共查询到19条相似文献,搜索用时 421 毫秒
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转子作为魔角旋转(MAS)探头一个至关重要的部件,是固体样品高速旋转的载体,被广泛应用于各种固体核磁共振(NMR)实验.但国内关于MAS转子的研究极少,以至其长期被国外市场垄断.本文通过对MAS转子的深入研究,设计了常规的4 mm MAS转子;并对MAS转子进行了流固耦合仿真,分析其应力应变大小;同时进行了模态仿真,确定了MAS转子的各阶振型及临界转速;最后制作了转子,进行了转速测试和固体NMR实验.结果表明,本文设计和制作的转子能在14 kHz转速下正常运行,并在4 kHz及12.5 kHz转速下采集了金刚烷标样的1H NMR信号,结果表明该转子能满足常规固体NMR实验的需求. 相似文献
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非设计工况下1+1/2对转涡轮性能研究 总被引:1,自引:0,他引:1
为了研究和改善1 1/2对转涡轮性能,本文对1 1/2对转涡轮两种转速下不同落压比共16种工况进行了数值研究,并与实验结果进行了对照.结果表明近设计工况下计算结果和实验值吻合较好.1 1/2对转涡轮出口背压对高压转子性能影响较小,对低压转子性能影响较大,这导致变工况下1 1/2对转涡轮高低压轴出功比变化较大.通过对某典型非设计工况和设计工况下的流场结构的分析发现非设计工况下1 1/2对转涡轮高压动叶中发生了明显的流动分离.高低压动叶不能很好地匹配,需要采取合理的流动控制措施去改善已有1 1/2对转涡轮的变工况性能. 相似文献
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《工程热物理学报》2020,(7)
针对凝汽器背压高和管内结垢问题,研发了具有自清洁能力的管内扰流物。为研究凝汽器管内置扰流物(内插转子)的综合性能,搭建了流动及抑垢实验台,建立了MRF数值模型。通过数值和实验方法,分析了内插转子的管内流动、换热及抑垢特性。结果表明,与传统转子相比,新型转子在阻力降低1/2的同时,增强换热10%~15%。其中空的结构形式对中心区域扰动较弱,能防止阻力增加过大。而对壁面附面层的层流底层的扰动,可增加壁面处的温度梯度有利于强化换热。内插转子可使污垢长期处于诱导期,避免管内污垢过快附着和增长。应用于某300 MW机组凝汽器,测算数据表明具有较高的运行稳定性和可靠性,在不同的负荷下均能提高真空度,起到节能降耗的效果。 相似文献
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离心泵瞬态操作条件下内部流动的数值模拟 总被引:5,自引:1,他引:4
为研究离心泵在瞬态操作条件下的内部非定常流动演化过程,分析外部瞬态特性的内流机理,采用滑移网格方法对快速启动过程中的离心泵内部流动进行数值模拟.建立了包含循环管路和泵在内的完整系统模型,分析了叶轮从静止到最高转速的瞬态过程的流动演化,比较了管路阻力特性对瞬态特性的影响,探讨了数值方法对求解三维瞬态流动的适应性.分析结果表明,基于非定常流动分析的瞬态外特性预测结果与实验结果能较好吻合,所采用的计算方法和得到的结果为瞬态操作条件下离心泵内部流动的诊断和优化建立基础. 相似文献
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周向弯曲低压轴流风机叶顶泄漏流动数值研究 总被引:8,自引:0,他引:8
本文采用数值模拟的方法,对三种带有周向弯曲叶片的低压轴流通风机(原型叶轮、周向前弯及后弯叶轮)的叶顶泄漏流动进行了研究。在数值计算与试验测量结果较为吻合的条件下,从流场和压力场等不同角度分析探讨了叶片周向弯曲后,叶顶泄漏流动和泄漏涡的形成和发展规律。数值计算结果表明,叶顶周向前弯加剧了泄漏涡与主流的掺混;周向后弯叶轮比前弯叶轮有助于减弱叶顶泄漏流动;强度大、衰减慢的泄漏涡,降低了叶顶的通流能力,同时与主流的掺混加剧也增大了叶轮的端部损失;此外,顶部间隙高度的增加,泄漏流动加强,旋涡的起始点更靠近叶片后缘。 相似文献
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S.E. Wright 《Journal of sound and vibration》1976,45(2):165-223
Rotor spectra from a variety of axial flow machines have been compared and acoustic trends examined. Types of rotor considered in the investigation included aircraft propellers, helicopter rotors, jet engine compressor and by-pass fans and a range of domestic, automotive and industrial cooling fans. Rotor sizes varied from 15 in to 60 ft in diameter and tip speeds from 200 ft/s to transonic speeds.The study showed that the acoustic output from these various rotor devices can be described by a common characteristic spectrum. In particular, the minimum broad band noise generated by ducted and free field rotors corresponds to laminar and turbulent boundary layer shedding, and discrete excess noise is generated by various degrees of impulsive blade loading. Finally the study showed that aerodynamic details can be interpreted from the acoustic spectra, and as a result, new insight into the mechanisms of rotor noise has been formed. 相似文献
