A new heavy fuel engine is now under bench test in preparation for a first flight in the second quarter of 2010 for the Naval Air Systems Command's (NAVAIR) Ultra endurance unmanned aerial vehicle (UE-UAV) programme.

To be used for the US Navy's Small tactical unmanned aerial system, tier II UAV programme's vehicles, the Cosworth engine uses compression ignition as part of its fuel intolerant design that enables it to run on diesel, JP-5 and JP-8. The US Navy's target for its power output is 10hp (7.46kW) engine.

The bench tested engine has been designed and developed by UK Formula one engine specialist Cosworth, which won the third phase contract for UE-UAV. In the third quarter of 2008 Cosworth was awarded the sole phase three contract after participating with other companies in the first two phases. A Cosworth proof of concept engine has already flown at 10,000ft (3,050m) powering a UAV.

"We have used modified commercial off the shelf components to reduce their weight as compressor ignition units are normally heavy. The way we inject the fuel is critical to the way it works," says Cosworth principal engineer John Vaughn.

He explained to Flightglobal that the engine uses mechanical injectors from automotive diesel engines because they are very robust but that in the future more advanced diesel technology would be adopted. The heavy fuel UAV engine will also have features to reduce vibration and a controller to stop fuel overfill that can cause visible exhaust smoke.

The engine was designed using computational fluid dynamics with a combination of 1D and 3D simulations. The simpler 1D work described mass flow through a tube while the 3D simulation described events in the combustion chamber. British Petroleum supplied different fuels to Cosworth for the engine's development.

Source: Flight International