Advanced Propulsion

Module aims

The aims of this course are to introduce students to the complexities of high-speed propulsion, and how alternative technologies can be employed in operational conditions where conventional gas turbines are no longer practical. Concepts of compressible reacting internal flows, thermodynamics and gasdynamics will be applied to the analysis of advanced engines.

Learning outcomes

Knowledge and understanding
On successfully completing this course unit, students will be able to:
Identify and carry out a thermodynamic and gas dynamic analysis of engines used in high-speed flight.

Skills and other attributes

Intellectual skills

  • Identify the limitations of conventional turbofans and turbojets in high-speed applications;
  • Identify the limitations of ramjets and the complexities of supersonic ramjets;
  • Identify and analyze a number of non-air-breathing and combined-cycle engines;
  • Discuss the thermodynamics of combustion and detonation

Practical skills

  • Design inlet geometries to extend the operational envelope of turbojets to supersonic flight;
  • Design compressor nozzles geometries for high-speed applications;
  • Design and carry out a thermodynamic and gas dynamic analysis of a complete ramjet engine;

Transferable skills
Analytical and numerical solution of problems in gas dynamics and propulsion.
 

Module syllabus

This is an advanced course in the aerodynamic and thermodynamic analysis of propulsion systems for high-speed flight. The fundamental physics of compressible, reacting flows will be reviewed. The design and analysis of supersonic intakes and both external and internal compressors will be introduced. The limitations of subsonic combustion will be discussed, in the context of high-speed flight. Students will also be introduced to design practice for diverging nozzles, including a review of method of characteristics for 2D nozzle design and approximate methods for 3D bell, spike and aerospike nozzles. Propulsion systems for high-altitude, high speed flight will also be introduced, including solid, liquid and hybrid rocket engines, pulse-jets and pulse-detonation engines, including the thermodynamic cycle analysis of these systems.

Lecture 1-2: Overview of history and challenges of high-speed flight; review of compressible flow (governing equations, isentropic flow, normal shocks, oblique shocks and P-M waves)
Lecture 3-4: Limitations of conventional turbomachines in high-speed flight; extension of turbojet envelope, design of supersonic inlets and techniques for shock-swallowing; external compression and ramp inlet design.
Lecture 5-6: Ramjets. Intake-to-nozzle design of ramjet engines for specified flight conditions, including thermodynamic efficiency and cycle analysis.
Lecture 7-8: Supersonic nozzle design. Review of method of characteristics for 2-D nozzles, and Rao's method for length-thrust tradeoff. External expansion, exact and approximate spike nozzle design.
Lecture 9-10: Rocket engines. Concepts of mono- and bi-propellant propulsion. Review of rocket types: cold-gas, hot-gas, gas-pressurized, solid fuel, turbopump and hybrid. Dynamics of single- and multi-stage rocket launch; analytical justification of staging. Thermodynamic cycle analysis of turbopumps with cryogenic fuels; Rankine cycle with liquid hydrogen; practical design issues for cryogenic turbopumps.
Lecture 11-12: Hybrid propulsion systems. Analytical justification for airborne rocket launch. Rockoons, air-launched rockets and the HARP Martlet. Turbomachine boosting and oxidizer-injection; thermodynamic analysis of mass-injection pre-compression cooling, experimental findings and coolant issues. Compressionless propulsion, harmonic pulse-jets and the Lenoir cycle.
Lecture 13-14: Pulse-detonation engines. Introduction to detonation thermodynamics and the Chapman-Jouguet model. Thermodynamics and gas-dynamics of detonations and the thermodynamic efficiency of the Humphrey cycle. Approximate methods for the determination of detonation velocity in hydrogen-air mixtures; introduction to fuel-air detonation data plots and approximate methods for pulse-detonation engine design. Practical issues in PDE design, material limitations and the continuous-detonation engine.
Lecture 15-16: Alternative energy in aviation. The concepts of energy-density and power-density. Comarison of hydrogen-air, hydrogen-oxygen and hydrocarbon-air combustion to existing alternative energy sources. Batteries, fuel cells and bio-kerosene. Combustionless turbopropulsion. HALE aircraft propulsion, dirigibles and safety considerations.

Pre-requisites

AERO50009 Propulsion and Turbomachinery

Teaching methods

Lectures and tutorials; individual and group project work

Assessments

Examined Assessment
2 hour written examination in Summer term (75%),
Coursework Assignment (25%)

Non-Examined Assessment
N/A.

Reading list