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Characterizing dilute combustion instabilities in a multi-cylinder spark-ignited engine using symbolic analysis
C S Daw1, C E A Finney2, B C Kaul2
1Fuels, Engines, and Emissions Research Center, Energy and Transportation Science Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA dawcs@ornl.gov.
Summary
High exhaust gas recirculation (EGR) in engines causes combustion instabilities. Symbolic analysis revealed four-cylinder engines can lock in phase, alternating between two states, impacting efficiency and emissions.
Area of Science:
- Internal combustion engine research
- Thermodynamics and combustion science
- Automotive engineering
Background:
- Advanced internal combustion engines use high exhaust gas recirculation (EGR) to improve efficiency and reduce emissions.
- High EGR levels can cause significant combustion oscillations and control challenges.
- Combustion instabilities may propagate between cylinders via residual exhaust gases.
Purpose of the Study:
- To characterize multi-cylinder combustion oscillations in an experimental engine with external EGR.
- To investigate the impact of increasing EGR levels on combustion stability.
- To explore symbolic analysis as a diagnostic tool for combustion instabilities.
Main Methods:
- Utilized symbolic analysis to study combustion oscillations in a four-cylinder experimental engine.
- Operated the engine with varying levels of external exhaust gas recirculation (EGR).
- Analyzed combustion data to identify patterns and coupling between cylinders.
Main Results:
- At low EGR, intra-cylinder oscillations and intermittent cylinder coupling were observed.
- At higher EGR, all four cylinders synchronized and alternated between two distinct bi-stable combustion states.
- Symbolic analysis effectively characterized these multi-cylinder combustion instabilities.
Conclusions:
- High EGR levels induce complex combustion instabilities in multi-cylinder engines.
- Cylinder phase-locking and bi-stable combustion states are significant phenomena at elevated EGR.
- Symbolic analysis offers a valuable method for diagnosing and understanding engine combustion instabilities.
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