| Summary: | 碩士 === 中原大學 === 機械工程研究所 === 101 === 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.
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