Steam Condenser - Definition, Working, Types and Advantages

Steam Condenser is a mechanical device which converts the low pressure exhaust steam from the turbine into water. Or in other words it is a device which is used to condense exhaust steam of the turbine into water. It does so with the help of cooling water circulated into it from the cooling tower.

It works to achieve two main objectives

1. To maintain low pressure (below atmospheric pressure) at the outlet of the steam turbine so as to obtain the maximum possible energy.
2. To supply pure feed water to the hot well and from hot well the water is again pumped to the boiler with the help of boiler feed pump.

Requirements of Steam Condensing Plant

The principle requirements of steam condensing plant are:

Steam Condensing Plant


1. Condenser:  It is a closed vessel used to condense the steam. The low pressure steam gives off its heat to the coolant (here water from cooling tower) and gets converted into water during the process of condensation.

2. Condensate Extraction Pump: It is a pump which is installed in between the condenser and hot well. It transfers the condensate from the condenser to the hot well.

3. Hot Well: It is a sump that lies in between the condenser and boiler. It receives the condensate from the condenser by condensate pump. The feed water is transferred from the hot well to the boiler.

4. Boiler Feed Pump: It is a pump installed in between the hot well and boiler. It pumps the feed water from the hot well to the boiler. And this is done by increasing the pressure of condensate above boiler pressure.

5. Air Extraction Pump:  It is a pump used to extracts or removes the air from the steam condenser.

6. Cooling Tower: It is a tower which contains the cold water and this water is made to circulate within the condenser for cooling of steam.

7. Cooling Water Pump: It is a pump lies in between the cooling tower and condenser. It circulates the cooling water through the condenser.

Working 

The steam condenser receives the exhaust steam from one end and comes in contact with the cooling water circulated within it form the cooling tower. As the low pressure steam comes in contact with the cooling water, it condenses and converts into water. It is connected to the air extraction pump and condensate extraction pump. After the condensation of steam, the condensate is pumped to the hot well with the help of condensate extraction pump. The air extraction pump extracts the air from the condenser and creates the vacuum inside it. The vacuum created helps in the circulation of cooling water and flow of condensate downward.

Classification of Steam Condenser

The steam condenser is classified as

1. Jet condensers or mixing type condenser
2. Surface condenser or non-mixing type condenser

Jet Condenser

Jet condenser is a condenser in which the condensate gets mixed with the cooling water. That’s why it is also called as mixing type condenser.

This type of condenser is used sometime because it lost some of the condensate and requires high power for the pump during the process of condensation.

In jet condenser, as the condensate is not free from the salt, so it cannot be used as feed water for the boiler. It can be used at the place where sufficient amount of good quality water is available.

Types of Jet Condenser

(i) Parallel Flow Jet Condenser

Parallel flow and Counter Flow Jet Condenser


In parallel flow jet condenser, the steam and water enters into the condenser at the top and leaves at the bottom.

The cooling water and steam enters at the top. As both steam and cooling water mix with each other, the steam gets condense. The condensate, cooling water and air moves downward and it is removed by two separate pumps known as air extraction pump and condensate extraction pump. The condensate pump transfers the condensate to the hot well and from there the extra water is made to flow in cooling water tank or pond through overflow pipe.

(ii) Counter Flow or Low Level Jet Condenser

In counter Flow or low level jet condensers, the steam enters at the bottom and the cooling water at the top. The steam flows upward and meets the cooling water coming downward.

In these types of steam Condensers, the air pump is located at the top. Air pump creates vacuum and this vacuum draws water from the cooling tower. The cooling water enter into the condenser and falls on the perforated conical plate. The perforated conical plates convert the cooling water into a large number of jets as shown in the figure. The falling jet of water caught in the trays and from there it escapes out in second series of jets and meets the exhaust steam entering at the bottom. As the steam mix with the water, it gets condense. The condensate and cooling water moves down through a vertical pipe to the condensate pump. And finally the pump delivers it to the hot well.

(iii) Barometric or High Level Jet Condenser

Barometric or High Level Jet Condenser


Barometric or high level jet condensers are provided at high level with a long vertical discharge tube or tailpipe. It does not have condensate extraction pump and the condensate and cooling water flows in the hot well because of the gravity. An injector pump is used to flow cooling water at the top of the condenser.

