Thrust- Reverser Unit flow visualisation – TRUflow – has investigated several visualisation techniques using a static demonstrator as a workbench for these measurement techniques. Following this investigation, a Wind Tunnel Test (WTT) was carried out aiming to prove the efficacy of these techniques. In parallel, TRUflow is developing and verifying a numerical methodology for the evaluation of TRU cascades. The numerical and experimental data will be fused together to generate a reduced-order model of the TRU unit suitable for design.
TRUflow is developing novel measurement techniques for the visualisation and evaluation of reverse flow interactions with fan aerodynamics in short slim engine nacelle designs. The evaluation of such flow interactions will be critical in the design of the next generation of ultra-high bypass ratio (UHBR) aero engines. UHBR engine architectures offer increased propulsive efficiency through operation at reduced specific thrust, enabled by increased engine diameter. This poses challenges, both in terms of the aerodynamics of the isolated nacelle, and the potential for interference effects between the different engine components such as the Thrust Reverser Unit (TRU).
Background
In 2001, the Advisory Council for Aviation Research and Innovation in Europe (ACARE) published the much referenced ‘Vision’ for 2020 which set targets of 50% reductions in fuel-burn and perceived noise, and 80% in landing/take-off NOx emissions, relative to year-2000 aircraft. This ambitious target aimed to promote a secure European global leadership in the aviation market while simultaneously responding to societal needs. ‘FlightPath 2050’, further expanded these targets to 75% fuel reduction, 65% perceived noise and 90% landing/take-off NOx emissions by 2050.
| Target / passenger km, compared to Year 2000 | ACARE Vision 2020 | Flightpath 2050 |
|---|---|---|
| NOX | -80% | -90% |
| CO2 | -50% | -75% |
| Perceived Noise | -50% | -65% |
| Emission-free Taxiing | N | Y |
| Recyclable Air Vehicles | N | Y |
The massive challenges embodied in these documents are far from being an issue only for the European aviation community. For instance, similar initiatives proposed by NASA for the ‘N+2’ (service-entry 2025) and ‘N+3’ (service-entry 2030–2035) generations of aircraft demonstrate the heightened global awareness of the issues. These challenges have stimulated significant activity in wide ranging future technologies, from operation and airframe to advanced materials and control systems.
With the same goal of reducing emissions, current powerplant developments are striving towards ever increasing engine bypass ratios, facilitating increases in propulsive efficiency through operation at reduced specific thrust. The trend of moving towards Ultra-High Bypass Ratio (UHBR) engines operating at lower pressure ratios has led to the development of Short Slim Nacelles (SSN) with reduced penalty on weight and drag. The challenge now is the integration of engine components in the SSN, such as the Thrust Reverser Unit (TRU) and the fan. In order to ensure the required fan performance when the TRU is deployed, the flow topology needs to be correctly understood and simulated.
About The Project
The main objectives of the TRUflow project (Thrust Reverser Unit flow visualisation) are to design and validate novel flow diagnostic and visualisation technologies and to implement them in representative isolated and installed test rigs of TRUs. A static isolated demonstrator with an ejector and an isolated/installed test rig with a fan will be built during the TRUflow project. The minimum aim of the project is to take all selected technical approaches to TRL5 or higher.
Objective 1 – development of flow diagnostic techniques
- Preliminary study:
- Capture the top level requirements for the flow visualisation technology, through discussion with the Topic Lead, to be able to select baseline concepts
- Study state-of-the art of currently available concepts and methodologies and their potential application to the above requirements
- Down-selection of the most suitable approaches via a trade-off study to determine the best solution to meet the above requirements (there may be more than one candidate technology)
- Reporting of findings and production of a detailed implementation plan (this will vary depending on the technology used)
- Implementation:
- Procurement and/or production of suitable hardware
- Development of prototype flow visualisation systems in static test conditions with thorough performance characterisation
- Refinement of hardware implementation and post-processing algorithms
- Trial of hardware in simple, baseline flow conditions with representative challenges of later tests and comparison with established techniques (and literature)
- Delivery of a sensor package capable of fitting inside the isolated test rig and perform tests
- Delivery of a modified sensor package capable of fitting inside the installed test rig and perform tests
Objective 2 – generate a surrogate model
The second objective is the comparison of numerical simulations with experimental data obtained with the flow diagnostic techniques, with the purpose of generating a surrogate model for the TRU cascade for isolated and installed cases. The aim of this surrogate model is to generate a TRU cascade model that can be implemented as a boundary condition in any CFD solver to accelerate the design process. This objective will be achieved following this process:
- Improve the quality of the results of CFD through improved meshing and selection of the most appropriate turbulence model
- Use an efficient variable fidelity approach employing both unsteady and steady Reynolds-Averaged Navier Stokes (RANS) simulations
- Generate a simulation dataset that efficiently covers the design space, forming the basis of the surrogate model.
- Use the experimental data to validate the CFD data
- Use this data to generate a surrogate model of the TRU cascade and implement it into the CFD solver
In summary, the objectives of TRUflow project are:
- Development of measurement technique for the visualisation and evaluation of reverse flow interactions with fan in a static demonstrator of an isolated configuration with TRU
- Apply the novel techniques in a wind tunnel test of the isolated and installed configuration with TRU
- Numerically evaluate the isolated and installed configuration with TRU
- Generate a surrogate model for the TRU cascades and implement it into the CFD solver