What is a Steam Turbine : Working and Its Types

The scope of the steam turbine was in evolution in the first century itself where this device resembles a toy. Then, the practical application of steam turbine was invented and this stands as the base for the progression of other kinds of steam turbines. The modern kind of steam turbine was introduced in the year 1884 by the person Charles Parsons where the construction includes a dynamo. Later on, this device gained prominence in its operational ability and people adopted to implement in their operations. This article describes the concepts related to the steam turbine and its functionality.

What is Steam Turbine?

Definition: Steam turbine comes under the classification of a mechanical machine that isolates thermal energy form the forced steam and converts this into mechanical energy. As the turbine produce rotatory motion, it is most appropriate for the operation of electrical generators. The name itself indicates the device is driven by steam and when the vaporous stream flows across the turbine’s blades, then the steam cools and then expands thus delivering almost the energy that it has and this is the continual process.

The blades thus transform the device potential energy to that of kinetic movement. In this way, the steam turbine is operated to supply electricity. These devices make use of enhanced pressure of steam to rotate electric generators at extremely more speeds where the revolving speed of these are maximum than water turbines and wind turbines.

For instance: A conventional steam turbine has a rotating speed of 1800-3600 revolutions per minute nearly 200 times more spins than that of a wind turbine.

Steam Turbine Working Principle

The operating principle of this device is based on the dynamic movement of the steam. The increased pressure steam which comes out from the nozzles hits the revolving blades that are close-fitted to the disc which is placed on the shaft. As because of this increased velocity in the steam, it develops energetic pressure on the device blades where then the shaft and blades start to revolve in a similar direction. In general, the steam turbine isolates the energy of the stem and then transforms it into the kinetic energy which then flows through the nozzles.

So, the transform of kinetic energy performs mechanical action to the rotor blades and this rotor has a connection with the steam turbine generator and this performs as the intermediary. Because the construction of a device is so streamlined, it generates minimal noise when compared to other kinds of rotating devices.

In most of the turbines, the revolving blade speed is linear to that of the steam speed flowing across the blade. When the vapor gets expanded in the single-phase itself from that boiler force to the exhausted force, then the vapor velocity is extremely increased. Whereas the major turbine which is used in nuclear plants where the steam expansion rate is nearly 6 MPa to 0.0008 MPa having a rate of speed at 3000 revolutions per 50 Hz of frequency and 1800 revolutions at 60 Hz frequency.

So, many nuclear plants function as a one shaft turbine HP generator which has a single multi-stage turbine and three parallel LP turbines, an exciter along with the main generator.

Types of Steam Turbine

Steam turbines are classified based on many parameters and there are many types in this. The types to be discussed are as follows:

Based on the Steam Movement

Based on the steam movement, these are classified into different types which include the following.

Impulse Turbine

Here, the extreme speed steam that flows out from the nozzle hits the rotating blades which are placed on the rotor periphery section. As because of striking, the blades alter their rotating direction having no change in the pressure values. The pressure caused because of momentum develops the rotation of the shaft. Examples of this kind are Rateau and Curtis turbines.

Reaction Turbine

Here, the expansion of steam will be there in both the moving and constant blades when the stream flows across these. There will be a continuous pressure drop across these blades.

Combination of Reaction and Impulse Turbine

Based on the combination of reaction and impulse turbine, these are classified into different types which include the following.

• Based on Pressure Stages
• Based on the Steam Movement

Based on Pressure Stages

Based on pressure stages, these are classified into different types.

Single-stage

These are implemented for powering up centrifugal compressors, blower equipment, and other same kinds of tools.

Multi-phase Reaction and Impulse Turbine 

These are employed in an extreme range of capacities either minimal or maximal ranges.

Based on the Steam Movement

Based on the steam movement, these are classified into different types.

Axial Turbines 

In these devices, the flow of steam will be in the direction that is parallel to the rotor axis.

Radial Turbines 

In these devices, the flow of steam will be in the direction that is perpendicular to the rotor axis either one or two fewer pressure phases are made in an axial direction.

Based on Governing Methodology

Based on the governing methodology, these are classified into different types.

Throttle Management 

Here, fresh steam comes into via one or more concurrently functioned throttle valves, and this is based on power development.

Nozzle Management 

Here, fresh steam comes into via one or more sequentially opening regulators.

By-pass Management 

Here, steam drives both the first and the other intermediary phases of the turbine.

Based on Heat-drop Procedure

Based on the heat drop procedure, these are classified into different types.

Turbine Condensation through Generators 

In this, the steam force which is fewer than environmental pressure is fed to the condenser.

Turbine Condensation Intermediary Phase Extractions 

In this, steam is isolated from intermediary phases for commercial heating purposes.

Back-pressure Turbines 

Here, the exhausted steam is used for both heating and industrial applications.

Topping Turbines 

Here, the exhausted steam is used for lesser and medium force turbine condensation.

Based on Vapor Conditions from Inlet to Turbine

• Less pressure (1.2 ata to 2 ata)
• Medium pressure (40 ata)
• High pressure (> 40 ata)
• Very high pressure(170 ata)
• Supercritical (>225 ata)

Based on Industrial Applications

• Fixed rotational speed having stationary turbines
• Variable rotational speed having stationary turbines
• Variable rotational speed having non-stationary turbines

Difference between Steam Turbine and Steam Engine

The difference between these two is listed below.

Steam Turbine	Steam Engine
Minimal friction loss	Maximum friction loss
Good balancing properties	Poor balancing properties
Construction and maintenance is simple	Construction and maintenance is complicated
Can be good for high-speed devices	Only operates for minimal speed devices
Uniform power generation	Non-uniform power generation
Enhanced efficiency	Less efficiency
Appropriate for huge industrial applications	Appropriate for minimal industrial applications

Advantages/Disadvantages

The advantages of a steam turbine are

• The arrangement of the steam turbine needs minimal space
• Streamlined operation and reliable system
• Requires less operational cost and has only minimal spaces
• Elevated efficiency in the steam paths

The disadvantages of a steam turbine are

• As because of increased velocity, there will be enhanced frictional losses
• Has minimal effectivity which means the proportion of blade to steam velocity is not optimal

Applications of Steam Turbine

• Mixed pressure turbines
• Implemented in engineering domains
• Power generation tools

FAQs

1). What is a steam turbine efficiency?

It is defined as the proportion of work done on the rotating blades to the entire supplied energy both calculated for a kilogram of steam.

2). Which turbine is more efficient?

The most efficient turbines are impulse turbines.

3). How do you increase the steam turbine efficiency?

Efficiency can be augmented through steam turbine reheating, recovering feed heating of the turbine, and through the binary vapor cycle.

4). What is the steam turbine generator?

It is the initial power transformation device in the power plant.

5). How can steam turn a turbine?

Through heating of water to the temperature that it gets converted to steam.

This is all about steam turbines. The good rotational balance and minimal hammer blow allow these devices to be utilized in various industries. The question that arises here is to know about the applications of steam turbines.