Types of Diesel engine

Two types of diesel engines are available

1. Two stroke/Two stroke cycle engine
2. Four stroke/Four stroke cycle engine

Two stroke engine is, one working stroke occurs in (in each cylinder) for every revolution of the engine crankshaft. That is every alternate stroke is a firing stroke.


Four stroke engine is, one working stroke offers(in each cylinder) for every two revolutions of the engine crankshaft, that is one firing or working stroke and three idling strokes for every two revolutions of the crankshaft.


Fundamental Difference between Two stroke and Four stroke
In the two stroke engine, a separate pump or blower is required to recharge the cylinder with air, whilst in the four stroke engine the working cylinder itself performs that duty.

What are the Compression Ratios for Diesel Engine?

Compression ratios for diesel engines vary between 12.5:1 to 19:1. Generally speaking,compression ratios are high in smaller high speed diesel engines than in large low speed diesel engines. This is chiefly due to the far greater rate of heat loss in the smaller cylinders,necessitating the use of a higher ratio in order to achieve the necessary temperatures for ignition purposes.

Compression ratio of an Engine

The compression ratio of an engine is the ratio of the sum of the swept and clearance volumes in each cylinder to the clearance volume.
if,For example, the cylinder holds 64cm3 of air when the piston is at the bottom of its stroke,and there is only a 4 cm3 space left when the piston is at the top of its stroke,the engine has a compression ratio of 16:1

Usual Compression ratios for petrol engine

Between 7:1 and 10:1

Clearence Volume Definition

This is the space or Volume remaining in the cylinder and or cylinder head where the air charge is compressed by the piston.

Swept Volume or Capacity of a Cylinder

This is the space or volume swept out in the cylinder by the piston,and is equal to the product of the piston stroke and its cross-sectional area.

What are Hybrid Cars?

What are Hybrid Cars?

Everyone talks about environment friendly cars about decade or two ago. Finally, some automotive researches given the answer for it. ” The Hybrid Cars”. Hybrid cars have lot more advantages more than being environment friendly and reducing our carbon foot print. Rise in oil prices which ultimately causing raise in prices at the gas pump, continues as oil is a limited resource. Hybrid technology being environment friendly and being friendly to your pocket is now well developed and well recognized around the world.

How Hybrid cars work?

Before we move on to this topic let’s have a look how Gasoline and Electric cars work separately

· Simplest explanation for gasoline powered car is, gasoline is supplied to the engine by the fuel tank. Gasoline is then ignited and used to power the transmission, which will transfer the energy to wheels to move the car.

· An electric engine uses batteries to provide power to engine. The energy is again sent to the transmission which drives the vehicle. Electric car doesn’t produce emission because there is no process of combustion occurring. However electric batteries needed to be charged regularly because of their low capacity. They generate less power than a combustion engine and provide less performance than a strictly gasoline powered engine.

Each one of them has their own Advantages and Disadvantages.

How Electric batteries are charged

Gasoline car batteries are tend to charge their batteries using motion of the car. Electric engines uses the same theory, to recharge their batteries. The slandered car battery, though, is only required to recharge a small portion of the components in a gasoline car and is not required to drive the vehicle. This means a smaller battery can be used and the regular driving of the vehicle ensures that the battery remains charged and serviceable.

Combined power sources-Hybrid Cars

Combination of electric motor and gasoline engine in hybrid cars give greater performance and longer travelling distances than an electric car. Also hybrids utilize the electric batteries to reduce the emissions and improve fuel consumption.

Combining Gas and Electric power

This is not easy task for the engineers and automotive manufacturers to achive. So they have come up with different methods to combine this two power sources.

The Parallel hybrid-Transmission power from both sources simultaneously. The transmission is connected directly to the both gasoline engine and electric motor. When the car is driven it draws power form both motor and gasoline engine.

The series hybrid-The fuel tank is directly connected to a combustion engine where gasoline is used to create combustion power. This power is not transmitted directly to the transmission as in a gasoline car. The engine is used to power a dual purpose generator. The electric power generated by the generator can then be used to recharge the batteries or to drive the transmission and provide the car with the propulsion power it needs.

Advantages of Hybrid engine

· Gasoline engine used in hybrid cars is much smaller than the Standered gasoline car

· Better fuel consumption

· Less emissions

How hybrid cars work to use different energy sources

Generally, a hybrid car uses the petrol engine for constant and ideal driving conditions such as steady and constant speeds. Because it is much smaller, this already means a reduction in emissions while providing a more than adequate amount of power necessary to drive the car under these conditions.

The electric motor comes in to play when car need extra pressure and extra speed.When the car is driven us hill , accelerating and driving in difficult conditions electric motor will provide and additional push to make gasoline engine more comfortable.

Full Hybrids and Semi Hybrids

Semi hybrids

· Two engines

· One running on liquid fuel and the other running on batteries

· Even so the motor unit is not effective at running the auto alone

· It truly is there to assist gasoline or diesel engine

· Electronic motor is referred to as “assist”

· Preserves money on fuel

· But when the car is moving engine is burning the fuel constantly.

Full Hybrid

· Both engines are capable of powering the car independently

· As long as you are running on electricity, that you are running at zero expense in your wallet and zero emissions to the environment.

· When you are accelerating both engines working in union.

· Switching of power sources is occurred automatically without any instruction of a driver.

Diesel engines classed as an internal-combustion engine.Why?

The diesel engine,like the petrol engine,converts the latent heat energy of the fuel into mechanical work. The heat in the fuel is released by combustion, and is transferred to a working substance. The diesel engine is classified as an internel combustion engine because this working substance actually takes part in the process of combustion ; it is,in fact,air.

In the steam engine,the working fluid does not take part in the combustion of the fuel,and it cannot therefore be classed as "Internal combustion"