Aerospace Propulsion option - MSc in Thermal Power and Propulsion

To make students familiar with design, operation, computation and performance criteria of gas turbine (GT) combustion and reheat systems and to explore issues related to gas turbine pollutant emissions.

Introduction to GT combustor design considerations and sizing methodologies:
Diffusion and pre-mixed flame characteristics; GT combustor design features and performance requirements; Design considerations and main functions of the primary, intermediate and dilution zones; Fundamental aspects of the ignition process; Sources of pressure loss; Performance criteria and requirements for pre-combustor diffusers; Faired and dump diffusers; Combustor sizing methodologies based on the pressure loss approach, combustor efficiency requirements and altitude relight requirements.

Combustion efficiency:
Definition of combustion efficiency and combustion efficiency requirements; Evaporation rate controlled systems – influence of fuel type, turbulence and pressure, drop size and residence time; Mixing rate controlled systems; Reaction rate controlled systems – derivation and significance of the “” parameter.

Overview of GT generated pollutants:
Products of combustion and their consequences; Mechanisms of formation of GT pollutants;
Effects on the environment and/or human health; Overview of limitation strategies and associated challenges; Emissions legislation and targets.

GT combustor heat transfer and cooling:
Combustor buckling and cracking; Need for efficient methods of liner cooling; Heat transfer processes (Internal and external radiation, internal and external convection, conduction); Calculation of uncooled liner temperature; Effect of chamber variables on heat transfer terms, liner wall temperature and liner life; Film cooling techniques; Advanced wall cooling techniques; Combustor liner materials and thermal barrier coatings.

GT fuels
Appraise types and properties of fuels; Methodologies to calculate combustion temperatures for various fuel types, mixture strengths and pressures (both non-dissociated and dissociated).

Computational methods for GT Combustors
Role of CFD in combustor design and development; Application of CFD for preliminary design, prognostics and diagnostics of combustion systems.

Introduction to GT afterburners:
Requirement and principle of afterburning; Effects of afterburning on engine performance; General arrangement, main components and design features of afterburners; Ignition methods for GT afterburners; Control requirements and methods for engines with afterburners; Considerations for selection of convergent and convergent-divergent nozzles..

On successful competition of this module you should be able to:

1. Explain and evaluate the concepts underpinning the design of gas turbine combustors and reheat systems for both aero and stationary gas turbines, and explain the influence of the design choices on overall engine configuration and performance; 
2. Assess the influence of: fuel types and preparation, combustion efficiency, ignition requirements, diffuser performance, operational criteria, pollutant emissions and legislation, cooling and material technology on combustor sizing, design and performance; 
3. Apply heat transfer techniques to the calculation of combustor liner temperature and assess the effect of materials, advanced cooling methods and thermal barrier coatings on the life of a combustor liner; 
4. Employ methodologies to calculate combustion temperatures for various fuel types, mixture strengths and pressures;  
5. Distinguish between simple and more advanced computational methods for combustor performance prediction in terms of their modelling and capabilities.

To familiarise students with engine systems or engine designs for stationary and aero gas turbines and technical reporting by examples and sources systematic analysis.

Assessments of engine systems, auxiliaries, families of engines, and/or engine and component designs for both aero and stationary gas turbines are addressed by means of a 'Systems Symposium', run by the MSc class. Topics covered by the systems symposium include: intake systems for aero engines and industrial gas turbines; anti-icing systems for aeroengines and industrial gas turbines; start systems for aeroengines and industrial gas turbines; start sequences for industrial gas turbines; compressor bleed and variable guide vanes; variable geometry nozzle guide vanes; gas path sealing of aero gas turbines; noise control of gas turbines; air filtration for industrial gas turbines; compressor and turbine cleaning systems; full authority and other electronic control systems; key gas turbine component design technologies, etc. Topics may also cover design technologies of gas turbine engines and their components, different families of engine products of major gas turbine manufacturers in different countries, comparison of competitive engines, etc. The objective is to undertake an evaluation of a specified aspect of gas turbine engineering, to make a presentation and to provide a technical review paper or design and assessment on a particular subject. Another aspect of the module is that the presentations are made in a conference format which requires the MSc students to work together to plan, organise and execute the events.


