About IC engine nptel

 About Internal Combustion Engine:

IC Engine of high compression ratio requires petrol with octane ratings that are sufficiently high to ensure efficient combustion. An economical way of achieving this property has been the use of anti-knocking, such as TTE&TTM LEDs at concentrations up to 0.84 g l−1

. It was increasingly recognized, however, that lead is toxic and nondegradable, so its use in this way was gradually phased out. This action, which has been to the benefit of human health and the environment, required the reformulation of fuels to provide the desired high-octane ratings by the use of oxygenates. Fuel oxygenates are oxygen-rich compounds that act as octane enhancers, bringing the additional benefit of making petrol burn more completely, thereby reducing exhaust emissions. Oxygenates can be blended into petrol in two forms: alcohols (such as methanol or ethanol) or ethers.

Two Stroke and four-stroke cycle engine:-
2 stroke cycle:- in a two stroke engine the working cycle is completed at intu stock of the Piston for one revolution of the crankshaft.

4 stock cycle:- in four stroke engine working cycle is completed in four stroke of the Piston or to revolation of the crankshaft.


Operation in a cycle:- when an engine is working continuously we many consider a cycle starting from any stock. We know that when the engine returned back to the stock where it started we say that one cycle has completed. The following sequence of operation in a cycle is widely used.
1) suction stroke:- In this stock the fuel vapour in correct proporition in supplied to the engine cylinder.
2) compression stroke:- in this topic the fuel vapour is compressed in the engine cylinder.

3) expansion for working stroke:- stop the fuel vapour is fired just before the compression is complete. Result in the sudden rise of pressure due to expansion of the combustion product in the engine cylinder. The sudden rise of pressure causes the position with a great force and rotation the crankshaft. The crankshaft in turn drives the machine connected to it.

4) exhaust stroke:- In this stock the burnt gases executed from the engine cylinder so as to make space available for the face fuel vapour.


Advantages and disadvantages of 2 stroke over 4 stroke cycle engines:-
Advantages:-
1) cycle engineer give twice the number of power stroke than the four stroke cycle engine at the same engine speed. Critically a two stroke cycle engine should develop twice the power as that of a four stroke cycle engine.

2) for the same power developed a two stroke cycle engine is lighter less bulky and occupies less floor area.

3) two stroke cycle engine has a lighter flywheel and gives higher mechanical efficiency than a four stroke cycle engine.

Disadvantages:-
1) the thermal efficiency of a two stroke cycle engine is less than of a four stroke cycle engine because a two stroke engine has less compression ratio than that of a four stroke cycle engine.
2) the overall efficiency of a 2 stroke cycle engine is also less than that of a four stroke cycle engine.
3) the consumption of lubricating oil is large in a two stroke cycle engine because of high operating temperature.