Aircraft

Rolls-Royce believes its "holy grail" quest for a low-noise high-efficiency open rotor engine could finally have ended following promising early tests - but admits that secret studies have been conducted to understand the likely public reaction to such a radical novel engine concept.

Speaking at the Royal Aeronautical Society's Greener By Design conference this week about the engine maker's design and validation efforts on its experimental open rotor engine, R-R senior project engineer Dr Mark Taylor reported that the first part of a comprehensive validation programme was recently completed and initial results not only in line met expectations, but represented "a very big step" in its open rotor programme.

"Based on this new and innovative technology, Rolls-Royce believes a quiet and efficient open rotor engine is realisable," said Taylor. "Relative to today's aircraft, a future open-rotor powered aircraft could save approximately $3 million and 10,000t of carbon dioxide a year per aircraft."

But R-R recognises that passenger acceptance of these next generation engine designs could prove as challenging as the technology. Taylor said confidential studies are being conducted "to understand the public impact when introducing radical concepts". He added: "We have found however that when you take people through it, they seem to accept it more readily."

Much of the technology development for an open rotor design with an acceptable level of noise and propulsive efficiency has been funded through European Union framework programmes such as Dream, but Taylor said that in addition to expected features such as multiple blades and gap optimisation, R-R is working on "extra stuff" that he cannot talk about.

However, he described one technology, in which he has been involved in development, as "the secret sauce". The intellectual property for this does not feature within Dream and a patent is at the ballot stage, he added.

Taylor outlined the initial results from R-R's open rotor noise testing using a 1/6th scale rig that has been run in multiple configurations to optimise performance and noise and recently completed a low-speed acoustic test campaign at the German/Dutch DNW windtunnel facility in the Netherlands.

This 71cm (28in) diameter rig is being transported to the UK's Aircraft Research Association windtunnel in Bedford for high-speed performance testing, with results expected at the end of November.