Effects of jet nozzle aspect ratio and reynolds number on flow and heat transfer characteristics of vortex cooling

A proper vortex chamber structure is established in terms of blade leading edge cooling. The influence of jet nozzle aspect ratio and Reynolds number on flow field and heat transfer characteristics of vortex cooling is numerically analyzed by means of 3-D steady RANS equations coupled with standard k-ω turbulence model. Based on numerical data, the heat transfer correlations are summarized with respect to the Nusselt number, jet nozzle aspect ratio and Reynolds number. Results show that high speed rotational flow is formed by the impingement air, thus the heat transfer intensity is significantly enhanced. When jet nozzle aspect ratio increases from 0.2 to 9, the outer rotation region, air speed and turbulence kinetic energy decrease at first and then increase, while the static pressure ratio increases at first and then decreases. A larger jet nozzle aspect ratio results in more uniform Nusselt number distribution in the circumferential and axial direction. An increase in Reynolds number leads to pronounced increases in air speed, turbulence kinetic energy, static pressure ratio and wall Nusselt number. However, the flow characteristics are not sensitive to Reynolds number. The globally averaged Nusselt number increases as Reynolds number increases, but decreases at first and then increases as jet nozzle aspect ratio increases. The heat transfer correlation can be used to accurately predict the vortex cooling heat transfer coefficient with a deviation less than 10%. © 2015, Xi'an Jiaotong University. All right reserved.