Two-stroke engine is a combustion engine in which combustion occurs in one cycle two pistons move, in contrast to the four-stroke engine that has four pistons move in a single combustion cycle, although the four processes (intake, compression, power, exhaust) also occurs.
Two-stroke engine has also been used in diesel engines, notably opposed piston design, low-speed vehicles such as large ship engines and V8 engines for trucks and other heavy vehicles.
Work principle
To understand the working principle, it should be understood that the applicable standard term in automotive engineering:
> TDC (top dead point) or TDC (top dead center), the position of the piston is at the uppermost point in the cylinder or the piston is at the farthest point from the crankshaft (crankshaft).
> TMB (bottom dead point) or BDC (bottom dead center), the position of the piston is at the lowest point in the engine cylinder or piston is at its closest to the crankshaft (crankshaft).
> Space rinse ie where there is room under the piston crankshaft (crankshaft), often referred to as crank tub (crankcase) serves the gases of the mixture of air, fuel and lubricants can be mixed evenly.
> Flushing (scavenging), namely the process of spending combustion gas and process gas inlet for combustion in the combustion chamber.
The piston moves from the TDC to the TMB.
1. When the piston moves from TDC to the TMB, it will suppress the rinse chamber under the piston. The further the piston leaving the TMA to the TMB, the pressure in the chamber increases rinse.
2. At some point, the piston (piston rings) will pass through a landfill gas and gas inlet orifice. The position of each of the hole depends on the designer's design. Generally the piston ring will pass through the drain hole first.
3. At the time of the piston ring passing through the drain hole, the gas in the combustion chamber out through the drain hole.
4. At the time of the piston ring passes through the hole of entry, the gas pressure in the rinse chamber will be pumped into the combustion chamber as well as encouraging existing gas in the combustion chamber out through the drain hole.
5. Piston keep pressing until the point TMB rinse chamber, while pumping gas in the rinse chamber into the combustion chamber.
the second step
The piston moves from BDC to TDC.
1. When the piston moves TMB to the TMA, it will suck the result of a mixture gas of air, fuel and lubricants into the rinse chamber. This mixing is done by a carburetor or injection system. (See also: The fuel system)
2. As it passes through the hole entry and the sinkhole, the piston will compress the gas trapped in the combustion chamber.
3. The piston will continue to compress the gas in the combustion chamber until the TMA.
4. Just before the piston at TDC, the spark plug lit to burn off gas in the combustion chamber. Time spark before the piston to TDC in order to make the peak pressure in the combustion chamber due to combustion occurs when the piston starts to move from TDC to BDC because the combustion process itself takes from start to spark until the gas is burned completely.
Differences in the design of the four-stroke engine
In the two-stroke engine, in one rotation of the crankshaft (crankshaft) occurs one combustion process while the four-stroke engine, a combustion process takes place in two rounds of the crankshaft.
In the four-stroke engine, requiring the valve mechanism (valve mechanism) in working with the function of opening and closing the pit entry and pit disposal, while the two-stroke engine, piston and piston ring serves for opening a hole and cover the income and the sinkhole. At first the two-stroke engine is not equipped with a valve, in the development of one-way valve (one way valve) is installed between the rinse chamber with the carburetor with the aim of:
1. In order for the gas that has entered the wash chamber does not return to
carburetor.
2. Maintain the pressure in the rinse chamber when the piston compresses the space
rinse.
Entry holes and drain holes on two-stroke engines found on the cylinder wall, while the four-stroke engine found in the cylinder head (cylinder head). This is the most important reason to use a two-stroke engine oil side.
Advantages and disadvantages
Advantages of two-stroke engines
Compared to four-stroke engine, the advantages of two-stroke engines is:
1. The two engines no more powerful than the four-stroke engine.
2. Engine two was smaller and lighter than the four-stroke engine.
> The combination of both the above advantages make the ratio of weight to power (Power to weight ratio) engine two better than four-stroke engine.
3. The two-stroke engine cheaper production costs because of the simple construction.
Although it has the advantages mentioned above, it is rarely used in vehicle applications primarily because the car has its drawbacks.
Shortage of two-stroke engines
Shortage of two-stroke engine compared to a four-stroke engine
1. The efficiency two-stroke engine is lower than the four-stroke engine.
2. The two machines do not require oil mixed with fuel (oil side / two stroke oil) for lubrication of the engine cylinders.
> Both of the above resulted in operating costs over two-stroke engine
higher than the four-stroke engine.
3. two-stroke engine produces more air pollution, pollution occurs from
burning oil and gas side of the room to rinse the incoming terlolos
directly into the sinkhole.
4. Lubrication is not as good as two-stroke engine four-stroke engine, resulting in age
component parts in the combustion chamber is relatively lower.
Application
Two-stroke engine is applied to a gasoline engine or a diesel engine. Two-stroke gasoline engine is used most widely in small engines, such as:
a. Motorcycle engine.
b. Machine of the saw (chainsaw).
c. Lawn mower.
d. Snowmobile.
e. Engines for model aircraft, and so on.
A large two-stroke engines usually type diesel engine, while the two-stroke engine size was very rarely used.
Development
The use of direct injection technology with the aim of lowering exhaust emissions.
Because the exhaust emissions is difficult to meet the UNECE standard Euro II, the use of two-stroke engines for motorcycles are increasingly rare.
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