Start-Up and Steady-State Performance of a New Renewable Hydroprocessed Depolymerized Cellulosic Diesel (HDCD) Fuel in Multiple Diesel Engines

A new Hydroprocessed Depolymerized Cellulosic Diesel (HDCD) fuel has been developed using a process which takes biomass feedstock (principally cellulosic wood) to produce a synthetic fuel that has nominally 1/2 cyclo-paraffins and 1/2 aromatic hydrocarbons in content. This HDCD fuel with a low cetane value (Derived Cetane Number from the Ignition Quality Tester, DCN = 27) was blended with naval distillate fuel (NATO symbol F-76) in various quantities and tested in order to determine how much HDCD could be blended before diesel engine operation became problematic. Blends of 20% HDCD (DCN = 45), 30%, 40% (DCN = 41) and 60% HDCD (DCN = 37) by volume were tested with conventional naval distillate fuel (DCN = 49). Engine start performance was evaluated with a conventional mechanically Direct Injected (DI) Yanmar engine and a Waukesha mechanical indirect injected (IDI) CFR diesel engine, and showed that engine start times increased steadily with increasing HDCD content. Longer start times with increasing HDCD 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 were common during engine run-up. Additionally, steady state engine testing was also performed using both engines. HDCD has a significantly higher bulk modulus than F76 due to its very high aromatic content, and the engines showed earlier Start of Injection (SOI) timing with increasing HDCD content for equivalent operating conditions. Additionally, due to the lower DCN, the higher HDCD blends showed moderately longer Ignition Delay (IGD) with moderately shorter overall burn durations. Thus, the mid-combustion metric (CA50: 50% burn duration Crank Angle position) was only modestly affected with increasing HDCD content. Increasing HDCD content beyond 40% led to significantly longer start times.