Diesel / Heavy Fuel UAV Engines

Diesel and other heavy fuels such as jet fuel are used in a number of UAV (unmanned aerial vehicle designs), especially military drones. This allows armed forces to utilize a single fuel across all land vehicles, aircraft and equipment for simplified supply chains and logistics.

Some engine designs are capable of running on both diesel and kerosene-based heavy fuels such as JP-5, JP8 and Jet-A1.

Piston-Driven Heavy Fuel Engines

Dual Cylinder Heavy Fuel UAV Engine by Sky Power International

Piston-driven diesel and heavy fuel UAV engines typically operate on different principles to gasoline-powered internal combustion engines (ICEs). Gasoline engines mix fuel with air, compress this mixture and then ignite it with a spark. Diesel and heavy fuel engines do not require spark plugs – instead, they compress the air only, and then inject fuel into this compressed air, relying on the heat to ignite the fuel. Due to the higher pressures involved, diesel and heavy fuel ICEs tend to be bulkier and thus suited to drones with higher payload capacities.

UAV Turbine Engines

Diesel and heavy fuel are also used to power UAV turbine engines, which include turbojet, turboprop and turboshaft engines. These engines mix air and fuel, ignite the mixture, and use the resulting stream of gas to propel the UAV.

Advantages of using heavy fuel for drone engines

Diesel and heavy fuels are denser than gasoline, due to being made up of longer-chain hydrocarbon molecules. This affects their properties, and in general, makes them harder to ignite. Other properties of heavy fuels include:

• Being hard to ignite makes heavy fuel safer to use, store and transport than gasoline.
• Remaining liquid at lower temperatures, makes these fuel types more suitable for drones flying in cold environments or at high altitudes.
• More energy per unit volume due to higher density, makes heavy fuels ideal for drone designs where the limiting factor is the size of the fuel tank and not the mass of fuel carried.