These types of jet condensers are used at a high level with a vertical discharge pipe. In this condenser, the steam enters at the bottom and flows in upward direction and meets with the down coming cooling water. Its working is similar as the low level jet condenser. The vacuum is created at the top of the condenser shell. With the help of vacuum and injector pump, the cooling water is moved to the top of the condenser. The condensate and cooling water comes down in the hot well through a long vertical discharge pipe. And finally the extra hot water flows to the cooling tank or cooling pond by an overflow pipe

(iv) Ejector Condenser

Ejector Condenser


In ejector condensers, it has a non-return valve through which exhaust steam enters, hollow truncated cones, and diverging cone.

In these condensers, the cooling water is injected at the top. The steam enters into the condenser through a non-return valve. The steam and water mixes with each other while passing through series of hollow truncated metal cones and steam changes into water. At the end of the metal cones a diverging cone is present. When the condensate passes through diverging cone, its kinetic energy is partly transformed into pressure energy.
The condensate and cooling water is then discharged to the hot well.

Surface Condensers

Surface Condensers


Surface condenser is a type of steam condenser in which the steam and cooling water do not mix with each other. And because of this, the whole condensate can be used as boiler feed water. It is also called as non-mixing types condenser.

The figure above shows the longitudinal section of a two pass surface condenser. It consists of a horizontal cylindrical vessel made of cast iron and packed with tubes. The cooling water flows through these tubes. The ends of the condensers are cut off by the perforated type plates. The tubes are fixed into these perforated type plates. It is fixed in such a manner that any leakage of water into the center of condensing space is prevented. The water tubes are passed horizontally through the main condensing space. The exhaust steam from the turbine or engine enters at the top and forced to move downward due to the suction of the air extraction pump. In this steam condenser, the cooling water enters into boiler through lower half of the tubes in one direction and returns in opposite direction through the upper half as shown in the figure above.

This type of condenser is used in ships as it can carry only a limited quantity of water for the boiler. It is also widely used for the land installation where there is a scarcity of good quality of water.

Types of Surface Condensers

The surface condenser on the basis of direction of flow of condensate, the arrangement of the tubing system and the position of the extraction pump are classified as

(i) Down Flow

Types of Surface Condenser ( down flow and Central Flow)


In Down flow surface condenser, the steam enters at the top of the condenser and flows downwards over the tubes due to the gravity and air extraction pumps. The condensate gets collected at the bottom and then pumped with the help of condensate extraction pump. The pipe of dry air extraction pump is provided near the bottom and it is covered by baffle plates so as to prevent the entry of the condensate into it.

The steam in down flow condenser flows perpendicular to the direction of flow of cooling water, so it is also called as cross-surface condenser.

(ii) Central Flow

In central flow condenser, the steam enters at the top of the condenser and flows in downward direction. In this the suction pipe of the air extraction pump is provided in the center of the tube nest as shown in the figure. Due to this placement of the suction pipe in the center of the tube nest, the exhaust steam flows radially inward over the tubes towards the suction pipe. The condensate is collected at the bottom of the condenser and pumped to the hot well.

We can say that it is the improved form of the down flow surface condenser.

(iii) Regenerative 

In regenerative surface condensers, the condensate is heated by the use of regenerative method. In that the condensate is passed through the exhaust steam coming out from the turbine or engine. This raises its temperature and it is used as the feed water for the boiler.

(iv) Evaporative

 Evaporative Surface Condenser


In evaporative surface condensers, the steam enters at the top of the condenser in a series of pipes over which a film of cold water is falling. At the same time, current of air is made to circulate over the film of water. As the air circulates over the water film, it evaporates some of the cooling water. As a result of this rapid evaporation, the steam circulating inside the series of pipes gets condensed. Remaining cooling water that left is collected at an increased temperature and reused. It is brought to the original temperature by adding required quantity of cold water.

Advantages of Steam Condenser

  • It increases the efficiency of the plant.
  • It reduces the back pressure of the steam and as a result of this, more work can be done.
  • It reduces the temperature of the exhaust steam and this allows to obtain more work.
  • It allows the reuse of condensate for the feed water and hence reduces the cost of power generation.
  • The temperature of the condensate is more than the feed water. This reduces the supply of heat per kg of steam.

