Page 43 - Piston Engine-Based Power Plants

CHAPTER 4 4

Spark Ignition Engines

Spark ignition engines are the most popular reciprocating engines.
Engines of this type can be found in many road cars as well as in some
larger vehicles. They are used in small mechanically driven tools such
as lawn mowers and chain saws and they can be used for a variety of
power generation services including emergency backup and grid sup-
port as well as base-load supply.
The engines can burn a variety of fuels. The most common is gaso-
line (petrol) but they can burn a range of gaseous and liquefied gas
fuels including natural gas, propane, biogas and landfill gas. Liquid
fuel, gasoline, is the preferred fuel for most mobile applications
because of its relatively high energy density but for stationary applica-
tions the use of gaseous fuel, particularly natural gas, is common and
becoming increasingly popular.
Most spark ignition engines are four stroke; two-stroke engines of this
type are generally only used for small mechanical devices. The latter are
also popular in motor cycles although most advanced motor cycles now
use four-stroke engines. For power generation applications, engine sizes
range from less than 1 kW to around 10 MW. Reciprocating engines
larger than this are normally large, slow-speed diesel engines.
The spark ignition engine premixes the fuel with air before admit-
ting the mixture into the cylinder of the device. Various mechanical
and electrical systems have been developed to carry out this mixing.
The fuel mixture is then compressed before being ignited with an elec-
trical spark. In some more complex engines there is a pre-ignition
chamber where a fuel-rich mixture is ignited first, with this ignition
then spreading into the main cylinder. The precise fuel and the compo-
sition of the air fuel mixture will influence performance parameters
such as the efficiency and the level and type of engine emissions.

Another important variable is the compression ratio which indicates
the degree to which the gases are compressed before they are ignited.

Piston Engine-Based Power Plants. DOI: https://doi.org/10.1016/B978-0-12-812904-3.00004-5
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