Overview
In a modern aero engine, up to 20% of the main annulus flow is bled off to perform cooling and sealing functions. The vicinity of these bleed ports and flow sinks is characterised by complex unsteady swirling flows, which are not fully understood. Even the most up-to-date numerical tools have difficulties predicting the behaviour of the secondary flow system when interacting with the main annulus.
The project addressed interactions between main gas path and secondary flow systems in commercial gas turbines in response to Research Activity AERO-2005-1.3.1.2a Concepts and technologies for improving engine thermal efficiency and reducing secondary air losses.
Technical Challenges:
- Understanding of interactions between annulus gas flow and air system (unsteady, 3-dimensional, interaction with blades).
Objectives:
- Reduce turbine rim sealing air mass flow.
- Improve turbine efficiency / minimise flow distortions caused by sealing air e.g. by better geometry.
- Improve CFD tools for complex interactions between air system and main gas path (turbines and compressor).
Expected Benefits:
- SFC, component life, reliability, development cost, better tools.
The targeted outcome contributed to the ACARE goal of reduced CO2 emissions via reduced fuel burn of 2% to improve the environment and strengthening the competitiveness of European gas turbine manufacturers.
Experiments were planned on turbine disc rim and compressor manifold cavity heat transfer, hot gas ingestion, and spoiling effects of cooling air flow and their impact on turbine and compressor performance, as well as a reduction of secondary air losses.
The experimental data was used for better understanding of the complex flow phenomena and improvements of platform and cavity design. Furthermore, the industrial partners will validate their design tools with these test data and improve their prediction capability of secondary flow systems when interacting with the main gas path. The expected results are a reduction of cooling and sealing airflow rates, improvements of the turbine and compressor efficiency and increase of the safety margin of the engine components by better cooling.
Funding
Results
Within MAGPI, experiments were conducted on turbine disc rim and compressor manifold cavity heat transfer, hot gas ingestion, and spoiling effects of cooling air flow and their impact on turbine and compressor performance, as well as on reduction of secondary air losses.
These experimental data, obtained at four rigs, have been used for better understanding of the complex flow phenomena and improvements of platform and cavity design.
Furthermore, the industrial partners validated their design tools with these test data and improved their prediction capability of secondary flow systems when interacting with the main gas path.
Innovation aspects
Main improvements include:
- Experiments provided reliable rig test data to validate improved CFD/FE methods,
- Effective coupled CFD/FE convective heat transfer method demonstrated – this method will be applied as design tool,
- Alternative cooling flow configuration shows potential to improve rim seal cooling effectiveness,
- Effect of different rim seal geometries on hot gas ingestion and pressure loss.
Technical Implications
Obtained technical results are:
- Improved knowledge of the interaction phenomena and its effect on cavity heat transfer, spoiling and performance.
- Experimental results for validation of improved numerical tools for secondary flow systems.
- Optimised design methods and CFD best practice guidelines.
Readiness
The targeted outcome will contribute to the ACARE goals to improve the environment and strengthen the competitiveness of European gas turbine manufacturers:
- reduced CO2 emissions via reduced fuel burn (reduced cooling air flow, increase of turbine and compressor efficiency);
- weight decrease (turbine disc and compressor casing);
- increase of critical parts life;
- improved reliability;
- reduced development time (better methods for design of cooling system and off-takes).