Comparison of Jet and Surface Condenser in Tabular Form

S.no
Jet Condenser
Surface Condenser
1.
Exhaust steam and cooling water mixed with each other.
Exhaust steam and cooling water are not mixed with each other.
2.
It is less suitable for high capacity plants.
It is more suitable for high capacity plants.
3.
The condensing plant using this type of steam condenser is simple and economical.
The condensing plant using surface condenser is costly and complicated.
4.
Condensate is wasted and cannot be reused.
The condensate is reused.
5.
Less quantity of circulating water is required.
Large quantity of circulating water is required.
6.
It has low maintenance cost.
It has high maintenance cost.
7.
In jet condenser, more power is required for the air pump.
In surface condenser, less power is required for the air pump.
8.
High power is required for water pumping.
Less power is required for water pumping.

Cochran Boiler - Main Parts, Working, Advantages and Disadvantages

What is Cochran Boiler?

Cochran Boiler is a vertical drum axis, natural circulation, natural draft, low pressure, multi-tubular, solid fuel fired, fire tube boiler with internally fired furnace.

  • It is the modified form of simple vertical boiler. In this boiler, the fire tubes are placed horizontally.
  • The efficiency of this boiler is much better than the simple vertical boiler.

Main Parts and Construction

Cochran Boiler


1. Shell: It has a vertical axis cylindrical drum with hemispherical dome type shell at the top.

2. Grate: It is the platform on which the solid fuel is burnt.

3. Combustion Chamber: The burning of fuel takes place in the combustion chamber.

4. Fire Tubes: Cochran boiler has multi tubular fire tubes. The hot flue gases from the combustion chamber travels to the smoke box through these fire tubes. The fire tubes helps in the exchange of heat from the hot flue gases to the water.

5. Fire Hole: It is the hole provided to fire the fuel inside the furnace.

6. Furnace: It lies at the bottom of the boiler. Furnace is the place where all the fuel is burnt. Without furnace the working of this boiler is not possible.

7. Chimney:  The chimney is attached to the smoke box. It transfer smoke to the environment. The size of chimney is small as compared with other boiler.

8. Fire Brick Lining. The fire brick lining is present in the combustion chamber and helps in the combustion of the fuel.

9. Manhole: A manhole is provided for the cleaning and inspecting of the boiler from inside.

10. Flue Pipe: It is a small passage connecting the fire box and combustion chamber. The hot gases enters into combustion chamber through the flue pipe.

Other Boiler mountings and accessories attached to the this boiler are:

1. Pressure Gauge: It measures the pressure of steam inside the boiler.
2. Safety Valve: It blows off the extra steam when the steam pressure inside the boiler reaches above safety level.
3. Water level Indicator: The position of the water level in the Cochran boiler is indicated by the water level indicator.
4. Stop Valve: Stop valve is used to transfer steam to the desired location when it is required. Otherwise it stops the steam in the boiler.
5. Blow off Cock: It is used to blow off the settle down impurities, mud and sediments present in the boiler water.

Also Read: Babcock and Wilcox Boiler – Construction, Working, Application, Advantages and Disadvantages

Working

  • In Cochran boiler first the fuel is inserted into the fire box and placed on the grate. The fuel is ignited through the fire hole provided at the right bottom of the boiler.
  • The fuel is burnt in the fire box and due to the burning of the fuel, smoke and hot flue gases emerges out. The hot flue gases enter into the combustion chamber through flue pipes.
  • From the combustion chamber hot gases enters into the fire tubes. The fire tubes are surrounded by water. The hot flue gases inside the tubes exchange the heat from the hot gases to the water. Due to the exchange of heat, the temperature of the water start increasing and it gets converted into steam. The steam produced rises upward and collected at top of the boiler in the hemispherical dome. An anti-priming pipe is installed at top of the boiler which separates the water from the steam and makes it dry steam. This dry steam is then transfer to the turbines through the steam stop valve.
  • The hot flue gases and smoke after exchanging heat moves to the smoke box. From the smoke box the burnt gases and smoke is discharge to the atmosphere through the chimney.
  • Burnt fuel is transferred to the ash pit. Blow off cock is preset at left bottom of the boiler and is used to blow of the impurities, mud and sediment from the boiler water.
  • A fusible plug is also provided at top of the combustion chamber. When the temperature of the combustion chamber crosses the permissible level, the fusible plug melts and the water through the combustion chamber enter into the furnace of the boiler and stop the fire. In this way a big fire accident can be prevented to take place and also protects the boiler from damage.
  • Various boiler mounting and accessories are attached to the boiler for its efficient working.

