Session: 12-14 Film cooling computational studies

Submission Number: 178960

Detached Eddy Simulations of Leading-Edge Sweeping Jet Film Cooling: The Effect of Inflow Turbulence 

The escalating demand in modern gas turbine engines for increased thrust, power, and efficiency by minimizing specific fuel consumption motivates the development of cooling technologies. The thrive for achieving enhanced efficiency forces the turbine inlet temperature (TIT) to go beyond the limit of melting threshold of component materials, establishing the need of cooling as a non-negotiable defense. Conventional film cooling techniques using different types of holes are often hindered by the formation of a detrimental Counter-Rotating Vortex Pair (CRVP), which compromises effectiveness by lifting the coolant from blade surface. Recent advancements, particularly involving the use of unsteady jets in film cooling, have unlocked a promising new opportunity in advanced gas turbine thermal management research area. There are reported work which are focusing application of sweeping jets for both suction and pressure surfaces of the blade. The reported work for application of sweeping jet film cooling near leading edge is sparse.

Present paper reports numerical investigations on the application of sweeping jet film cooling at the leading edge of nozzle vane. Reported investigations into film cooling performance relied on a conventional URANS methodology using turbulence closure with a k−ω SST model. These studies included examining the impact of varying turbulence intensity with different blowing ratios over a flat plate. Through this methodology, the effects of mainstream turbulence on film cooling effectiveness were not conclusive. This happened may be due to the inability of the URANS model to resolve the bigger length-scale turbulence. The present work includes the assessment of film cooling performance by varying the turbulence intensity for different blowing ratios over a flat plate. For this purpose, DES simulations were carried out using Ansys fluent 2024®. This approach ensures the direct resolution of large-scale turbulent structures, therefore enabling a conclusive analysis of mainstream turbulence effects on film cooling effectiveness. The parametric study includes the effect of variation in mainstream turbulence intensity varied at three levels - 0.5%, 5%, and 10% for different blowing ratios in the range of 0.5 to 1 over the flat plate, keeping the density ratio constant at 1.8.

The mainstream flow was achieved by imposing the favorable pressure gradient of the HP turbine NGV suction surface on a flat plate. The freestream Reynolds number (1 x 10⁶) along with the Cp distribution of VKI LS 89 NGV suction surface were ensured for the engine matching conditions. The numerical investigations were performed to study the effects of varying turbulence intensities for different blowing ratios on sweeping jet film cooling. An array of three sweeping jets in the reversed hole configuration was placed near the leading edge of the HP turbine NGV with a pitch of 6D with a translation periodic boundary condition.

Previous experimental investigation suggests that mainstream turbulence intensity has a higher impact on film cooling effectiveness for lower blowing ratios as compared to those of higher blowing ratios on suction surface. However, from the prior URANS investigation, the interaction of mainstream flow with the coolant jet was found to be negligible for near leading-edge region. As a result, the effect of mainstream turbulence intensity on film cooling effectiveness is quite trivial to understand. The present investigation using DES methodology helps to understand the constrains of the URANS model application by resolving the mainstream unsteady turbulence more adequately. The paper in detail will be discussing the detailed analysis for assessment of effect of inflow turbulence on cooling effectiveness over a flat plate particularly near leading edge.

Presenting Author: Chetankumar Mistry Indian Institute of Technology Kharagpur

Presenting Author Biography: Prof. Chetan Mistry is faculty at IIT Kharagpur.

Authors:

Suryansh Mohanty Indian Institute of Technology Kharagpur
Hitesh Sharma Indian Institute of Technology Kharagpur
Arnab Roy Indian Institute of Technology Kharagpur
Chetankumar Mistry Indian Institute of Technology Kharagpur