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Performing Analysis including Fans and Utilizing Results in Many Areas

A fan is considered to be relatively unsuitable for thermo-fluid analysis among electronics components. Because a fan is a moving component, flow around the fan is normally extremely complicated. We interviewed a staff of ORIENTAL MOTOR CO., LTD. (hereinafter, Oriental Motor) about their present status of CFD (Computational Fluid Dynamics) analysis and designing case studies of fans, and how to effectively utilize simulation results. The company is known for fan motors used in specialized products such as "super computers".

Takahiro Ito
TM department
Chief researcher, Ph.D. (Engineering)

 Oriental Motor is a development company of a large variety of motor products such as precision miniature motors, and total systems including control circuit for fans. They provide products to a wide range of areas: industrial machineries, laboratory devices, and medical devices. In the company, TM (thermal management) department is in charge of thermal management, which is mainly for developing fan motors. The department proposes new propeller fans, blowers, and cross-flow fans for general electronic appliances such as personal computers, and also total systems for thermal management. One of their best products is fan motors for specialized products such as super computers. The company has long established a system for rapidly developing and manufacturing high-mix low-volume products. That know-how is utilized in the development of fan motors, too.

Background of Applying CFD Analysis for Fan

 Fluid engineering has been utilized for analyzing various types of blades for many years, especially for analyzing large scale products such as screws for marine vessels and blades for windmills. Although heavy industry companies manufacturing these large scale products generally developed their own analysis programs, fluid analysis of fans for electronic devices has lagged behind them. For one thing, the analysis method for a large-scale blade cannot be simply applied to the analysis for electronic devices. Normally, fluid over a blade does not flow along the blade, slightly separating from the blade. The conditions or states of fluids separating from a blade are widely different between a small size fan (a few centimeters in diameter) and a large-scale blower (nearly one meter in diameter). Thus, for design engineers of fluidic devices, these fans seem to be in completely different dimensions. Also, for many electronics manufacturers, a fan was just a single component of an electric device, so they could not afford to invest their time and money just for a fan design. Therefore, most design engineers had to repeat trial and error themselves and largely depended on their experiences for the fan design and development, and thermal management using a fan.

 Under these circumstances, there was almost no research paper on this topic when Takahiro Ito, senior researcher of TM department of Oriental motor, started to work on fan designing in 1988.

Fig.1 Standard product "MRS25" equivalent to the fan used for the original "Earth Simulator"

Development of a Fan for "Earth Simulator"

  Mr. Ito is an expert of fan development. One of the products he developed at Oriental Motor is a fan for "Earth Simulator" (see reference.1), which is utilized for a climate prediction by Japan Agency for Marine-Earth Science and Technology. Approximately 400 computers, each of them sized 100 ×140×200 centimeters, are located in a spacious machine room like a gymnasium. This whole system is called "Earth Simulator". There is an air-conditioning room at the basement where 6 fans are used to pump up the cold air to the above for cooling one computer. Here, overall 2,400 fans are used for the system.

  Since a manufacturer of the Earth Simulator stuck to air cooling rather than water cooling, they demanded a fan with extremely high performance. Above all, their demand for countermeasures against the high levels of noise from 2,400 fans was hard to deal with. At that time, Oriental Motor did not use any sound analysis tool, not even a tool for thermo-fluid analysis. Thus, the company used "Rapid Prototyping Machine" to create a prototype with resin, repeating the measurements of the P-Q characteristics and sounds. Generally, several prototypes are enough for the development of standard products of the company; however, they spent six months in creating more than 60 prototypes to develop a fan for the Earth Simulator.

  The completed product is 25cm in height and width with forty times more flow rate than a fan for a regular personal computer. At present, they sell the fan as "MRS25" (Fig.1, 2). Now, the fan is widely used for the devices requiring a large amount of wind power such as specialized computers with high calculation efficiency for a semiconductor inspection equipment, and inverters for wind and solar power generation.

Fig.2 Image of CFD analysis for the product adopted in "Earth Simulator

Introducing Analysis Tool because of the Importance of Visualization

 At that time, design engineers of Oriental Motors did not rely on any simulation software to develop a fan for the Earth Simulator. While they gained many valuable experiences through the trial and error process, they went through a lot of troubles for the development and realized the importance of visualizing flow. They could not find out the causes of undesirable results unless they could watch the flow. Ideally, the flow should be measured directly; however, it was not realistic to buy extremely expensive flow measuring devices. Plus, capturing the flow through tiny gaps between blades would be difficult even with the device. Here, Mr. Ito adopted "PHOENICS". The price of the software was reduced to about two million yen at that time. With this software, they gained some achievements in thermal design for electric devices and were appreciated by their customers. Still, it was not efficient enough for analyzing a fan because the mesh lacked smoothness to predict phenomenon over a fan. It was said that meshing took almost two weeks even for specialists, and this was not realistic for many design engineers.

*All product and service names mentioned are registered trademarks or trademarks of their respective companies.
*Contents and specifications of products are as of May 16, 2011 and subject to change without notice. We shall not be held liable for any errors in figures and pictures, or any typographical errors.

Company Details


Founded 1950
Description of Business Development, manufacture and sale of small precision motors and electronic circuits for motion control
President Yoshio Kuraishi
Headquarters TOKYO
Capital 4 billion Yen



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