Advantages and Disadvantages

Advantages

(i) Low initial installation cost.
(ii) It requires less floor area.
(iii) Easy to operate and handle.
(iv) Transportation of Cochran boiler is easy.
(V) It can use all types of fuel.

Disadvantages

(i) Low rate of steam generation.
(ii) Inspection and maintenance is difficult.
(iii) High room head is required for its installation due to the vertical design.
(iv) It has limited pressure range.





Types of Gears- Spur Gear, Helical Gear, Bevel Gear etc.

In this article we will learn about different types of gears used to transmit powers from one shaft to another. The various gear types obtained on the basis of different criteria are spur gear, helical gear, spiral gear, bevel gear, miter gear, rack and pinion, etc. Here we will discuss about each type in brief. Gears are basically used to transmit powers from one shaft to another.

The classification of the gears is done on the following basis:

1. On the Basis of Arrangement of Shafts of Gears

(i) Parallel Gears

Types of gears (spur gear)


When two parallel and coplanar shafts are connected by gears as shown in the figure above, the types of gears are called as spur gears. The arrangement of gears is called spur gearing.
Spur gears have teeth parallel to the axis of the wheel.
Examples: Spur gear, helical gear, double helical gear (herringbone gear)

(ii) Intersecting Gears



When two non-parallel or intersecting but coplanar shafts are connected by the gears as shown in the figure given above is called bevel gears. And such arrangement is called as bevel gearing.
Examples: Bevel gear, helical bevel gear, miter gear.

(iii) Non-Intersecting and Non-Parallel

Types of gears (spiral gear)


When non-intersecting and non-parallel i.e. non-coplanar shafts are connected by gears as shown in the figure given above is called as skew bevel gears or spiral gears. And the arrangement is called as skew bevel gearing or spiral gearing.
Examples: Spiral gears.

2. On the Basis of the Peripheral Velocity of the Gears

(i) Low Velocity: The gears which possess velocity less than 3 m/s are called low velocity gears.
(ii) Medium Velocity: The gears which have velocity in between 3 m/s and 15 m/s are called as medium velocity gears.
(iii) High Velocity: The gears which possess velocity more than 15 m/s are called as high velocity gears.

3. On the Basis of the Types of Gearing.

(i) External Gearing

External gearing


When gears of two shafts mesh externally as shown in the figure given above, than the gears are called as external gears. In external gearing the larger of the two meshed gears is called spur or gear and the smaller is called as pinion. The motion of the two wheels in external gearing is always unlike (i.e. if one moves clockwise than other will move in anticlockwise direction).

(ii) Internal Gearing

Internal Gearing


When the gears of the two shafts mesh internally with each other as shown in figure given above, than it is called as internal gearing. In internal gearing the larger of the two wheels is called as annular wheel and the smaller wheel is called as pinion. The motion of the two wheels in the internal gearing is always like (i.e. if one moves clockwise than the other will also moves in clockwise direction).

(iii) Rack and Pinion

Rack and Pinion gear


Sometimes what happen, the gears of a shaft meshes externally and internally with the gears in strait line (i.e. strait line is also defined as the wheel of infinite radius). Such type of gear is known as rack and pinion. In rack and pinion types of gears the straight line gear is called rack and the circular gear is called pinion. Rack and pinion gears are used to convert linear motion into rotary motion and vice-versa.

4. On the Basis of the Position of Teeth on the Gear.

Straight, inclined and curved gear

(i) Straight

Straight gears have straight teeth on the surface of the wheel rim. For example: Spur gear.

(ii) Inclined

The inclined gears have inclined teeth on the surface of the wheel rim. For example: Helical gears.

(iii) Curved

Curved gears have curved teeth on the surface of the wheel. For example: Spiral gears.

Types of Gears 



Types of Gears

Now we will discuss each classification of gears one by one in detail.

1. Spur gear

spur gear is the simplest types of gear among all types of gears and easy to manufacture. It has straight teeth parallel to the axis of the wheel or shaft. It is used to transmit power between parallel shafts. Only one tooth of the spur gear meshes at a time. It is regularly used for speed reduction or increase, resolution and accuracy enhancement for positioning systems, torque multiplication. It creates noise during its operation.

