Effect Of Flow Field Vortex Core Distribution On Heat Transfer Performance In Ribbed Channels With Two Coolants

Using advanced gas turbine blade cooling technology is an effective way to enhance the reliability of gas turbine blades working in high temperature condition and remain their longevity. In terms of present research results of air and steam cooling technology in ribbed channels of gas turbine blades, the secondary flow or vortex structure in ribbed channels has a significant contribution to the heat transfer of ribbed channels, but the vortex generation, evolution, morphology characteristics and how they exerting an important effect on the performance of heat transfer in ribbed channels is not clear currently.The main research work of this thesis contains: numerical simulation is performed on air and steam cooled channels with rib angleo o o o?=30 45,,60 90,, ducts aspect ratio W/H=2/1 for Re=10000-80000 by using numerical simulation method; the grid independent of the ribbed channels has been investigated and the reliability of numerical simulation results have also been verified by comparing with the experimental results; the effect of rib angles, Reynolds number, the flow coolants on the vortex generation, evolution, morphological characteristics, vortex distribution and heat transfer performance of ribbed channels are analyzed and illustrated by using flow field vortex core technology; finally, the numerical simulation results of heat transfer performance, friction and heat transfer factor of air and steam cooling channels with different rib angles are given.Result indicates that: the rib angles exerts a significant impact on vortex characteristics and its distribution in ribbed channels, but for Reynolds number and the flow coolants; the vortex system in ribbed channels for ? ?30o 45、o 60、o are largely consisted of dispersed vortex on the left wall, longitudinal vortex on the rib side wall and main vortex on the center of mainstream near the right wall, bifurcation of longitudinal vortex is occurred for o? ?30 ribbed channel, except for o o? ?45 60、 channels, but the coverage region of longitudinal vortex in downstream for ? ?60o channel is broader than ? ?30o 45、o channels; the vortex system for ? ?90o channel mainly contains transverse vortex with discontinuity and single structure and distribute periodically in fully-developed channel.The region swept by longitudinal vortex on rib side wall in ribbed channels can get a higher Nu distribution. The Nu on rib side wall distributes periodically along the main flow direction and decreases gradually along the radial direction in channels, which is mainly caused by the vortex strength with constant and periodical distribution along the main flow direction and gradually decreasing along the radial direction in channels. The bifurcation of longitudinal vortex for ? ?30o channel weakens the heat transfer performance of longitudinal vortex, resulting in the lowest Nu distribution on rib side wall; the longitudinal vortex for o? ?60 channel has the widest affection region, which results in the highest Nu distribution on rib side wall. The region swept by transverse vortex and the fluid reattachment area can obtain a higher Nu distribution for ? ?90o channel, furthermore, the Nu distribution along the main flow direction and radial direction in channel is evenly distributed. The vortex strength is enhanced by increasing of Reynolds number, which significantly improves the vortex heat transfer performance. Steam has a better thermal properties than air, thus the heat transfer performance of steam is higher than air.The vortex strength, the vortex core location relative to boundary layer, the radius of vortex in channels are all the important parameters for vortex heat transfer performance. The result of this thesis could provide a reference for active controlling the heat transfer of vortex and has a certain significance to further optimize the heat transfer performance of gas turbine blades in ribbed channels.