Heat exchanger design in combined cycle engines

Helen Webber, Simon Feast, Alan Bond

Research output: Contribution to journalArticleResearchpeer-review

26 Citations (Scopus)


Combined cycle engines employing both pre-cooled air-breathing and rocket modes of operation are the most promisingpropulsion system for achieving single stage to orbit vehicles. The air-breathing phase is purely for augmentation of the mission velocity required in the rocket phase and as such must be mass effective, re-using the components of the rocket cycle, whilst achieving adequate specific impulse. This paper explains how the unique demands placed on the air-breathing cycle results in the need for sophisticated thermodynamics and the use of a series of different heat exchangers to enable precooling and high pressure ratio compression of the air for delivery to the rocket combustion chambers. These major heat exchanger roles are; extracting heat from incoming air in the precooler, topping up cycle flow temperatures to maintain constant turbine operating conditions and extracting rejected heat from the power cycle via regenerator loops for thermal capacity matching. The design solutions of these heat exchangers are discussed.

Original languageEnglish
Pages (from-to)122-130
Number of pages9
JournalJournal of the British Interplanetary Society
Issue number4
Publication statusPublished - Apr 2009
Externally publishedYes


  • Combined cycle engines
  • Heat exchangers
  • Precoolers
  • SABRE engine

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