To achieve lower Specific Fuel Consumption (SFC) and CO2/NOx emissions, modern turbomachineries operate at high velocities and high temperature conditions. The lack of confidence in the prediction of combustor-turbine interactions leads to apply extra safety margins on components design. Therefore, the understanding of combustor-turbine flow field interactions is mandatory to preserve High Pressure Turbine (HPT) life and performance when optimising the design of new HPT.
Furthermore, FACTOR project addresses two of the six activities fixed in the ACARE Strategic Research Agenda summarized in the work programme 2010:
- Greening of Air Transport
- Improving cost efficiency
Regarding cost efficiency, FACTOR project will address the following requirements having an important impact:
- Take the correct decisions during the first iterations of the conceptual design phase: by developing existing CFD techniques (based on URANS and LES mainly), assessing their reliability to bring them to an industrial maturity level (gain of 2 TRL for each technique). This will help designers to optimize future designs in terms of robustness and costs, including a 20% increase in components life duration.
- Make relevant choices for the technical concept: by maturing CFD techniques, FACTOR will have then a strong impact in predicting the aero-thermal behaviour of the combustor turbine interaction, thus, avoid unsafe and expensive flight tests.
- Make available a European test facility: by upgrading an existing test facility with all European motorists, this will benefit to Aeronautics community and decrease the costs thanks to a collective effort.
The FACTOR objective is to optimise the combustor-turbine interactions design to develop low-cost turbines and reduce SFC by 2%, HPT weight by 1.5% and accordingly engine cost by 3% compared to the results from the TATEF2 and AITEB2 projects. To achieve this objective, FACTOR will develop and exploit an innovative test infrastructure coupling a combustor simulator with a HPT for aerodynamic and aero-thermal measurements. The infrastructure will improve the knowledge of aero-thermal external flows since the inlet profile of the turbine and the secondary flows will be modelled and optimised together in the same facility, under engine representative conditions.
Collected data will be fed into the design techniques and simulation software used to optimise HPT components. In parallel, the use of advanced CFD (e.g. LES or DES) will provide new knowledge on wall temperature and heat transfer predictions. This will be particularly important to design future combustor-turbine systems in an integrated manner, especially for the next generation of lean burn combustion systems having complex and severe flow constraints. By optimising the combustor-HPT interaction, FACTOR project will contribute to achieving the 50% CO2 and 80% NOx reductions ACARE 2020 environmental objectives. FACTOR will also strengthen the competitiveness of the European aero-engine industry by making available a new test infrastructure with experimental abilities beyond those of the US.
The technical Work Breakdown Structure is split as follows:
- WP1 - Component design and manufacturing: Study and design separate combustor and turbine concepts that will be integrated together to ensure mechanical, thermal and aerodynamic performances match specifications.
- WP2 - Instrumentation design & manufacturing and rig adaptation: Upgrade the new turbine test rig hosted by DLR to ensure that the combustor / turbine module and the necessary equipments and services (fluid piping, instrumentation accesses, etc.) are achieved.
- WP3 - Integration: Perform the components integration activities within the whole test rig.
- WP4 - Measurement campaign:Perform aerodynamic and aero thermal measurements to build-in the most all comprehensive data base.
- WP5 - Lean burn influences on low turning strut heat transfer: Carry-out the aerodynamic and heat transfer measurements on the Oxford Turbine Research Facility
- WP6 - Synthesis of experiments and computations:Lead the pre-test and post-test CFD activities. Ensure appropriate interaction between the partners involved in the experimental and numerical activities. Establish data transfer formats between the partners. Analyze the generated CFD data and write guidelines on modeling combustor-turbine interaction.
In addition, a dissemination and exploitation work package, WP7 - Dissemination and Exploitation, will focus on the integration of requirements of the SAGE (i.e. engine) ITD platform of CLEAN SKY and support the corresponding transfer of results. This work package will also rely on interactions with ERCOFTAC (European organization for Flow, Turbulence and Combustion) and
Aero engine evolutionary design
Gas turbine performance strongly depends on the flow field inside the combustor. EU-funded scientists advanced aero engine design by treating the combustor and turbine as a system instead of optimising each component separately.
Internal combustion engines or gas turbines are increasingly designed to operate under extreme conditions of temperature and pressure. Such conditions increase thermal efficiency and decrease emissions. Industry typically includes large safety margins due to lack of detailed knowledge of combustor–turbine interactions.
Scientists initiated the EU-funded project 'Full aero-thermal combustor-turbine interaction research' (http://www.factor-fp7.eu/ (FACTOR)) to enhance understanding of flow field interactions in high-pressure turbines (HPTs). The resulting knowledge should lead to low-cost turbines with longer operating lifetimes and higher performance.
FACTOR relied on results and guidelines from previous relevant EU-funded projects, and sought to create new links among European combustor and turbo machinery experts. A new turbine test facility in Germany that couples a combustor with an HPT simulator for aerodynamic and aerothermal measurements intensified this effort.
The FACTOR test infrastructure was used to collect experimental data to enhance understanding of secondary flow transport and mixing mechanisms through the HPT. The integration of these experimental data into thermo-mechanical designs and simulation software should be used to optimise the new HPT components.
With the help of significant computational fluid dynamics results, scientists completed the rig module design. The combustor simulator was also completed, in addition to the mechanical design of the duct and low-pressure vane. Most of the HPT components were finalised and integrated into the rig.
Further understanding combustor–turbine interactions should lead to increased aero engine thermal efficiency. FACTOR results should significantly contribute to designing new internal combustion engines with high air–fuel ratios. Known as lean burn, these engines combust more fuel and emit fewer emissions.