A phenomenological model for near-nozzle fluid processes: Identification and qualitative characterisations

Dan Sykes, Viacheslav Stetsyuk, Jack Turner, Guillaume de Sercey, Martin Gold, Richard Pearson, Cyril Crua

Research output: Contribution to journalArticlepeer-review


It is well established that emissions and inefficiencies primarily arise from localised fuel rich regions, which do not undergo complete combustion. In order to achieve significant reductions in NOx and soot, modern engines employ multiple injection and flow rate profiling strategies. However, during the end of each injection event, the needle restricts the internal flow of fuel, rapidly reducing the inertia of the emerging spray. Atomisation is inhibited and large fluid structures are released into the cylinder. Once the flow subsides, fuel films remain on the nozzle surface well into the cycle. Fuel residing in the nozzle cavities emerges as the cycles progresses, amalgamating with the spray deposited films. The surface-bound fuel presents an ideal environment for deposit forming reactions and a medium for precursors to adhere onto. In order to better understand these processes we performed measurements of injection transients inside an optical reciprocating rapid compression machine, using high-speed long-distance microscopy to obtain detailed characterisations of fuel films on the surface of an injector. We summarise our observations into a new phenomenological model which describes the uncontrolled release of fuel over an entire engine cycle. This model identifies the micro-scale processes that lead to the ejection, accumulation and vaporisation of fuel in-between injection events. Characterisation of these critical, transient processes can support mitigation strategies that inhibit pollutants and the formation of injector deposits.
Original languageEnglish
Article number122208
Issue numberPart A
Publication statusPublished - 10 Nov 2021

Bibliographical note

Funding Information:
This work was supported by the UK’s Engineering and Physical Science Research Council [EPSRC grants EP/K020528/1 and iCASE Studentship 1793447 ] and BP International Ltd .

Publisher Copyright:
© 2021 The Author(s)


  • High-speed microscopy
  • Dribble
  • Split injections
  • Cavitation
  • Rarefaction
  • Spray wetting
  • Fuel discharge
  • Gas ingestion
  • Surface films
  • Low load
  • Idling
  • Near-nozzle region
  • Injector deposits


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