The blade shape design is one of the most important factor for improvement of efficiency or noise reduction of a centrifugal fan. However, it is not easy to analyze flow through impeller blades both theoretically and experimentally. This paper describes the experimental technique for velocity measurements in the centrifugal fans by means of image processing of double-exposure particle-imaging patterns obtained by using dual-beam-sweep illumination technique. In order to develop fundamental technique, the measured velocity field of flows through the impeller blades of the basic model of the centrifugal fan are compared with the results obtained by 3D numerical analysis. And then the method is applied to measurements of flow through the multi-blade fan. The results obtained give useful data to consider the characteristics of the fan.

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This paper is concerned with the mixing process of two dimensional confined laminar jet flow. In order to simulate these phenomena, numerical calculation and visualization experiment by Hydrogen Bubble Method are done. As a result, are made clear size, location and shape of the recirculation zone for effect of flow rate, nozzle-throat ratio and Reynolds number.

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Noncontact and nondestructive visualization of 3D temperature is under investigation by acoustic tomography. A new method to reconstruct the 3D temperature distribution from the projected ultrasonic phase differences is applied to this process in the present paper. With an experimental system consisting of several pairs of ultrasonic sensors, an axisymmetric temperature field is visualized. The whole visualization is realized at three typical cross sections of the temperature field and tries to show the expected 3D images. The temperature profiles reconstructed by this acoustic tomography agree well with the results of the ther-mocouple measurements. As a result, the procedure proposed in this paper is verified to be reasonable.

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