Archive for March 2010

Working of Four-Stroke Engine

The biggest difference to notice when comparing figures between a 2-stroke engine and 4-stroke engine is that the spark-plug fires once every revolution in a two-stroke engine but in case of four-stroke engine the spark fires once every other revolution. First of all lets discuss about the working of four-stroke engine...

 Today most of the cars use what is called Four-Stroke Combustion Cycle to convert gasoline into motion. The four-stroke approach is also known as the Otto cycle, in honor of Nikolaus Otto, who invented it in 1867. They are-
  • Intake Stroke
  • Compression Stroke
  • Combustion Stroke
  • Exhaust Stroke

Step 1
The piston starts from the top, the intake valve is opened by the Camshaft, and the piston moves down to let the engine take in a cylinder-full of gasoline and air. Only the tiniest drop of gasoline needs to be mixed into the air for this to work.--------This all Process is called Intake Stroke.
Intake Stroke of Four Stroke Engine

Step 2
Then the piston moves back to compress this fuel & air mixture. This all makes the mixture more denser, internal temperature of the cylinder increases. Hence--------Compression Stroke makes the Explosion more powerful.
Compression Stroke of Four Stroke Engine

    Step 3
    And when the piston reaches the top of the cylinder, the spark plug emits a spark and ignites the gasoline. The gasoline charge in the cylinder explodes, driving the piston downwards.-------This is called as Combustion Stroke.
    Power Stroke of Four Stroke Engine

    Step 4
    Once the piston hits the bottom of its stroke, the exhaust valve opens and the exhaust leaves the cylinder to go out the tailpipe.-------This is called Exhaust Stroke.
    Exhaust Stroke of Four Stroke Engine
      Now, in the next section we'll learn about two stroke engines and diesel engines, what's the basic difference and similarities between them---
      Mar 25, 2010
      Posted by Sayantan Mandal

      Piston Engine Parts

      Now you all know about different types of engines. Now let's start with the Internal Combustion engine's first part i.e. PISTON ENGINE.

      Piston Engines are be classified further based on engine's cycle.... Ya, in case of Piston engine we have:
    1. 2 stroke engine
    2. 4 stroke engine
    3. And, 6 stroke engine

    4. But all of them has somewhat same kind of configuration. So before beginning the lesson let's get introduced with the parts it possesses 
      Illustrated Diagram Of A BASIC Internal Combustion Engine
      Illustrated Diagram Of A BASIC Internal Combustion Engine

      Spark Plug
      The spark plug supplies the spark that ignites the air/fuel mixture so that combustion can occur. The spark must occur at right moment so that everything work properly.

      Its a cylindrical piece of metal that moves up and down inside the combustion chamber

      When the piston is moved up and down, the converts that motion into a circular motion just like a crank on a jack-in-the-box does.

      Its opens the space from where the mixture of air/fuel enters and the exhaust exits. Actually two valves are present one for the Intake and the other for Exhaust. Note-That both valves are closed during compression and combustion and therefore the combustion chamber is sealed for middle two stroke.

      Connecting Rod
      It connects the piston to the crankshaft. It can rotate at both ends so that its angle can change as the piston moves and the crankshaft rotates.

      Its around the crankshaft and oil to lubricate the Connecting rod and the crankshaft.

       Here's the original of DI-section of an Internal Combustion Engine:
      Original DI-Section Pic
      Di-section Pic OF Internal Combustion Engine

      Let start with -

    5. 4 stroke engine
    6. Then we'll learn about 2 stroke engine
    7. Then about the advantages & disadvantages between the above two
    8. And, at last we'll see the working of 6 stroke engine

    9. Mar 24, 2010
      Posted by Sayantan Mandal

      Internal Combustion Engine

      Actually the basic concept behind an Internal Combustion Engine to be called as an Internal Combustion Engine is that the fuel which is available to it is burned inside the core of the engine or in other words the combustion process is carried out internally inside the box of the engine...

      Di-section Of An Piston Engine
      Di-section Of An Piston Engine

      The basic principle behind any Internal Combustion Engine-

      If you put a tiny amount of high-energy fuel (like gasoline) in a small, enclosed space and ignite it, an incredible amount of energy is released in the form of expanding gas. This large amount of energy can be used to propel a potato to a height of 500 feet. You can also use it for more interesting purposes. Then just think about it, if you can harness this incredible amount of energy in a useful way & could be able to create a cycle that allows you to set off explosions like this hundreds of times per minute, then we have is the basic core of an engine!!!

      In fact there are many types of internal combustion engines available today, which uses various different methods to burn the fuel inside the engine. They are based on engine configuration:

      • Piston Engines - Piston Engines are classified further based on engine's cycle...
        • Four Stroke Engines - Fuel is burned in 4 stroke of the piston i.e. two times ups and two times downs, with spark every other revolution.
        Internal Combustion Engine
        • Two Stroke engines - Fuel is burned in a single revolution i.e. in 2 stroke, one up and one down, with spark every revolution.
        Yamaha Two/2 stroke engine
        • Diesel Engines - Here fuel is also burned in 4 stroke of the piston but without the spark, Yes!!! it doesn't have a spark plug in it. Fuel is burned using internal heat of the cylinder during compression.
        Diesel Engine
      • Wankel Engine
      • Turbines
      Getting confused?!!
      Why don't get back and have a brief info about the Classification Of Engine......