Outline syllabus for a few sample individual topics:
• Ignition system: Requirements and problems of altitude relight. Types of system -booster coils, high frequency, high energy and their applications.
• Starting Systems: Electrical systems - low and high voltage, turbine systems- cartridge, iso-propyl nitrate, fuel-air, gas turbine, low pressure air and hydraulic systems and their applications.
• Air systems: requirements, methods of cooling, pressure balancing of end loads, sealing, and applications.
• Preliminary design of axial high pressure compressor: requirements, design criteria, preliminary design, analysis of design results, etc.
• CFM56 engines: development history, OEM, product description, key technologies, future development, etc.

On successful completion of this module a student should be able to:
1. Compose a structured technical report in the form of a conference paper and a technical presentation.
2. Conduct a systematic analysis of a range of sources to identify, analyse and assess the main technologies of a key aspect of gas turbine engineering.
3. Report and defend the technical outcomes of the systematic analysis in the form of a conference paper and presentation.
4. Work effectively with others in groups to deliver a Gas Turbine Systems Symposium on the basis of a scientific conference.
5. Collaborate in different capacities to formulate a business/management plan to market and communicate the Engine Systems Symposium to the wider gas turbine community for encouraging the attendance of external agencies. 

To familiarise students with the common problems associated with the mechanical design and the lifing of the major rotating components of the gas turbine engine.

Loads/forces/stresses in gas turbine engines: The origin of loads/forces/stresses in a gas turbine engine such as loads associated with: rotational inertia, flight, precession of shafts, pressure gradient, torsion, seizure, blade release, engine mountings within the airframe and bearings. Discussion of major loadings associated with the rotating components and those within the pressure casing including components subject to heating.

Failure criteria: Monotonic failure criteria: proof, ultimate strength of materials. Theories of failure applied to bi-axial loads. Other failure mechanisms associated with gas turbine engines including creep and fatigue. Fatigue properties including SN and RM diagrams, the effect of stress concentration, mean stress etc. Cumulative fatigue, the double Goodman diagram technique to calculate the fatigue safety factor of gas turbine components. Methods of calculating the creep life of a component using the Larson-Miller Time-Temperature parameter.

Applications: The design of discs and blades. Illustration of the magnitude of stresses in conventional axial flow blades by means of a simple desk-top method to include the effects of leaning the blade. The stressing of axial flow discs by means of a discretised hand calculation which illustrates the distribution and relative magnitude of the working stresses within a disc. The design of flanges and bolted structures. Leakage through a flanged joint and failure from fatigue.

Blade vibration: Resonances. Desk top techniques for calculating the low order natural frequencies of turbomachine blades. Allowances for the effects of blade twist and centrifugal stiffening. Sources of blade excitation including stationary flow disturbance, rotating stall and flutter. Derivation of the Campbell diagram from which troublesome resonances may be identified. Allowances for temperature, pre-twist and centrifugal stiffening. Methods for dealing with resonances.

Damage Mechanisms and Lifing: Fundamentals of Creep and Fatigue damage mechanisms. Material, design and operational parameters that affect creep and fatigue. Experimental and test procedures to characterise creep and fatigue damage. Classification of Fatigue-Low Cycle and High Cycle and use of appropriate methods: Strain Vs Stress Methods. Cumulative damage assessment using cycling counting and linear damage rules -Milner Approach.  

To equip students with background knowledge of aircraft propulsion, component performance integration.

The course is divided into two major components: Aircraft Engine and Component Performance and System Performance and Integration

Aircraft Engine and Component Performance
Three main topics are dealt with in this section: Aircraft Performance, Jet Engine Performance, Intakes and Exhaust Systems.

• Aircraft Performance:
Deals with the major topics of flight and aerodynamics, such as lift, drag, range, performance and a section on the design of aircraft for different purposes.

• Jet Engine Performance:
Focuses mainly on the off-design performance of jet engines. Engine behaviour at different altitudes, flight speeds, ambient conditions and throttle settings are described. This topic features a presentation on the design of engines for various types of aircraft.

