Starting to Unpick the Unique Air–Fuel Mixing Dynamics in the Recuperated Split Cycle Engine

Simon A Harvey, Konstantina Vogiatzaki, Guillaume De Sercey, William Redpath, Robert Morgan

Research output: Contribution to journalArticlepeer-review


In this work air fuel mixing and combustion dynamics in the recuperated split cycle engine (RSCE) are investigated through new theoretical analysis and complementary optical experiments of the flow field. First, a brief introduction to the basic working principles of the RSCE cycle will be presented, followed by recent test bed results relevant to pressure traces and soot emissions. These results prompted fundamental questioning of the air-fuel mixing and combustion dynamics taking place. Hypotheses of the mixing process are then presented, with differences to that of a conventional Diesel engine highlighted. Moreover, the links of the reduced emissions, air transfer processes and enhanced atomisation are explored. Initial experimental results and Schlieren images of the air flow through the poppet valves in a flow rig are reported. The Schlieren images display shockwave and Mach disk phenomena. Demonstrating supersonic air flow in the chamber is consistent with complementary CFD work. The results from the initial experiment alone are inconclusive to suggest which of the three suggested mixing mechanism hypotheses are dominating the air–fuel dynamics in the RSCE. However, one major conclusion of this work is the proof for the presence of shockwave phenomena which are atypical of conventional engines.
Original languageEnglish
Article number2148
Issue number8
Publication statusPublished - 12 Apr 2021

Bibliographical note

Funding Information:
Funding: The authors acknowledge funding by the UK’s Engineering and Physical Science Research Council support through the grant EP/P012744/1.

This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited


  • Air–fuel mixing
  • Atomisa-tion
  • Efficiency
  • Emissions
  • Internal combustion engine
  • Recuperated split cycle engine
  • Thermal propulsion system


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