Undergraduate Teaching 2022-23

Engineering Tripos Part IB, 2P8: Aerothermal Engineering, 2017-18

Engineering Tripos Part IB, 2P8: Aerothermal Engineering, 2017-18

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Dr G Pullan and Dr C Hall

Timing and Structure

Easter Term: 14 lectures + 2 examples classes, 4 lectures/week.


The aims of the course are to:

  • Understand why current engines on large airliners look as they do, how they work and how they are specified.
  • Determine what is needed to propel a new large airliner.
  • Appreciate the mixture of physical modelling and empirical input necessary to make the decisions to allow a design to proceed, as well as the need for compromises.


As specific objectives, by the end of the course students should be able to:

  • Calculate the major parameters of the engine (this will be carried out in the form of exercise questions throughout the course).
  • Make appropriate design choices for engine components.
  • Sketch a cross-section of the engine showing principal components with appropriate parameters.
  • Calculate the effect of speed and altitude on engine performance.


Modern jet engines are amongst the most expensive mechanical engineering devices to design and develop; a new engine is expected to cost several billion pounds. Why is it so expensive? Why do they look the way they do?

Many of the most important decisions are taken at an early stage of design using fairly simple procedures, similar to those that can be used in lectures and example classes. The constraints, especially those associated with material properties, need to be known or specified, together with estimates for the likely level of aerodynamic performance. From these the desirable type of engine configuration can be specified, preliminary choices for the main components (compressor and turbine) can be made and a sketch of the engine layout can be drawn.

Introduction to Aircraft Propulsion

  • Operating principles,key aircraft parameters, nacelle/wing arrangements
  • Design constraints, environmental issues and fuel burn.

Aircraft performance

  • Basic aircraft aerodynamics, sizing the wing, lift-drag relationships.
  • Breguet range equation, estimation of aircraft fuel burn and emissions.
  • Thrust requirements, trade-offs between weight and performance.

Generation of thrust

  • Momentum analysis, propulsive efficiency, overall efficiency.
  • Choice of engine type for given duty; high subsonic cruise compared with supersonic operation.

Thermodynamic Analysis of Gas Turbine

  • Power generation: effect of pressure ratio, temperature ratio and component efficiency.Relationship between thermal efficiency and cycle efficiency.
  • Jet propulsion as a means for utilisation of power.

Choice of Engine

  • Selection of bypass ratio and calculation of corresponding engine mass flow.
  • Turbine inlet temperature and blade cooling.
  • Calculation of fuel consumption in determining fan diameter.

High Speed Flow of Gas

  • Subsonic and supersonic flow, nozzle flow, choking.

Dimensional Analysis

  • Dynamic scaling of jet engine.
  • Start-of cruise is the design condition - estimating thrust and fuel consumption at off-design conditions, such as take off.
  • To consider requirements for thrust in case of engine failure at take off or cruise.

Turbomachinery Principles

  • General introduction to operation of compressors and turbines.
  • Selection of number of stages in compressor and turbine.

Appraisal of Design

  • Having specified overall size, bypass ratio, turbine inlet temperature, sketch engine layout and compare with existing designs.


Please see the Booklist for Part IB Courses for references for this module.

Examination Guidelines

Please refer to Form & conduct of the examinations.


The UK Standard for Professional Engineering Competence (UK-SPEC) describes the requirements that have to be met in order to become a Chartered Engineer, and gives examples of ways of doing this.

UK-SPEC is published by the Engineering Council on behalf of the UK engineering profession. The standard has been developed, and is regularly updated, by panels representing professional engineering institutions, employers and engineering educators. Of particular relevance here is the 'Accreditation of Higher Education Programmes' (AHEP) document which sets out the standard for degree accreditation.

The Output Standards Matrices indicate where each of the Output Criteria as specified in the AHEP 3rd edition document is addressed within the Engineering and Manufacturing Engineering Triposes.

Last modified: 31/05/2017 10:02