Difference Between SI Engine and CI Engine

In this article we will discuss about the difference between SI engine and CI engine. The spark Ignition (SI) engine, as its name indicates uses spark to ignite the fuel. And in Compression Ignition (CI) engine, the air is compressed within the cylinder and the heat of this compression air is used to ignite the fuel. Since spark and compressed air is used to ignite the fuel in these engines, so they are called as spark ignition (SI) engine and compression ignition (CI) engine.
Difference Between SI engine and CI engine

SI Engine (Spark Ignition Engine)

Spark Ignition (SI) Engine is a type of engine in which the combustion takes place by the spark generated by the spark plug. It uses petrol as fuel and works on Otto cycle. In the spark ignition engine the air fuel mixture is inserted into the cylinder with help of carburetor. The compression of the fuel takes place but it has low compression ratio. The fuel is ignited by the spark generated by the spark plug. SI engine produces less noise and vibration and their starting is very easy. They are light in weight and have less maintenance cost. They are mostly used in light commercial vehicles such as scooters, motorcycles cars etc.

CI Engine (Compression Ignition Engine)

Compression Ignition (CI) Engine is an engine in which the combustion of fuel takes place by the heat of the compressed air. It uses diesel as fuel and works on Diesel cycle. In the compressed ignition engine, only air enters into the cylinder during suction stroke. It has high compression ratio because of the high ignition temperature of the diesel fuel. The fuel is ignited by the heat of the compressed air. Due to high compression ratio it produces more power. Due to incomplete combustion of the fuel, it produces more hydrocarbons which lead to air pollution. The noise and vibration problem is there in the CI engines. The maintenance cost of the CI engine is more as compared with the SI engines. They are mostly used in heavy duty vehicles such as buses, trucks, railways, ships etc.

Difference Between SI Engine and CI Engine in Tabular Form

S.no
Parameter
SI Engine
CI Engine
1.
Definition
It is an engine in which the spark is used to burn the fuel.
It is and engine in which heat of compressed air is used to burn the fuel.
2.
Fuel used
Petrol is used as fuel.
Diesel is used as fuel.
3.
Operating cycle
It operates on Otto cycle.
It operates on Diesel cycle.
4.
Compression ratio
Low compression ratio.
High compression ratio.
5.
Thermal efficiency
High thermal efficiency.
Less thermal efficiency.
6.
Method of ignition
Spark plug is used to produce spark for the ignition.
Heat of compressed air is used for the ignition.
7.
Engine Speed
High speed engines.
Low speed engines.
8.
Pressure generated
Low pressure is generated after combustion.
 High pressure is generated after combustion.
9.
Constant parameter during cycle
Constant volume cycle.
Constant pressure cycle.
10.
Intake
Air + fuel.
Only air.

Weight of engine
Si engine has less weight.
CI engine are heavier.
12.
Noise production
It produces less noise.
It produces more noise.
13.
Production of hydrocarbon
Less Hydrocarbon is produced.
More hydrocarbon is produced.
14.
Starting
Starting of SI engine is easy.
Starting of CI engine is difficult.
15.
Maintenance cost
Low
High
16.
Vibration problem
Less
Very High
17.
Cost of engine
Less cost
High cost
18.
Volume to power ratio
Less
High
19.
Fuel supply
Carburetor
Injector
20.
application
It is used in light commercial vehicles like motorcycle, cars etc.
It is used in heavy duty vehicles likes bus, trucks, ships etc.

So now, I hope you have clearly understood about the difference between SI engine and CI engine. If you have any confusion related to that than feel free to ask through your comments. If you find it informative or useful than share it for others.

Types of Springs

Since there are many types of springs but here I will discuss their types only on the basis of their shapes and how the load force is applied on them. The springs are defined as an elastic body which stores mechanical energy and gets distorted when loaded and regains its original shape when load is removed.  Springs main function is to get distorted when it is loaded and recover its original shape when load is removed.

