Engine Efficiency
In an IC engine, air and
fuel are mixed to a combustible mixture that’s ignited and releases
energy in the form of heat. The amount of heat released depends on multiple factors. While the amount of
fuel within the cylinder is the primary determinant of the
energy content of the trapped air/fuel mixture and thus the total amount of heat that can be released, a number of secondary factors are also important. These secondary factors include details about the
fuel composition such as the type of elements contained in the
fuel and the nature of the bonds joining the elements together. For engines, the net
energy released from combustion is typically represented by the lower heating value (LHV) of the
fuel since the water produced by combustion is assumed to remain in the vapor state. Figure 2 shows the LHV of a range of fuels that could be used in an internal combustion engine versus their stoichiometric air
fuel ratio. Notice that for hydrocarbon fuels, the LHVs are very similar and considerably higher than for fuels containing oxygen. Oxygenated functional groups contribute less net
energy during combustion while contributing significantly to the fuel’s mass and volume.
High Impact List of Articles
Relevant Topics in