声场流化床A类颗粒浓度分布研究

在内径140 mm,高1 600 mm的鼓泡流化床中,以流化催化裂化(FCC)颗粒为流化介质,采用光导纤维探针测定不同轴/径向位置的颗粒浓度分布.考察了操作气速和外加声场对密相区颗粒浓度的影响.结果表明,鼓泡床密相区颗粒浓度沿轴向逐渐减小,沿径向呈抛物线分布.声场的引入可以降低颗粒起始流化速度:声压级越大,起始流化速度越小:固定声压频率在150 Hz时颗粒起始流化速度最小.1随着声压强度的增大,床层中心区和上部密相区颗粒浓度增大.固定声压级,频率在100～400 Hz颗粒浓度较大,频率低于100 Hz或高于400 Hz时,声波的作用效果减弱.     

纳米TiO_2颗粒在声场导向管喷动流化床中的流化特性

在内径120 mm的半圆柱型声场导向管喷动流化床中,以平均粒径290 nm的TiO_2颗粒为原料,高速空气射流为喷动气,考察了操作条件、声参数(频率和声压)对纳米颗粒在声场导向管喷流床中的流态化特性的影响。结果表明:声波可以有效抑制沟流,改善环隙流化质量,防止射流旁路,从而促使粉体稳定循环,加快循环速率;同时声波可以显著地降低纳米TiO_2颗粒的最小喷动速度,声波频率一定时,最小喷动速度随声压的增加而减小;声压一定时,最小喷动速度在声波频率为80 Hz时达到最小值,低于或者高于80 Hz,最小喷动速度都会增大。     

基于虚拟仪器的活塞发声腔校准系统的设计与实现

随着次声校准的需求越来越多,而传统的互易法校准在低频段受气体泄漏影响很大,校准效果不好,新式的激光式活塞发声腔校准法更适用于次声传声器校准。设计并实现了一套基于虚拟仪器的激光式活塞发声腔校准系统,采用超低频振动台技术,其活塞位移失真度很小,腔体中声压级稳定,声压级范围大。校准系统的软件设计灵活方便,加入声压反馈后能得到声压级很稳定的声源。     

可吸入颗粒物声场团聚实验研究

在中等强度驻波声场中,对燃煤可吸入颗粒物进行团聚清除实验研究。系统研究声场频率、声压级、可吸入颗粒质量浓度及颗粒在声场中的停留时间对团聚清除效率的影响。实验结果表明:颗粒在声场中团聚的最佳声波频率为1 416 Hz;声压级越高越有利于颗粒的团聚,声压为128 dB时颗粒质量清除效率高达27.8%;可吸入颗粒质量浓度增大,颗粒清除效率降低;颗粒在声场停留时间为9—11 s时,团聚清除效率达到最大值。颗粒粒径影响声波团聚过程,粒径1.1μm与4.7—10μm颗粒的清除效率高于1.1—4.7μm颗粒的清除效率。     

声场高温流化床流化特性

在内径50 mm、高1000 mm的声场高温鼓泡流化床中,研究Geldart A, B两类颗粒的流化特性,考察了床层温度、声波频率及声压级对流化床最小流化速度的影响. 结果表明,引入声场后,颗粒的最小流化速度随温度升高而下降;固定温度及频率,最小流化速度随声压级增大而减小;固定声压级与温度,颗粒最小流化速度随声波频率增大先减小后增大,存在一个最佳频率范围. 对床内压力波动信号进行分析,得出声场影响高温流化床流化质量的判据：当声压大于110 dB、频率在100~200 Hz范围内时压力波动偏差与最小流化速度值最小.     

锂掺杂氧化锌纳米颗粒晶体结构与光学特性分析

利用溶胶-凝胶法制备了Li_xZn_(1-x)O纳米颗粒,分析了锂掺杂对氧化锌纳米颗粒晶体结构与光学特性的影响。结果表明,锂掺杂会使氧化锌所受应力由压缩应力变为伸张应力,晶粒尺寸随锂掺杂量增加而减小,并且使氧化锌容易朝向(002)方向成长,造成结构系数TC(002)增大。光致发光光谱观测揭示锂掺杂能促使氧空位相关缺陷增多,同时也使得近能带发光强度增强。拉曼光谱显示多声子模态随锂掺杂量增加而减弱,且掺杂量为0.10(物质的量分数)时多声子模态信号最小,而掺杂量为0.15(物质的量分数)时多声子模态信号再度增强。多声子模态信号与非辐射复合相关,多声子模态信号越弱表示非辐射复合缺陷越少,故造成光致发光光谱的NBE峰强度增强。     

声场流化床中超细颗粒聚团受力与尺寸

在内径40 mm的流化床中,采用平均粒径为7.4 mm的超细铁矿颗粒进行声场流态化实验. 结果显示,聚团尺寸随声压级增大逐渐减小,在固定声压级的条件下存在最优声波频率,本实验为130 Hz. 由铁矿颗粒声场流态化中聚团受力分析提出聚团受力平衡模型,当促进聚团破碎的力和促进聚团形成的力相等时,计算出一定频率不同声压级下的聚团尺寸,在频率130 Hz、声压120.5 db下,根据模型计算得到的聚团直径为384 mm,而通过最小流化速度计算值为367 mm,二者较接近.     