The various applications of springs are as follows


  • To cushion, absorb or control energy due to shock and vibration as in bike or car springs, railway buffers, shock absorbers, aircraft landing gears and vibration dampers.
  • To apply forces, as in brakes, clutches and spring loaded valves.
  • To controls the motion by maintaining contact between two elements as in cams and followers.
  • To measure forces, as in spring balances and engine indicators.
  • To store energy, as in toys and watches.

Types of springs



On the basis of shape the types of springs are

1. Helical Springs or Coil Springs

It is a spring which is made up of a wire coiled in the form of helix. It is made to handle tensile and compressive loads.

2. Conical and Volute Springs

These are the compression spring have conical shapes. The conical springs are wounded with a uniform pitch whereas the volute springs are wounded in the form paraboloid with constant pitch and lead angles. Under compression, coils of these springs slide past each other and make the spring to compress to a very shorter length.

3. Torsion Springs

It is a spring that works on torsion or twisting. It stores the mechanical energy when twisted.

4. Laminated or Leaf Springs

It is a type of spring which is mostly used in automobile suspension, electrical switches and bows. It consists of a number of flat plates (known as leaves) of varying lengths held together by means of clamps and bolts

5. Disc or Belleville Springs

It is a disc shaped spring. It is commonly used to apply tension to a bolt. It is also called as Belleville washers and conical compression washers

On the basis of how the load force is applied springs are classified as

1. Tension or Extension Spring 

Tension or extension springs works on the application of tension loads. When tensile load is applied to this spring it extends to some length.

2. Compression Spring

The compression springs are designed to operate when compressive load is applied to it. It contracts under compression.

3. Torsion Spring

It is designed to work under twisting. It stores mechanical energy when twisted.

4. Constant Spring

It is a type of spring in which the supported load remains the same throughout the deflection cycle.

5. Variable Spring

Variable spring is a spring in which the resistance in the coil to load varies during compression.

This is all about different types of springs. If you find anything missing or incorrect than comment us. And if you find this article informative than don’t forget to like and share on Facebook and Google+


Difference Between Turbocharger and Supercharger

In this article we will learn about the difference between turbocharger and supercharger. They both are force induction system i.e. they compressed the air from the atmosphere and sends it to the engine cylinder. The compressed air allows double amount of fuel to enter into the cylinder for combustion. This doubles the power of engine. Turbocharger and supercharger perform the same operation, so most of us are unable to find difference between them. Here in this article I will try to clear all your doubts about turbocharger and supercharger.


What is Turbocharger?

It is a forced induction system that uses exhaust gases energy to compress the air form the atmosphere and sends it to the engine cylinder. The compressed air is rich in oxygen and so the quantity of the fuel entering into the cylinder is doubled. Now the fuel burnt into the cylinder produces double power as it was producing without the turbocharger.

The turbocharger is not directly connected to the engine. It works more efficiently on high speed and spins upto 150000 rpm. Its installation is not easy and has complex design as compared with the supercharger. It experiences lag problem due discontinuous energy supply from the exhaust.

The schematic diagram of turbocharger is shown below.          


    

 What is Supercharger?

It is also a forced induction system that compresses the air and sends it to the engine cylinder. it is generally placed on the top of the engine and directly connected to the engine crankshaft for its working. It doubles the power of engine. They are simple in design and installation. They can work on low rpm and its spin speed is upto 50,000 rpm. It more reliable and has negligible lag.

The schematic diagram of supercharger is shown below.


