RB211-GZero retrofit

September 26 2012 - TI Staff

 

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The RB211-Gzero retrofit upgrade provides existing users of industrial RB211-C and RB211-G gas generators, utilising RT-56 and RT-62 power turbines, with a nominal 10 per cent power increase depending on ambient temperature. Available from 37,465 to 45,316 horsepower at ISO conditions, more than 700 RB211 units have been sold, recording over 30 million operating hours.

The RB211-Gzero upgrade can be easily achieved with minimal modification to the existing package design during routine unit overhaul. This cost-effective and simple retrofit approach ensures facility down-time is minimised, while performance, power and operator profitability are optimised.

The industrial RB211 has been refined through in-field experience, including remote and offshore operations where availability and rugged reliability are of crucial importance.

Track record of performance enhancements
Rolls-Royce has a proven track-record of applying systematic product enhancement and upgrade improvements to increase power output and enhance the efficiency and emissions performance of equipment for owner operators. The first RB211 gas turbine went into service in 1974, rated at 26,418 horsepower. Year on year our team of expert design and field-service engineers has applied fleet performance data insights from operating hours accumulated in the field to drive continuous RB211 unit performance improvements. These have included power and efficiency upgrades and improvements such as the RB211-GT, RB211-H63 and now the RB211-Gzero.

Cost effective solution minimises downtime
RB211-Gzero is a power enhancement programme particularly relevant to operators of the 440-plus worldwide installed fleet of RB211-C and -G gas generators with RT-56 or RT-62 power turbines.

The programme offers operators an upgraded version of the RB211-G gas generator which, when harnessed to a power turbine, delivers enhanced prime mover power capacity. The RB211-Gzero gas generator upgrade is achieved with increased air flow featuring zero-staging, partial re-blading of the intermediate pressure compressor and upgrading of the inlet vane of the power turbine to suit the higher flow.

For existing RB211-C engines, the conversion, easily made during the overhaul cycle in one of the Rolls-Royce approved repair and overhaul bases worldwide, combines the existing -C to –G turbine refit with the RB211-Gzero compressor upgrade to create the RB211-Gzero gas generator. The new RB211-Gzero engine is interchangeable with the current -G engine, with similar dimensions and interfaces.z

Ease of gas generator refit is a key element of the upgrade alongside minimal package alteration to ensure a cost-effective modification in the field with minimal downtime.

Technical benefits
The RB211-Gzero upgrade focusses on two of the five RB211 modules: air intake and intermediate pressure compressor. The remaining three modules remain unchanged and are taken from the donor engine during retrofit.

Module 1, the air intake casing, has been redesigned and shortened to ensure identical engine interface length is maintained, compensating for the increased length of module 2, the intermediate pressure compressor. A redesigned elliptically-profiled nose bullet extends further forward in the air stream and achieves ideal airflow entry to the compressor.

Core elements of the upgrade focus on the intermediate pressure compressor module. Here the existing stage one disc and blade row is removed and replaced with a new stage zero and stage one discs and blade assembly, designed to mate with the existing stage two-to-five drum assembly.

The new RB211-Gzero stage zero and stage one discs are in titanium and replace the existing stage one steel disc. Blades on the new discs feature an elliptical leading edge design for improved efficiency. High wedge-angle and 3D tangentially-bowed vane technology from the Rolls-Royce Trent aero family contribute to improved compressor efficiency across the widest operating range. The total number of variable-geometry stages increases from one on the RB211-G to three: one row of variable inlet guide vanes and two stages of variable stator vanes.

Flexible, modular package for ease of maintenance
Engineered as a modular package, the RB211-Gzero is factory tested and ready for rapid, low-risk installation and commissioning. The RB211-Gzero design incorporates most engine accessory systems integral to the package, simplifying installation.

The modular design allows the RB211-Gzero gas generator modules to be removed and replaced, individually with new or leased modules at a service centre, while the originals are being repaired or overhauled.

Technical description
ISO power                              32MW (43,000 SHP)

10 per cent increase from RB211-G

Up to 31 per cent increase from

RB211-C, depending on existing

package configuration

Efficiency                               37.7 per cent

Heat rate                                9541kJ/kWh

Compressor ratio                  23.4

Exhaust gas flow                   102 kg/s

Exhaust gas temperature     477oC

Gas generator                       RB211-G/RB211-C

Combustion                           Phase II, DLE

Pk1 to PhII conversion required

Power turbine                        RT56/RT62

Starter                                    Existing start system

 

Scope of work
Gas generator                       Upgrade to Gzero, standard at overhaul base

Power turbine                        1st stage PT vane

Thrust bearing

 

Package*                               New bleed ducting

Cyclonic separator

Gas generator mounting bolt

Fuel controls system          Change operating limits

 

* site survey will be required to determine additional package scope of work