Order of Fuels based on Increasing Donation Tendency in SI Engine

There are various factors that affect the performance of a spark-ignition (SI) engine, and the donation tendency of the fuel is one of them. The donation tendency refers to the ability of the fuel to donate electrons to the combustion process, which affects the combustion efficiency and the power output of the engine. The following is the correct order of fuels based on increasing donation tendency in SI engines:

1. Hydrocarbons


2. Methanol


3. Ethanol


4. Gasoline

Explanation of the Order of Fuels

Hydrocarbons

Hydrocarbons are the simplest and most basic fuels used in SI engines. They are composed of carbon and hydrogen atoms, and they have a very low donation tendency. This means that they do not donate many electrons to the combustion process, which results in a lower combustion efficiency and power output compared to other fuels.

Methanol

Methanol is a simple alcohol that has a higher donation tendency than hydrocarbons. It contains an oxygen atom in its molecular structure, which makes it more reactive and willing to donate electrons to the combustion process. This results in a higher combustion efficiency and power output compared to hydrocarbons.

Ethanol

Ethanol is a more complex alcohol that has a higher donation tendency than methanol. It contains two oxygen atoms in its molecular structure, which makes it even more reactive and willing to donate electrons to the combustion process. This results in a higher combustion efficiency and power output compared to methanol and hydrocarbons.

Gasoline

Gasoline is the most complex and sophisticated fuel used in SI engines. It is composed of a mixture of hydrocarbons and other compounds, such as oxygenates and additives. Gasoline has a high donation tendency due to the presence of oxygenates and other reactive compounds, which makes it the most efficient and powerful fuel for SI engines.