Story ID: 402
Rolls Runs New Lean-burn Combustor
By: Ian Goold
Caption: Rolls is focussing on refining next-gen lean-burn combustor as it eyes closer engine-airframe integration, and electrification.
Word Count: 453
Rolls-Royce (Stand N23) is planning further flight-, ground-, and rig-testing of its advanced “lean-burn” combustor system (ALECSys) demonstrator that was first run last month, according to R-R Civil Aerospace future programs chief engineer, Phil Curnock. The technology, which introduces a new lean-burn concept to a more traditional engine design, has been demonstrated on an Advance 3 rig and ground-tested on a modified Trent 1000 engine.

In a similar set-up, it could be demonstrated on a flying testbed in about two years’ time, said the manufacturer. Before then, further testing will involve exercises such as starting after a long cold “soak” and checking for the safe shedding of ingested ice—work that will be conducted in Manitoba, Canada. The ALECSys technology also will be tested on an outside noise-testing rig to determine any change in sound levels, said Curnock.

Leaner fuel/air mixtures help to control combustion temperature, greatly reducing the amount of oxides of nitrogen (NOx) emissions, according to Rolls-Royce. "Incorporation of a lean-burn combustion system also enables higher peak temperatures in the engine for improved efficiency, fuel burn, and CO2 emissions," said the British engine manufacturer.

The development of ALECSys is funded in part by the European Union's Clean Sky SAGE (Sustainable And Green Engine) program.

The ALECSys activity is just one of several "areas of focus" for product innovation as Rolls-Royce continues efforts to optimize gas-turbine technology. The manufacturer also is looking closely at increased integration between airframes and powerplants, as well as increased electrification of aircraft—an area in which Rolls-Royce says developments are "relentless" and in which it claims to be a driving force.

Curnock said the architecture of the company's established Trent engine family has made “good steps” in the past 20+ years, but that increased integration between engine and airframe is “really the key” to further developments, along with electrification.

Although he sees the Trent XWB engine as representing the best of current technology, Rolls-Royce is evolving two new powerplant generations with its Advance design (using core developments for service-entry in in the first half of the next decade) and UltraFan (which introduces a gearbox to drive a larger fan and removes the low-pressure) for operations after 2025. 

As the manufacturer continues to optimize its engines, Curnock said that the Advance and UltraFan developments are exploiting progress in propulsive efficiency, with ever-increasing bypass ratios employing bigger, slower fans, and thermal efficiency by running smaller, hotter cores at higher pressure ratios.

R-R forecasts a 20-year demand for 31,650 new commercial aircraft, of which some 8,500 will be twin-aisle designs (accounting for about 27 percent of units, but 50 percent of both thrust and value) and around 15,000 single-aisle models.