The NO x and N 2 O Emission Characteristics of an HCCI Engine Operated With n-Heptane

This paper presents the oxides of nitrogen (NO x ) and nitrous oxide (N 2 O) emission characteristics of a Cooperative Fuel Research (CFR) engine modified to operate in homogeneous charge compression ignition (HCCI) combustion mode. N-heptane was used as the fuel in this research. Several parameters were varied, including intake air temperature and pressure, air/fuel ratio (AFR), compression ratio (CR), and exhaust gas recirculation (EGR) rate, to alter the HCCI combustion phasing from an overly advanced condition where knocking occurred to an overly retarded condition where incomplete combustion occurred with excessive emissions of unburned hydrocarbons (UHC) and carbon monoxide (CO). NO x emissions below 5 ppm were obtained over a fairly wide range of operating conditions, except when knocking or incomplete combustion occurred. The NO x emissions were relatively constant when the combustion phasing was within the acceptable range. NO x emissions increased substantially when the HCCI combustion phasing was retarded beyond the optimal phasing even though lower combustion temperatures were expected. The increased N 2 O and UHC emissions observed with retarded combustion phasing may contribute to this unexpected increase in NO x emissions. N 2 O emissions were generally less than 0.5 ppm; however, they increased substantially with excessively retarded and incomplete combustion. The highest measured N 2 O emissions were 1.7 ppm, which occurred when the combustion efficiency was approximately 70%

Effect of renewable fuel components on combustion and emission performance of an HCCI engine

Renewable fuels usually consist of paraffinic hydrocarbons and are free of sulfur and aromatics. Although most renewable fuels meet the conventional fuel requirements for internal combustion engine applications, differences in fuel properties between renewable fuels and petroleum-based fuels still exist. The effect of renewable fuels on conventional diesel engines has been investigated by many researchers. However, few studies have been conducted on the effect of renewable fuels on combustion and emission performance of homogeneous charge compression ignition(HCCI)engines. In this paper, the combustion and emission characteristics of an HCCI engine are experimentally investigated when four neat renewable fuel components and their blends with a petroleum-based diesel were used. The ratios of renewable fuel components in the blends were changed from zero to 100%. The experiments were conducted over a wide range of operational conditions. Energy efficiency and regulated emissions data were collected and analyzed. The results suggest that compared to the petroleum-based diesel fuel, all four investigated renewable fuel components increase the fraction of heat release during low temperature stage and reduce the ignition temperature when applied to an HCCI engine. As a result, the investigated renewable fuel components advance combustion phasing of an HCCI engine. While three of the four investigated renewable fuel components improve the energy efficiency when blended with the petroleum-based diesel, one renewable fuel component deteriorates energy efficiency. The effects of renewable fuel components on emissions vary, with some reducing emissions while others not having a clear trend affecting emissions.NRC publication: Ye

The NOx and N2O emission characteristics of an HCCI engine operated with n-Heptane

This paper presents the oxides of nitrogen (NOx ) and nitrous oxide (N2 O) emission characteristics of a Cooperative Fuel Research (CFR) engine modified to operate in homogeneous charge compression ignition (HCCI) combustion mode. N-heptane was used as the fuel in this research. Several parameters were varied, including intake air temperature and pressure, air/fuel ratio (AFR), compression ratio (CR), and exhaust gas recirculation (EGR) rate, to alter the HCCI combustion phasing from an overly advanced condition where knocking occurred to an overly retarded condition where incomplete combustion occurred with excessive emissions of unburned hydrocarbons (UHC) and carbon monoxide (CO). NOx emissions below 5 ppm were obtained over a fairly wide range of operating conditions, except when knocking or incomplete combustion occurred. The NOx emissions were relatively constant when the combustion phasing was within the acceptable range. NOx emissions increased substantially when the HCCI combustion phasing was retarded beyond the optimal phasing even though lower combustion temperatures were expected. The increased N2 O and UHC emissions observed with retarded combustion phasing may contribute to this unexpected increase in NOx emissions. N2 O emissions were generally less than 0.5 ppm; however, they increased substantially with excessively retarded and incomplete combustion. The highest measured N2 O emissions were 1.7 ppm, which occurred when the combustion efficiency was approximately 70%.Peer reviewed: YesNRC publication: Ye

Effect of renewable diesel and jet blending components on combustion and emissions performance of a HCCI engine

Renewable diesel and jet blending components may be produced by hydrotreating waste fats and vegetable oils. The resulting hydrocarbon components are paraffinic in nature and free of sulfur and aromatics. An isomerization process may follow to improve the cold weather properties. The main differences between renewable diesel and jet blending components is that the jet blending components are more volatile, have a lower cetane number and a much lower cloud point. In this study, different percentages of hydrotreated renewable diesel and jet components were blended into an ultra-low sulfur diesel (ULSD) fuel and their effect on homogeneous charge compression ignition (HCCI) combustion and emissions performance was investigated. The experiments were conducted using a Co-operative Fuel Research (CFR) engine coupled to an eddy-current dynamometer. The percentage of renewable blending components was varied from 0 to 100%. HCCI combustion and emissions data was collected at a single relative air/fuel ratio (\u3bb) = 1.2 and engine speeds of 900 and 1200 rpm for each fuel blend. The experimental results indicate that the renewable diesel and jet blending components increased the heat release during low temperature stage and reduced the auto-ignition temperature compared to the ULSD fuel, which tended to advance the combustion phasing at a fixed compression ratio. The thermal efficiency was not significantly affected by renewable jet and diesel blends up to 10% by volume, but the renewable jet improved the thermal efficiency while the renewable diesel blends deteriorated thermal efficiency for higher percentage blends. The renewable jet fuel component improved unburned hydrocarbon (HC) emissions, but the renewable diesel component did not have a significant effect on HC emissions. Both renewable fuel components reduced CO emissions at a fixed compression ratio, but there was not a clear trend for CO emissions at the optimal thermal efficiency condition when renewable components were blended with the ULSD fuel. The NOx emissions were extremely low and did not show a clear trend as the percentage of renewable blending components increased.NRC publication: Ye

An experimental and modeling study of HCCl combustion using n-heptane

Peer reviewed: YesNRC publication: Ye