Research On Effects Of Wall Roughness And Cascades Flow Separation In Millimeter-Scale Internal Flows

The characteristics of millimeter-scale flow at low Reybolds number are one of the essential components for the design of centimeter-scale Micro Turbo Engine (MTE). On this condition, this paper reseached the effects of the wall roughness on the flow friction resistance and the different flow separation performance of the micro blades.The first experimental investigation was made in the 300mm×20mm×0.5mm rectangular and straight micro channel with different roughness values and different roughness texture directions on the insides surface and consisted of flow flux measurements of the microchannel and static pressure measurements alone the channel for the goals to search the effect of different surface roughness values and different roughness texture directions on the flow characteristics and explore the difference characteristics between millimeter-scale flow and general flow. The results of this experimental investigation hereinbefore, together with other data, indicated the ideas that in the microchannel whose height was 0.5mm, Reynolds numbers when flow transition occurred on the extent of 400-1200 was less than the ones of the general scale. Furthermore, on the condition of the same roughness value level, there was more influence on the flow with the roughness of transverse direction and oblique direction than of longitudinal direction and Reynolds numbers when flow transition occurred was less, too. On the same condition, flow friction occured by the transverse direction roughness was greater than oblique direction roughness which was greater than longitudinal direction roughness, too.After that, another experimental investigation was made in 5 micro compressor cascade channels which were designed on the foundation of NACA 65-810 blade airfoil and consisted of the 7 points static pressure measurements on the convex surface of the balde in the mid-channel via 7 micro static pressure holes whose diameter were all 0.1mm in order to search the flow separation laws of micro compressor cascade at different angles of attack and uncover the flow separation on the convex surface that's different from the general-sacle. The results of this experimental investigation, together with other data, showed the conclusions that pressure coefficient of the convex surface was far less than the general and the laminar separation section move up about 15% of the chord. With the same angle of attack, pressure coefficient would ascend with the raise of Reynolds numbers on the extent of 13300-38900. On the whole, however, the separation position on the convex surface kept the same.