Mercury 50 recuperated

Solar Turbine’s 4 MW class Mercury 50 recuperated gas turbine, initially unveiled in late 1997 (see Modern Power Systems, February 1998), was finally declared to be commercially available in December 2003.

In the intervening period Solar has developed a series of improvements to the engine, recuperator and package to address issues exhibited during the field evaluation programme.

In the course of this programme the Mercury 50 has completed more than 40 000 hours of operating experience at field evaluation sites in California, Colorado, Illinois and South Carolina in the United States and in France and Australia.

These field evaluation sites provided Solar with valuable data regarding the operation of the generator sets over a variety of conditions, including a range of ambient temperatures, different fuel properties, as well as numerous customer-driven operating scenarios.

Solar made a decision to invest in the success of the programme and has addressed the issues through a continued and rigorous

development effort. The most significant improvements to the product have been those that have extended the durability of the recuperator, which is subject to large thermal shocks. Since the initial field evaluation, the recuperator material has been upgraded (from 347 stainless steel to Alloy 625) and structural design integrity has been enhanced.

Performance improvements were also made in the compressor and turbine sections, including adoption of a higher firing temperature.

The Mercury 50 will be introduced with a nominal power rating of 4600 kW and a heat rate of 8863 Btu/kWh, efficiency of 38.5% (at the terminals on a 59°F day at sea level). The exhaust temperature is 705°F with an exhaust flow of 141 430 lb/h.

The Mercury 50 is the result of a co-operative effort between Solar and the US Department of Energy to produce gas turbines that are more efficient, cleaner and less expensive to operate than today’s turbines.

The programme’s multi-faceted goals centred around a reduction of NOx to 9 ppmv or less, improved efficiency and a reduction in the busbar cost of power, all while maintaining a high level of reliability, availability, maintainability, and durability.

To optimise the design of the engine around the recuperated cycle, an innovative engine arrangement was pursued. The compressor section was placed behind the combustor and

turbine sections of the engine, yielding a unique flow path. In addition to the unique arrangement, a number of new technologies have been incorporated into the design of the Mercury 50, including vortex cooled turbine blades and

advanced compressor aerodynamics.

The Mercury 50’s Ultra Lean Premix (ULP) combustion system also represents a substantial technology development milestone in Solar’s ongoing efforts to achieve further emissions reductions.

Using Solar’s next generation ULP combustion system, the Mercury 50 is available with a 5 ppm NOx guarantee, with the CO and UHC guarantees both at the 10 ppm level.

Solar believes the performance characteristics of the Mercury 50 allow its appeal to go well beyond traditional industrial cogeneration or combined heat and power (CHP) applications. The company says the Mercury 50 is well suited for commercial CHP or building cooling, heating and power (BCHP) applications, where steam loads are less than 25 000 lb/h and chilled/hot water is required. The Mercury 50 is also well suited for intermediate peaking applications, such as economic dispatch for municipal utilities and rural electric co-operatives, distributed generation applications such as utility grid support, shoulder management for municipal and rural electric cooperatives and load following.

Solar Turbines says it is currently in discussions with a customer who will be the first to operate a new Mercury 50 pre-production unit. This unit is scheduled to be commissioned by December of 2004.

The company is accepting orders for production units, which will be available for shipment in the first half of 2005.

Basic data for Mercury 50 standard package

Gas turbine

• Mercury 50, recuperated, single-shaft

• Axial compressor

10-stage

variable inlet guide vanes and stators

compression ratio, 9.9:1

inlet airflow, 39.2 lb/sec (17.9 kg/sec)

speed, 14 179/14 186 rpm (50/60 Hz)

vertically split case

• Annular combustion chamber

ultra-lean-premix combustion system

8 fuel injectors

torch ignitor system

• Proximity probe vibration transducers

• Turbine

2-stage, reaction

clockwise rotation

• Bearings

radial: 3 viscous damped rolling element

thrust: 1 unclamped rolling element

Recuperator

• Primary surface type

• Alloy 625 construction

Main reduction drive

• Epicyclic type

double helical gearing

1500 or 1800 rpm (50 or 60 Hz)

acceleration vibration transducer

Generator

• Continuous duty rating

• Salient pole, 3 phase, 6 wire, wye connected, synchronous with brushless exciter

• Permanent magnet

• Open drip-proof construction

• Rolling element bearings

• Velocity vibration transducers

• NEMA Class F insulation

Package

• Single skid

maintains turbine, reduction drive and generator alignment

contains all major turbine systems

• Direct-drive AC start system

• Natural gas fuel system

• Turbotronic 4 control system

ControlLogix processor

standard display with discrete event log, strip chart, historical trend, maintenance screen

gas turbine and generator control

vibration and temperature monitoring

auto synchronising

kW control

kVAR/power factor control (optional)

combination generator control module with load share, synchronisation, voltage control, reactive power control, generator protection

• Integrated lube oil system

main/pre/post lube pump

backup lube pump

air and oil cooler

integral lube oil tank

lube oil tank heater

simplex lube oil filter

oil mist eliminator

Solar/Systems come together

As from 1 January 2004, Caterpillar subsidiary Solar Turbines Incorporated and Caterpillar International Power Systems have aligned to form Caterpillar Power Generation Systems, a marketing organisation representing Solar gas turbines and Caterpillar Motoren (CM) long-stroke, medium-speed reciprocating engines.

This new entity aims to offer customers what it calls “an optimised solution” by drawing on two proven technologies, Solar gas turbines and CM engines.

Caterpillar Power Generation Systems will represent both the Solar and CM product brands for power generation applications, and will be responsible for the marketing, sales, product management and order fulfilment activities of both brands. The individual product organisations will provide engineering, manufacturing and packaging operations. Service will be provided for turbines and reciprocating engines respectively through Solar’s customer services organisation and the Caterpillar dealer organisation.

Solar Turbines products to be marketed under the CPGS organisation will include the Saturn 20, Centaur 40 and 50, Mercury 50, Taurus 60 and 70, Mars 90 and 100, and Titan 130 for power generation applications. They will continue to be sold through Solar’s direct sales channel.

Caterpillar Motoren products now marketed under the CPGS organisation include the medium speed reciprocating engine families CM20, CM25, CM32, GCM34 and CM43. These engine platform designs are based on proven heavy fuel experience and are suitable for developing areas where the quality and availability of fuel varies, yet the need for reliable electricity is imperative.