Difference between Turbocharger and Supercharger in Tabular Form

S.no
Turbocharger
Supercharger
1.
Turbocharger is a forced induction system that compresses the atmospheric gases and sends it to the engine cylinder.
Super charger is also a forced induction system. It compresses the atmospheric air and sends it to the engine cylinder.
2.
It uses exhaust gases for its energy.
It is connected to the crankshaft of the engine for its energy.
3.
It is not directly connected to the engine.
It is directly connected to the engine through belt.
4.
It has smog altering equipment which helps in lowering the carbon emission.
It doesn’t have wastegate, so the smog emits from the supercharger.
5.
It spins with a speed upto 150000 rpm.
It spins with a speed upto 50000 rpm.
6.
It is much quieter than supercharger.
It is not so quieter.
7.
It is less reliable.
It is more reliable.
8.
Maintenance is not easy.
Maintenance is easy.
9.
Turbocharger delivers their boost better at high rpm.
Supercharger can deliver their boost at lower rpm.
10.
It is more efficient.
It is less efficient.
11.
The compressed air in turbocharger has high temperature.
The compressed air in supercharger has less temperature.
12.
It requires intercooler for the compressed air to lower its temperature.
It may or may not require intercooler. But in some types, it requires intercooler.
13.
It is more complex.
It is less complex.
14.
It has lag problem due to discontinuous supply of energy.
It has negligible lag problem because of continuous supply of energy by crankshaft.
15.
The compressor is rotated by the turbine.
The compressor is rotated by the engine crankshaft through a belt.


For better explanation about difference between turbocharger and supercharger, must watch the video given below:


Lever Safety Valve - Definition, Main parts and Working

In this article you will learn about the lever safety valve – definition, main parts and working. It is used for the boiler. The main purpose of this safety valve is to prevent the explosion of boiler due to the increased steam pressure.
lever safety valve

Definition

It is a type of safety valve which is used to maintain a constant safe working pressure inside a boiler.  It blows off the extra steam when the steam pressure exceeds the safe working pressure and prevents explosion.

Main parts

Lever Safety Valve Working

A lever safety valve consists of a valve body that has flange fixed to the steam boiler. The valve seat made of bronze is screwed to the body. The valve seat contains the valve which is also made up of bronze. Since the valve seat and valve is made up of same material, the rusting is prevented. The strut transmits the thrust on the valve. One end of the lever is fixed as fulcrum. Other end is attached to the load. A guide is also provided to move the lever vertically.

Working 

  • In lever safety valve, during the normal pressure inside the boiler, the valve remains in the seat. The thrust applied by the strut made the valve to stay in the seat until the steam pressure exceeds the safe working pressure. 
  • As the steam pressure inside the boiler exceeds the safe working pressure, the valve rises above the seat and steam blows off outside the boiler. The valve returns back to its normal position when the pressure inside the boiler falls back to its normal pressure. 
  • The valve rises in the condition when the steam pressure force becomes greater than the thrust applied by the strut on the valve. The thrust on the valve can be varied by varying the load attached at one end of the lever.

Loeffler Boiler - Construction, Working with Diagram

Loeffler Boiler is a forced circulation, high pressure, and water tube boiler with internally fired furnace. In this boiler, the 2/3 of superheated steam is used to evaporate the water in the evaporating drum and remaining 1/3 of the steam from the superheater is used by the turbine. A steam circulating pump is used to circulate the steam into the boiler

Working Principle

Its main working principle is to evaporate the feed water by the use of superheated steam from the superheater. 2/3  of the total steam generated by the superheater is made to flow into the evaporator drum. The superheated steam changes the feed water into saturated steam. And 1/3 part of the superheated steam is used by the turbine to do work.

Construction or Main Parts

The main parts of Loeffler boiler are

Loeffler Boiler


1. Economiser: It preheats the feed water before entering into the evaporating drum.
2. Evaporating drum: It is placed at lower portion of the boiler. It contains the mixing nozzle. Here the feed water is converted into saturated steam with the help of the superheated steam from the superheater.
3. Steam circulating pump: It is present in between the evaporating drum and radiant superheater. It circulates the steam into the boiler
4. Radiant superheater: It superheats the steam with the help of radiations produced by the burnt fuel in the boiler.
5. Convective superheater: Convective superheater superheats the steam to the desired temperature of about 500 oC.
6. Mixing nozzle: It is present inside the evaporating drum. It mixes the steam from the superheater with feed water and evaporates them.

