Pre-Chamber Ignition
A road towards High Efficiency Natural Gas Engines
Ashish Shah, Per Tunestål and Bengt Johansson
Lund University, Sweden
Energirelaterad fordonsforskning 2014
2014-10-08
Gothenberg, Sweden
Outline
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Introduction
Motivation and relevance
Past activities and results obtained
Future plans
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Introduction
• Administrative details of the project
Name
Gas Engine Project
Phase 6: 2010-01-01 to 2013-12-31
Timeline
Phase 7: 2014-01-01 to 2017-12-31
Principal beneficiary Lund University
Volvo, Volvo Cars, Scania, Cummins, Toyota,
Other partners in
Chevron, Loge, Dantec, Swedish Biomimetics
the project
and Wärtsilä
Competence Center Combustion Processes,
Parent program
KCFP
KCFP in total is 101 MSEK for phase 7. The gas
Total support
engine project part of that is 12.12MSEK.
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Introduction (cont.)
• Aim – Develop combustion strategies for internal
combustion engines operating on gaseous fuels for heavy
duty applications with comparable or better fuel
efficiency and operating load range than diesel
counterparts
• Current focus is on study of alternative ignition
techniques for heavy duty natural gas engines with the
following objectives:
– Extend the limit of combustion dilution with excess air, Exhaust
Gas Recirculation (EGR) or both.
– Increase the maximum operating load
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Motivation and Relevance
• Natural Gas – an attractive alternative fuel
– Lower specific CO2 emissions
– Availability – naturally occurring and renewable
alternatives (e.g. biogas etc.)
• Variety of applications – heavy duty on-road vehicles
(e.g. trucks with LNG), marine engines and power
generation (e.g. Wärtsilä and MAN products)
• Increasing network on natural gas fueling stations in
Sweden and worldwide.
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Why Pre-chamber ignition?
Problems with open chamber spark ignited engines
 Simple and cheap
 Well developed and mature
technology
 Limit of dilution with excess air or EGR
– combustion instability
 High temperature combustion – High
heat losses and NOx emissions
 Maximum load limited by knock
 Knock limited combustion phasing
advance – loss in efficiency
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Why Pre-chamber ignition?
Pre-chamber ignition – a possible solution
(≈ 5% Vc)
 Spatially distributed ignition source
 Less affected by cyclic variation of main chamber charge motion
 Burning jets provide much higher ignition energy than a spark
 Pre-chamber over heating may cause charge pre-ignition
 Resulting ignition mechanism is less understood due to its fluid
dynamic and chemical kinetic complexities
(≈ 95% Vc)
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Different strategies
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Experiments and Results
obtained so far…
2011 - 2014
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Experimental Setups
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Experimental Setups (cont.)
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Lean limit with excess air
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Indicated Efficiency
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NOx emissions
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Effect of Pre-chamber geometry
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Effect of Pre-chamber geometry (cont.)
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Conclusions
• A pre-chamber ignition device without additional fueling
reduces cyclic variations of combustion event but is not
capable of considerably extending the lean limit.
• A pre-chamber with additional fueling can considerably
extend the lean limit of operation and hence improve
indicated efficiency and reduces NOx emissions
• A larger pre-chamber provides higher ignition energy but
size is limited by fraction of pre-chamber combustion
before main chamber ignition.
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Future Plans
• Study pre-chamber ignition at full load conditions
(IMEPg > 20 bar)
• CFD simulations of pre-chamber jets based on
experimental pressure data to understand ignition
mechanism resulting from PC jets
• Optical diagnostics of pre-chamber ignition in the
Wärtsilä large bore engine through optical access to the
main chamber and/or pre-chamber.
• Optical diagnostics of knock phenomenon with prechamber ignition.
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Future Plan (cont.)
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Thank you
Comments/Questions?
Ashish Shah
Ph.D Student
Division of Combustion Engines
Lund University
ashish.shah@energy.lth.se
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