Session: 12-01 Turbine Film Cooling

Paper Number: 81360

81360 - Film Cooling and Cold Streaks Tracking on a Fully Cooled Nozzle Guide Vane Under Representative Combustor Outflow Conditions 

The pronounced non uniform temperature distribution in the core engine flow path is a recurring problem that needs to be faced during gas turbine engines design process. Specifically, turbine entry conditions are usually characterised by severe temperature distortions, often referred to as hot and cold streaks, ascribed to combustor burners and combustor liners cooling systems. The problem of temperature non-uniformity still persists at the exit of the nozzle guide vane, where additional cold streaks, in the form of the vane film-cooling flows are involved.

A precise knowledge of the thermal field and its evolution is thus essential to mitigate the impact that these distortions have on both turbine performance and lifetime. Several literature studies focus on the description of streaks migration through a direct investigation of the thermal field. While these approaches provide an effective evaluation of the global results, a deeper understanding of the evolution of hot and cold flows can be required, to fully support design and modelling procedures. For this goal, experimental techniques based on the detection of tracer gases can be effectively adopted.

In this study, a concentration probe based on the fluorescence behaviour of an oxygen sensor, developed and characterized in a previous work, was adopted within a non-reactive test rig made by a three-sector combustor simulator, coupled with a film-cooled nozzle guide vane (NGV) cascade. In particular, the probe was traversed on the NGV cascade exit plane to track the position of the film cooling flows on such a position. In addition, this measurements are coupled with adiabatic film-cooling effectiveness evaluations carried out on the NGV surfaces employing the Pressure Sensitive Paint (PSP) technique in order to highlight the film cooling behaviour on the airfoils and provide a better understanding of the probe’s results.

Overall, the work reports a thorough analysis of the film-cooling behaviour and of cold streaks migration and redirection, induced by a realistic combustor-outlet swirl profile on a fully cooled cascade. In this way a global understanding of the occurring phenomena is provided, as well as useful pieces of information that can be adopted for the design phases of both the NGV and of the following rotor cascade.

Presenting Author: Giulia Babazzi University of Florence

Presenting Author Biography: Giulia Babazzi is a PhD Student at the Department of Industrial Engineering of the University of Florence. She previously completed an MSc in Thermal Power at Cranfield University and she got a master degree in Mechanical Engineering at the University of Florence. Her current research focuses on studying alternative fuels combustion characteristics in gas turbine combustors through combustion diagnostics techniques

Authors:

Giulia Babazzi University of Florence
Tommaso Bacci University of Florence
Alessio Picchi University of Florence
Bruno Facchini University of Florence
Simone Cubeda Baker Hughes