The Scaling of Loss Pathways and Heat Transfer in Small Scale Internal Combustion Engines

The rapid expansion of the remotely piloted aircraft market includes an interest in 10 kg to 25 kg vehicles (Group 2) for monitoring, surveillance, and reconnaissance. Power plant options for those aircraft are often 10 cm3 to 100 cm3 displacement internal combustion engines. Both power and fuel conversion efficiency decrease increasingly rapidly in the aforementioned size range, with fuel conversion efficiency falling from approximately 30% for automotive and larger scale engines (greater than 100 cm3 displacement) to less than 5% for micro glow fuel engines (less than 10 cm3 displacement).