Working

  • In loeffler boiler, the feed pump forces the water to enter into the economiser. The economiser preheats the feed water and then it is passed to the evaporator drum
  • The evaporator drum has nozzles. The 2/3 of the superheated steam from the superheater enters into the nozzles of the evaporator drum and the nozzles mix this superheated steam with the feed water. This changes the feed water into saturated steam. This saturated steam is then drawn from the evaporating drum by a steam circulating pump and allows it to passes through the radiant superheater.
  • The radiant superheater superheats the saturated steam with help of radiation energy produce from the burning of the fuel. The radiant superheater tubes are placed in furnace. The heat transfer to the water takes place through the radiation produced. After the radiant super heater, the steam is passed to the convective superheater.
  • The convective superheater is placed in the path of hot flue gases. It superheats the steam coming from the radiant superheater to a temperature of about 500 oC. This superheated steam is than flows to the turbine and evaporating drum. In this boiler, the 2/3 part of the superheated steam is used to evaporate the feed water into the evaporating drum and remaining 1/3 part  flows to the turbine.
  • Loeffler boiler has the capacity to produce 100 tonnes/ h of steam at a temperature of 500 oC and pressure of 140 bar.

Advantages

  • It can use salt water for the steam generation.
  • The problem of deposition of sediments and scale in the boiler tubes are eliminated.
  • It is compact in size.



Locomotive Boiler - Construction Working and Application with Diagram

Locomotive boiler is a horizontal drum axis, multi-tubular, natural circulation, artificial draft, forced circulation, mobile, medium pressure, solid fuel fired fire tube boiler with internally fired furnace. It is used in railway locomotive engines and in marine. It is a mobile boiler and has high steam generation rate.

Construction

The construction or main parts of a locomotive boiler are:

Locomotive Boiler

1. Fire hole: It is a hole provided at the rear end of the boiler. The solid fuel is inserted and ignited into the furnace through this hole.

2. Fire box: It is a box in which the burning of the fuel takes place.

3. Grate: Grate is a platform on which the solid fuel is kept and burnt.

4. Fire brick arch: It is a brick arch placed inclined over the grate. It prevents the entry of the ash, dust and burnt fuel particles into the fire tubes. It provides a way to the hot flue gases to travel a definite path before entering into the fire tubes of the boiler.

5. Boiler tubes: They are the fire tubes through which the hot flue gases passes and exchange the heat with surrounding water.

6. Smoke box: According to its name, it is a box in which the smoke of the burnt fuel after passing through the fire tubes gets collected. From there it is exhausted in the environment by the chimney.

7. Blast pipe: It is pipe provided above the steam engine. The exhaust steam passes through this blast pipe. It is used to create the artificial draft that pushes the smoke out  through the chimney and creates suction for the hot flue gases. The suction created allows the hot flue gases to move forward through the fire tubes.

8. Steam pipe: It is a pipe through which the steam passes. We have two steam pipes; one is main steam pipe present in between the superheater header and dome. And second one is that which connects the superheater exit end to the steam engine.

9. Superheater: It superheats the steam to the desired temperature before entering into the cylinder of the steam engine.

10. Super heater element pipes: These are the pipes of superheater through which the steam travels and gets superheated.

11. Dome: It is present at the top and contains the regulator for regulating the steam produced through the steam pipe.

12. Regulator valve: It is a valve that regulates the steam through main steam pipe for superheating.

13. Safety valve: It is used to maintain the safe working steam pressure in locomotive boiler. It blows off steam when the pressure of the steam increases above safety level and prevents blasting of the boiler.

14. Superheater header: It is the head of the superheater which accepts the steam form the steam pipe.

15. Chimney: It is used to throw out the exhaust smoke and gases to the environment. The length of the chimney is very small in this boiler.

