Many of the engines used in Remotely Piloted Aircraft (RPA), come directly from the remote-control (R/C) aircraft market, which turn a propeller but are not necessarily built for the greatest efficiency or reduced fuel consumption. The DoD “single fuel concept” is pushing these platforms to be able to operate with JP-8 using an Otto Cycle engine. Additionally, with increased environmental concern with fossil fuels, possible future DoD requirements could require the use of bio-derived liquid fuels.
The research presented in this paper takes steps to satisfying both the efficiency and single fuel requirements. The Fuji BF-34EI engine was successfully shown to operate effectively with JP-8, Diesel, Algae-based Diesel and Camelina based Hydroprocessed Renewable Jet fuel. When generally compared over the entire engine operating map, between AVGAS and JP-8, the latter is shown to present a 10-20% lower brake specific fuel consumption (BSFC). When variable spark ignition is used for running the heavy fuels, allowing for a greatly retardation in timing, knock is shown to be eliminated. Comparing to the fielded system (AVGAS Carbureted), yielded a decrease in specific fuel consumption of up to 43% and 54% for JP-8 and Camelina, respectively. Using fuel injection and spark optimization with the heavy fuels, BSFC was decreased by up to 14% and 32% for JP-8 and Camelina, respectively, when compared to AVGAS.