Investigation On Flow And Heat Transfer Characteristics In High Blockage Ribbed Channel Of Turbine Blade

With the increase of turbine inlet temperature,the thermal load on turbine blades becomes more and more serious.It is urgent to take effective cooling measures to protect the blades.Ribbed channel is a widely used internal cooling structure for turbine blades.For large aero-engines such as turbofan,the blockage ratio of ribbed channels in turbine blades is generally less than 0.1,but for medium and small aero-engines such as turboprop and turboshaft,blockage ratio is generally greater than 0.15.The flow and heat transfer characteristics of ribbed channels with high blockage ratio are quite different from those of low blockage ratio.In order to obtain the variation of flow and heat transfer characteristics in ribbed channels with high blockage ratio,two kinds of cross-section channels,special-shaped and rectangular,were designed.The effects of non-dimensional geometric parameters and inlet Reynolds number on the flow and heat transfer characteristics were investigated experimentally and numerically.Non-dimensional geometric parameters include blockage ratio(e/d),rib chamfer radius to rib height ratio(r/e),rib width to hydraulic diameter ratio(w/d)and aspect ratio of channel(L/W).The main conclusions are as follows:(1)The influence of blockage ratio on heat transfer characteristics is the most significant.With the increase of e/d,the average Nusselt number ratio on the wall of special-shaped and rectangular channels increases significantly,especially at high blockage ratio.(2)The effect of rib chamfer radius to rib height ratio on heat transfer characteristics is the weakest.With the increase of r/e,the average Nusselt number ratio of rectangular channel and ribbed side of special-shaped channel decreases slightly,while that of non-ribbed side and leading edge increases slightly at first and then decreases slightly.(3)For special-shaped channels,excessive and small ratio of rib width to hydraulic diameter is not conducive to heat transfer enhancement,there is an optimal value,which makes the heat transfer enhancement ratio on the wall of the channel the highest.The average Nusselt number ratio of rectangular channel decreases monotonically with the increase of w/d.(4)With the increase of aspect ratio,the average Nusselt number ratio of rectangular channel and ribbed side of special-shaped channel increases gradually,while that of non-ribbed side increases first and then decreases,and that of leading edge decreases first and then increases slightly.(5)The geometric parameters have the same effect on the flow resistance of the special-shaped and rectangular channels.The flow resistance increases with the increase of e/d and L/W,and decreases with the increase of r/e and w/d.The effect of e/d is most pronounced,while r/e has the least influence among the four parameters.(6)With the increase of inlet Reynolds number,the heat transfer coefficient increases remarkably,but the change of Reynolds number does not affect the flow field structure in the channel,and the heat transfer enhancement ratio does not change significantly when Reynolds number increases.