Technology Description of reciprocating Engine
by Starlight Generator dieselgeneratortechTechnology Description of reciprocating
2.3.1
Basic Processes
There
are two primary reciprocating engine designs relevant to stationary power
generation applications – the spark ignition Otto-cycle engine and the
compression ignition Diesel-cycle engine. The essential mechanical components
of the Otto-cycle and Diesel-cycle are the same. Both use a cylindrical combustion
chamber in which a close fitting piston travels the length of the cylinder. The
piston connects to a crankshaft that transforms the linear motion of the piston
into the rotary motion of the crankshaft. Most engines have multiple cylinders
that power a single crankshaft.
The
main difference between the Otto and Diesel cycles is the method of igniting
the fuel. Spark ignition engines (Otto-cycle) use a spark plug to ignite a
pre-mixed air fuel mixture introduced into the cylinder.
Compression
ignition engines (Diesel-cycle) compress the air introduced into the cylinder
to a high pressure, raising its temperature to the auto-ignition temperature of
the fuel that is injected at high pressure.
Engines
are further categorized by crankshaft speed in revolutions per minute (rpm),
operating cycle (2- or 4-stroke), and whether turbocharging is used.
Reciprocating engines are also categorized by their original design purpose,
such as automotive, truck, industrial, locomotive and marine. Hundreds of small-scale
stationary power, CHP, irrigation, and chiller applications use automotive
engine models.
These
are generally low-priced engines due to the economies of scale of large
production volumes.
Truck
engines have the cost benefit of production volume and are designed for a
reasonably long life (e.g., one million miles). A number of truck engines are
available as stationary engines. Engines intended for industrial use are
designed for durability and for a wide range of mechanical drive and electric
power applications. Their sizes range from 20 kW up to 6 MW, including industrialized
truck engines in the 200 to 600 kW range and industrially applied marine and
locomotive engines above 1 MW.
There
are 2-cycle engines in stationary power applications, particularly in standby
service. However, most spark ignition and the diesel engines relevant to
stationary power generation applications complete a power cycle in four strokes
of the piston within the cylinder as shown in Figure 2-1.
1.
Intake stroke – introduction of air (diesel) or air-fuel mixture (spark
ignition) into the cylinder.
2.
Compression stroke – compression of air or an air-fuel mixture within the
cylinder. In diesel engines, the fuel is injected at or near the end of the
compression stroke (top dead center or TDC), and ignited by the elevated
temperature of the compressed air in the cylinder. In spark ignition engines, the
compressed air-fuel mixture is ignited by an ignition source at or near TDC.
3.
Power stroke – acceleration of the piston by the expansion of the hot, high
pressure combustion gases.
4.
Exhaust stroke – expulsion of combustion products from the cylinder through the
exhaust port.
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Created on Apr 19th 2019 01:25. Viewed 186 times.