Effects of Low-Cetane Fuels in Compression Ignition Engines

Abstract

The U.S. Army requires blended fuels to have a cetane rating of at least 40, but sustainable aviation fuels (SAFs) have very low cetane numbers (DCN ~15), causing delayed combustion. While the link between altered combustion and engine wear is known, this thesis directly correlates low-cetane fuels with specific durability indicators.A CI V8 engine was tested with a baseline fuel (DCN 43.7) and two low-cetane fuels (DCN 34.8, 29.8) across 19 operating conditions. Peak pressure, pressure rise rate, and crankshaft twist were synthesized into a novel Composite Durability Indicator (CDI). CDI results show low-cetane fuels increase durability concerns at high- and low-speed conditions relative to identical conditions at baseline, but these increases only exceed the maximum baseline concern at high speeds. At high speed, crankshaft twist was found to bias opposite the direction of rotation, suspected to result from elevated cylinder pressure during the compression stroke.