AEROENGINE AEROACOUSTIC INTERACTIONS

Traditionally both computational and experimental turbomachinery studies explore isolated components. However, the recent Stanford University whole engine simulation, acknowledges that strong component interactions can take place, and that to advance understanding these interactions must be accounted for. This is strong motivation for connecting Savill and Peake's recent EPSRC computational modelling work on the fan and outlet guide vanes to Tucker's recent EPSRC funded simulation work on the jet, through the fan bypass flow. Once connected, we then wish to extend further downstream, ultimately exploring the interaction of the nacelle shear layer and jet with the deployed wing flap of the airframe. The key objective for computer models is to predict engine-airframe-pylon interactions. Here, moving in this direction, we wish to perform ambitious large eddy simulation and analytical studies to predict the fan, outlet guide vane, pylon interaction along with other bypass duct component interactions (a real bypass duct is not a clean geometry with multiple gas path blockages). We then wish to feed this information into the jet nozzle, exploring the scattering of the upstream sound by the jet pipes and the interaction of this with the downstream airframe. The physical insights and models gained should lay foundations for quieter more environmentally friendly aircraft. Notably, the study will endeavour to exploit the traditional triad of measurement, analytical analysis and computation. However, the former will be based on existing data.

The potential benefits to society and hence impact beyond academia of this project is high, the project's nature being industrially and environmentally inspired. With the projected demand for air transport set to double the world aircraft fleet by 2020 it is becoming urgent to take steps to reduce the environmental impact with respect to pollutant and noise emissions. At the same time continual reductions in permitted take-off noise levels are placing the commercial viability of more established plane models in jeopardy giving strong economic implications for the current work. With regards to the UK economy we expect that the current work will have strong technological impact, especially for Rolls-Royce Plc. Tucker and Peake are based in a University UGTP (University Gas Turbine Partnership), while Savill works with Departmental colleagues within the Cranfield Performance UTC (University Technology Centre) and Cranfield has an established Partnership with Airbus. We expect strong engagement with Rolls-Royce Plc from the start. This will naturally take place through continuing the regular interactions we have with the engineers at Rolls-Royce. The methods will help ensure that imperative regulatory noise emissions targets can be met, and the potential to manufacture quieter and more efficient engines offers tremendous competitive business advantage; thus creating greater wealth for the UK and securing employment. The project will itself produce three highly trained aerodynamicists/aeroacousticians - who will have benefitted from regular supervision by investigators with diverse and in depth expertise as well as their own interactions with Rolls-Royce & Airbus staff. This training should thus be of direct value to the UK science/technology base, and there is a well-established recruitment route for such researchers into Rolls-Royce and Airbus from both the Cambridge Whittle Laboratory and the Cranfield Department of Power & Propulsion. Improved computational and mathematical modelling technology will additionally offer the potential for substantially reduced design costs and time to market for aero engines. We will disseminate the computational procedures to the industries as well as the wider R&D community. In summary, the planned work has great environmental importance for directly improving the quality of people's lives. It also has commercial importance, potentially safeguarding UK jobs in a high technology area. This is because greater physical understanding, better mathematical models, and valuable new predictive technology for aerodynamic and acoustics design will be created. This will ultimately result in more environmentally friendly and hence commercially competitive aircraft that can be bought to the market more quickly and at lower cost. The LES, acoustic and computational technology devised during the project along with the physical insights should thus all have substantial impact.