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Rolls-Royce Aero-Derivative Combustion Turbine Background
2-2
seven-stage low pressure compressor (LPC), six-stage high pressure compressor (HPC) driven
by a single-stage high pressure turbine (HPT), and a single axial stage, low pressure turbine
(LPT) which drives the LPC via an inner coaxial shaft, for a total of 5 pre-balanced modules.
The RB211 for power generation is derived from the three-spool aero RB211 flight engine in
which a final three-stage turbine drives a single-stage wide-chord fan.
Figure 2-1
Industrial RB211: Gas Generator and Free Power Turbine
The standard combustor is a single, fully annular, combustion chamber with eighteen air-spray
burners with atomizing fuel nozzles for liquid fuel. The DLE combustion system was introduced
in 1994 that resulted in a radical design change to the combustion module. The design change
includes nine reverse-flow radial combustors. Each combustion chamber contains a two-stage
combustion assembly with the air and fuel divided between the series-staged combustors. The
combustion module has the same physical dimensions as the standard module and is completely
upgradeable for all RB211 units without incurring a major overhaul. Combustors can be
configured for gas, liquid or dual fuel capability.
The RB211 incorporates an industrial type, free power turbine on a large pedestal base that
supports both the power turbine and the gas generator. The power turbine (for earlier models RT
56 and RT 62) is a two-stage free power turbine that uses journal bearings and mineral oil for
lubrication. Aimed at the pipeline/compressor drive application (oil and gas market) the power
turbine is design to rotate at 4800 to 4880 rpm. The RB211 is a hot end drive. For utility
applications, a reduction gearbox is required to reduce the speed to 1500 or 1800 rpm to drive a
four-pole generator for 50 and 60 hertz utility applications.
The new three-stage RT61 free power turbine, based on the aero Trent 800 engine’s turbine, is
designed for improved efficiency and is used with the uprated RB211. The new design
incorporates a three-stage, free power turbine but is lighter in weight with modular construction