Rolls-Royce's strategy of backfeeding technology from the Trent XWB into new variants of previous engines - such as the Trent 1000-TEN - is also benefitting in-service powerplants, and certain improvements can be retrofitted during shop visits.

"What we've done over the last couple of years is use some Trent 1000 and XWB technology in the Trent 900," says Peter Johnston, head of customer marketing for civil large engines.

The current production standard engine for the Airbus A380 is the Trent 900EP (enhanced performance), and this will be replaced by an EP2 standard from next year. Also on offer are upgrades for the Trent 700 powering A330s, the Trent 800 for the Boeing 777 and the A340-500/600's Trent 500.

Rolls-Royce Trent 900


Rolls-Royce has used Trent XWB and Trent 1000 technology to improve the efficiency of its Trent 900 engine

The changes are "mainly around aerodynamic improvements", says Johnston. The Trent 1000 introduced elliptical leading edge compressor blades which provide better efficiency across the compression system. These are available as a retrofit kit for the Trent 800 and 500 (both of which are now out of production) and the first engines are going through overhaul, says Johnston.

Elliptical blades are fitted to every stage of the intermediate and high-pressure compressors of these engines and provide a 0.5% fuel burn benefit for the Trent 500, and 0.7% for the Trent 800 "depending on how the engines are used", says Johnston.

This translates to approximately $200,000 of fuel savings per aircraft per year. "That's not a huge engineering change but well worth having for an airline," says Johnston.

The Trent 700 was the first Trent engine to enter service - in 1995 - and it powers more than 500 in-service A330s. The production rate is at its highest ever level.

The Trent 700EP was introduced in 2009 and is the current build standard offering 1.3% better fuel burn than the original engine. Some elements are offered as a retrofit kit to give just over a 1% improvement. About half of in-service engines have been retrofitted to the Trent 700EP standard, says Johnston.

Among the improvements are an optimised turbine case cooling system, super polished turbine components, and tightened aerodynamic standards around the spinner.

The Trent 700EP2 was announced at the Farnborough air show in 2012, and improves fuel burn by a further 1%. It will be the new build standard from 2015 and aligns with the availability of a 242t maximum take-off weight development of the A330.

"We're taking the aerodynamic technology we've used previously on rotor blades and putting them onto the stator blades, the non-moving blade components, and we're doing quite a lot of work on sealing. Anything that can improve sealing has a very powerful effect on fuel burn," says Johnston.

"We're not sure yet how much of it will be retrofittable, but the intention is that we will have a Trent 700EP2 retrofit kit."

He says the Trent 700EP2 will offer a further $250,000 per year fuel burn saving compared with the EP.

The Trent 900 has been in service five years and now powers 56 A380s with six operators, and has accumulated more than 2 million flying hours. British Airways becomes a new operator this year. All Trent 900s are operated under TotalCare agreements and - unlike other Trent models - incremental upgrades are provided by R-R as part of this programme.

All new engines delivered since early 2012 have been the 900EP standard. Testing of an EP2 standard will start later this year.

The 900EP introduced elliptical leading edge compressor blades, reduced low-pressure turbine (LPT) tip clearances, and a coating on the high-pressure compressor drum to reduce clearances.

The Trent 900EP2 further optimises turbine case cooling using technology from the Trent XWB to modulate tip clearances. There is also improved LPT sealing, and an optimised intermediate-pressure compressor. With aerodynamic improvements introduced for the core air inlet, an additional fuel burn benefit of 0.5-0.8% will be delivered at entry into service in mid-2014, says Johnston.

Source: Flight Daily News