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Designing and testing aero engines is a long process involving years of research and development, but accurate mathematical modelling can save companies considerable amounts of time and money by solving design problems before engines are actually built.

The hydra code rolls royces standard aerodynamic design tool Rolls-Royce plc

A central issue in engine design is the ability to model the way that air flows around every single component of the engine, since this can substantially affect performance and efficiency. Computational fluid dynamics (CFD) software, which uses numerical methods to analyse problems involving fluid flows, is the key tool required to do this. The complexity of the problems requires the use of very large computers. Professor Mike Giles has worked in computational fluid dynamics for many years and his work on the HYDRA code underpins the way that Rolls-Royce now designs and builds its engines.

In 1993 Giles established the Rolls-Royce University Technology Centre (UTC) in Computational Fluid Dynamics to investigate mathematical and computational techniques for use in the analysis and design of turbomachinery. Research was based on identified Rolls Royce requirements, and carried out in collaboration with Rolls-Royce CFD specialists and with other University Technology Centres, bringing together a large body of expertise. Many of the new developments were pioneered by Giles and his team, and they were also responsible for combining all the advances into HYDRA, whose key features included:

  • the ability to model and analyse fluid flow problems in the context of highly complex engine geometries which were previously difficult to assess
  • the efficient simulation and computation of three-dimensional unsteady flows through an engine, including modelling shock oscillations
  • a new adjoint sensitivity approach, which makes design optimisation quicker and more efficient
  • the ability to run efficiently on clusters of thousands of computers

The specific UTC at Oxford came to a natural end in 2007 after 14 very successful years, recognising that the increasingly collaborative approach to code development was the way forward.  However, the continuing and growing impact of HYDRA is testimony to the far-sightedness of Professor Giles’ research and the collaboration he helped establish.

Since 2009, HYDRA has been used by Rolls-Royce in almost every aspect of its aerodynamic design work. HYDRA’s ability to simulate the flow of air through the turbomachinery components of gas turbine engines and their installations is crucial to Rolls-Royce's design capability, since engines are now designed almost exclusively through computer simulation with experimental testing carried out afterwards to verify the performance of the final design.

Rolls-Royce uses HYDRA in various ways: to assess the aerodynamic efficiency of a design; to assess the unsteady aerodynamic forces acting on blades due to the passing of neighbouring blade rows; to assess the possibility of self-induced vibrations; and to quantify the heat transfer from the very hot gases coming out of the combustor into the high pressure turbine blades. Recent Rolls-Royce products such as the Trent 1000 engine (which powers Boeing 787 aeroplanes) and the newer Trent XWB (the most efficient large aero engine in the world) have made extensive use of HYDRA’s enhanced design capabilities. The Rolls-Royce technological development webpage openly credits HYDRA as one of the key pieces of technology that make up ‘The Rolls-Royce Engineering System’.

The improved accuracy of HYDRA has allowed savings in rig testing and has contributed to increases in engine efficiency. The Trent XWB is Rolls-Royce's fastest-selling Trent engine ever.

‘World-class performance’ - A customer’s assessment of the Rolls-Royce swept fan technology, designed using HYDRA

Research funded by Rolls-Royce.

Photograph of the Trent 1000 engine reproduced with the permission of Rolls-Royce plc, copyright © Rolls-Royce plc 2012.