超声波声场模拟及除垢实验研究

发布时间：2018-05-18 07:39

  本文选题：超声波 + 换能器　； 参考：《长沙理工大学》2014年硕士论文

【摘要】：换热器是暖通空调、热能工程、化工等领域的主要换热设备,这些设备在运行中普遍存在结垢现象,从而导致其传热效果下降,并影响设备安全。目前,常规除垢方法存在维护成本高、产生化学废液等问题,难以满足生产工艺需求,超声波除垢技术以其绿色环保、成本低廉、效果明显等优点得到推广。但是在工程应用中,由于超声波参数匹配及换能器布置不合理会造成除垢效率下降,以及换热器部分区域无除垢效果。因此,深入研究超声波除垢效率和范围是非常必要的。据有关学者研究,超声波的指向性决定了除垢范围,而声强则对除垢效率有一定影响。本文在点声源指向性函数基础上,建立了非点声源的指向性函数和声强的数学模型,并利用MATLAB软件模拟计算了在不同频率、换能器半径参数下超声波指向性函数分布情况,以及超声波声强与换能器半径、超声波频率、辐射角度之间的关系。根据模拟计算,得出以下结论：(1)超声波频率为28kHz时,换能器半径越大,指向性函数分布范围越小,声场逐渐向换能器垂直方向聚集,当换能器半径为50mm时,超声波指向性范围集中在换能器中心区域。(2)换能器半径为30mm时,频率越大,指向性函数范围越小,频率为60kHz时,超声波指向性范围达到最小。(3)超声波声强与功率的平方根成正比,与传播距离的二次方成反比,功率越大,声强越大；传播距离越远,声强越小。(4)超声波频率为40kHz时,随着换能器半径增大,换能器垂直方向处的声强值逐渐增大,其它辐射角度处的声强值较小,当半径为50mm时,声强在换能器垂直方向处达到最大。本文在理论研究的基础上,还进行了超声波除垢实验,根据实验研究,得出以下结论：(1)频率为20 kHz时,除垢范围最大,随着频率的增大,除垢范围逐渐缩小,集中在换能器圆心的垂直方向附近,换能器半径对除垢范围的影响规律与频率类似。除垢范围受频率和换能器半径的影响规律与指向性函数模拟图形吻合。(2)换能器中心处,除垢效率最大,随着角度向两边扩散,除垢效率逐渐减小；当频率为20kHz、换能器半径为15mm时,各辐射角度处除垢效率相差不大,在50%～60%之间,随着频率或换能器半径的增大,换能器两边的除垢效率低,中心处的除垢效率高,最大达到了95.5%。实验结论与声强模拟图形基本吻合。
[Abstract]:Heat exchanger is the main heat exchanger in the fields of HVAC, thermal engineering, chemical engineering and so on. The scaling phenomenon exists in the operation of these equipments, which results in the decrease of heat transfer effect and affects the safety of the equipment. At present, the conventional scale removal methods have the problems of high maintenance cost, chemical waste liquid and so on, so it is difficult to meet the requirements of production process. Ultrasonic scale removal technology has been popularized because of its advantages of green environment protection, low cost and obvious effect. However, in engineering application, the efficiency of scale removal will decrease due to ultrasonic parameter matching and unreasonable arrangement of transducer, and there is no scaling removal effect in some parts of heat exchanger. Therefore, it is necessary to study the efficiency and scope of ultrasonic scale removal. According to relevant scholars, the directivity of ultrasonic wave determines the scale of scale removal, and the intensity of sound has a certain effect on the efficiency of scale removal. Based on the directivity function of point sound source, a mathematical model of directivity function and sound intensity of non-point sound source is established, and the distribution of ultrasonic directivity function under different frequency and transducer radius parameters is simulated by MATLAB software. And the relationship between ultrasonic intensity and transducer radius, ultrasonic frequency, radiation angle. According to the simulation calculation, the following conclusion is drawn: when the ultrasonic frequency is 28kHz, the larger the transducer radius is, the smaller the distribution range of directivity function is, and the sound field gradually accumulates to the vertical direction of transducer. When the transducer radius is 50mm, When the radius of the transducer is 30mm, the larger the frequency, the smaller the range of directivity function, and when the frequency is 60kHz, The directivity range of ultrasonic wave is the smallest, the ultrasonic intensity is directly proportional to the square root of the power, and inversely proportional to the second power of the propagation distance. The greater the power, the greater the sound intensity, and the farther the propagation distance, the smaller the sound intensity. 4) when the ultrasonic frequency is 40kHz, With the increase of the radius of the transducer, the sound intensity in the vertical direction of the transducer increases gradually, and the sound intensity at the other radiation angles is smaller. When the radius is 50mm, the sound intensity reaches the maximum in the vertical direction of the transducer. On the basis of theoretical research, the ultrasonic scale removal experiment is carried out in this paper. According to the experimental study, the following conclusions are drawn: when the frequency is 20 kHz, the scale removal range is the largest, and with the increase of the frequency, the scale removal range is gradually reduced. The effect of the transducer radius on the scale removal range is similar to that of the frequency. The effect of frequency and transducer radius on the scale removal range coincides with the simulation pattern of directivity function. At the center of the transducer, the scale removal efficiency is the greatest, and the scale removal efficiency decreases gradually with the angle diffusing to both sides. When the frequency is 20 kHz and the transducer radius is 15mm, the efficiency of scale removal at each radiation angle is not different. Between 50% and 60%, with the increase of frequency or the radius of the transducer, the efficiency of scale removal on both sides of the transducer is low, and the scale removal efficiency at the center of the transducer is high, with the maximum of 95.5%. The experimental results are in good agreement with the sound intensity simulation pattern.
【学位授予单位】：长沙理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU83
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本文编号：1904998