Recent Advances in Ultra Super Critical Steam Turbine Technology
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Recent Advances in Ultra Super Critical Steam Turbine Technology M. Boss GE Energy, Steam Turbine Technology 1 River Road, Schenectady, NY 12345 Abstract – With the continuing drive to reduce power plant emissions including green house gases, coal fired power plants have been moving to higher ultra-supercritical (USC) steam conditions in addition to advances in technology. GE Energy has designed the next generation USC steam turbine generator with a rating of 1000 MW to address the need for higher efficiency coal fired power plants. With inlet steam conditions of 260 bar and 610ºC / 621ºC (3770 psi and 1150F / 1180F), the primary objective for the advanced technology USC 1000 MW steam turbine is high efficiency. To achieve this higher cycle efficiency, the design utilizes advanced steam turbine technology and system design and a longer last stage bucket design in addition to ultra supercritical steam conditions. Performance enhancing technology is being applied to turbine buckets, nozzles and seals. In addition to improvements to steam path components, performance gains are achieved by optimizing stationary components such as valves, inlets, and exhausts using advanced CFD tools. This USC project illustrates the latest design and technology capabilities of GE Energy and sets the standard for future 1000 MW USC applications. 1. INTRODUCTION GE Energy was an early entrant into USC steam turbine technology with the first unit shipped in 1956 with inlet steam conditions of 310 bar / 621C (4500 psi / 1150F). Since then, GE has shipped 77GW of steam turbines (125 units) with supercritical steam conditions. GE designed the world’s most powerful USC steam turbine rated 1050 MW operating at 250 bar / 600C / 610C (3626 psi / 1112F / 1130F). This 1000 MW USC steam turbine design is a natural evolution of GE’s USC technology. GE continues to develop and refine USC steam turbine technology. With the emerging interest in reducing emissions, including green house gases from coal 1

fired power generation, GE Energy is striving to increase USC PC generation output and efficiency in its development of this 1000MW USC PC platform. Every 1% improvement in plant efficiency results in approximately 2.5% reduction in green house gas emissions. To satisfy this objective, GE Energy is looking to achieve the following advances in PC generation technologies: MW rating: 1000MW MGR Reheat steam temperature: 621C (1150F) Condenser pressure: 1.5” Hg (NR Back Pressure: 2.5” Hg) 4 flow, 45 inch Last Stage Blade Cycle: Single Reheat Regenerative 2. TECHNOLOGY of USC STEAM TURBINE 2.1...

rate gain is usually larger, approaching 0.6-0.7%. Changing the final feedwater temperature, adding a HARP, and setting the reheater pressure obtain the best relative heat rate impact. The use of advanced reheat steam conditions strongly affects the inlet temperature to the low-pressure (LP) turbine section. An increase in hot reheat temperature translates into an almost equal increase in crossover temperature for a given crossover pressure. However, the maximum allowable LP inlet temperature is limited by material considerations associated with the rotor, crossover and hood stationary...

The turbine cost increases and plant cost increases would then be compared to the expected kilowatt outputs to optimize the plant Cost of Electricity. In the case of the 3.5” HgA, the 4flow 40” would be higher cost than the 4-flow 33.5”, and the footprint of the 40” LP section would be larger also. In the case of the 1.5” HgA chart, the 6-flow LP section would require the additional LP turbine section, and additional condenser, as well as a larger footprint for the 45” LP section. These considerations resulted the selection of a 4-flow 45” LP section design. The overall turbine...

i) Improvement of in the power density of steam turbines such as; Increased number of stages Decreased inner ring diameter Optimized stage reaction levels Optimized Stage energy levels ii) Mechanical design elements including: Advanced sealing Integral cover bucket (ICB) Full Arc, hook diaphragm 1st stage Advanced cooling scheme iii) Improved HP/IP/LP shell design iv) Advanced LP design with 45 inch last stage blade 3. HIGH/INTERMEDIATE PRESSURE TURBINE DESIGN 3.1 High Pressure (HP) Section Design 3.1.1 Section Design Figure 2 shows the HP cross-section. The HP section is designed in a...

conventional to GE 4 casing, 4-flow turbine construction. © 2007, General Electric Company Figure 2 - HP Section Arrangement 3.1.2 High Pressure Steam Path The HP steam path has 10 stages. The first stage is full-arc admission. The HP staging is designed in a manner typical for GE’s proven designs using Dense PackTM steampath components. The buckets of the first four stages are made of nickel-based material due to the high temperature creep requirements. The remaining buckets are conventional 12Cr materials. All 10 stages will utilize integral cover buckets (ICB) with advanced tip seals....

3.2 Intermediate Pressure (IP) Section 3.2.1 Section Design Figure 4 shows the intermediate-pressure cross-section. The IP section is designed in a double flow configuration. Steam enters the section through two pipes in the lower half. Two feed water heater extractions are taken from the lower half. The IP exhaust uses two cross over connections from the upper half arranged in the manner conventional to GE 4 casing, 4-flow turbine construction. Single shell construction is used. The shell is split and bolted at its horizontal joint to minimize clearances and reduce manufacturing cost. The...

The biggest advance in steam turbines in recent years has been Aerodynamics. GE has continued to develop advanced aerodynamic vane shapes based on 100 years of experience coupled with 3D CFD (computational fluid dynamics) and GE’s HP test facility. The addition of CFD in the last 10-15 years has resulted in great strides in steam turbine aerodynamics. Figure 5 shows the Steam Path Efficiency % evolution of aerodynamic shapes over the years. Advanced - Vortex Advanced -Vortex pound Lean • Com pound Lean Nozzle • Bow ed Nozzle Partitions Partitions Controlled -Vortex Controlled- Vortex •...