Rolls-Royce is developing a low-emissions combustion system for its turbofan aircraft engines, the ALECSys (Advanced Low Emissions Combustion System) demonstrator engine, that has entered its final phase of testing in Tucson, Arizona. The engine was fitted to the Rolls-Royce Boeing 747 Flying Test Bed for flights up to 40,000 feet and engine relights under various conditions.
It is fair to say that the commercial aviation industry produces a considerable amount of carbon dioxide (CO2) emissions. Boeing estimated the aircraft it delivered in 2020 will each produce 1 million tons of carbon dioxide over a 20-plus-year lifespan. For comparison, it would take 11,900 new Toyota Corollas to produce 1 million tons over a similar time span. However, Rolls-Royce and several other manufacturers are looking for ways to reduce the environmental impact of their products.
The ALECSys (Advanced Low Emissions Combustion System) demonstrator engine utilises an innovative lean-burn combustion system that improves the pre-mixing of fuel and air prior to ignition. Rolls-Royce claims the resultant cleaner fuel combustion produces lower nitrogen oxide and particulate emissions. Also, the ALECSys demonstrator tested running a 100-per cent mix of Sustainable Aviation Fuel during ground tests.
Simon Burr, Director of Product Development and Technology, Civil Aerospace, Rolls-Royce, said:
“We are very pleased to see the ALECSys engine now flying. This flight testing is a key part of our drive to not only improve engine efficiency but all aspects of environmental performance. It is part of the wider Rolls Royce sustainability strategy, which also includes support for the increased use of sustainable aviation fuels (SAF) and intensive research into alternative propulsion architectures and technologies.”
It isn’t clear when the technology from the ALECSys demonstrator engine will find its way into production Rolls-Royce engines, but the claimed gains in efficiency would be groundbreaking. ALECSys is part of the UltraFan engine program, claiming to offer a 25 per cent improvement in fuel efficiency compared to the first generation of Rolls-Royce Trent engines.