Dickerson, T., McDaniel, A., Williams, S., Luning-Prak, D. et al., "Start-up and Steady-State Performance of a New Renewable Alcohol-To-Jet (ATJ) Fuel in Multiple Diesel Engines," SAE Technical Paper 2015-01-0901, 2015, doi:10.4271/2015-01-0901.
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. Longer start times with increasing ATJ content were the result of some engine cycles with poor combustion leading to a slower rate of engine acceleration towards rated speed. A repeating sequence of alternating cycles which combust followed by a non-combustion cycle are common during engine run-up. ATJ has a significantly lower bulk modulus than JP5, and thus all three engines showed later Start Of Injection (SOI) timing with increasing ATJ content. Additionally, due to the lower DCN, the higher ATJ blends showed moderately longer Ignition Delay (IGD). Thus, the mid-combustion metric (CA50: 50% burn duration Crank Angle position) was retarded with increasing ATJ content, away from ideal combustion phasing. It was seen that the 70% JP5-30% ATJ blend with DCN = 40 was the highest concentration of ATJ tested without substantially increasing engine start times.