Performance of a Small Internal Combustion Engine Using N-Heptane and Iso-Octane

摘要

With the sustained interest in Unmanned Aircraft Systems (UAS) and Micro Air Vehicles (MAV), the military services have a real need for vehicles powered by an internal combustion (IC) engine that can run efficiently on heavy hydrocarbon fuels, especially JP-8 due to established logistics. This thesis concerns the results of running a two horsepower, 4-stroke, spark-ignition engine (FUJI BF34-EI) with both iso-Octane and n-Heptane. Results include the knocking characteristic of this engine with n-Heptane, a comparison of the brake specific fuel consumption (BSFC) of the two fuels in a factory delivered engine configuration over a 17x10 APC propeller loading, a comparison of the heated fuel effects on BSFC and torque of the two fuels and the effects of varied spark timing with n-Heptane on BSFC and torque. It is shown with stock ignition timing and fuel at ambient temperature, n-Heptane exhibits on average less specific fuel consumption than iso-Octane; specifically, an average of 4.1% over the entire engine loading and 12.61% over the stock propeller engine loading. It is concluded that the knocking characteristic of a zero octane number (ON) fuel using a stock configuration in this engine is negligible, thus allowing the USAF to run any ON fuel for this particular engine. Additionally, with spark timing advanced or retarded beyond the stock setting, it is shown to decrease BSFC on average 9.4% with n-Heptane. Lastly, the performance effects of heating n-Heptane up to 344K and iso-Octane up to 311K are shown to be negligible.