2. Helical Gears

The helical gears have inclined teeth (teeth cut at an angle to the face of the gear) on the surface of the wheel. Its operation is smoother and quitter as compared with the spur gear. It is mostly commonly used in transmission gear boxes.

Helical gear can be further sub divided into two types

(i) Single Helical Gears

It is gear that has inclined tooth on its wheel surface. Single helical gear possesses axial thrust.

(ii) Double Helical Hears or Herringbone Hears

Herringbone gear is a type of double helical gear in which there is side to side combination of two helical gears of opposite hands. If we look from the top than each helical groove on this gear looks like V letter. The herringbone or double helical gears have zero axial thrust which is not so with the single helical gear. Unlike helical gears it has advantage of transmitting power smoothly because it meshes two teeth at time.

3. Bevel Gears

These are the gears which transfers powers between two non parallel or intersecting shafts. These types of gears are mostly commonly used in the differentials drive of automobile.

The bevel gear are further classified as

(i) Straight Bevel Gear

This gear has straight teeth, conical pitch surface and tapering towards apex.

(ii) Skew Bevel Gears or Spiral Bevel Gear

this has curved teeth at an angle that allows gradual and smooth contact of the tooth.

(iii) Zerol Bevel Gear

these gears are similar to the bevel gear but it has curved teeth with a spiral angle of zero, so the ends of the tooth align with the axis.

(iv) Hypoid Bevel Gear

these types of gears are similar to the spiral bevel gear but the pitch surface is hyperbolic and not conical.

(v) Miter Gear

It is a type of bevel gear in which the two shafts are intersects at right angles with each other. It is used to transmit powers at right angles.

4. Internal Gearing

In internal gearing the two gears are meshed internally with each other.

5. External Gearing

In external gearing the two shafts are connected with the gears that mesh with each other externally.

6. Rack and Pinion Gears

In rack and pinion gears, a shaft meshes externally and internally with a straight line gear. The circular gear is called as pinion and the straight line gear is called as rack. The rack and pinion gear is shown in the figure given below.

7. Worm Gear

A worm gear is a arrangement of two gears in which one gear is called as worm ( gear in the form of screw) meshes with a worm gear ( similar as spur gear). The two elements are called as worm screw and worm wheel. Worm gears are used in presses, rolling mills, on rudders and worm drive saws etc. 

This is all about the types of gears used in power transmission from one shaft to another. If you have any query about this than comment us. And if you found this article informative and useful than share and like us on Facebook and Google+.


Babcock and Wilcox Boiler – Construction, Working, Application, Advantages and Disadvantages

In this article we will learn about Babcock and Wilcox Boiler- Main parts, working, advantages and disadvantages with application. This boiler is generally used to produce high pressure steam, and this high pressure steam is used to produce electricity in power generation industries. It is also used in the area where high pressure steam is required. So let’s begin our journey to do detail study about it.

What is Babcock and Wilcox Boiler?

It is a Horizontal drum axis, natural draft, natural circulation, multitubular, stationary, high pressure, solid fuel fired, externally fired water tube boiler.

It was discovered by George Herman Babcock and Stephen Wilcox in the year 1967. And if was named after its discoverer as Babcock and Wilcox boiler. 

Construction

Babcock and Wilcox Boiler


The various main parts of Babcock and Wilcox Boiler are as follows

1. Drum: It is horizontal axis drum which contains water and steam.

2. Down Take Header: It is present at rear end of the boiler and connects the water tubes to the rear end of the drum. It receives water from the drum.

3. Up Take Header: it is present at front end of the boiler and connected to the front end of the drum. It transports the steam from the water tubes to the drum.

4. Water Tubes: They are the tubes in which water flows and gets converted into steam. It exchanges the heat from the hot flue gases to the water. It is inclined at angle of 10-15 degree with the horizontal direction. Due to its inclination the water tubes do not completely filled with water and the water and steam separated out easily.

5. Baffle Plates: Baffle plates are present in between water tubes and it allows the zigzag motion of hot flue gases from the furnace. 

6. Fire Door: It is used to ignite the solid fuel in the furnace.

7. Grate: It is a base on which the burning of the solid fuel takes place.

8. Mud Collector: It is present at the bottom of down take header and used to collect the mud present in the water.

9. Feed Check Valve: it is used to fill water into the drum.

10. Damper: It regulates the flow of air in the boiler.

The various boiler mounting and accessories used in this type of boiler are:

1. Superheater: It increases the temperature of saturated steam to the required temperature before discharging it from steam stop valve.

