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Reactivity Controlled Compression Ignition (RCCI) natural gas/diesel dual-fuel combustion has been shown to achieve high thermal efficiency with low NOX and PM emissions, but has traditionally been limited to low to medium loads. High BMEP operation typically requires high substitution rates (i.e., >90% NG), which can lead to high cylinder pressure, pressure rise rates, knock, and combustion loss. In previous studies, compression ratio was decreased to achieve higher load operation, but thermal efficiency was sacrificed. For this study, a multi-cylinder heavy-duty engine that has been modified for dual-fuel operation (diesel direct-injection and natural gas (NG) fumigated into the intake stream) was used to explore RCCI and other dual-fuel combustion modes at high compression ratio, while maintaining stock lug curve capability (i.e., extending dual-fuel operation to high loads where conventional diesel combustion traditionally had to be used).

Combustion losses are one of the largest areas on inefficiency in natural gas/diesel dual-fuel engines, especially when compared to the traditional diesel engines on which they are based. These losses can vary from 1-2% at high load, to more than 6% of the total fuel energy at part load conditions. For diesel/natural gas dual-fuel engines, the three main sources of combustion losses are: bulk losses (increasing air-fuel ratio, AFR, to the premixed fuel’s lean flammability limit), crevice losses (premixed fuel trapped near valve pockets and top ring lands unable to oxidize), and blow-through losses (fumigated fuel/air intake charge passes through the cylinder and out the exhaust valve during valve overlap). In order to improve overall engine efficiency and decrease greenhouse gas emissions, these losses must be minimized.

This study examines some of the factors associated with soft tissue neck injuries in the UK. The data were drawn from a retrospective study of vehicle crash injuries in which the overall soft tissue neck injury rate was 16%. This study shows how although it is commonly assumed that such injuries are a rear impact phenomenon, over 50% of the injuries occur in frontal crashes. In front and rear impacts, these injuries are undoubtedly associated with seat-belt use. The incidence of neck injury has been shown to double over the ten-year period of the study with the effect more prominent in females. Such injuries are also more likely to be self-reported than clinically diagnosed. Head restraints have not been found to mitigate neck injuries in either front or rear impacts at a statistically significant level. A slight but non-significant trend towards reduced neck injury rates is observed in cases of seat back yielding in a rear impact.