声场高温流化床流化特性的实验研究

本文系统分析了温度、声波频率、声压级对GeldartB类颗粒初始流化速度和反应器内压力波动的影响规律。实验结果显示:当反应器内加入声场,颗粒的初始流化速度随着温度的升高急剧下降,随声压级的增大而减小,随声波频率的增大先减小后增大,并存在一个最佳频率范围。当温度超过400℃后,声压级对颗粒最小流化速度的影响增大。压力波动标准方差随气速的增大而增大;当声压级大于110 dB和声波频率处于100～200 Hz时压力波动标准偏差和颗粒初始流化速度达到最小值。     

结构对抗性消声器影响的性能分析

提高消声器设计水平对于提升我国机械质量有重要的意义。插入损失和压力损失是评价消声器消声性能和空气动力性能的两个非常重要的评价指标。本文利用COMSOL软件研究消声单元结构对消声器速度场和压力场的影响。当插入管长度相同时,消声器的出口处气体流速基本相同,位于内插管根部位置出现气流"盲区"。入口内插管的压降随插入管长度的增加而增加,当入口插入管长度为0时,出口插入管长度增加,入口处的声压保持基本不变,出口声压发生变化,且在入口区域,声压逐渐减小在扩张室入口两侧存在最小值。扩张室内,最大声压级发生在出口位置的两侧,且较小声压级区域随出口插入管长度的增加而减小。     

固体颗粒对油水界面性质及乳状液稳定性的影响

采用界面张力仪、表面粘弹性仪和Zeta电位仪,研究了固体颗粒对胜利原油油水界面性质及乳状液稳定性的影响。结果表明,固体颗粒的存在使得油水界面张力及界面剪切粘度增加,O/W型乳状液的稳定性增加,而且随固体颗粒浓度增加,乳状液稳定性增强;在0.21~500μm范围内,固体颗粒粒径减小,其与原油形成的O/W乳状液稳定性增强,乳状液内部油珠表面Zeta电位负值增加。     

Flow characteristics in an acoustic bubbling fluidized bed at high temperature

The pressure fluctuation of the quartz sand and SiO₂ particles was investigated using pressure transducer in high temperature fluidized bed with sound assistance. The effects of bed temperature, sound wave frequency, and sound pressure level (SPL) on the pressure fluctuation were examined. It indicates that the minimum fluidization velocity decreases with an increase in sound pressure level at the same sound frequency. At the same SPL and bed temperature, there always exists an optimal frequency range achieving good fluidization quality. As the sound frequency increases, the minimum fluidization velocity decreases firstly and then increases. Based on the statistical analysis of pressure signals, the effect of sound frequency on the fluidization quality at high-temperature fluidized bed was presented. On basis of discrete wavelet transform, an original signal was resolved into five-detailed scale signal. Furthermore, the peak frequency for Scale 3 detail signal represents the bubbling frequency.     

超细颗粒在声场流化床中的流化特性

在内径为130mm的声场流化床中,以原生纳米级SiO2超细颗粒为物料,在声压水平为0～140dB、声波频率为0～500Hz范围内系统地考察了声波对超细颗粒流化特性的影响。结果表明：当声波频率为100～150Hz、声压大于130dB时,声波可以有效地消除节涌、抑制沟流、降低临界流化速度,显著地改善纳米SiO2颗粒的流化质量。在频率一定的情况下,声压越高,超细颗粒的临界流化速度越低,流化质量越好。当频率低于100Hz或高于150Hz时,随着频率的进一步降低或增加,超细颗粒的临界流化速度都增大,甚至又出现节涌和沟流。声波的效果减弱甚至消失。     

Single-layer graphene sound-emitting devices: experiments and modeling

Single-layer graphene (SLG) was demonstrated to emit sound. The sound emission from SLG had a significant flat frequency response in the wide ultrasound range from 20 kHz to 50 kHz. SLG can produce a sound pressure level (SPL) as high as 95 dB at a distance of 5 cm with a sound frequency of 20 kHz. The SPL value is among the highest reported to date for sound-emitting devices (SEDs) based on the thermoacoustic effect. A theoretical model was established to analyze the sound emission from SLG. The theoretical results are in good agreement with the experimental results. Conventional acoustic devices with a large size can be reduced to the nano-scale by using this novel SLG-SED material. It has the potential to be widely used in speakers, buzzers, earphones, ultrasonic transducer, etc.     

