Dr David Toal from the Rolls-Royce University Technology Centre for Computational Engineering in Southampton recently gave a talk on turbine blade design in the presence of uncertainty and (despite a power outage in most of Southampton that afternoon) presented the associated design and research challenges.
Dr Toal introduced the audience to several engineering challenges including the complex aerodynamic shape, mechanical issues such as the high rotational speeds, creep and fatigue as well as the extremely high temperatures (in excess of 1700K) encountered in gas turbines, well above the metal’s melting point and requiring complex cooling schemes. Technologies used to cool turbine blades for example include highly sophisticated internal cooling channels, film cooling and thermal barrier coatings. On top of all that, complicated manufacturing restrictions must be considered.
Another aspect is to incorporate design uncertainties that can be encountered during operation. For example:
- aerodynamic (combustion and nozzle guide vane exit pressures, turbulence levels, …)
- structural (material properties, loads, …)
- thermal (fluid temperature, hot spot location, …)
- manufacturing (blade shape, position, hole diameter, angle, fir tree shape, …)
The PhD project at the NGCM in Southampton, sponsored by the EPSRC and Rolls-Royce deals with this kind of research. The uncertainties in the cooling hole geometry will need to be quantified and the impact of any variations will need to be simulated (and validated) using CFD to determine what impact these changes have on the blade’s temperature. Then, using the automated simulation system, a design optimisation can be performed. The final challenge will be to make this kind of optimisation affordable despite the complexity of the optimisation due to the large number of design variables.
Posted by Jan Kamenik