Session: Poster Session

Paper Number: 162635

Heat Transfer Augmentation at Hp Turbine Ngv Leading Edge With Sweeping Jet Film Cooling 

Film cooling is one of the most effective turbine blade cooling techniques, enabling modern gas turbines to operate at elevated temperatures. Incorporating unsteady jets in film cooling opened the domain of advanced research in gas turbine cooling technology. The use of pulsating and oscillating jets for film cooling has been studied extensively. A sweeping jet employed as a film cooling stream over the suction surface of an HP turbine NGV is a promising notion.

In this numerical investigation, the effects of various coolant-blowing configurations on sweeping jet film cooling were studied with an array of sweeping jets in the reversed hole configuration placed near the leading edge of the HP turbine NGV. The adiabatic film cooling effectiveness along with augmentation in heat transfer coefficient were examined to assess the overall performance of film cooling. 3D-URANS simulations were carried out using Ansys fluent 2022®.

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. Three sweeping jets were placed on the suction surface at 3.4% of the chord length away from the leading edge. Initially, the effect of the blowing ratio was studied by increasing the blowing ratio of all three holes. Then, the effect of jet focusing was investigated by increasing the blowing ratio of the middle jet while keeping the coolant flow rate of the neighboring jets constant. The freestream temperature was kept at 300 K and the coolant stream was supplied at 167 K maintaining a density ratio (DR) of 1.8.

The results of the investigation suggested that sweeping jets placed in a row may never be in sync and a natural phase difference will always exist which causes asymmetrical interactions of neighboring sweeping jets making the entire process highly unsteady. The reversed hole configuration causes the ‘blobbing’ of the coolant stream which further enhances the unsteadiness and uncertainty of sweeping jet film cooling. An increase in the blowing ratio causes an increased size of blobs and also an increased frequency of oscillation. The combined effect of these two promotes diffusion of coolant stream resulting in an improvement in lateral spreading at the cost of cooling effectiveness.  It was observed that the jet focusing reduced heat transfer augmentation by up to 9% without significantly affecting the film cooling effectiveness in the leading edge region this suggests that the region of 1.5 to 2 % of the chord length after the hole exit may benefit from this technique.

Presenting Author: Hitesh Sharma Indian Institute of Technology Kharagpur

Presenting Author Biography: Hitesh Sharma is a PhD student at the Department of Aerospace Engineering at Indian Institute of Technology Kharagpur, India. He received his Masters from the Department of Mechanical Engineering, NIT Manipur, India, with a specialization in Thermal and Fluids Engineering. He is currently working on experimentally investigating the aerodynamic and thermal behaviors of HP turbine Nozzle Guide Vanes in gas turbines.

Authors:

Hitesh Sharma Indian Institute of Technology Kharagpur
Arnab Roy Indian Institute of Technology Kharagpur
Chetan Mistry Indian Institute of Technology Kharagpur