Combustion of liquid, solid and gaseous fuels
Combustion of liquid.pptx (Size: 46.29 KB / Downloads: 45)
Fuel is a substance which undergoes a chemical reaction with an oxidizer to liberate heat.
Combustion converts the chemical energy in fuels to thermal energy and this is used to run heat engines.
Fuels used need to be abundant, affordable, easily transported, clean and preferably renewable.
In engineering fuels are classified as solid, liquid and gaseous fuels.
In society fuels are divided into fossil fuels and bio fuels, and renewable and non renewable fuels
Liquid fuels are those ones that are transported within the combustion device as a liquid.
Liquid fuels do not undergo combustion directly. They need to be converted to vapor before combustion.
They are derived primarily from crude oil. Other sources include biomass, oil shale, tar sands and coal.
Liquid fuels such as gasoline, diesel, gas turbine fuels and fuel oils are obtained through fractional distillation, cracking and reforming crude oil.
Characterization of liquid fuels
The important properties include heating value, specific gravity, viscosity, volatility, flash point, auto ignition temperature, octane and cetane number
Volatility is measured by Reid vapor pressure which is the equilibrium pressure exerted by vapor over liquid. It affects engine startup and transient performance.
Flash point is the minimum temperature at which the fuel will rapidly catch fire when exposed to an open flame above the mixture.
Auto ignition temperature is the lowest temperature required to initiate self sustained combustion in a standard container in atmospheric air in the absence of a flame.
Liquid fuel types
Automotive gasoline: it is a selected blend of alkanes, cycloalkanes, alkenes and aromatics. Ethanol is added to prevent knocking.
Diesel fuel: It is a mixture of C10 to C 15 hydrocarbons with higher boiling point range than gasoline. They have low volatility and high viscosity. They are classified into grade 1-D,2-D and 4-D depending on the speed of the engine.
Gas turbine fuels: They have a wide range of boiling points and are not limited by antiknock or ignition delay requirements.
Fuel oil: It is a very heavy residual fuel consisting of the remains after all distillation products are completed. It has high viscosity. It can be used in heavy duty industrial gas turbines.