磁性奈米流體應用於揚聲器音圈性能之研究

Research on the performance of loudspeaker voice coils using magnetic nanofluids

許學文(Hsueh-Wen Hsu)

指導教授 ： 翁輝竹

中原大學/工學院/機械工程研究所/碩士(2013年)

https://doi.org/10.6840/cycu201301053

摘要

本論文完成磁性奈米流體應用於揚聲器音圈性能之分析。主要目的在探討不同載液及粒子體積分率對揚聲器音圈散熱、頻率響應及失真之影響。首先，我們製備水基、煤油基及矽油基磁性奈米流體，並調配不同固相粒子體積分率之磁性奈米流體測試樣品。接著，透過所設計之熱傳導係數測量儀，量測出流體熱傳導係數。進一步，添加流體於揚聲器磁隙中，藉由直接法量測音圈溫度以分析音圈散熱。最後，透過聲學測試系統分析音圈頻率響應及失真。
研究結果發現，流體內奈米粒子體積分率增加，熱傳導係數隨之增加，且趨近線性關係。針對音圈散熱分析，隨著粒子體積分率增加，散熱效果越好。然而，由於水基與煤油基磁性奈米流體在測試過程中會有噴濺現象，致使散熱未達預期效果；而矽油基磁性奈米流體並無此現象，其散熱效果相對穩定。針對頻率響應分析，在頻率約100~300 Hz，隨著粒子體積分率增加，音圈頻率響應有壓抑更明顯的趨勢，而更以矽油基磁性奈米流體壓抑最為明顯，煤油基磁性奈米流體最小。針對失真分析，在頻率約150~700 Hz，隨著粒子體積分率增加，音圈失真有隨之變大的趨勢，而更以矽油基磁性奈米流體影響音圈失真最為明顯，煤油基磁性奈米流體最小；在頻率約700 Hz之後，音圈失真均有變小的趨勢。

關鍵字

揚聲器 ； 散熱 ； 磁性奈米流體 ； 音圈 ； 熱電偶

並列摘要

This research conduct the analysis of the performance of loudspeaker voice coils using magnetic nanofluids. The main purpose is to investigate the influences of carrier liquid and particle volume fraction on the heat rejection, frequency response, and distortion of loudspeaker voice coils. First, we prepare water-based, kerosene-based, and silicone-oil-based magnetic nanofluid test samples of different solid-phase particle volume fractions. Then, we design a thermal conductivity meter and determine the values of the thermal conductivity for different samples through the meter. Further, we add a fluid in the magnetic gap of the loudspeaker and measure the voice coil temperature by using the direct method, so as to analyze the coil heat rejection. Finally, we analyze the coil frequency response and distortion through a acoustic test system.
Results show that as the particle volume fraction increases, the thermal conductivity increases, and tends to linearly relationship. For coil heat rejection analysis, it is found that the heat rejection is enhanced as the particle volume fraction increases. However, because water-based and kerosene-based magnetic nanofluids may have splattering phenomena in the test process, the heat rejection may not reach the anticipated effect; but for silicone-oil-based magnetic nanofluids, fluids do not have this phenomenon, and its heat rejection effect is relatively stable. For frequency response analysis, in the range of about 100~300 Hz, as the particle volume fraction increases, the coil frequency response tends to be repressed more obviously. The phenomenon is most obvious for silicone-based magnetic nanofluids and smallest for kerosene-based magnetic nanofluids. For distortion analysis, in the range of about 150~700 Hz, along with the particle volume fraction increases, the coil distortion tends to be become large. Silicone-based magnetic nanofluids have the greatest influence on the coil distortion, and kerosene-based magnetic nanofluids have the smallest. After the frequency of about 700 Hz, the coil distortion tends to be become small.

並列關鍵字

thermal couples ； voice coils ； heat rejection ； loudspeakers ； magnetic nanofluids

參考文獻

Ahuja, A. S., 1975, “Augmentation of heat transfer in laminar flow of polystyrene suspensions,” J. Appl. Phys., 46, 3408–3425.

Buhe, B., Lin, S. D., Huang, B., Liu X. H., and Chi, J. L., 2010, “Preparation of ferrofluids and their application in loudspeaker,” Met. Funct. Mater., 17, 40–43.

Choi, S. U. S., 1995, “Enhancing thermal conductivity of fluid with nano–particles,” ASME Fluids Eng. Div., 231, 99–105.

Hamilton, R. L. and Crosser, O. K., 1962, “Thermal conductivity of heterogeneous two-component systems,” Ind. Eng. Chem. Fundam., 1, 187–191.

IEC-60628-1, 2003, Sound system equipment. Part 1:general, Internation Electrotechnical Commission.