2. Pressure Gauge: It is used to check the pressure of steam within the boiler drum.

3. Water Level Indicator: It shows the level of water within the drum.

4. Safety Valve: It is a valve which acts when the pressure of steam within the boiler drum increase above the safety level. It opens and releases the extra steam in the environment to maintain the desired pressure within the boiler.

Working:

Now let’s discuss the working of Babcock and Wilcox boiler step by step.
  • First the water starts to come in the water tubes from drum through down take header.
  • The water present in the inclined water tubes gets heated up by the hot flue gases. The coal burning on the grate produces hot flue gases and it is forced to move in zigzag way with the help of baffle plates.
  • As the hot flue gases come in contact with water tubes, it exchanges the heat with water and converts it into steam.
  • The steam generated is moved upward and through up take header it gets collected at upper side in the boiler drum.
  • An anti-priming pipe is provided in the drum. This anti-priming pipe filters the water content from the steam and allows only dry steam to enter into superheater.
  • The superheater receives the water free steam from the anti-priming pipe. It increases the temperature of steam to desired level and transfers it to the steam stop valve. 
  • The superheated steam from the steam stop valve is either collected in a steam drum or made to strike on the steam turbine for electricity generation.
For Better Explanation of Working of Babcock and Wilcox Boiler, Watch the Video Given Below:



Application

The Babcock and Wilcox boiler are generally used to produce high pressure steam in power generation industries. The high pressure steam so generated is used to produce electricity. 

Advantages and Disadvantages

Advantages 

  • Steam generation capacity is high. It is about 2000 to 40000 kg/hr.
  • It occupies less space.
  • Replacement of defective tubes is easy.
  • It is the only boiler that is used to generate large quantity of heat in power stations.
  • The draught loss is minimum.
  • Inspection of this types of boiler can be done anytime during its working.

Disadvantages 

  • High maintenance cost.
  • It is not much suitable for impure and sedimentary water. In case of impure and sedimentary water, scale may deposit in the tubes and this leads to overheating and bursting of tubes. That’s why water treatment is must before feeding into the boiler.
  • Continuously supply of feed water is required for the working. In the case if feed water is not continuously supplied even for a short period of time, the boiler gets overheated. Water level must be carefully watched during the operation of the Babcock and Wilcox boiler.


Difference Between Impulse and Reaction Turbine

In this article we will discuss about all the major difference between impulse and reaction turbine. These both types of turbine are used in power plants for the generation of electricity. Instead of their same work of producing electricity, they are differing from each other in much respect. Here will discuss about various differences among them in detail.

Difference Between Impulse and Reaction Turbine


Difference Between Impulse and Reaction Turbine

S.no
Impulse Turbine
Reaction Turbine
1.
In impulse turbine the steam flows through the nozzle and strike on the moving blades.
In the reaction turbine, first the steam flows through the guide mechanism and then flows through the moving blades.
2.
Steam strikes on the buckets with kinetic energy.
The steam glides over the moving blades with both pressure and kinetic energy.
3.
During the flow of steam through moving blades, its pressure remains constant.
During the flow of steam through moving blades its pressure reduces.
4.
The steam may or may not be admitted to the whole circumference.
The steam must be admitted over the whole circumference.
5.
The blades of impulse turbine are symmetrical.
The blades of reaction turbine are not symmetrical.
6.
While gliding over the blades the relative velocity of steam remains constant.
In reaction turbine, while gliding over the blades the relative velocity of steam increases.
7.
For the same power developed, the number of stages required is less.
For the same power developed, the number of stages required is more.
8.
The direction of steam flow is radial to the direction of turbine wheel.
The direction of steam flow is radial and axial to the turbine wheel.
9.
It requires less maintenance work.
It requires more maintenance work.
10.
It is suitable for low discharge.
It is suitable for medium and high discharge.
11.
Pelton Wheel is the example of impulse turbine.
Francis turbine, Kaplan turbine etc. are the examples of reaction turbine.

