Turbine_Presentation_Binay Roy

Introduction

• Turbines presented by Binay Roy.

What is a Turbine?

• A turbine is a device that converts heat energy of steam into kinetic energy and then into rotational energy.

• The motive power in a steam turbine is derived by the change in momentum of a high-velocity steam jet hitting a curved blade that can rotate.

• The basic cycle for steam turbine power plants is known as the Rankine cycle, which is often modified with superheating, regenerative feed water heating, and reheating.

Basic Principles of Steam Turbine

• Steam turbines operate on the principle of converting high-pressure and temperature steam into high kinetic energy, providing torque to a moving rotor.

• Energy conversion requires:

  • Converging and diverging sections.

  • A drop in steam pressure through passages, leading to an increase in velocity.

  • A change in motion direction resulting in a change of momentum (force) that drives the rotor.

Working Principle of Steam Turbine

• High-pressure steam passes through a row of fixed blades in a stationary casing causing a pressure drop across the blades, resulting in high steam velocity at the exit.

• The high-velocity steam then impacts rotating blades on the rotor shaft, generating a driving force that causes rotation.

• A stage of a turbine refers to a set of fixed and rotating blades mounted on the rotor.

Types of Turbines

1. Impulse Turbine

   • Pressure drop occurs only in the nozzle.

   • Uses kinetic energy of steam striking moving blades (buckets).

   • Example: Pelton Wheel.

2. Reaction Turbine

   • Pressure drop occurs in both fixed and moving blades.

   • Steam glides over moving blades, utilizing both pressure and kinetic energy.

   • Examples: Francis turbine, Kaplan turbine.

Differences Between Impulse and Reaction Turbine

• Impulse Turbine

  1. Steam flows through nozzle and strikes moving blades.

  2. Constant pressure across moving blades.

  3. Requires fewer stages for same power.

  4. Lower maintenance needed.

• Reaction Turbine

  1. Steam flows through guide mechanism first.

  2. Pressure reduces as steam flows through moving blades.

  3. Requires more stages for same power.

  4. Higher maintenance required.

Compounding of Steam Turbine

• Compounding refers to multi-staging of a steam turbine to reduce rotor speed, preventing high vibrations and other drawbacks of single-stage turbines.

• Achieved by arranging multiple stages on the same rotor shaft, allowing each stage to extract energy from steam, leading to lower speeds.

Necessity of Compounding

• Advantages of Compounding:

  • Reduces rotor speed, thereby reducing vibrations and centrifugal force risks.

  • Improves energy utilization across stages.

Methods of Compounding

1. Velocity Compounding:

   • Steam velocity decreases over multiple stages. Components include a single set of nozzles and sets of moving and fixed blades.

2. Pressure Compounding:

   • Total pressure drop is divided across multiple stages with sets of nozzles and moving blades.

3. Pressure-Velocity Compounding:

   • Combines advantages from both methods.

   • Multiple stages where each stage has nozzles, moving blades, and fixed blades.

Turbine Component Overview

• Components include:

  • Casing

  • Rotor

  • Blades

  • Sealing system

  • Stop & control valves

  • Couplings and bearings

  • Barring gear

Key Turbine Features

• Example turbine features include:

  • Tandem compound-reaction-single reheat condensing type turbine.

  • High, intermediate, and low-pressure stages of varying reaction stages.

Shaft Sealing

• Shaft seals prevent leakage and maintain pressure balance. Sealing types vary between high, intermediate, and low-pressure turbines.

Differential Expansion

• The differential expansion between rotor and casing affects operational stability, particularly in high and intermediate pressure turbines.

Axial Shift in Rotors

• Axial shift results from direct pressure thrust and velocity components across moving blades. Proper balancing is essential during operation.

Turbine Cycle Performance

• Efficiency and heat rate measurements are critical for operational optimization.

Factors Affecting Heat Rate

• High superheat and reheat temperatures, feedwater heating, and turbine performance directly impact cycle efficiency.

Conclusion

• Comprehensive understanding of turbine principles, types, compounding methods, and efficiencies is crucial for optimizing steam turbine performance.

Acknowledgments

• Presented by Binay Roy on 12/21/2024.