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A new Alcohol To Jet (ATJ) fuel has been developed using a process which takes biomass feedstock to produce a branched butanol molecule. Further dehydration, reforming and hydro-treating produced principally a highly branched C12 iso-paraffin molecule. This ATJ fuel with a low cetane value (DCN = 18) was blended with Navy jet fuel (JP5) in various quantities and tested in order to determine how much ATJ could be blended before diesel engine operation became problematic (the US Navy and Marine Corps may use jet fuel in their diesel engines). Blends of 20%, 30% and 40% ATJ (by volume) were tested with jet fuel. The Derived Cetane Number (DCN) falls from 45 for the base JP5 to 38 with the 40% ATJ component blended in. Engine start performance was evaluated on two Yanmar engines and a Waukesha CFR diesel engine and showed that engine start times increased steadily with increasing ATJ content.

A new alternative fuel has been tested in a number of engines and compared to conventional Navy diesel fuel performance using in-cylinder based diagnostics and brake performance comparisons. This new fuel is derived from a Direct Sugar to Hydrocarbon (DSH) process in which sugar and yeast produce a farnesene type hydrocarbon molecule (branched hydrocarbon with multiple double bonds) which is then processed into a moderately branched single alkane molecule (> 98% purity) with a moderately higher cetane number than conventional diesel fuels. This new fuel was extensively characterized and has a lower density, viscosity and bulk modulus as compared to conventional diesel fuel. These physical property differences lead to later Start of Injection times in three diesel engines (AM General GEP, Waukesha CFR and Yanmar). However, due to the increased reactivity of DSH, ignition delay is reduced - faster across most of the speeds and loads tested.

Alternative diesel fuels from various renewable sources have recently been achieving high volume production status. These fuels are generally paraffinic in nature, and are notably absent of aromatic and cyclo-paraffinic hydrocarbon compounds. Combustion differences exist with these new fuels. Ignition delay and combustion duration are often different than conventional fuels leading to changes in combustion phasing and thus differences in engine brake metrics. How much of an indicated combustion change is acceptable? Currently no alternative fuel combustion acceptance criteria or metrics exist for new alternative fuels in diesel engines. In this paper a proposed set of indicated combustion acceptance criteria is presented with companion data from two new hydro-treated renewable fuels in a legacy military diesel engine. The three combustion criteria are: 1. relative change in ignition delay, 2. Angle of Peak pressure (AOP location) and 3. relative maximum rate of heat release.