Also Read: Lamont Boiler - Main Parts, Working, Advantages and Disadvantages

Working

  • In locomotive boiler, first the solid fuel (coal) is inserted on the grate and is ignited from the fire hole. The burning of the fuel starts and it creates hot flue gases. A fire brick arch is provided that makes the flow of hot flue gasses to a definite path before entering into the long tubes (fire tubes). It also prevents the entry of burnt solid fuel particles into the fire tubes.
  • The hot flue gases passes through the long fire tubes and heats the water surrounding them. Due to the heating the water gets converted into saturated steam and gets collected at the top.
  • The saturated steam from the dome enters into the main steam pipe through the regulator valve. The steam travels in the main steam pipe and reaches to the superheater header. Form header, the steam enters into super heater element pipes. Here it is superheated and then the superheated steam enters into the steam pipe of the smoke box.
  • The steam form the superheater goes to the cylinder containing piston. The superheated steam made the piston moves within the cylinder. The piston is connected to the wheels of the steam engine and the wheels start rotating.
  • The exhaust steam from the cylinder enters into the blast pipe. The burnt gases  and smoke after passing through the fire tubes enters into the smoke box. The exhaust steam coming out from the blast pipe pushes the smoke out of the boiler through the chimney. Here the smoke cannot escapes out form the boiler by its own, so artificial draft is created by exhaust steam coming out from the steam engine. This artificial draft created pushes the smoke out of the smoke box and creates suction for the hot flue gases.
For better explanation of the working of locomotive boiler watch the video:


Advantages and Disadvantages

Advantages

  • It is portable.
  • It is capable of meeting sudden and fluctuating demands of steam.
  • It is cost effective boiler.
  • It has high steam generation rate.
  • It is compact in size and its operation is easy.

Disadvantages

  • It faces the problems of corrosion and scale formation.
  • Unable to work under heavy load conditions because of overheating problems.
  • Some of its water space are difficult to clean.

Application

Locomotive boilers are mostly used in railways and marines. The efficiency of this boiler is very less. It cannot work in heavy load conditions because this leads to the overheating of the boiler and finally gets damage. They are also used in traction engines, steam rollers, in portable steam engines and some other steam road vehicles.

Lamont Boiler - Main Parts, Working, Advantages and Disadvantages with Diagram

What is Lamont Boiler?

Lamont boiler is a high pressure, forced circulation, water tube boiler with internally fired furnace. An external pump is used to circulate the water within small diameter water tubes of the boiler. This boiler was invented by Walter Douglas La-Mont in the year 1925. At that time this boiler was invented to use in ships.

Working Principle

It works on the principle of forced circulation of water within the boiler with the help of centrifugal pump. Its working is totally depends upon the pump. The centrifugal pump circulates the mixture of steam and water through the small diameter tubes of the boiler.

Main parts or Construction

The main parts of Lamont boiler are

Lamont Boiler


1.Feed pump: It supply the feed water into the boiler form hot well.

2.Economizer: It increases the temperature of the feed water to some degree.

3.Steam separating drum: As its names indicates, the steam separating drum separates the steam form the water. The steam gets collected at the upper portion and water at the lower portion of the drum.

4.Circulating pump: It is a centrifugal pump driven by the turbine. It circulates the water from the steam separating drum to the small diameter tubes of the radiant superheater, convective superheater and back to the steam separating drum.

5.Radiant evaporator: It evaporates the water steam mixtures with the help of radiation.

6.Convective evaporator: It changes the mixtures of steam and water into saturated steam through convective mode of heat transfer.

7.Superheater: It superheats the steam to the desired temperature for striking on the turbine blades.

Also Read: Difference Between Fire Tube Boiler and Water Tube Boiler
Also Read: Lancashire Boiler Construction, Working with Diagram

Working

  • In Lamont boiler, the feed pump circulates the water in the economiser of the boiler. The economiser heats the water to some degree. From economiser, water enters into steam separating drum.
  • From steam separating drum the mixture of water and steam is forced circulated through the radiant evaporator by an external centrifugal pump. In forced circulation, the pressure of circulation of water through the tubes is more as compared with the natural circulation.
  • Radiant evaporator heats the water and changes it into steam. Form radiant evaporator the water-steam mixture passes through the convective evaporator. Here the temperature of the fluid increase and most the water gets converted into saturated steam. And after that the saturated steam enters into the steam separator drum.
  • The steam separator drum as names indicates separates the steam from water. The steam gets collected at the upper portion of the drum. From steam separator drum, steam passes through the superheater. The super heater increases the temperature of the steam to the desired level. And finally the superheated steam is either transfer to the steam collecting drum or made to strike on the blades of the turbine.
  • The working pressure, temperature and capacity of this boiler is 170 bar, 773 K and 50 tonnes/h.

