The gas turbine engine is a complex machine requiring operation at extremes of pressure and temperature and demanding expertise at the highest level of engineering technology.
Concurrent engineering practices in the industry require the individual to have a thorough appreciation of the interaction between the various components of the engine. In addition, interactions between aerodynamics, thermodynamics and mechanical integrity for a particular component must be thoroughly understood if an individual is to make a useful contribution in gas turbine design and performance assessment.
Who should Attend
The course is designed for new graduates/trainees or equivalent who will be closely involved in engine design or performance evaluation in the gas turbine manufacturing or user industries. The course will also be of value to experienced engineers in the gas turbine manufacturing and user industries who have a need for an overview of the design and performance of the whole engine.
On completion of the course, the delegate should be able to:
- make a reasoned selection of the major performance parameters according to engine application.
- broadly understand the impact on design and performance of the joint constraints of mechanical and thermal issues and the need for adequate off- design performance.
Gas turbine fundamentals
Fundamental fluid mechanics applied to the gas turbine engine. Properties of gases including entropy and viscosity. Reynolds number effect and qualitative treatment of boundary layer behaviour. Adiabatic and isentropic flow, static and stagnation conditions. Mass flow functions and choking.
Gas turbine performance
An introduction to ideal cycles. Component and cycle efficiencies and their relationship with specific consumption and air miles per gallon. Design-point analysis of turbojet, turboprop and turbofan (bypass) cycles. Influence of pressure ratio, peak temperature, by-pass ratio and flight conditions on specific thrust and fuel consumption. Use of non-dimensional groupings.
Gas turbine applications
Comparison of behaviour of different engine types; choice of engine parameters for given duty.
Axial compressor design and performance
Overall problems of diffusing airflows. The overall compressor characteristic, real and ideal, stall and choke, the surge line, running line, effect of changes in inlet pressure and temperature. Off-Design performance, use of variable IGV's, air bleed, multi-spooling. Choice of annulus geometry, tip speed, etc.
Axial turbine design and performance
Overall problems of expanding airflows. The importance of passage shape. Choice of blade profile shape, prescribed velocity distribution. The axial turbine stage, velocity triangles, reaction, stage loading and flow coefficients; Limiting values. Design for maximum power, effect of Mach number, effect of choking and changes of inlet temperature and pressure. Factors affecting efficiency, efficiency correlations. Choice of design point according to application.
The following topics are treated at an introductory level:
Burning velocity; effects of pressure, temperature and turbulence. Performance criteria of combustion chambers; combustion efficiency, stability and ignition performance, temperature traverse quality. Fuel injection methods; spray injection, vaporising tubes, airblast atomisers. Gaseous pollutants, mechanism of production of CO, NOx, UHC and aldehydes. Carbon formation and exhaust smoke, use of alternative and residual fuels in gas turbines. Combustor cooling.
Hydrocarbon fuel molecular structure and behaviour. Conventional petroleum fuel types and preparation. Laboratory test methods and results. Significance of test results in fuel handling and combustion performance. Aviation fuel specifications, and reasons for recent amendments. Current problems: thermal stability, linear temperature, smoke formation, etc. Expected changes in fuel quality. Alternative fuels for use in the short and long term.
Origin of loads on gas-turbine components. Factors and strength criteria for proof, ultimate, creep, fracture and fatigue cases. Integrity of specific components such as discs, blades, shafts, combustion chambers, casings, flanges, etc. Cumulative creep. Fatigue and Fracture Mechanics -. Effects of cyclic loading. Paris Law, mean stress effects. Types of vibration encountered in the gas turbine. Blade modes of vibration, including centrifugal and thermal effects. Methods of determining natural frequencies. Production of frequency diagram and methods of overcoming vibration problems. Critical speeds of shafts and alleviation by means of squeeze-film damper bearings.