Natural parenting : back to basics in infant care

Peer reviewe

CHARACTERIZATION OF HARD AMORPHOUS-CARBON FILMS IMPLANTED WITH NITROGEN-IONS

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An Investigation of the Combustion Process of a Heavy-Duty Dual Fuel Engine Supplemented with Natural Gas and Hydrogen

This paper compares the effects of the addition of hydrogen (H2) or natural gas (NG) on the combustion of a heavy-duty diesel engine converted to operate under gaseous fuel-diesel dual fuel combustion mode. The parameters examined include the start of combustion (SOC), heat release process, peak heat release rate (PHRR), and combustion duration. Significant positive effects on the combustion process were only observed with the addition of a relatively large amount of H2 or NG. When operated at low load, the addition of a large amount of H2 or NG reduced the heat release rate (HRR) of the premixed combustion. By comparison, the addition of a relatively large amount of H2 or NG at high load significantly increased the PHRR of the diffusion combustion. The addition of H2 has more significant impact on the PHRR than NG. The addition of NG retarded the SOC while the impact of the addition of H2 on SOC was relatively mild. The significant variation in HRR and its phasing make it necessary to further optimize the combustion of a dual fuel engine. The impact of the addition of gaseous fuel on the brake thermal efficiency was also examined and discussed. The increased thermal efficiency was only observed with the addition of relatively large amount of H2 or NG at medium to high load. The improved thermal efficiency was due to the decrease in combustion duration and the shifting of the combustion phasing toward the optimal one. The decreased thermal efficiency observed at low load was due to the low combustion efficiency of the gaseous fuel supplemented

An investigation of the combustion process of a heavy-duty dual fuel engine supplemented with natural gas or hydrogen

This paper compares the effects of the addition of hydrogen (H2) or natural gas (NG) on the combustion of a heavy-duty diesel engine converted to operate under gaseous fuel-diesel dual fuel combustion mode. The parameters examined include the start of combustion (SOC), heat release process, peak heat release rate (PHRR), and combustion duration. Significant positive effects on the combustion process were only observed with the addition of a relatively large amount of H2 or NG. When operated at low load, the addition of a large amount of H2 or NG reduced the heat release rate (HRR) of the premixed combustion. By comparison, the addition of a relatively large amount of H2 or NG at high load significantly increased the PHRR of the diffusion combustion. The addition of H2 has more significant impact on the PHRR than NG. The addition of NG retarded the SOC while the impact of the addition of H2 on SOC was relatively mild. The significant variation in HRR and its phasing make it necessary to further optimize the combustion of a dual fuel engine. The impact of the addition of gaseous fuel on the brake thermal efficiency was also examined and discussed. The increased thermal efficiency was only observed with the addition of relatively large amount of H2 or NG at medium to high load. The improved thermal efficiency was due to the decrease in combustion duration and the shifting of the combustion phasing toward the optimal one. The decreased thermal efficiency observed at low load was due to the low combustion efficiency of the gaseous fuel supplemented

An Investigation of NO2 Emissions from a Heavy-Duty Diesel Engine Fumigated with H2 and Natural Gas

The oxides of nitrogen (NOx) emissions of diesel engines consist of nitric oxide (NO) and nitrogen dioxide (NO2). Although emitted at small amounts, NO2 has higher toxicity and causes more health and environmental issues than NO. This research investigates the impact of the addition of hydrogen (H2), natural gas (NG), and engine load on NO2 emissions from a heavy-duty diesel engine converted to operate using dual fuel combustion mode. The substitution of a small amount of H2 or NG for the diesel fuel substantially increased NO2 emissions, but had a very mild impact on the combustion process. In comparison, the substitution of a large amount of H2 and NG for the diesel fuel dramatically altered the combustion process and produced more NO2 than the diesel-only operation, but produced less NO2 than the addition of a small amount of H2 and NG. A preliminary analysis revealed a firm correlation between NO2 emissions and the emissions of the unburned H2 or CH4, and their relative emissions. The importance of the unburned fumigation fuels in enhancing NO2 formation in dual fuel engines was also supported by the data reported in the literature. The portion of supplemental fuels entrained into the diesel spray plume and simultaneously burned with the diesel fuel may not contribute to the increased NO2 emissions from dual fuel engines