Analysis of radical behavior under knocking operation in a spark ignition engine
Conference
·
OSTI ID:20019072
There are strong demands today to improve the thermal efficiency of internal combustion engines in order to promote energy conservation and the resolution of environmental issues. A major factor impeding further improvement of the thermal efficiency of spark-ignition engines is knocking. If knocking could be suppressed, it would allow the use of a higher compression ratio for improved thermal efficiency, and thereby reduce fuel consumption. As a result, atmospheric emissions of CO{sub 2} would also be reduced. The behavior of the end gas in an actual engine during the process from the onset of preflame reactions to the occurrence of knocking, including the chemical reactions involved, is still not clearly understood. This study focused on light emission behavior at wavelengths corresponding to the spectra of the formaldehyde, (HCHO, characteristic spectrum of 395.2 nm), HCO (329.8 nm) and OH (306.4 nm) radicals. Investigations were made of the role of low-temperature flames in the preflame reaction region of a spark-ignition engine under the occurrence of autoignition leading to knocking. The measurements obtained for HCHO when the blended fuel (20 RON) was used as the test fuel showed an increase in emission intensity in the early period of the preflame reactions under normal combustion, followed by a decline in intensity. Under a condition of severe knock induced by an overheated cylinder head, it was observed that the maximum emission intensity decreased. These tendencies are thought to correspond to the passage and degeneracy of a cool flame. When isooctane (100 RON) was used as the test fuel, the measurements obtained for HCHO showed an increase in emission intensity in the preflame reaction period, behavior thought to indicate the passage of a cool flame, but the characteristics associated with the degeneracy of a cool flame were not observed.
- Research Organization:
- Nihon Univ., Tokyo (JP)
- OSTI ID:
- 20019072
- Country of Publication:
- United States
- Language:
- English
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