• Intakes and Exhaust Systems:
Outlines the major design features and operation of the components for subsonic and supersonic aircraft applications.

System Performance and Integration:
This portion of the course starts with the analysis of fundamental aerodynamics of unducted and ducted bodies. This is followed by the development, via the formal definitions of thrust and drag and the concept of stream-tube momentum force, of the relationship between the net propulsive force of the powerplant, engine thrust and nacelle forces. Alternative performance accounting relationships are developed for various choices of thrust interface using force, drag and the hybrid force/drag method. These are employed to illustrate the interplay between component forces. The treatment addresses the long and short-cowl podded nacelles, appropriate to civil engine installations, on- and off-wing; and the highly integrated installations encountered in military aircraft.

• Dr Richard Adams

The importance of technology leadership in driving the technical aspects of an organisation’s products, innovation, programmes, operations and strategy is paramount, especially in today’s turbulent commercial environment with its unprecedented pace of technological development. Demand for ever more complex products and services has become the norm. The challenge for today’s manager is to deal with uncertainty, to allow technological innovation and change to flourish but also to remain within planned parameters of performance. Many organisations engaged with technological innovation struggle to find engineers with the right skills. Specifically, engineers have extensive subject/discipline knowledge but do not understand management processes in organisational context. In addition, STEM graduates often lack interpersonal skills.

• Engineers and Technologists in organisations:
  • the role of organisations and the challenges facing engineers and technologies,
• People management:
  • understanding you, understanding other people, working in teams and dealing with conflicts.
• The Business Environment:
  • understanding the business environment; identifying key trends and their implications for the organisation.
• Strategy and Marketing:
  • developing effective strategies, focusing on the customer, building competitive advantage, the role of strategic assets.
• Finance:
  • profit and loss accounts, balance sheets, cash flow forecasting, project appraisal.
• New product development:
  • commercialising technology, market drivers, time to market, focusing technology, concerns.
• Business game:
  • Working in teams (companies), you will set up and run a technology company and make decisions on investment, R&D funding, operations, marketing and sales strategy,
• Negotiation:
  • preparation for negotiations, negotiation process, win-win solutions.
• Presentation skills:
  • understanding your audience, focusing your message, successful presentations, getting your message across.

On successful completion of this module you should be able to:

• Recognise the importance of teamwork in the performance and success of organisations with particular reference to commercialising technological innovation,
• Operate as an effective team member, recognising the contribution of individuals within the team, and capable of developing team working skills in yourself and others to improve the overall performance of a team,
• Compare and evaluate the impact of the key functional areas (strategy, marketing and finance) on the commercial performance of an organisation, relevant to the manufacture of a product or provision of a technical service,
• Design and deliver an effective presentation that justifies and supports any decisions or recommendations made,
• Argue and defend your judgements through constructive communication and negotiating skills.

To inform course members of the different types of gas turbine; their applications, design and transient performance.
To provide course members with the ability to undertake gas turbine component performance calculations, diagnostics and to perform evaluations of gas turbine performance and deterioration.

Gas Turbine Types and Applications
Effect of design pressure ratio and turbine temperature on the basic gas turbine cycle. Modifications of the basic cycle, compounding, intercooling, reheating, heat exchange, bypass and fan cycles. Simulation of the above.

Performance and Simulation
Design point performance of turbojet and turboshaft cycles, effect of bypass ratio. Off design performance, effect of ambient temperature, altitude, throttle setting and flight speed. Non-dimensional representation. Gas turbine simulation. Effects of bleeds and power offtakes. Compressor turbine matching. Gas turbine degradation. Simulation and diagnostics of the above. Component maps. Surge alleviation, performance improvements, steady state and transient performance. Off-design performance calculations and iteration techniques Accelerations, decelerations, effects on surge margin. Transients of single shaft and multi-shaft engines. Transient performance simulation. Effects of heat transfer on transient performance.
Software used for gas turbine performance simulation: TURBOMATCH

Diagnostics and Monitoring.
Description of gas turbine performance degradation and faults.
Description of most used gas turbine condition monitoring techniques.
Software used for diagnostics: PYTHIA

To familiarise students with compressor and turbine aerodynamic design and performance by instruction, investigation and example. To introduce students to the technology of gas turbine blade cooling through analytical and practical approaches of heat transfer principles, convection cooling, impingement film transpiration cooling and liquid cooling.

