May 172012
 

     Four Stroke Spark Engine

As the name implies, it works on four stroke principle and charge is ignited with the help of  spark plug. Four stroke spark ignition engines are used in all cars and light commercial vehicles usually referred to as four-stroke petrol engines.

Intake Stroke (Suction Stroke) :- When we revolve the engine crankshaft through cranking handle or self starter, the inlet valve opens and the piston being tied up with crankshaft with the help of connecting rod travels toward Bottom Dead Centre (B.D.C). When the piston moves towards B.D.C. partial vacuum is created on top of piston in the combustion chamber. Due to this partial vacuum, air-fuel mixture is drawn into the combustion chamber through open inlet valve. The volume of air fuel mixture getting into the combustion chamber depends upon the speed of piston as well as on throttle opening.  When the piston reaches B.D.C., the inlet valve closes, whereas in actual practice this valve remains open up to 50 degree after B.D.C.

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 Posted by at 7:45 pm
May 162012
 

Any machine which converts heat energy into mechanical work is called Engine. There are various types of engine used in automobile as defined below:

Heat Engines:

  1. External Combustion Engine                                                                                                    

     1.1 Steam Engine      1.2 Turbine (Steam)

  2. Internal Combustion Engine  

    2.1 Spark Ignition Engine                                                                                                                                                                                                                                                            (a) Two Stroke Engine  (b) Four Stroke   Engine

   2.2 Compression Ignition Engine                                                                                                                                                                                                                              (a) Two Stroke Engine  (b) Four Stroke  Engine

   2.3 Wankle Engine                                                                                                     

   2.4 Gas Turbine

External Combustion Engine:- External Combustion Engines are those engines where fuel is burnt outside the combustion chamber such as steam engine and steam turbine.                                                                                                                                                                                                          Internal Combustion Engine:- Internal Combustion engines are those engines where fuel is burnt inside the combustion chamber such as petrol, diesel and wankle engines.

 

 Posted by at 9:55 pm
May 162012
 

 PURPOSE OF BRAKING SYSTEM

We know that safety of passengers in a moving vehicle depends upon the steering system and as well as good brake system. The brake system calls for more efficient brakes as compared to the brake systems employed in olden days when maximum speed was much less as compared to the fast running vehicles manufactured now-a-days.

 

 

 

 

 

 

 

Requirements of a Good Braking System

1. The brake should stop the vehicle in shortest possible distance and time.
2. The brake should work equally good or fair or bad roads.
3. Padal effort applied by the driver should not be more so as not to strain the driver.
4. Brake should work equally good in all weathers.
5. It should have less wearing parts.
6.It should require little maintenance.
7. Brakes, when applied should not disturb steering geometry.
8. When brakes are applied, the vehicle should not pull to one side.
9. There should be minimum sound when brakes are applied.
10. An independent parking brake system should be available to put to use in case of emergency.

 Posted by at 7:08 pm
May 152012
 

STEAM ENGINE

A steam locomotive is a track locomotive that produces its power through a steam engine. These locomotives are oxyacetylene by torrid some comburant substantial, unremarkably combust, wood or oil, to expose clean in a vessel, which drives the clean engine. Both provide and wet supplies are carried with the move, either on the move itself or in wagons pulled down.

Clean locomotives were position mature inBritain and dominated line transportation until the midsection of the 20th century. From the crude 1900s they were gradually superseded by machine and technologist locomotives.

 

 Posted by at 7:45 pm
May 142012
 

DIESEL ENGINE [Compression Ignition Engine]

 

Compression ignition engine are usually called as Diesel Engine named after Dr. Rudolf  Diesel who invented this in the year 1897. Using fuel with higher specific gravity and less volatile and therefore, less infammable.
In diesel engines, only air is changed in the cylinder through inlet valve. In compression stroke when both valves are closed this air is compressed, due to this, its temperature rises and before the piston reaches Top Dead Centre, diesel oil is injected in the combustion chamber in fine atomized form. When this atomized spray comes in contact with hot compressed air, the ignition takes place. In these engines, spark plugs for igniting the fuel are not provided, the fuel which is in atomized form, gets ignited due to the high temperature of compressed air. That is why it is known as compression ignition engine. These engines are available in both 4-stroke and in 2-stroke cycle.

Working of Four stroke Diesel Engines

1. Suction or Induction stroke. When the piston moves from TDC to BDC, the inlet opens and due to the downward movement of piston, a partial vacuum is created in the cylinder above the piston. Due to this partial vacuum, air is sucked in. At the end of stroke, the inlet valve closes.

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 Posted by at 3:12 pm