Analysis of Large Turbines P M V Subbarao Professor Mechanical Engineering Department Generalization of Sir Parsons Concept……

Parsons Steam Turbines : Multistage Reaction Turbines

General Rules for Design of Large Impulse-Reaction turbine The shape of the blade must be viable . The height of blade must vary at a uniform rate, thus contributing to more economic designs. As a result of enthalpy drop occurring in the moving blades, there is a considerable amount of pressure is exerted on the rotor. This is transmitted to thrust bearing. To void large axial thrust it is usual to allow: Low degree of reaction in high pressure stages. In large steam turbines (>300 MW), it is now usual to allow 60 – 70% of degree of reaction in low pressure stages.

Generalization of Degree of Reaction U Vr1 Va1 Vr2 Va2 b1 a1 a2 b2 The reaction effect is an addition to impulse effect. Define the degree of reaction p va vr A Physical Linkage between Momentum and Energy transactions

First Law Analysis of Reversible Reaction Stage First law for fixed blades: First law for relative flow through moving blades: 2 1

DoR of Reversible General Reaction Blading True Power lost by steam in a stage = Power gained by rotor blade 2 1

Relative Acceleration of Steam

Capacity of A General Reaction Stage The driving force on wheel Power Output of the blade : Diagram Efficiency or Blade efficiency:

Stage Sizing Steam Path

Linearization of Reaction Stage Equations

Blade velcoity factor, f

For a given shape of the blade, the efficiency is a strong function of U/Vfitc. For maximum efficiency:

Performance of Degree of Reaction Specific Power output

Selection of Degree of Reaction hstage L increasing L1 L2 L3 L4 An Isentropic Analysis only !!! Still All the Steam Power Cannot be Converted into Mechanical Power ?

Stage Sizing Steam Path

Large Power Plants : Selection of Speed Swallowing Capacity : Loading Capacity : Power Capacity :

Mechanical Arrangements of Steam Turbines Solutions to Turbo-machinery Issues. Tandem Reheat Steam Turbine Cross Compound Steam Turbine

Tandem Reheat Steam Turbine

Cross Compound Reheat Steam Turbine

Tandem-compound four-flow steam turbine

Large-Capacity Steam Turbines for Fossil Thermal Power Plant