Combustion Definitions Flashcards
With regard to the combustion process, explain, the meaning of excess air supply
(c) the effects of an inadequate air supply.
It means that there is an excess amount of oxygen relative to the amount of fuel being burned. The excess air is typically expressed as a percentage above the stoichiometric air-to-fuel ratio.
With regard to the combustion process, explain, the reason for always providing excess air
Providing excess air ensures complete combustion of the fuel. Incomplete combustion can result in harmful byproducts, such as carbon monoxide (CO) and unburned hydrocarbons. By supplying excess air, there is enough oxygen available to react with all the fuel molecules, promoting the conversion of fuel to carbon dioxide (CO2) and water (H2O), which are less harmful emissions.
With regard to the combustion process, explain, the effects of an inadequate air supply.
Insufficient air supply can result in reduced combustion efficiency, leading to wasted fuel and decreased energy output. Incomplete combustion can also lead to the buildup of carbon deposits, often referred to as “soot” or “carbon fouling.
Explain the process of combustion.
The combustion process begins with ignition, Ignition can occur through a spark. Once the fuel reaches its ignition temperature, it starts to break down.
As the fuel heats up, it undergoes a process called thermal decomposition. During this stage, the high temperature causes the fuel to break down into smaller, more reactive molecules.
Once the fuel has decomposed, it combines with oxygen from the air in an exothermic chemical reaction. where it releases a significant amount of heat energy.
A visible flame is produced and the heat generated during combustion is released into the surrounding environment.
The heat energy from combustion is converted into mechanical energy.
Explain stoichiometric conditions for combustion
Is the ratio of air to fuel. When a combustion reaction occurs under stoichiometric conditions, all of the fuel is consumed, and there is precisely enough oxygen available to react with it. This results in the most efficient combustion, with minimal unburned fuel or emissions.
State the chemical formulae for EACH of the following compounds associated with combustion:
(i) Water;
(ii) Carbon dioxide;
(iii) Carbon monoxide;
(iv) Sulphur dioxide.
Water: H2O
Carbon dioxide: CO2
Carbon monoxide: CO
Sulphur dioxide: SO2
State TWO reasons why it is undesirable to have insufficient air supplied in a combustion
process.
Incomplete Combustion: When there is not enough air supplied to support the combustion of fuel, incomplete combustion occurs. Incomplete combustion means that not all of the fuel is burned completely. This results in the formation of harmful byproducts, including carbon monoxide (CO) and unburned hydrocarbons (HC).
Reduced Power Output: Inadequate air supply can result in a reduction in the power output of the combustion process. This will lead to reduced power generation capacity in engines. It can also lead to increased fuel consumption, raising operational costs.
State the chemical formula for EACH of the following combustion product compounds and identify the
meaning of each symbol:
(a) water;
(b) carbon dioxide;
(c) carbon monoxide;
(d) sulphur dioxide.
Water:
Chemical Formula: H2O
Meaning of Symbols:
H: Represents hydrogen, a colorless, odorless, and highly flammable gas.
2: Indicates that there are two hydrogen atoms in each molecule of water.
O: Represents oxygen, a colorless, odorless, and essential gas for combustion and respiration.
Carbon Dioxide:
Chemical Formula: CO2
Meaning of Symbols:
C: Represents carbon, a non-metallic element that is a fundamental component of organic compounds.
O: Represents oxygen, a colorless, odorless, and essential gas for combustion and respiration.
2: Indicates that there are two oxygen atoms in each molecule of carbon dioxide.
Carbon Monoxide:
Chemical Formula: CO
Meaning of Symbols:
C: Represents carbon, a non-metallic element that is a fundamental component of organic compounds.
O: Represents oxygen, a colorless, odorless, and essential gas for combustion and respiration. In this case, there is only one oxygen atom per molecule.
Sulphur Dioxide:
Chemical Formula: SO2
Meaning of Symbols:
S: Represents sulfur, a non-metallic element that can be found in various compounds, including those in fossil fuels and ores.
O: Represents oxygen, a colorless, odorless, and essential gas for combustion and respiration. In this case, there are two oxygen atoms per molecule.
2: Indicates that there are two oxygen atoms bonded to one sulfur atom in each molecule of sulfur dioxide.
Explain the meaning of the term stoichiometric air requirement.
The term “stoichiometric air requirement” refers to the precise amount of air (or oxygen) that is chemically needed to completely combust a specific quantity of fuel in a combustion process.
In other words, it represents the ideal or theoretical air-to-fuel ratio required for complete combustion with no excess air or unburned fuel left over.
