曲がりディフューザ内の流れの可視化と数値計算 案内羽根そう入による効果

Abstract

In our previous experiments using a wind tunnnel, the flow in a two-dimensional curved diffuser with logarithmic spiral angle was clarified quantitatively about the variation of spiral angle and the existence of a guide vane. The wind tunnel method however requires much time for preparation of the experimental system and for the main experimental procedure.We have recently devised a new experimental method for identifying optimum diffuser forms in less time than that required by the conventional technique. This new method involves visualization of flow (using dye streaks and condensed milk) and numerical calculation using the finite element method. The results obtained with this new method were compared with those obtained with the wind tunnel method to assess its usefulness.The results of numerical calculation approximately agreed with the findings from flow visualization. The analysis using this method showed that the flow in the diffuser was improved by the existence of a guide vane, although some differences were observed depending on the magnitude of the logarithmic spiral angle. These findings are consistent with those obtained in our previous wind tunnel experiments. This method involving flow visualization and calculation is therefore expected to provide a simple and useful means of determining ideal forms of curved diffusers.