DATE:                        4.3.25

TIME:                         12:00pm

LOCATION:              33-116

SPEAKER:                Professor Robert Miller, University of Cambridge

TOPIC:                        Irreversibility and Loss: A New Practical Relationship

Abstract

The talk will describe a new relationship between an irreversibility in a system and the increase in that system’s energy which is unavailable for work extraction. The ideas presented also provide an explanation for a longstanding, and puzzling, asymmetry observed between the impacts of irreversibility, in thermal mixing compared to velocity mixing, on turbine efficiency, thus removing previous empirical ‘work arounds’ in gas turbine engine design. The root cause of the asymmetry is the definition of available energy in terms of a universal reversible machine, i.e., a reversible adiabatic turbine, or piston-cylinder combination, plus a reversible heat engine. That definition is shown to be inconsistent, in many cases, with the actual method of extracting work from a flow. In such cases, only the direct work transfer, by the turbine or piston, bringing the flow to the environmental pressure, is relevant, rather than a process including reversible heat transfer to bring the flow to the environmental temperature as well. The talk will include examples to illustrate the concepts that underpin the new relationship and their application in situations of high technological interest.

Biography

Professor Rob Miller is the Chair in Aerothermal Technology at the University of Cambridge. He serves as Co-Director of the Whittle Laboratory and Director of the Rolls-Royce University Technology Centre in Cambridge. He is also the founder of the Aviation Impact Accelerator (AIA), a global initiative that brings together leading experts to develop evidence-based tools aimed at raising ambition and driving action toward achieving net zero aviation. He is currently leading the development of the new Whittle Laboratory which will open in early 2026. His research has received the American Society of Mechanical Engineers’ Gas Turbine Award four times, the AIAA Airbreathing Propulsion Award, and the Institution of Mechanical Engineers Thomas Hawksley Gold Medal. He is a Fellow of the Royal Academy of Engineering and a member of the UK Government’s Jet Zero Forum.