      Shaft Engine

      Shaft engines are those kind of engines which transmits its rotatory power or torque using a Drive Shaft. Drive Shaft are subject ttorsion and shear stress.

      Drive Shaft has a great history....

      Do you remember the old steam locomotives, they used to have a long steel rod mounted on the wheels of the steam engine. It used to slide length-wise and varying its length effectively. Ya, its a kind of drive shaft (as shown in pic) called 'quill drives'.
      Photo Courtesy TijsB

      I remember when i used to go to school, i often see a rotating cylindrical rod beneath a truck. I used to think how this rotating rod is moving the wheels of the truck. Actually that rotating rod is noting but a Drive shaft which is transmitting the power to the wheels.
      Photo Courtesy troymckaskle
      The above pic shows a pickup truck with 4 wheel drive. You can see two shaft in front of the power assembly which is driving the front tyres. 

      So all this is Drive Shaft all about....

      Now Shaft Engines are of two Types:

      Classification of Engines

      Have u ever wondered how a BMW run/races around tracks & streets just using gasoline (which we commonly say petrol). You might have heard things like "V-10 engines" and "dual overhead cams" and "triple fuel injection." But what does all this mean?

      Many of you simply out of curiosity want to know and understand what actually is going on behind the big confusing jumble of metal, tubes and wires.

      To be straight, the purpose of a gasoline car engine is to convert gasoline into motion. Actually the car burns the gasoline inside its engine. Therefore, a car engine is an internal combustion engine -- as combustion takes place internally inside.

      There are typically three types of engines-
      • Shaft Engines - These are the engines where power is transmitted (usually torque produced by engine) using a Drive Shaft.
        • Internal Combustion Engine - Here gasoline is burned inside an engine. They are much better and gives good performance and are also very efficient than External Combustion Engine. There are different kinds of Internal Combustion Engine:
          • Piston engine
          • Wankel engine
          • Turbines:
            • Turboprop
            • Turboshaft

      Bmw internal combustion engine
      Photo Courtesy TheCarShooters
        • External Combustion Engine - A steam engines and steam boats are a good example of External combustion engine. The fuel (coal, wood, oil, whatever) in a steam engine burns outside the engine to create steam, and the steam creates motion inside the engine. These engines are very much heavy and bulky than Internal combustion engine.
      External Combustion (steam) engine
      Steam Engine

      • Reaction Engines - Such engines are based on the Newton's third Law of Motion i.e.  "For every action force there is an equal, but opposite, reaction force". Such engines provides a thrust which propelles the mass/ body forward by throwing out gases at high speed or we can say reaction mass.
        • Tubines
          • Turbojet
          • Turbofan
          • Propfan
        • Rocket-powered
        • Motorjet
        • Pulsejet
        • Ramjet
          • Scramjet

      • Other Type of Engines - These are miscellaneous engines, whose working is fuel by different Working Substance. 
        • Human-powered
        • Electric
        • Nuclear
        • Hydrogen

      Mar 22, 2010
      Posted by Sayantan Mandal

      How Heat Engine Works

      Do you know that a BMW car engine or its aircraft engine is actually a heat engine. Before we get into various combustion engine lets get into the basics, the building blocks of an ENGINE. It all starts with the concepts of thermodynamics,

      In Thermodynamics, Heat Engine is a device by which a system is made to undergo a cyclic process that results in conversion of of heat or thermal energy to mechanical work..

      Lets think the way Carnot thought, which leaded to the the invention of the car engine:

      Schematic representation of a heat engine
      Lets the circle in the middle be an engine and the box at the right be an external HOT reservoir and at the left be an external COLD reservoir:
      1. It consists of a working substance - the system. For example, a mixture of fuel vapor and air in a gasoline or a diesel engine or steam in steam engine are the working substance.
      2. The working substance goes through a cycle consisting of several processes. In some of these processes, it absorbs a total amount of heat QH from an external reservoir at some external temperature TH.
      3. In some other processes of the cycle, the working substance releases a total amount of heat QC to an external reservoir at some lower temperature TC.
      4. The work done (W) by the system in a cycle is transferred to the environment via some arrangement(e.g. the working substance may be in a cylinder with a moving piston that transfers mechanical energy to the wheels of a vehicle via a shaft).

      Actually the engine is taking heat energy from hot reservoir  releasing it to cold reservoir and delivers work W to the surrounding.
      therefore work,
      Total Work, dW = dQc - ( -dQh )

      And its efficiency,
      Efficiency, n=W/Qh

      The cycle repeats itself again and again to get useful work......

      For more info you can always refer to wikipedia, Here's the LINK: Heat Engine
      Mar 21, 2010
      Posted by Sayantan Mandal

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