Modern Energetics
Chapter 1


The Steam Turbine

 

Table of contents

1. Turbine types

   1.1. Direction of flow

   1.2. Cylinder and exhaust arrangements

   1.3. Speed of rotation


2. Efficiency and output

   2.1. Output limitations

      2.1.1. Steam valve pressure drop

      2.1.2. Swallowing capacity

   2.2. Moving blades

      2.2.1. Impulse-type turbine

      2.2.2. Reaction-type turbine

      2.2.3. Effect on turbine design

      2.2.4. Blade efficiency

      2.2.5. Modern blading designs

      2.2.6. LP turbine blading

   2.3. The effect of clearances on real designs

      2.3.1. Profile loss

      2.3.2. Secondary loss

      2.3.3. Tip leakage

      2.3.4. Disc windage

      2.3.5. Lacing wires

      2.3.6. Other losses

      2.3.7. Wetness loss

      2.3.8. Annulus loss

   2.4. Stage efficiency and the condition line

      2.4.1. Efficiency of stage

      2.4.2. The condition line

      2.4.3. Cylinder efficiency

      2.4.4. Leaving loss

      2.4.5. Hood loss

      2.4.6. Wetness loss

      2.4.7. Partial admission


3. Thermodynamics of the steam cycle

   3.1. Development of the modern steam cycle

      3.1.1. The steam cycle

      3.1.2. The Rankine cycle

      3.1.3. Practical cycle using superheat

      3.1.4. The reheat cycle

      3.1.5. Regenerative feedheating

   3.2. Cycle efficiency and heat rate

      3.2.1. Cylinder efficiency

      3.2.2. Heat rate

   3.3. Terminal conditions

      3.3.1. Effect of steam inlet conditions

      3.3.2. Effect of reheat conditions

      3.3.3. Effect of pressure loss in pipework and valves

      3.3.4. Effect of final feed temperatures

      3.3.5. Effect of exhaust pressure

   3.4. Superheat cycle

      3.4.1. Steam conditions

      3.4.2. Reheat

      3.4.3. Double reheat

      3.4.4. CEGB cycles

      3.4.5. Turbine designs

   3.5. Wet steam cycle

      3.5.1. The PWR steam cycle

      3.5.2. Cycle considerations

      3.5.3. Full-speed or half-speed machines


4. Economics of the steam cycle

   4.1. Choice of exhaust pressure

      4.1.1. Thermodynamic optimisation

      4.1.2. General economic optimisation of plant

      4.1.3. Economic optimisation of exhaust pressure, condenser and CW system

   4.2. Regenerative feedheating

      4.2.1. Feedheating plant stages — superheat cycles

      4.2.2. Feedheating plant stages — wet steam cycle

      4.2.3. Feedwater de-aeration

      4.2.4. Low pressure feedwater heaters

      4.2.5. High pressure feedwater heaters

      4.2.6. Summary

   4.3. Choice of feed pump and drive system

      4.3.1. Feed pump size and number

      4.3.2. Feed pump duty, margins, and the need for variable speed

      4.3.3. Economic comparison of steam turbine drives with electric motor drives

      4.3.4. Economic comparison of variable-speed motor (VSM) drive with induction motor plus fluid-coupling drive

      4.3.5. Example of the results of an overall comparison of the through-life costs of four feed pump system options

   4.4. Turbine by-pass systems

      4.4.1. Superheat plant

      4.4.2. By-pass capacity

      4.4.3. System effects

      4.4.4. Improvement of start-up capability

      4.4.5. PWR wet steam plant


5. Turbine blading

   5.1. Impulse stages

      5.1.1. Moving blades — details and construction

      5.1.2. Fixed blades — details and construction

      5.1.3. Velocity-compounded stage

   5.2. Reaction stages

      5.2.1 Fixed and moving blades — details and construction

   5.3. Low pressure stages

      5.3.1. Aerodynamic and mechanical constraints

      5.3.2. Blade tip restraint

      5.3.3. Baumann exhaust

   5.4. Moving blade root attachments

      5.4.1. Fir-tree roots

      5.4.2. Pinned roots

   5.5. Diaphragm construction and support

      5.5.1. Kinematic support

      5.5.2. Radial support pads

      5.5.3. Diaphragm construction

   5.6. Blading materials

      5.6.1. 12% Cr steels

      5.6.2. Titanium

   5.7. Blade vibration control

      5.7.1. Natural frequencies and excitation frequencies

      5.7.2. Sources of vibration excitation

      5.7.3. Verification of estimated natural frequencies and wheel chamber tests

      5.7.4. Methods of vibration control

   5.8. Erosion protection

      5.8.1. Erosion mechanism

      5.8.2. Erosion progression

      5.8.3. Protection and erosion shield materials


6. Turbine casings

   6.1. Forms of casing construction

      6.1.1. High pressure casings

      6.1.2. Intermediate pressure casings

      6.1.3. Low pressure casings

   6.2. Horizontal joints

      6.2.1. Flange design

      6.2.2. Bolting

   6.3. External connections

      6.3.1. Steam inlets — HP and IP

      6.3.2. HP exhausts

      6.3.3. IP exhausts

      6.3.4. Use of thermal skirts and piston rings

      6.3.5. LP cylinders

      6.3.6. Bled-steam connections

   6.4. Casing materials

   6.5. Support and alignment

      6.5.1. HP and IP cylinder supports

      6.5.2. LP cylinder supports

   6.6. Casing and diaphragm glands

   6.7. Lagging


7. Turbine rotors and couplings

   7.1. Types of rotor construction

      7.1.1. Design for high temperature operation

      7.1.2. Cooling of IP rotors

   7.2. Rotor materials

      7.2.1. HP and IP rotors

      7.2.2. LP rotors

   7.3. Rotor testing and balancing

      7.3.1. Thermal stability

      7.3.2. Overspeed testing

      7.3.3. Rotor balancing

      7.3.4. Critical speeds

      7.3.5. Rotor fast fracture risk assessment

   7.4. Couplings

      7.4.1. Flexible couplings

      7.4.2. Semiflexible couplings

      7.4.3. Rigid couplings

   7.5. Rotor alignment

      7.5.1. Alignment technique

      7.5.2. On-line monitoring


8. Bearings, pedestals and turning gear

   8.1. Journal bearings

      8.1.1. Construction

      8.1.2. Instrumentation

      8.1.3. Bearing performance

      8.1.4. Factors affecting bearing life

   8.2. Thrust bearings

   8.3. Pedestals

   8.4. Oil sealing arrangements

   8.5. Turning gear

      8.5.1. Hand barring arrangement

      8.5.2. Electrical turning gear (ETC)


9. Turbine applications

   9.1. Power generation

   9.2. Mechanical drive

   9.3. Combined heat and power (CHP)

   9.4. Combined-cycle plant


10. Future outlook

   10.1. Unit size and rating

   10.2. Supercritical plant

   10.3. Turbine blading development


11. References