Comparison Between Impulse and Reaction Turbine

  • In impulse turbine the steam flows through the nozzle and strikes on the moving blades. In reaction turbine steam first flows through the guide mechanism and then flows through the moving blades.
  • In impulses turbine, steam strikes on the moving blades with kinetic energy only. But in the reaction turbine, the steam which glides over the moving blades possesses both pressure and kinetic energy.
  • In impulse turbine the pressure of steam remains constant during its flow through the moving blades. But in reaction turbine, the pressure of steam reduces during its flow through the moving blades.
  • In impulse turbine the steam may or may not be admitted to the whole circumference. In reaction turbine the steam must be admitted to the whole circumference.
  • The blades of the impulse turbine are symmetrical where as in reaction turbine it is not symmetrical.
  • The relative velocity of steam in impulse turbine remains constant but in Reaction turbine it increases while gliding over the blades.
  • For the same power developed, the number of stages required in impulse turbine is less where as in reaction turbine the number of stages required is more.
  • The steam flow in impulse turbine is radial to the turbine wheel where as in reaction turbine steam flow is radial and axial to the turbine wheel.
  • If we talk about the maintenance work, then impulse turbine has less maintenance work as compared with the reaction turbine.
  • Impulse turbine is suitable where discharge is low and reaction turbine is suitable for medium and high discharge.
  • Pelton wheel is the example of impulse turbine whereas Francis turbine, Kaplan turbine etc. are the examples of reaction turbine.

This is the difference between impulse turbine and reaction turbine. If you have any query related to this article than comment us. If you find this article useful than don’t forget to like us on Facebook and Google+.


Types of Wind Turbines - Horizontal Axis and Vertical Axis Wind Turbines

In this article we will learn about different types of wind turbines with their advantages and disadvantages and difference between them. Basically the turbines are used to convert the wind energy into electrical energy with the help of a generator. It extracts the energy from the wind and converts it into mechanical energy and then this mechanical energy is used to derive a generator and we get electricity. So let’s begin our journey to learn about types of wind turbines.
Types of Wind Turbines

Image Source: https://commons.wikimedia.org/wiki/File:HAWT_and_VAWTs_in_operation_medium.gif

Types of Wind Turbines

The wind turbines are basically divided into two types. Before discussing about wind turbine types in detail, I want to tell you about what is wind turbine?

What is Wind Turbine?

It is a mechanical machine that converts kinetic energy of the fast moving winds into electrical energy. On the basis of axis of rotation of the blades, it is divided into two parts.

1. Horizontal axis wind turbine (HAWT)
2. Vertical axis wind turbine (VAWT)

1. Horizontal Axis Wind Turbine (HAWT)

It is a turbine in which the axis of rotation of rotor is parallel to the ground and also parallel to wind direction.

They are further divided into two types

(i) Upwind turbine
(ii) Downwind turbine

(i) Upwind Turbine

The turbine in which the rotor faces the wind first are called upwind turbine.
  • Today most of the HAWT is manufactured with this design.
  • This turbine must be inflexible and placed at some distance from the tower.
  • The basic advantage of this turbine is that, it is capable of avoiding wind shade behind the tower.
  • It requires yaw mechanism, so that its rotor always faces the wind.

(ii) Downwind Turbine

The turbine in which the rotor is present at the downside of the tower is called downwind turbine. In these types of wind turbines, the wind first faces the tower and after that it faces the rotor blades.
  • Yaw mechanism is absent in this turbine. The rotors and nacelles are designed in such a way that the nacelle allows the wind to flow in a controlled manner.
  • It receives some fluctuation in wind power because here the rotor passes through the wind shade of the tower. In other words the rotor is present after nacelle of the tower and this create fluctuation in the wind power.

Advantages and Disadvantages of HAWTs

The various advantages and disadvantages of the horizontal axis types of wind turbines are:

Advantages

  • It has self-starting ability. It does not require any external power source to start.
  • It has high efficiency as compared with the HAWT.
  • Capable of working in high wind speed condition.
  • In the case of slow wind condition, its angle of attack can be varied to get maximum possible efficiency.
  • Since all blades of this turbine work simultaneously, so it is capable of extracting maximum energy form the wind.

Disadvantages

  • Its initial installation cost is high.
  • It requires large ground area for its installation.
  • Because of its giant size of blades and towers, it becomes difficult to transport it to the sites.
  • High maintenance cost.
  • Creates noise problem.
  • It cannot be installed near human population.
  • It is not good for the bird’s population. They are killed by its blades rotation.

