Flightglobal. The European project DREAM (valiDation of Radical Engine Architecture systeMs) began wind tunnel open-rotor blade testing in Russia earlier this month; results will be available by the end of the year.
An open rotor engine is a modified turbofan, with the fan blades placed outside the engine nacelle. Last seriously explored in the 1980s, the open rotor prototypes (such as the GE36 from General Electric) delivered a 30%+ increase in fuel efficiency. Noise, vibration, size and maintenance were issues with the open rotor concepts at the time.
|Direct-drive open rotor engine. Click to enlarge.|
DREAM is targeting the development of contra-rotating open rotors with variable pitch blades which are known to provide 10 to 15% fuel burn reduction but are noisier than high bypass turbofans. Recent progress in aero-acoustic modeling and design allow this architecture to be reconsidered for short / medium haul aircraft.
One fifth- and one seventh-scale blade testing is being carried out at Russia’s Central Aerohydrodynamic Institute on existing electrically powered rigs at speeds of up to Mach 0.85.
DREAM is a three-year €40 million (US$57 million) project led by Rolls-Royce to investigate open-rotor engines and new fuels. DREAM’s fuels work is studying synthetic kerosene produced using the Fischer-Tropsch process as well as biofuel candidates.
In the US, GE Aviation and NASA are also beginning a wind-tunnel test program to evaluate counter-rotating fan-blade systems for open rotor jet engine designs. (Earlier post.)