补气增焓热泵机组在供热工况下的噪声特性

以自行开发的一台补气增焓空气源热泵机组为实验对象,通过分步运行法对机组噪声源进行识别和频谱分析,研究变工况下机组供热性能及噪声变化规律,通过对噪声特性和变化规律原因的探究,为针对性地降低机组噪声提供了方向。结果表明：风机旋转噪声频率和压缩机激励频率接近时,噪声声压级会放大;风机在部分负荷工况下从高转速切换到低转速,噪声下降了6.44 dB;补气提高了补气压力和吸气压力,导致管路噪声增大,−12℃环境温度下噪声较补气阀关闭时增加了1.05 dB;主路阀开度100%时噪声声压级较开度30%时增加了2.1 dB,主路膨胀阀开度对噪声的影响大于补气膨胀阀。     

聚合物基复合材料隔声性能的研究

分析了无机粒子填充聚合物复合材料的隔声原理，指出其隔声效果的改善可归因于粒子使声波多次折射、散射和绕射导致传播路径增加，以及粘弹性的改变令声能消耗增大。测试了几种聚合物基复合材料的隔声性能，结果表明，隔声效果服从质量定律，且含中空粒子的复合材料具有更优越的隔声性能。     

Experimental study of acoustic agglomeration of coal-fired fly ash particles at low frequencies

This paper presents an experimental study of acoustic agglomeration of coal-fired fly ash particles in travelling sound waves. The ranges of variation of the main physical parameters are as follows: acoustic frequency, f = 700-3000 Hz; sound pressure level (SPL), SPL = 130-147 dB; residence time, t = 3-7 s; aerosol number concentration, N₀ = 1.0 × 10⁵-3.7 × 10⁵ /cm³. A 68.4% decrease in total number concentration is gained under an SPL of 147 dB and a frequency of 1400 Hz. Aggregates larger than 10 µm are observed in scanning electron microscopy photographs. The results show that the effect of sound waves is very sensitive to the frequency change, which means that orthokinetic interaction governs the process. There exists an optimum frequency for a given particle size distribution, which decreases slightly as SPL increases. The influences of SPL, residence time and initial total number concentration are also studied.     

Noise control and experimental study of a highpressure oil pump enclosure

ABSTRACT

The present experimental study has been conducted to evaluate the impact of an acoustic enclosure of high-pressure oil pump, which is used to reduce the noise emission of an automobile engine. The enclosure is double-layered and made of nylon 66 (PA66) as an outer structure and polyurethane foam as the inner material. The sound signals of the engine were measured separately without an acoustic enclosure and covered by the enclosure. The signals were measured with 5 microphones around the engine under two electric loading conditions (0% and 100% load). The results revealed that the sound pressure level (SPL) of the engine increased significantly with the high-pressure oil pump installed, and the gap between SPL was larger for 100% load than 0% load. Furthermore, the enclosure of high-pressure oil pump was effective to attenuate the engine noise at almost the entire audio frequency range. The SPL reduced approximately 2?dB within nearly the entire test frequency range, supporting the remarkable noise reduction effect of the high-pressure oil pump enclosure.     

Quantitative analysis of the effects of ultrasound from an odor sprayer on moth flight behavior

A piezoelectric sprayer was recently developed for precision release of odor stimuli in olfactory research. The device replaces conventional dispensers used to release semiochemicals in studies of moth flight toward odor sources. However, the device generates high-frequency sounds in the range that some moths can hear. Ultrasound from the standard set-up sprayer had a considerable impact on flight behavior of the silver Y moth, Autographa gamma, tested in a flight tunnel. It was affected at all behavioral stages when the dispenser was driven at 120 kHz. Only 5% of the moths reached the source when exposed to 120-kHz sound from the dispenser compared to 65% in the control group without sound. The proportion taking flight was also reduced. Hearing threshold curves obtained electrophysiologically revealed that moths were sensitive to the frequency range at which the sprayer was operated and that sound intensity from the sprayer was up to 40 dB above the moths' electrophysiological hearing threshold. The audiogram for A. gamma was similar to audiograms obtained for other noctuids. Hearing sensitivity was highest at around 15 kHz, where the threshold was 35 dB SPL (sound pressure level). The threshold increased with frequency up to 94 dB SPL at 160 kHz. We improved the sprayer to operate at 300 kHz, which is beyond the hearing ability of most insects with ears. At this high frequency, the moths' sensitivity to ultrasound is reduced considerably, and we did not observe any effect on flight behavior compared to a control group without sound. Accordingly, this new piezoelectric sprayer can be used with ultrasound-sensitive insects and insensitive insects alike.