Thermofluids: Introduction to aerodynamics, thermofluids, and compressible flows.

Compressor Design and Performance

Overall performance:  Fundamentals of axial flow compressors.  Overall performance, achievable pressure ratio and efficiency. The effect of Reynolds number,                            Mach number, and incidence. Definition of isentropic and polytropic efficiency, effect of pressure ratio, performance at constant speed, surge and surge margin definitions, running line, choking effects.

The axial compressor stage: Stage loading and flow parameters, limitation in design on pitch line basis. Definition and choice of reaction at design, effect on stage efficiency. Loss sources in turbomachines and loss estimation methods. The ideal and real stage characteristic, stall and choke. The free vortex solution, limitations due to hub/tip ratio. Off-design performance Choice of overall annulus geometry, axial spacing, aspect ratio, limitations of rear hub/tip ratio. Compressor blading: selection of blade numbers, aspect ratio and basic blade profiling.

Compressor design example: Multi-stage compressor design example carried out for a HPC.

Turbine Design and Performance

Overall performance: the expansion process and characteristics, annulus layout and design choices, choice of stage loading and flow coefficient, engine overall performance requirements, overall annulus geometry and layout; rising line, constant mean diameter and falling line.

The axial turbine stage: Aerodynamic concepts and parameters, velocity triangles, reaction, stage loading, flow coefficients. The ideal and real characteristic. Design  for maximum power: effect of choking and change of inlet temperature and pressure.  Stage efficiency, overtip leakage, profile losses, correlations. Three-dimensional design aspects. Radial equilibrium and secondary flows.

Turbine blading: choice of base profile, blade numbers and aspect ratio. Zweiffel's and alternative lift coefficients.

Turbine Design Example: An aerodynamic design example is carried out for a HPT Heat Transfer Principles: Brief review of heat transfer principles and physical significance of non-dimensional groupings. Conditions around blades, boundary layers, external heat transfer coefficient distribution, effect of turbulence. Root cooled blades and NGVs, analytical and numerical methods of determining spanwise temperature distribution. Fibre strengthened and nickel base alloys.

Need for high turbine entry temperature: effect on engine performance.

Development of materials, manufacturing processes and cooling systems.

Convection Cooling: Convectively cooled aerofoils: analytical approach for metal and cooling air spanwise temperature distribution. Cooling passage geometry and heat transfer characteristics. Cooling efficiency, cooling effectiveness and mass flow function: application at project design stage for determining metal and cooling air temperatures. Methods for optimising cooling system design: secondary surfaces and multipass. Internal temperature distribution of cooled aerofoils: calculations, comparisons with experimental results.

Impingement, Film and Transpiration Cooling: Principles steady state and transient performance, characteristics, advantages, limitations, comparison with convection cooling. Cooling air feed and discharge systems. Integration of cooled turbine with aerodynamic performance and main engine design. Co-ordination of design responsibilities. Example of cooled turbine stage design.

Liquid Cooling: Liquid cooling: principles, advantages and limitations, practical examples.

On successful completion of this module students should be able to:

1. Identify and analyse the design and performance characteristics of turbomachinery components;
2. For given inlet conditions and requirements, determine the aerodynamic performance characteristics of a turbomachine and comment on the feasibility of the design; 
3. Differentiate the key design choices for axial compressors and turbines; 
4. Construct an assessment of the aspects which affect the design and performance of axial turbomachines;
5. Apply formulations and critical evaluations of underpinning turbo-machinery theories; 
6. Explain the requirement for ethical and professional conduct in the use of data and in the presentation of results and calculations;
7. Explain the major differences between the various heat transfer and cooling architectures and apply the concepts and theories of heat transfer and different cooling technologies to the cooling of turbine blades to produce a realistic assessment of their cooling requirements.