Development of Lean-Burn Low-NOx Combustion Technology at Rolls-Royce Deutschland

Abstract

Lean-burn combustion technology is identified to be the key technology for aero-engine combustion systems to achieve future legislative requirements for NOx. The lean-burn low NOx combustor development at Rolls-Royce Deutschland RRD for the upcoming generation of aero-engines is presented, which has been supported by the German aeronautical research programme. The down selection process of different injector concepts is described in detail to develop lean-burn fuel injection technology up to a technology level for engine application. Initial concept validation with testing on single sector combustion rigs applying advanced laser measurement techniques is followed by high power single sector emission tests to prove low emission characteristics. Climbing the level of technology readiness, which is in each phase substantiated by intense CFD simulations, the most promising low emissions design concepts have been investigated for unrestricted combustor operability compared to conventional rich burn systems. Altitude relight, weak extinction margins, fuel staging optimisation and combustion efficiency in the vicinity of staging points have been optimised on different sub-atmospheric, atmospheric, medium and high-pressure test vehicles. The validation process concludes with sub-atmospheric and high-pressure testing within a fully annular test environment before the final lean-burn fuel injector configuration has been selected for core engine testing to prove emission performance and operability of the fuel-staged combustion system. Two fuel injector configurations were successfully tested in a high-pressure fully annular rig. The combustor module and both injector standards have been cleared for core engine operation.