The ALECSys demonstrator in a Trent 1000 donor engine, was able to halve certain types of emissions at while running at cruise, compared to today’s levels (Image source: Rolls-Royce, plc).

Rolls-Royce starts lean-burn combustion engine icing tests

In March, a new demonstrator engine by Rolls-Royce, featuring a cutting-edge lean-burn and low-emissions combustion system for future jet engine programs, began icing tests at the Global Aerospace Centre for Icing and Environmental Research in Manitoba, Canada.

The novel Advanced Low Emissions Combustion System (ALECSys) demonstrator technology tested at temperatures of 4℉ (-20℃) to expose the engine to severe environmental operating conditions it might endure during operation. Rolls-Royce is currently processing results and data initially obtained from a testbed at its headquarters in Derby, England as it’s nearing release.

“The Manitoba facility offers the opportunity to expose the engine to some of the most severe environmental operating conditions to which an aero-engine might be exposed in service operation, including conditions of engine core ice build-up and shedding,” says Andy Geer, Rolls-Royce chief engineer and head of technology programs.

The Rolls-Royce and other large aerospace engine companies will eventually adopt one form or another of high-technology combustion systems to meet ever-tightening environmental regulations. While forms of lean burn combustion systems have operated in industrial gas turbines for years, only recently did manufacturers begin rolling out the latest generation of aero gas turbine products.

Rolls-Royce is among the major gas turbine engine manufacturers developing a variation of this technology-led solution for combustion emissions reduction. Lean burn systems modify the conditions under which air and vaporized fuel are introduced to the combustion system of an engine to ultimately minimize the production of emissions. Utilizing this kind of combustion system enables higher temperatures in the engine for improved efficiency, fuel burn, and carbon dioxide emissions.

The ALECSys, which constantly monitors the environmental conditions and the pilot’s thrust requirements, alters the mixture of fuel and air delivered to various injection points. Rolls-Royce aims to put the lean burn systems to use to reduce nitrous oxides, unburnt hydrocarbons, and carbon particulates. So far, testing the ALECSys in a Trent 1000 “donor” engine has shown to halve nitrogen oxides at cruise, compared to today’s levels.

“Our computer models have given us an in-depth understanding of how the system works in extremes of cold and this series of tests will physically validate that. We are confident that this will offer significant benefits for our customers,” says Geer. 

ALECSys received funding from the European Union’s Clean Sky SAGE (Sustainable And Green Engine) program. This is just one aspect of Rolls-Royce’s wider IntelligentEngine plan to create future products to improve reliability and efficiency with new digital capabilities, and engines that are increasingly connected and contextually aware. That vision also includes core architecture used in both their Advance3 test engine, which ran for the first time in November, and the UltraFan, which Rolls-Royce will make available in 2025. Equipped with a “Power Gearbox” to work efficiently at an aerospace record of high bypass ratios reaching 70,000hp, the UltraFan offers a geared, scalable design suitable for both widebody and narrowbody aircraft—and nets 25 percent better fuel efficiency than first generation of Rolls-Royce Trent engines.

Further testing of ALECSys in Manitoba is likely to occur once the local weather conditions have warmed sufficiently to allow Rolls-Royce to explore a different range of operational cases.

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