An experimental study of negative valve overlap injection effects and their impact on combustion in a gasoline HCCI engine

Detailed Speciation of Emissions from Low-Temperature Combustion in a Gasoline HCCI Engine

“…It should be noted that these relatively high HC levels were caused by the impact of wall-side effect at low temperatures inside the combustion chamber. The previous studies [25,35] showed that early NVO injection of fuel modifies its chemical composition to a high extent. For this reason, it is expected that the fractional composition of unburned hydrocarbons will be altered, too.…”

“…The introduction of fuel in an early stage of the NVO period (during exhaust compression) enables fuel reforming, which results in the production of auto-ignition-promoting species like ethane, ethylene, acetylene, formaldehyde, and methanol [25][26][27][28]. The occurrence of these species in the combustible mixture advances the start of combustion by several degrees when compared to the mixture preparation outside of the cylinder under the same thermal conditions [29,30].…”

“…The occurrence of these species in the combustible mixture advances the start of combustion by several degrees when compared to the mixture preparation outside of the cylinder under the same thermal conditions [29,30]. However, thermal NVO processes are widely recognised as dominant in combustion control [23,25]. Nevertheless, the utilization of direct fuel injection for combustion control and extension of engine operating range into a low load regime causes chemical modifications of fuel.…”

“…Nevertheless, the utilization of direct fuel injection for combustion control and extension of engine operating range into a low load regime causes chemical modifications of fuel. Clearly, variations in hydrocarbon structure in the combustible mixture are reflected in the fractional compositions of the unburned hydrocarbons [25]. Thus special attention should be paid to species concentrations in exhausts emitted by HCCI engines controlled by direct fuel injection during the NVO period.…”

The use of different types of piston in an HCCI engine: A review

“…Models of these engines address the control and operation range extension via the modification of fuel characteristics and advanced control in the mixtures of air and fuel. New models designed through numerical simulations provide optical diagnostics to reveal the in-cylinder combustion process [18]. The stratification process also extends the potential of HCCI operation for higher loads and low-temperature combustion [19].…”