目前市面上電腦CPU所使用的水冷套件模組中，都有水泵及風扇兩個需要供電的動力元件，而本研究設計開發的水動力風扇即是利用水泵推動的流體來帶動風扇旋轉，以達到省去風扇供電及電子元件壽命的顧慮；水動力風扇的作動原理是利用水泵推動的流體先帶動水動力葉輪旋轉後，接著旋轉葉輪再帶動風扇葉片旋轉，為讓水動力風扇可順利達到一般12025風扇的轉速區間。首先針對影響葉輪轉速的水動力組件進行流場模擬分析，接著針對其葉片間距、葉片與衝擊水流的接觸面積及接觸角度所造成的分散動能等缺點提出優化方案。於優化的過程發現，水流沖擊葉片後的流動空間及與所搭配的葉形是重要設計參數，合適的規劃可以有效提升葉輪的轉速；且經過實際樣品的測試驗證後，得知利用數值模擬求得在葉輪扭矩等於零時的轉速具有參考價值，雖然因有些條件並未被考慮計算而導致誤差，但還是可以比較出不同葉輪型式之優劣排序。最後將水動力葉輪組件成功的與12025風扇作結合，做出水動力風扇的原型，並讓其風扇葉片在水泵推動的流體帶動下，成功的讓風扇轉速達到912RPM。

The CPU liquid cooling module normally consists of the pump, the water block, and the radiator equipped with an axial-flow fan for dissipating the thermal energy to its environment. Among these four components, water pump and cooling fan are the active parts, which need the external power input and are worn out frequently. It follows that the reliability becomes an obstacle in selecting the liquid cooling solution. To relieve this concern, this research proposes an innovative idea to extract flow energy from the cooling stream generated by the pump, and use it as the power source for the cooling fan. Hence, the reliability issue can be significantly lessened since this water-driven fan becomes a passive component.
In this work, numerical and experimental technologies are integrated to design and validate this water-driven cooling fan. Firstly, numerical visualization is utilized to identify the adverse flow patterns inside the water-driven motor of the 12cm-in-diamteter cooling fan for serving the foundation of improving design alternatives. Several essential parameters, such as the angle between inlet and outlet of the impinging stream, geometric shape, number, and arrangement of blades, and buffer gaps on the motor housing, are investigated systematically via the CFD tool. Also, The superior performance of water-driven motor is evaluated by its rotating speed, which can be determined by the zero-torque condition. As a result, the calculated rotating speed of the 5-blade design can be enhanced from 1,043 to 1,694 rpms for the best design, which has the buffer gaps on motor casing and the two-level arrangement on the blades.
Furthermore, three mockups representing the maximum, medium, and low rotating ranges are manufactured via CNC technique for checking the validity of CFD prediction. Consequently, it is found that CFD and test results are in the similar trend while a roughly 30% deference is observed. This deviation is contributed to the unconsidered drags from the bearing and other assembly issues. In summary, this work establishes a systematic evaluation scheme to design a water-driven fan for the CPU liquid cooling system. Also, this innovative fan design is constructed successful to generate a rotating speed at 912 rpm, which is within the operating range for the 12cm-in-diameter cooling fan on the market nowadays.

[1] http://www.silverstonetek.com.tw/
[2] Kubota, T. and Kawakami, H., "Observation of Jet Interference in 6-Nozzle Pelton Turbine", Fuji Electric Review, Vol. 36, No. 2, pp. 70-76, 1990.
[3] Alexandre, P., François, A., Jean, L. K., and Mohamed, F., "Flow in a Pelton Turbine Bucket: Numerical and Experimental Investigations" , Transactions of ASME, Vol. 128, pp. 350-358, 2006.
[4] Anagnostopoulos, J. S. and Papantonis, D. E., "A Numerical Methodology for Design Optimization of Pelton Turbine Runners", HYDRO 2006, Greece, 25-27 Sept., 2006.
[5] Antonio R., Giorgio P., Giovanna C., Alberto S., and Guido A., "Influence of the Bucket Geometry on the Pelton Performance", Proc IMechE Part A: J. Power and Energy, Vol. 228, PP. 33-45, 2014.
[6] Wei, X. Z., Yang, K., Wang, H. J., Gong R. Z., and Li, D. Y., "Numerical Investigation for One Bad-Behaved Flow in a Pelton Turbine", International Symposium of Cavitation and Multiphase Flow ISCM, 2014.
[7] 蘇宗寶, “離心式泵”, 徐氏基金會出版, 1986.
[8] Hong, S. S. and Kang, S. S., “Flow at the Centrifugal Pump Impeller Exit with Circumferential Distortion of the Outlet Static Pressure”, ASME, Journal of Fluids Engineering, Vol. 124, pp. 314-318, 2002.

[9] Gonzalez, J., Fernandez, J., Blanco E., and Santolaria, C., "Numerical Simulation of the Dynamic Effect Due to Impeller-Volute Interaction in a Centrifugal Pump", Transactions of ASME, Journal of Fluids Engineering, Vol. 124, pp. 348-355, 2002.
[10] Mou, J. J., Liu, F., Gu, Y., Zheng, S., Shi, H., Wang, R., Wang, Y., and Wang, C., "Effect of the Setting Angle of a Volute Tongue on Non-Overloading Performance of Centrifugal Pumps" Journal of Harbin Engineering University, Vol. 36, No. 8, pp. 1092-1097, 2014.
[11] Xu, Y. G., Song, W. W., Fa, J., and Jin, Y. X., "Analysis of the Influence of Different Area Ratio Volute on the Performance of Centrifugal Pumps", China Academic Journal Electronic Publishing House, No. 8, pp. 172-175, 2015.
[12] ANSYS Fluent, “User’s Guide-14. 5”, ANSYS Inc., 2012.
[13] Lobanoff, V. S. and Ross, R. R., “Centrifugal Pumps Design and Application”, Gulf Publishing Company, 1992.
[14] Launder, B. E. and Spalding, D. B., “Lectures in Mathematical Models of Turbulence”, Academic Press, London, England, 1972.
[15] Taguchi, G., “Performance Analysis Design”, International Journal of Production Research, Vol. 16, pp. 521-530, 1978.