2. Vertical Axis Wind Turbine (VAWT)

It is a turbine in which the axis of rotation of the rotor is perpendicular to the ground and also perpendicular to the wind direction.
  • It can operates in low wind situation.
  • It is easier to build and transport.
  • These types of Wind turbines are mounted close to the ground and are capable of handling turbulence in far better way as compared with the HAWT.
  • Because of its less efficiency, it is used only for the private purpose.
VAWTs are further classified as 
(i) Darrieus turbine
(ii). Giromill turbine
(iii) Savonius turbine

(i) Darrieus Turbine

Darrieus turbine is type of HAWT. It was first discovered and patented in 1931 by French aeronautical engineer, Georges Jean Marie Darrieus. It is also known as egg beater turbine because of its egg beater shaped rotor blades.

  • It consists of vertically oriented blades which are mounted on a vertical rotor. It is not a self-starting turbine and hence a small powered motor is required to start its rotation.
  • First the Darrieus turbine is rotated by using a small powered motor. Once it attains sufficient speed, the wind flowing across its blades generates lift forces and this lift forces provides the necessary torque for the rotation. As the rotor rotates, it also rotates the generator and electricity is produced.

(ii) Giromill Turbine: 

It is similar to the Darrieus turbine but the difference is that, it has H-shaped rotor. It works on the same principle of Darrieus turbine. 
  • This turbine has H- shaped rotor. Here Darrieus design which has egg beater shaped rotor blades are replaced by straight vertical blades attached with central tower with horizontal supports. It may consists of 2-3 rotor blades.
  • Giromill turbine is cheap and easy to build as compared with Darrieus turbine. It is less efficient turbine and requires strong wind to start. Same as darrieus types of wind turbines, it is also not self- starting and requires small powered motor to start. It is capable of working in turbulent wind conditions.

(iii) Savonius Turbine

Savonius turbine is HAWT.It was first discovered in 1922 by a Finnish Engineer Sigurd Johannes Savonius. It is one of the simplest turbine among all known turbines.
  • It is a drag-type device and consists of two or three scoops. If we look it from above than it looks 'S' shape in cross section. The scoops of these turbines have curvature shape and because of that, it experiences less drag when it moves against the wind instead of moving with the wind.
  • Since it is a drag-type machine, it is capable of extracting very less amount of wind power as compared with other similar sized lift-type turbines.

Advantages and Disadvantages of Vertical Axis Wind Turbine

Advantages

  • It is simple in design and easy to construct and transport.
  • It can be easily installed to desired location.
  • It requires less ground area for its installation.
  • Initial installation cost is very less as compared with the HAWT.
  • It can work in turbulent wind condition.
  • It is omni-directional and hence do not need to track winds.
  • They are smaller in size and hence can be used for domestic or private purpose easily.
  • They have low maintenance cost as compared with the HAWT.

Disadvantages

  • It is less efficient. The efficiency of this turbine is about 30-35%.
  • They are not self-starting. A small powered motor is needed to start it.
  • Guy wires may required to support this turbine.

Difference between Horizontal Axis Wind Turbine and Vertical Axis Wind Turbine

The various difference between horizontal axis and vertical axis types of wind turbines in tabular form are given below:

S.no
Horizontal Axis Wind Turbine
Vertical Axis Wind Turbine
1.
In HAWTs, the axis of rotation of the rotois Horizontal to the ground.
In VAWTs the axis of rotation of the rotor is perpendicular to the ground.
2.
Yaw mechanism is present.
Absence of Yaw mechanism.
3.
It has high initial installation cost.
It has low initial installation cost.
4.
They are big in size.
They are small in size.
5.
Its efficiency is high.
It has low efficiency.
6.
It requires large ground area for installation.
It requires less ground area for installation.
7.
High maintenance cost.
Low maintenance cost as compared with HAWT.
8.
They are self-starting.
They are not self-starting.
9.
They are unable to work in low wind speed condition.
They are capable of working in low wind speed condition.
10.
Difficult in transportation.
Easy in transportation.
11.
They are mostly used commercially.
They are mostly used for private purpose only.
12.
It cannot be installed near human population.
It can be installed near human population.
13.
It is not good for the bird’s population.
It is good for the bird’s population.


This is all about the types of wind turbines. If you observe anything missing or incorrect than comment us. And if you find this article useful than don’t forget share and like it on Facebook and Google+.