Study on the effects of narrow-throat pre-chamber geometry on the pre-chamber jet velocity using dual formaldehyde PLIF imaging

Qinglong Tang, Ramgopal Sampath, Priybrat Sharma, Manuel Echeverri Marquez, Emre Cenker, Gaetano Magnotti

Research output: Contribution to journalArticlepeer-review

28 Scopus citations


The effects of narrow-throat pre-chamber geometry on the main chamber combustion were investigated on a heavy-duty optical engine fueled with methane. Simultaneous dual formaldehyde PLIF imaging and OH* chemiluminescence imaging were applied to characterize the early-stage formaldehyde jet and flame jet discharge process. The formaldehyde jet velocity on the jet boundary was quantified by dual formaldehyde PLIF for the first time. Three narrow-throat pre-chambers with two rows of orifices on the nozzle and with different pre-chamber volume and inner throat diameter were studied under the same pre-chamber to main chamber fuel ratio and global excess air ratio of 2.0. The results indicate that the narrow-throat pre-chamber performance is not very sensitive to the pre-chamber volume. The pre-chamber with a larger volume produces only slightly higher pressure buildup in the pre-chamber () and similar main chamber combustion phasing and engine efficiency. The inner throat diameter is the key dimension in the narrow-throat pre-chamber design. A larger inner throat diameter produces a smaller peak and a slower jet penetration, resulting in longer combustion duration and lower engine efficiency. The formaldehyde PLIF shows that the main chamber combustion can be generally classified into two stages: the initial flame ignition and the following flame propagation. The maximum local formaldehyde jet boundary velocity of the narrow-throat pre-chamber with an inner throat diameter of 3.3 mm is up to about 280 m/s and it decreases dramatically when the inner throat diameter is increased to 5.3 mm. The flame jet characteristics of lower and upper orifices can be significantly different due to the local pressure difference between them in the pre-chamber throat. A smaller inner throat diameter results in a larger pressure difference between the lower and upper row orifices and could lead to weak upper-row flame jets. The narrow-throat pre-chamber design with an optimized inner throat diameter can produce high, fast jet penetration, and short combustion duration, which favor the lean limit operation and high engine efficiency.
Original languageEnglish (US)
Pages (from-to)111987
JournalCombustion and Flame
StatePublished - Jan 22 2022

Bibliographical note

KAUST Repository Item: Exported on 2022-01-25
Acknowledgements: The paper is based upon the work supported by Saudi Aramco Research and Development Center FUELCOM3 program under Master Research Agreement Number 6600024505/01. FUELCOM (Fuel Combustion for Advanced Engines) is a collaborative research undertaking between Saudi Aramco and KAUST intended to address the fundamental aspects of hydrocarbon fuel combustion in engines and develop fuel/engine design tools suitable for advanced combustion modes. The authors would like to thank Ponnya Hlaing and Moez Ben Houidi from KAUST for their lab support and Prof. Bengt Johansson from Chalmers University of Technology for his helpful suggestions.

ASJC Scopus subject areas

  • Energy Engineering and Power Technology
  • General Physics and Astronomy
  • General Chemical Engineering
  • General Chemistry
  • Fuel Technology


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