流-声-固耦合诱发结构振动及其抑制实验

流体诱发声共振引起叶片振动是压气机内部非同步振动问题的典型代表。现有研究多关注声共振中的涡声耦合,而对声共振引发的结构振动问题较少涉及。为了研究声共振中复杂的流-声-固三场耦合现象,在低速风洞中开展了铝制平板的声共振实验,对平板尾缘脱落涡脉动速度、管道内声压、平板振动进行了同步测量。实验结果捕获了频率锁定、幅值突跃现象,发现声共振引起的平板振动幅值可达流致结构共振幅值的50%,表明声共振诱发振动在工业应用中需引起重视。最后,研究了基于壁面非局域声衬的声共振抑制策略,实现了对管道内声压、平板振动的双重抑制。

火电厂大截面烟道低流速测量仿真研究

针对深度调峰背景下火电厂烟道烟气流速低、传统动压法测量精度不能满足要求等情况,基于COMSOL仿真软件,对烟道烟气流速尤其是5 m/s以下低流速超声测量进行了理论分析和数值仿真研究。论文首先介绍了时差法超声波测速原理并分析了主要误差来源,然后通过仿真获得了换能器“一发两收”下的流场分布特性、声-流耦合下的声波传播过程及换能器接收端面的声压分布情况,最后分析了不同流速下测量误差的变化趋势。模拟结果表明:在流速1~30 m/s的情况下,可将测量误差有效地控制在0.7%以内。回流式风洞实验结果表明超声波时差法在大截面低流速状态下具有较高的可靠性,在1~15 m/s速度范围内的最大测量误差为3.3%。

Electrical field tuning of magneto-Raman scattering in monolayer graphene

In this work, we report the electrical field tuning of magneto-phonon resonance in monolayer graphene under magnetic fields up to 9 T. It is found that the carrier concentration can drastically affect the G （E2g） phonon response to a varying magnetic field through a pronounced magneto-phonon resonance （MPR）. In charge neutral or slightly doped monolayer graphene, both the energy and the line width of the E2g phonon show clear variation with magnetic fields. This is attributed to magneto-phonon resonance between magnetoexcitations and the E2g phonons. In contrast, when the Fermi level of the monolayer graphene is far away from the Dirac point, the G band shows weak magnetic dependence and exhibits a symmetric line-shape. This suggests that the magneto-phonon coupling around 4 T has been switched off due to the Pauli blocking of the inter-Landau level excitations. Moreover, the G band asymmetry caused by Fano resonance between excitonic many-body states and the E2g phonons is observed. This work offers a way to study the magnetoexcitation phonon interaction of materials through magneto-Raman spectroscopy with an external electrical field.