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Tomo PE Jp Office
Tomo PE Jp Office Choose MSC Cradle CFD to Improve their CFD Modeling and Hypersonic Analysis Proces

[Vol. 1] SC/Tetra, a thermo-fluid simulation Software from Cradle is an indispensable analysis tool for Tomo PE Jp Office, a consulting services company that focuses on innovative CFD technologies. We interviewed the CEO, Teruhiko Tomohiro. He has been involved in research and development of various fan types from both aspects of experiments and simulation for many years. We also asked him about the recent analysis examples and expectations for CFD tools.

Picture 1: Mr. Teruhiko Tomohiro, Professional Engineer (Mechanical Engineering, Information Engineering), Tomo PE Jp Office

Tomo PE Jp Office is a technology driven consulting firm that is focused on design and development of fans. Proficient in innovative CFD technology, the company also provides consulting services and conducts lectures on advanced applications of CFD.

 

Teruhiko Tomohiro the CEO told us: “CFD is used in various fields. Although we can easily obtain analysis results, knowing ‘how to’ interpret the results can be challenging. Our office advises customers on solving these questions”.

 

Before starting his own company in 2011, Mr. Tomohiro worked with Panasonic for 30 years. During this time, his work has focused upon research and development of various types of products such as blowers, air conditioners, kerosene fan heaters, cooking appliances, and fuel cells, through combinational approach of simulations, prototyping, and testing. He has conducted several CFD analysis models to research the aerodynamic and noise performance of axial-flow, centrifugal, and cross-flow fans, and developed an in-house software tool for fan design.

 

With a profound background in CFD technology, Mr. Tomohiro was one of the first users of scSTREAM, a structured mesh thermo-fluid analysis software that was just released at that time. Later on, around 2000, he started using SC/Tetra, an unstructured mesh thermo- fluid analysis software. Since founding own office, SC/Tetra has been the essential tool for fan development projects in his business.

 

Unpredictable Performance of Cross-Flow Fans

Over the past years, Mr. Tomohiro and his team have provided a full range of CFD studies in support of their development process for cross-flow fans as well as basic propeller fans. Additionally, the team is involved in projects that simulate the ultrasonic wave propagation in a flow field.

Figure 1: Analysis example of a propeller fan
In recent years the countermeasures against performance have decreased. As such, noise caused by vortices at the tip of a propeller receive more attention (click to enlarge)
 

 

 

Figure 2 Airflow mechanism of cross-flow fans. Flow passing through the impeller twice with eccentric vortices (click to enlarge).

Figure 1 shows simulation results of a propeller fan. Most these studies investigate the effects of vortices (around the blade tips) on fan noise and performance. Figure 3 illustrates the wing tip vortex of a fan blade.

 

Cross flow fans are widely used throughout the HVAC industry as well as household air conditioners. Designed to prevent components from overheating, these special fans significantly differ from the ordinary centrifugal fans.

 

Cross flow fans consist of a long and thin cylindrical structure that blows wide uniform air flow. Air enters the front and top faces of the air conditioner and is blown into the cylinder through a curved impeller. Finally, the air flows out from the bottom side of the impeller (Figure 2).

Three main characteristics of a cross-flow fan include the flow behavior, the eccentric vortices generated inside of each part, and the number of blades. The name of cross-flow fan is originated from its characteristics that air comes out cross the whole with of the impeller (Figure 2). The generation of penetrating flow and eccentric vortex is a distinctive characteristic of cross flow fan. As a result, air transfers through and across impeller; the name ‘cross flow fan’ in fact derived from this phenomenon.

 

For the peculiarity of a cross-flow fan, Mr. Tomohiro says “The theoretical methods for design of propeller fans and turbo fans have already been established. However, as for cross-flow fans, there is no such theory defined.” In other words, some consumer electronic makers have released air conditioners that use cross-flow fans, but they have used the trial and error methods to come up with their designs.

 

Figure 3 shows the simulation results of the flow, where the impeller of a cross-flow fan was solely used. The impeller starts to rotate in the state of no wind and then the vortices are generated. Air partially flows into the cylinder and gets stronger as it passes through many points. The flows then merge together to generate one strong vortex. We can observe that the speed at which the resultant vortex rotates around the impeller is lower than the speed of the impeller itself.

 

Figure 3: Change of a flow field when only the impeller of a cross-flow fan rotates.
Multiple flows pass though the cylinder and merge to eventually form one fluid flow.
The speed of the resultant flow is lower than the rotational speed of the fan.
Color bar indicates the size of flow velocity.

 

As demonstrated, the flow field that a cross-flow fan generates is unstable. Generally, air conditioners have a container that is attached around the unstable flow field to make it stable. We can easily predict this phenomenon using a CFD simulation tool. “In a situation like this, we can only observe the air that flows through the impeller. Without using simulations, we are not able to capture the details on the fluid flows, how they are merged to eventually form a rotating force, or know when and why the vortices are generated.”

 

Several decades have passed after the first air conditioner was made and to date, the high performance ACs are designed based on testing and experiments.

 

After joining Panasonic, Mr. Tomohiro was first assigned to work on the design and development process of cross-flow fans. He is also experienced in flow measurements.

 

We can qualitatively predict the performance level of propeller and turbo fans, based on parameters such as scale and angle of each part or the number of blades.

 

However, as Mr. Tomohiro says “A cross-flow fan has very unique characteristics and therefore, detailed research on this subject is not available. I think we will be able to predict the performance of cross-flow fans based on theories, if more research is to be made.”

*All product and service names mentioned are registered trademarks or trademarks of their respective companies.
*Contents and specifications of products are as of January 31, 2017 and subject to change without notice. We shall not be held liable for any errors in figures and pictures, or any typographical errors in this brochure.

Company Details

 

Tomo PE Jp Office
Established April, 2011
Business Consulting on research, development, and design of fans
Consulting on computational fluid analyses
President & CEO Teruhiko Tomohiro
Head Office Ikoma City, Nara, Japan

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