Turbomachinery component manufacture by application of electrochemical, electro-physical and photonic processes
Introduction
The demand for turbomachinery systems such as aero-engines, stationary gas and steam turbines as well as turbochargers for engines is constantly growing due to the increasing worldwide requirement for energy and mobility. In contrast, conventional energy resources such as oil, gas and coal together with important raw materials are shrinking while environmental pollution due to CO2 and NOx emissions is on the rise. Thus, energy and fuel prices as well as costs for environmental protection and sustainability are constantly increasing, necessitating the development and introduction of highly efficient turbomachinery systems.
Taking the aerospace sector as an example, air traffic is resiliently growing at a rate of 4–5% a year both for revenue passenger (RPK) as well as cargo traffic tonne kilometres (RTK), practically doubling within 15 years. According to the ‘Global Market Forecast 2012-32’, Airbus predicts a doubling of the passenger aircraft fleet (≥ 100 seats: single/twin-aisle and very large) from 16,094 to 33,651 by 2032. Including replacements, some 28,355 new aircraft deliveries are anticipated. Similar numbers are presented in Boeing's ‘Current Market Outlook 2013-32’ showing the 20,310 aircraft (regional jets, single aisle, small/medium/large widebody) currently in service increasing to 41,240 by 2032 with new deliveries of 35,280 [29], [86], [123]. In terms of aeroengines, Rolls-Royce expects ∼68,000 deliveries (including business jets) over the period 2012-31, with a market value of $975 billion [164]. Adding to this, the servicing of commercial engines involving maintenance, repair and overhaul (MRO) is also growing in importance. Within GE Aviation, the service market for 2011 amounted to $7.2 billion while the new engine market was $4.9 billion [100].
Besides market growth, the challenges faced by industry are also growing, because future aircraft including the engines must also be more fuel efficient, quieter and cleaner due to official regulations and agreements. The new ACARE (Advisory Council for Aviation Research and Innovation in the EU) goals for 2050, schedule a reduction of 75% in CO2, 90% in NOx and 65% in noise relative to 2000 [2], [86]. In summary, there is an extensive and pressing need for design – as well as advanced manufacturing and repair technologies able to handle the current and growing future demands for turbomachinery components.
Section snippets
Challenges of turbomachinery component manufacture
Core functional components of turbomachinery systems are characterised by the use of dedicated high temperature, high specific strength and wear-resistant materials (Fig. 1).
Machining such “difficult-to-cut” materials using conventional means is very challenging, often resulting in low material removal rates (MRR), reduced precision due to high cutting forces, high tooling costs due to increased wear and consequently low process efficiency [178]. In addition, the resulting surface integrity is
Economical process chain analysis and cost modelling
For efficient turbomachinery component manufacture, an economic analysis of individual process technology alternatives as well as the resulting process chains is required. Machining processes with low material removal rates but relatively low machine running costs such as EDM must be evaluated in such a way in order to be competitive against other conventional or advanced manufacturing technologies. Therefore, by performing parallel technological and economic analysis of each operation, optimal
Summary and conclusions
The technical capabilities and areas of application of electro-chemical, electro-physical and photonic processes have been analysed showing the broad potential of ECM, EDM, additive manufacturing and laser material removal for the manufacture of turbomachinery components. Clear advantages have been identified for their use when machining advanced and difficult-to-cut materials, including high removal and deposition rates, superior geometrical precision and acceptable surface integrity. The case
Acknowledgements
The authors would like to express their sincere thanks to R. Perez (GF AgieCharmilles), M. Cuttell (Rolls-Royce), P. Harpham, J. Durrant (Siemens Industrial Turbomachinery); M. Zeis, D. Welling (WZL RWTH Aachen University); H. Krauss, J. Weirather (IWB, TUM) and O. Hentschel, M. Karg, C. Scheitler (LPT, Universität Erlangen) for their assistance in the paper preparation. We would also like to thank the STC-E members involved for their help.
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