Literature Review

INTRODUCTION:

Steam turbine is a rotating machine which converts heat energy of steam to mechanical energy. In India steam turbines of different capacities varying from 15MW to 500MW are employed in the field of thermal power generation. The design, material, auxiliary systems etc., vary widely from each other depending on the capacity of the sets.

Development of Steam Turbine:

Historically, first steam turbine was produced by Hero, a Greek Philosopher, in 120 B.C. In 1629, an Italian named Bean Actually antipated the boiler-steam turbine combination that is a major source of power today. Charles Parson introduced first Practical steam turbine in 1844, which was also of the reaction type. Just after five years, in 1889, Gustav

De Laval produced the first practical Impulse turbine.

* The first “turbine” was made by Hero of Alexandria in the second century.

* In the end of XVIII century the Industrial Revolution began (in 1770 first reciprocating piston steam engine invented by Thomas Newcomen and invented by James Watt started its work)

* The first steam turbines were constructed in 1883 by Dr Gustaf de Laval and in 1884 by sir Charles Parsons.

* In1896 Charles Curtis received a patent on impulse turbine.

* In 1910 was created radial turbine (Ljungström).

ABSTRACT

The development of country depends on the amount of power production; Thermal power plant plays a major role in power production. In thermal power plant, steam turbine is one of the essential components and it produces rotational work which is important for production.

Limited primary energy resources and awareness of environmental pollution has led to ever increasing and ever to develop new steam turbine power plant with the highest possible efficiencies. Their output even small step increase in efficiency can result in major saving for the consumer. As overall cycle efficiency is strongly dependent on steam turbine performance.

These efforts are directed primarily towards improvement in reducing the losses.

The main Objective of this project is to calculate the Thermal Analysis and performance of mini steam turbine.

TURBINE

A turbine transfers energy from a fluid to a rotor, a compressor transfers energy from a rotor to a fluid.

What exactly is the turbine?

Turbine is an engine that converts energy of fluid into mechanical energy.

The steam turbine is steam driven rotary engine.

A steam turbine is a mechanical device that extracts thermal energy from pressurized steam, and converts it into rotary motion. Its modern manifestation was invented by Sir Charles parson in 1884.

It has almost completely replaced the reciprocating piston steam engine primarily because of its greater thermal efficiency and higher power-to-weight ratio. Because the turbine generates rotary motion, it is particularly suited to be used to drive an electrical generator – about 80% of all electricity generation in the world is by use of steam turbines.

The steam turbine is a form of heat engine that derives much of its improvement in thermodynamic efficiency through the use of multiple stages in the expansion of the steam, which results in a closer approach to the ideal reversible process.

Turbines are rotating machines with unique construction and very efficient operation. The operating principle is simple; when a forcing agent such as wind, water, steam or gas is directed at the curved blades of the rotor mounted on a shaft, the forcing agent changes speed and direction and the kinetic energy produced, spins the rotor.

The shaft upon which the rotor is mounted, in turn produces mechanical power that can be used to operate motors, generators, hydraulic systems, compressors, gear drives, or any number of machines used for many applications.

While the principle of operation is simple, turbines themselves can be very complex in design and construction and each type offers its own challenges to the operator with regard to lubrication, maintenance, troubleshooting and overall reliability.

Types of Steam Turbine

Impulse Turbine

Reaction Turbine

Impulse Reaction turbine

Impulse turbine

These turbines change the direction of flow of a high velocity fluid or gas jet. The resulting impulse spins the turbine and leaves the fluid flow with diminished kinetic energy

There is no pressure change of the fluid or gas in the turbine blades (the moving blades), as in the case of a steam or gas turbine; all the pressure drop takes place in the stationary blades (the nozzles).

Before reaching the turbine, the fluid's pressure head is changed to velocity head by accelerating the fluid with a nozzle. Pelton wheels and de Laval turbines use this process exclusively

Reaction turbine

These turbines develop torque by reacting to the gas or fluid's pressure or mass. The pressure of the gas or fluid changes as it passes through the turbine rotor blades. A pressure casement is needed to contain the working fluid as it acts on the turbine stage or the turbine must be fully immersed in the fluid flow.

The casing contains and directs the working fluid and, for water turbines, maintains the suction imparted by the draft tube. Francis turbines and most steam turbines use this concept.

Construction of steam turbines

Classification of steam turbines

a) way of energy conversion

- Impulse turbines

- Reaction turbines

b) Flow direction

- Axial

- Radial

c) Number of stages

- Single stage

- Multi-stage

d) Rotational speed

- Regular

- Low-speed

- High-speed

e) Inlet steam pressure

- High pressure (p>6,5MPa)

- Intermediate pressure (2,5MPa <p<6,5MPa)

- Low-pressure (p<2,5MPa)

f) way of energy utilisation

- condensing

- Extraction

- Back-pressure

g) Application

- Power station

- Industrial

- Transport

Advantages of turbines

High efficiency

Simple design

High revolution

Types of Turbines

BASIC CONFIGURATION

Reaction Stage

Impulse Turbine Vs Reaction Turbine

Main Differences of Impulse and

Main difference between Impulse and Reaction turbine

1) In Impulse turbine the water flows through the nozzles and impinges on the buckets where as in Reaction turbine the water is guided by the guide blades to flow over the moving vanes.

2) In Impulse turbine the entire water energy is first converted kinetic energy but there is no energy conversion in Reaction turbine.

3) In Impulse turbine the water impinges on the buckets with kinetic energy where as in Reaction turbine the water glides with the moving vanes with pressure energy.

4) In Impulse turbine the work is done only by the change in the kinetic energy of the jet but in Reaction turbine the work is done partly by the change in velocity head, but almost entirely by the change in pressure head.

5) In Impulse turbine the pressure of flowing water remains unchanged and is equal to the atmospheric pressure but in Reaction turbine the pressure of flowing water is reduced after gliding over the vanes.

6) In Impulse turbine it is not essential that the wheel should run full. Moreover, there should be free access of air between the vanes and the wheel where as it is essential that the wheel should always run full and kept full of water in Reaction turbine.

7) In Impulse turbine the water may be admitted over a part of the circumference or over the whole circumference of the wheel but in Reaction turbine the water must be admitted over the whole circumference of the wheel.

8) It is possible to regulate the water without loss in Impulse turbine but in Reaction turbine it is not possible to regulate the flow without loss.