Research On Flow And Heat Transfer Mechanism Of Flow Spacing And Depth In The Cavity

Gas turbines and aero engines have always played an important role as important equipment for energy conversion in civil and military industries.The inprovement of aeroengine thrust and efficiency dependends on the increase of turbine inlet temperature,but the increment of turbine inlet temperature is limited by the high temperature performance of the turbine material and turbine cooling technology.The cavity cooling technology is introduced as an excellent passive cooling technology and applied to the trailing edge of turbine blades.The advantage of cavity cooling technology applied in the turbine blades is that it achieves better heat transfer performance with lower pressure loss.The research of cavity cooling origins with the spherical cavity cooling channel,and then the effect of the cavity'depth,shape and angle and the flow spacing and span spacing between the adjacent cavities on the flow and heat transfer performence are studied.In this paper,the effects of the internal flow spacing and cavity depth factors on the flow structure and heat transfer performance of the dimple channel and the elliptical cavity channel are studied.In this paper,the effects of the cavity's internal flow spacing and cavity depth on the flow structure and heat transfer performance of the double-dimple passage and the elliptical cavity passage are studied.With the increase of the flow spacing,the flow pattern of the boundary layer of the inner double-dimple cavity changes greatly,but the flow pattern of the boundary layer of the inner elliptical cavity does not change remarkably.The change mainly shows that the vortex of the initial separation and recirculating flow in the boundary layer of the doubledimple cavity are blocked by ridges and a lot of flow attachments appears in the latter dimple cavity of the double-dimple cavity.The comprehensive heat transfer coefficient of the heating surface of the two types of cavity passages declines with the increase of the flow direction spacing inside the cavity,while the comprehensive heat transfer coefficient of the double-dimple cavity is slightly higher than that of the elliptical cavity when the cavity's internal flow direction spacing is the same.The transient simulation study of the cooling passgage with a 0.25 D spacing's cavity surface shows that there are three main vortices in the double-dimple cavity: the horseshoe vortice on the leeward side,the tornado-like vortice middle in the middle of cavity and the hairpin vortice on the cavity's trailing edge,and some other vortices: the C-shaped vortice at the ridge and attached vortices at the cavity:s leading and trailing edges.The tornado-like vortice entrains the layer fluid of the former dimple inside the double-dimple cavity,resulting in good flow attachment in the latter dimple inside the double-dimple cavity,and the tornado-like vortice dominates the hairpin vortex pair on the cavity's trailing edge.The lifted hairpin vortex pairs and tornado-like vortex pairs' s advection causes heat transfer enhancements.At the same time,due to the existence of the ridge,the horseshoe vortice on the leeward side,the tornado-like vortice middle in the middle of cavity lead to the heat transfer enhancements at the ridge of the double-dimple cavity.