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从非定常效应看对旋风扇/压气机的工程实现 总被引:5,自引:0,他引:5
首先利用全隐格式的非稳态压力修正求解方法;计算对旋风扇级间流场非定常流动情况,并与实验结果进行了有益的对比;在动态实验研究中则通过单斜丝热线风速仪对对旋风扇级间速度场进行了详细分析,并揭示其级间非定常效应的独特规律:下游转子的非定常位势流作用在对旋级间流场的周期性非定常影响中占主导地位,级间径向速度的大小则主要与前级转子叶尖区和叶根区的二次流动旋涡强度有关.上述结果表明:对旋风扇/压气机的非定常效应对其性能有很大影响,如果很好地组织对旋叶轮的非定常流动气动布局,可进一步提高增压系统的压比、效率和稳定工作范围。 相似文献
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弯掠动叶对跨声压气机非定常气动负荷的影响 总被引:4,自引:0,他引:4
对一单级跨声压气机设计工况采用弯掠动叶前、后的非定常流场进行了数值模拟,深入分析了动叶弯掠对压气机叶片非定常气动负荷的影响.结果表明t动叶弯掠后,动、静叶的气动力和气动力矩时均值由于叶片负荷大小及分布的不同变化而产生不同程度的改变;由于动叶对下游静叶的尾迹和二次流干扰远强于动叶所受到的下游静叶的势流干扰,静叶的气动负荷发生较大波动;弯掠动叶减轻了端壁损失并且减弱了顶部泄漏涡强度和根部角区分离,从而减弱了对下游静叶的非定常干扰,这使得静叶各气动参数的波动幅值显著降低. 相似文献
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Adnan Mustafic Hsuan-Ming Huang Emmanuel A. Theodorakis Mark A. Haidekker 《Journal of fluorescence》2010,20(5):1087-1098
Molecular rotors are a group of fluorescent molecules that form twisted intramolecular charge transfer states (TICT) upon
photoexcitation. Some classes of molecular rotors, among them those that are built on the benzylidene malononitrile motif,
return to the ground state either by nonradiative intramolecular rotation or by fluorescence emission. In low-viscosity solvents,
intramolecular rotation dominates, and the fluorescence quantum yield is low. Higher solvent viscosities reduce the intramolecular
rotation rate, thus increasing the quantum yield. We recently described a different mechanism whereby the fluorescence quantum
yield of the molecular rotor also depends on the shear stress of the solvent. In this study, we examined a possible application
for shear-sensitive molecular rotors for imaging flow patterns in fluidic chambers. Flow chambers with different geometries
were constructed from polycarbonate or acrylic. Solutions of molecular rotors in ethylene glycol were injected into the chamber
under controlled flow rates. LED-induced fluorescence (LIF) images of the flow chambers were taken with a digital camera,
and the intensity difference between flow and no-flow images was visualized and compared to computed fluid dynamics (CFD)
simulations. Intensity differences were detectable with average flow rates as low as 0.1 mm/s, and an exponential association
between flow rate and intensity increase was found. Furthermore, a good qualitative match to computed fluid dynamics simulations
was seen. On the other hand, prolonged exposure to light reduced the emission intensity. With its high sensitivity and high
spatial and temporal resolution, imaging of flow patterns with molecular rotors may become a useful tool in microfluidics,
flow measurement, and control. 相似文献