What Do You Mean by Four Stroke?

Written by Thomas Yoon

What is a 4-stroke diesel engine?

Asrepparttar name suggests, these engines work on reciprocating actions of pistons. One stroke means one linear motion ofrepparttar 102781 piston in one direction. Whenrepparttar 102782 piston moves inrepparttar 102783 opposite direction, that is counted as another stroke.

For a 4-stroke engine,repparttar 102784 piston has to move up, then down, then up again, and then down again to complete one cycle ofrepparttar 102785 engine. In that 4 stroke ofrepparttar 102786 piston,repparttar 102787 crankshaft will have turned 2 revolutions.

The 4 strokes ofrepparttar 102788 piston is to complete 4 stages ofrepparttar 102789 combustion cycle. As you might have known, in order for a fire (or explosion) to occur to powerrepparttar 102790 engine, we need a fuel, a heat source, and oxygen coming together atrepparttar 102791 same time.

Atrepparttar 102792 start ofrepparttar 102793 cycle, air must be introduced intorepparttar 102794 combustion space insiderepparttar 102795 cylinder. Inrepparttar 102796 4-stroke (also called 4-cycle) engine, this isrepparttar 102797 air intake stroke. The piston moving down will suck fresh air intorepparttar 102798 cylinder through repparttar 102799 air inlet valve(s) that is opened.

The next stroke isrepparttar 102800 compression stroke. With allrepparttar 102801 valves atrepparttar 102802 cylinder head closed,repparttar 102803 piston moves up again. The air becomes compressed to a very high degree. So high thatrepparttar 102804 temperature ofrepparttar 102805 air becomes sufficiently hot to ignite a finely sprayed fuel mist on contact.

That is precisely what happens. Beforerepparttar 102806 piston reachesrepparttar 102807 top-dead center (the maximum heightrepparttar 102808 piston can reach before coming down again),repparttar 102809 fuel is injected as a very fine mist into combustion space atrepparttar 102810 piston top. In order for this fuel to be injected intorepparttar 102811 highly compressed air insiderepparttar 102812 cylinder repparttar 102813 fuel itself must be at a higher pressure. This is achieved by a fuel pump.

There is a reason for injectingrepparttar 102814 fuel slightly beforerepparttar 102815 piston reaches top dead center. The fuel takes some time to reach repparttar 102816 temperature that it can burn. Sorepparttar 102817 timing ofrepparttar 102818 injection ofrepparttar 102819 fuel is adjusted so that byrepparttar 102820 timerepparttar 102821 piston reaches slightly beyondrepparttar 102822 top dead center,repparttar 102823 fuel has acquiredrepparttar 102824 temperature high enough for ignition.

Why Select Two Strokes?

Written by Thomas Yoon

In our previous publication, we touched onrepparttar subject of 2-stroke diesel engines. http://www.free-engineering.com/fwezine26.htm . Today, we ask why we choose to use 2-strokes?

As you might remember, for a 2-stroke engine,repparttar 102780 piston has to move up, and then down to complete one cycle of repparttar 102781 engine. In those 2 strokes ofrepparttar 102782 piston,repparttar 102783 crankshaft will have turned 1 revolution. In those 2 strokes ofrepparttar 102784 pistonrepparttar 102785 engine has also completed 4 stages ofrepparttar 102786 combustion cycle - air intake, compression, combustion and exhaust.

Now, compare that with a 4-stroke engine. The piston moving down will completerepparttar 102787 air intake stroke. When it moves up again,repparttar 102788 piston completesrepparttar 102789 compression stroke. Next comesrepparttar 102790 injection of fuel. Combustion takes place. The piston is forced to move down byrepparttar 102791 pressure ofrepparttar 102792 gases. Whenrepparttar 102793 piston moves up again, it drives out allrepparttar 102794 exhaust gases inrepparttar 102795 exhaust stroke.

The piston in a 4-stroke engine will move 4 strokes in order to completerepparttar 102796 4 stages ofrepparttar 102797 combustion cycle - air intake, compression, combustion and exhaust.

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