| The improvement of turbine engine performance raises a great demand for turbine blade cooling technology.Ribbed cooling channel is a typical internal structure of turbine blade.The heat transfer profit of traditional channel with ribs is effective,yet the pressure loss is relatively larger.Thus,a new structure of pyramidal arrays was proposed in this paper,and numerical simulation was performed to study the flow and heat transfer characteristics in square channels with pyramidal arrays.To begin with,the effects of different macro parameters and shape parameters of pyramidal arrays on flow and heat transfer characteristics in static straight channel were compared and summarized.The traditional W-shaped ribs were selected as a baseline,and the Reynolds effects were also considered.The macro parameters included array configuration,different numbers of transverse rows and streamwise spacing ratios,the waist length,the top angle and the height of each pyramids.With respect to the simulation results,pyramidal arrays with the best performance were selected and then compared with W-shaped ribs in rotating straight channel and rotating U-shaped channel of the same size,and the influence of rotation on flow and heat transfer characteristics in these channels was also clarified.Results reveal that pyramidal arrays are effective to promote heat transfer and the reduction of pressure loss by generating longitudinal vortices.Upwind aligned is the most excellent with highest comprehensive heat transfer efficiency of the channel,and can be applied to a wider range of Reynolds numbers.On this basis,the optimal number of transverse rows are 4～6,the relationship between streamwise spacing ratios and flow or heat transfer characteristics in the channel exhibit linear correlation.The comprehensive heat transfer efficiency of the channel increases with the increase of the waist length;increases first and then decreases with the increase of the top angle and the height of each pyramids,and the specific transformation law is,to some extent,affected by other parameters and Reynolds numbers.The effect of rotation onflow and heat transfer characteristics in straight channel with pyramidal arrays is more obvious than that with W-shaped ribs.For the U-shaped channel,the flow and heat transfer characteristics and the effect of rotation in inlet channel are similar to those in straight channel,while the outlet channel with pyramidal arrays is more likely to be affected by the secondary flow produced by the U section.In addition,comprehensive heat transfer efficiency of inlet and outlet channel with pyramidal arrays are both increased by 20%than with W-shaped ribs on average of different rotation numbers. |
