고온 고압 조건에서 대체 연료의 점화 및 연소특성에 관한 연구
Ignition and Combustion Characteristics of Alternative Fuel under High-Temperature and High-Pressure Conditions
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The ignition and combustion processes of alternative fuels need thorough understanding within a ‘beyond-RON’ regime, under temperature and pressure conditions relevant to compression-ignition engines, in contrast to their spark-ignition counterparts. This study investigates the low- and high-temperature ignition and combustion processes in high-pressure spray flames of primary reference fuel (PRF80) using simultaneous 50-kHz formaldehyde (CH2O) planar laser-induced fluorescence (PLIF) and 100-kHz schlieren imaging. The experiments are performed within a constant-volume pre-burn chamber, utilizing a highly convergent single-hole injector provided by the Engine Combustion Network (ECN), specifically Spray A-3. Simultaneous high-speed imaging diagnostics reveal the early cool flame formation and its evolution, the sequential consumption of formaldehyde, high-temperature ignition, and the formation of polycyclic aromatic hydrocarbons (PAHs) in high-pressure PRF80 spray flames. At lower temperatures, a gradual increase in pressure traces and apparent heat release rate (AHRR) indicates low-temperature heat release (LTHR), with numerous spikes observed before high-temperature ignition. The efficiency decreases compared to higher temperatures at the lowest tested temperature condition (899 K). The differences in lowand high-temperature ignition delay times decrease rapidly with increasing ambient temperature, both becoming shorter. Additionally, the flame lift-off length (FLOL) and CH2O inception distances shorten as the ambient temperatures rise.
Abstract
The ignition and combustion processes of alternative fuels need thorough understanding within a ‘beyond-RON’ regime, under temperature and pressure conditions relevant to compression-ignition engines, in contrast to their spark-ignition counterparts. This study investigates the low- and high-temperature ignition and combustion processes in high-pressure spray flames of primary reference fuel (PRF80) using simultaneous 50-kHz formaldehyde (CH2O) planar laser-induced fluorescence (PLIF) and 100-kHz schlieren imaging. The experiments are performed within a constant-volume pre-burn chamber, utilizing a highly convergent single-hole injector provided by the Engine Combustion Network (ECN), specifically Spray A-3. Simultaneous high-speed imaging diagnostics reveal the early cool flame formation and its evolution, the sequential consumption of formaldehyde, high-temperature ignition, and the formation of polycyclic aromatic hydrocarbons (PAHs) in high-pressure PRF80 spray flames. At lower temperatures, a gradual increase in pressure traces and apparent heat release rate (AHRR) indicates low-temperature heat release (LTHR), with numerous spikes observed before high-temperature ignition. The efficiency decreases compared to higher temperatures at the lowest tested temperature condition (899 K). The differences in lowand high-temperature ignition delay times decrease rapidly with increasing ambient temperature, both becoming shorter. Additionally, the flame lift-off length (FLOL) and CH2O inception distances shorten as the ambient temperatures rise.
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