining the observer with the state feedback controller.Finally, digital simulation shows that the proposed output feedback controller not only eliminates the hysteresis loop associated with rotating stall and emergence of surge, but also extends the stable operating range of axial flow compressors effectively.Furthermore, being flexible in using pressure transducer and throttle valve as sensor and actuator respectively, which have been equipped in common engines, the proposed controller has good applicability.     

周期性脉动流对涡轮流量计测量精度影响的分析

提出流量计如何能在流动存在的情况下准确地测出测量。选择正弦脉动流讨论周期性脉动流对涡轮流量计测量精度的影响,认为脉动流频率的大小严重影响涡轮流量计测量精度,涡轮叶片转动惯量和稳态时的叶片转速也对精度有不同程度的影响。     

基于电磁感应原理的永磁旋转角加速度传感器研究

旋转系统的角加速度能够反映转轴对各种激励和动态干扰的响应,由此提出了一种基于电磁感应原理的永磁式旋转角加速度传感器。方法是通过永磁体建立恒定磁通,转子对磁通进行切割,存在瞬间角加速度时,传感器的输出绕组经过电磁耦合会产生与角加速度成正比的感生电动势。推导出了传感器的输出特性,并通过实验验证了传感器测量原理的正确性,经过理论分析得到旋转磁场的转速存在波动,是造成旋转系统产生角加速度的主要原因。构建了传感器系统的状态空间模型,对传感器的能控性和能观性进行了分析,并根据李雅普诺夫稳定判据,证明了传感器系统的大范围渐进稳定性。最后将传感器应用于振动转矩的测量并进行了标定,实验结果是该传感器的灵敏度约为39.08 mV/mN.m。     

基于多传感器融合的全地形机器人系统设计

针对因强降雨、堤防溃决、暴雨增水等因素导致的水位突然上升而泛滥和山洪暴发,形成复杂多变灾后的地形环境。设计了以FPGA为控制器的多传感器融合机器人,提高灾后救援效率。该机器人通过GPS为机器人作业划定区域,生命特征仪、力矩仪和空气质量仪等传感器采集环境数据,搭建非线性全地形机器人动态模型,利用六轴陀螺仪和霍尔传感器获取机器人状态,数据经过扩展卡尔曼滤波算法融合以及航迹算法推算后,获得机器人在灾后环境中的实际信息,使得机器人能够按要求进行搜救作业。实验结果表面,多传感器融合的机器人系统,能够在灾后环境完成信息采集与传输,具有较高的稳定性及准确性。     

Neural net based torque sensor using birefringent materials

Photoelasticity can be used to accurately measure surface strains or stresses in a part or structure. In this paper we describe the use of a photoelastic transducer and neural net image processing to estimate the torque of stationary and rotating shafts. A strain sensitive (photoelastic) plastic cylinder is attached to the shaft and illuminated by polarized light. As the shaft torque varies the photoelastic plastic displays the corresponding shaft strain as a two-dimensional fringe pattern when viewed through an optical polarizer. The strain that causes this observed optical pattern is a complex function of the torque applied to the shaft. In this paper, we describe the use of neural net image processing to estimate this function to realize an optical torque sensor. A CCD camera/image processing system was used to acquire and process the optical patterns. A neural net torque estimator was trained with these fringe patterns and tested against a laboratory strain gauge torque sensor. Our experiments show that the neural net torque estimator can accurately estimate (to within a few percent) the applied torque for both static and slowly rotating (<20 rpm) shafts.     

基于节流原理的新型流量传感器的特性分析

由于V形内锥式流量传感器的流出系数、压损等技术参数目前仍存在着不稳定因素,借助实流实验手段,分析了孔板式、纺锤式、V锥式三种节流方式下的流出特性,在相同流态下比较了它们的压损,证明了V锥式确实存在低压损特性。依据V形内锥式流量传感器特性参数的对比实验,详细分析了影响V形内锥式流量传感器流出系数的因素,并提出相应的改进方案。这对V形内锥式流量传感器的设计和制造有一定的促进作用。