Advantages and Disadvantages of Lamont Boiler

Advantages

(i). It can be easily started.
(ii). High steam generating capacity (about 50 tonnes per hour)
(iii). It has high heat transfer rate.
(iv). This boiler can be reassembled with the natural circulation boilers.
(v). Its design is simple.

Disadvantages

(i). There is a bubble formation at surfaces of the tubes in this boiler. This reduces the heat transfer rate to the steam.

Benson Boiler - Construction, Working Principle and Advantages with Diagram

What is Benson Boiler?

Benson Boiler is a high pressure, drum less, supercritical, water tube steam boiler with forced circulation. This boiler was invented in the year 1922 by Mark Benson. This boiler is a super critical boiler in which the feed water is compressed to a supercritical pressure and this prevents the formation of bubbles in the water tube surface. The bubbles do not form because at supercritical pressure the density of water and steam becomes same. It was Mark Benson who first proposed the idea to compress the water at supercritical pressure before heating into boiler and due to this the latent heat of water reduces to zero. As the latent heat of water reduces to zero the water directly changes into steam without the formation of bubbles.

Construction or Main Parts 

The main parts of Benson boiler are:


1. Air Preheater

It preheats the air before entering into the furnace. The preheated air increases the burning efficiency of the fuel.

2. Economiser

It heats the water to a certain temperature.

3. Radiant Superheater

It is super heater which heats the water with radiation produced by the burnt fuel. It raises the temperature to supercritical temperature.

4. Convection Evaporator

It evaporates the superheated water and converts them into steam. It does so by the convection mode of heat transfer to the water from the hot flue gases.

5. Convection Superheater

It superheats the steam to the desired temperature (nearly 650 degree Celsius).

6. Furnace

It is the place where the fuel is burnt.

7. Feed Pump

It is used to supply the water inside the boiler at supercritical pressure of 225 bars.

Also Read: What is Babcock and Wilcox Boiler?
Also Read: What is Cochran Boiler?

Working Principle

It works on the principle that the pressure of the water is increased to the supercritical pressure (i.e. above critical pressure of 225 bar). When the pressure of water is increased to the super critical level, the latent heat of water becomes Zero and due to this, it directly changes into steam without boiling. And this prevents the formation of bubbles at tube surface.

Working

In Benson Boiler, the feed pump increases the pressure of the water to the supercritical pressure and then it enters into the economiser. From economiser, the water the water passes to the radiant heater. Here the water receives the heat through radiation and partly gets converted into steam. The temperature raises almost to the supercritical temperature. After that mixture of steam and water enters into convective evaporator where it is completely converted into steam and may superheated to some degree. Finally it is passed through the superheater to obtained the desired superheated steam. This superheated steam is then used by turbines or engine to produce the electricity.

Advantages 

The various advantages of the boiler are
  • It is a drum less boiler and hence the weight of this type of boiler is 20 % less as compared with other types of boiler.
  • It is light in weight.
  • Occupy smaller floor area for its erection.
  • Explosion hazard is almost negligible because of use of smaller diameter tubes.
  • It can be started very easily within 15 minutes.
  • It avoids bubble formation due to the super critical pressure of water.
  • Transportation is easy.
  • This boiler may achieve thermal efficiency upto 90 %.

Application

This supercritical boiler is used in different industries to generate steam for the production of electricity or mechanical power. The average operating pressure, temperature and capacity of benson boiler is 650 degree Celsius, 250 bar and 135 tonnes/h.