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Mechanical Integrity of Gas Turbines
- 28 April - 02 May 2014
- Duration: 1 week
- Location: Cranfield campus
In the world of turbomachines, mechanical failures are expensive, often even more expensive than the failure to achieve a thermodynamic target. The modern trend is towards ever higher temperatures and rotating speeds making the attainment of mechanical integrity increasingly difficulty. However, the need for improved reliability and, in general, for lighter machines creates an enormous challenge to gas turbine engineers.
The School of Engineering in Cranfield has for many years had one of the largest programmes in the world of short courses in Gas Turbine Technology. The course, which deals with matters of mechanical integrity and lifing of gas turbines, both aeronautical and industrial, has been developed over the last 30 years as a component part of that programme.
The course aims to provide participants with the ability to carry out a simple stress and lifing analysis of turbmachine blades and discs. In addition, the determination of the natural frequencies of blades and their interaction with engine orders on Campbell diagrams will be addressed.
The course includes detailed coverage of the following topics:
How the Loads Arise
The origin of loads in a gas turbine engine is discussed. The major loads covered are those due to the engine cycle, rotational inertia, flight manoeuvre, precession, pressure, thermal gradient, torsion, seizure and blade release. Engine Mounting and bearing loads are also included.
At this stage the iterative loop load-geometry-stress-failure-redesign is completed by defining the various ways in which a material may fail and its strength defined. Monotonic properties,proof, ultimate etc. Creep properties, Larson-Miller, cumulative effects. Fatigue properties, SN and RM diagrams, influences such as stress concentration, mean stress etc. Cumulative fatigue, LCF, double-Goodman diagram technique, lifing rules, Neuber, “Rainflow” cycle counting. Fracture, LEFM, stress intensity factors, lifing from the Paris curve, damage tolerance, “retirement for cause” etc.
At this point methods for the design of specific components such as discs and blades are introduced: Axial flow discs, stressing by means of a discretised hand-technique which illustrates the distribution and relative magnitude of stresses within a conventional disc. Discussion of blade attachments. Axial flow blades: illustration of magnitude and distribution of stresses in a conventional axial flow blade by means of simple desk top methods, blade leaning etc. Flanges and bolted structures: design of flanged/bolted structures to resist leakage and failure from fatigue, bolt pitching rules etc.
In this section the main processes carried out by the vibration engineer are described. Determination of the natural frequencies of components such as blades, disc etc. both experimentally and from simple analytical techniques. In particular a reasonably accurate method for the determination of low-order natural frequencies of turbomachine blades are developed. Sources of excitation: stationary flow disturbances etc. Derivation of a figure which resonances may be identified, named variously the Campbell diagram, interference diagram, spoke diagram etc. Allowance for temperature, pre-twist and centrifugal stiffness. A methodology for dealing with resonances. Shaft Dynamics: critical speeds, squeeze-film dampers.
Gas Turbine Materials
Gas Turbine materials are required to withstand extreme stresses sometimes at temperatures in excess of their melting point. An overview of the latest materials technology for both hot and cold components is provided. The lectures cover advances in compressor blade materials, the technologies used in the manufacture of high temperature turbine blades and materials coating technologies.
- Whilst no precise academic standards are required, the course will be of greatest benefit to members with a background which helps them to understand the subject matter, probably in science or technology. However, the desire to understand can sometimes compensate for any lack of previous experience. The course should be of benefit to engineers who require a basic understanding of the processes involved in the mechanical design and the life estimation of major gas turbine engine components.
The course is presented through lectures and tutorials conducted by members of Cranfield University’s staff all of whom have considerable academic and industrial experience. Additional lectures will be presented by senior engineers from industry.
- This 5 day course is presented through a mixture of lectures, tutorials and worked examples. Printed course material is provided for delegates use during and after the course. Active participation from the delegates is strongly encouraged particularly during the worked examples in order to consolidate learning. All delegates will receive a Certificate of Attendance upon completion of this course.
The course fee includes refreshments and lunch during the day. Accommodation is not included and must be booked separately.
Cranfield University is located at the very heart of the UK – within the innovation triangle between London and the cities of Oxford and Cambridge.
Our central location provides easy access from the M1, excellent main line rail service as well as proximity to key international airports. Set in rolling countryside, Cranfield offers a rich, rural landscape complemented by thriving towns and picturesque villages.
- Road: We are just 10 minutes from Junctions 13 and 14 of the M1 motorway. There is free parking on campus.
- Rail: Milton Keynes or Bedford
- Air: London Luton (22 miles), Heathrow (50 miles) or Birmingham (70 miles).
Accommodation is available at Mitchell Hall which is located on campus. All rooms are en-suite and bookings are on a half-board basis from Sunday to Friday. If you would like to book accommodation for this short course at Mitchell Hall, please indicate this on the registration form and we will arrange this for you.
Alternatively, you may wish to make your own arrangements at a nearby hotel.