The objective of this project was to provide a novel, fully operational and commissioned test facility for the system verification of the new, highly complex lean burn engine control system necessary for more fuel efficient medium and large aero-engine system applications. This validation facility does not exist today and capability included interaction with the donor-engine fuel system with no adverse effect, system performance across the operational envelope, fault insertion, fuel spike measurement, high speed data logging and confirmation of adequate sensing and acquisition.
The approach was to connect the real fuel system components to a drive head using a test skid enabling donor engine and lean burn fuel control system components to be secured in engine and fuel pipe representative positions.
The project was split into nine work packages and the overall aim was to design, build and commission a lean burn system test facility utilising the expertise of Aero Engine Controls and SCITEK, an SME, both of whom have pedigree in the development and validation of aero engine control fuel systems.
Following successful completion of this project, the Partners anticipated upgrading test facilities to the new configuration for future validation of lean burn systems both for development platforms and original equipment manufacture, resulting in increased and sustained employment and supporting the production of potentially 3000 lean burn fuel systems per year.
Lean Burn technologies need to be implemented on future gas turbines. Such technologies are considered necessary in order to meet the future emissions requirements and maintain a competitive advantage in the market place.
Lean Burn fuel systems require improved verification rigs to deal with their inherent complexity and unique modes of operation relative to existing “rich burn” fuel systems. To develop these improvements in rig capability, Rolls-Royce Controls and Data Services Limited (CDS) has designed and built a Lean Burn Verification Rig (LeVeR).
LeVeR initially used an EEC to control the hydro-mechanical systems. However, the system was developed to alternatively use a bespoke test box in conjunction with the Hydro-Mechanical Rig (HMR) computers to provide a more flexible engineering solution.
The Advanced Generic Test Rig (AGTR) uses an Electronic Engine Controller (EEC) and Remote Data Concentrator (RDC) and provides an electrical simulation for the environment in which these units are designed to operate.
LeVeR builds upon the AGTR configuration by adding fuel system components i.e. hydro-mechanical unit (HMU), fuel pumps, hydro-mechanical staging unit (HSU), scheduling valves etc, in other words accurately modelling the core of the gas turbine engine and therefore providing a route to verify and de-risk hardware and performance before running on a gas turbine engine.
To date, rigs simulate core engine pressure by using a restrictor in the fuel delivery pipe. This is adequate for modelling the continuous fuel flow of rich-burn architecture engines.
Lean burn systems however require far higher air to fuel ratios for lean combustion whilst still maintaining combustion stability. This is achieved by using staged combustion, where the high air to fuel required for lean combustion is delivered in mains burners, but combustion stability is achieved by also using pilot burners. Consequently fuel flow delivery varies significantly between pilots and mains burners and a simple restrictor cannot accurately simulate engine pressure with these varying flows. The rig must therefore be able to reproduce the engine pressures seen during steady state and transient manoeuvres to provide accurate modelling.
The verification of Lean Burn systems requires a real engine pressurise simulation to establish the behaviour and effects on the system when valves, actuators and fuel pipes operate in this environment. The development and demonstration of this real engine pressure or ‘P30’ system is a fundamental requirement of the LeVeR project.
Where feasible the rig will model abnormal transient behaviours, such as engine surges. Test bed and EEC logged data has been gathered from engine development programmes to capture the characteristics for the P30 values ideally required do produce a real time engine model (RTEM).