Experimental And Numerical Study On The Cooling Characteristics Of Tree Branched Microchannels

Internal cooling is widely used in the cooling of heavy duty gas turbine blades.While the traditional ribbed blade internal cooling structure existing problems of large flow resistance,and the temperature distribution is not uniform,thus limiting the blade cooling efficiency.Therefore,to seek a new cooling technology has very important significance for promoting the development of heavy-duty gas turbine technology.The micro channel heat transfer technology and pit cyclone heat transfer enhancement technology due to its low flow resistance and high thermal transfer efficiency can replace the traditional ribbed channel so that the heat transfer performance of the blade is improved to ensure the safety and reliability of turbine blade.Firstly,according to the maximum factor η of heat transfer performance of blade cooling,the scaling ratio of structural parameters of tree like microchannel is determined.Secondly,based on the experimental results,the flow resistance and heat transfer characteristics of a smooth walled dendritic channel with different Reynolds number and heating power are investigated.In the analysis of heat transfer and micro channel flow,application of frictional resistance coefficient,Nusselt number and comprehensive heat transfer enhancement factor is to evaluate the channel.At the same time,the numerical flow in the micro channel in the research tree bifurcation fluid calculation method,analysis of the relationship between Nusselt number and the flow resistance coefficient and the overall heat transfer factor and coolant flow.Furthermore,the turbulence model is validated and the mesh independence is verified,and the turbulence model and the mesh number are determined.Finally,combining the micro channel with the dimple,the geometric model of the tree like microchannel with a concave wall is established.The spacing between two adjacent dimples are P/D=3,P/D=6 and P/D=9.By numerical calculation method,using air and steam as coolant,in the same conditions,the pit spacing on the cavity wall of tree like micro channel flow resistance and heat transfer characteristics were studied,and the smooth wall of tree like micro channel comparison.The flow pattern and convection heat transfer effect of fluid in a tree shaped bifurcation channel with a concave wall are analyzed.The conclusions obtained can be used for reference to promote the development of blade cooling technology.