Definition of fuel
Fuel refers to a substance that can be burned. According to the state of the substance, it can be divided into solid fuels, such as: coal, oil shale and coke after coal processing; liquid fuels such as petroleum and processed products such as gasoline and diesel; gaseous fuels such as gas and natural gas . According to the source, it can be divided into: natural fuels such as coal, oil, natural gas, oil shale, etc.; artificial fuels or synthetic fuels, such as synthetic petroleum, synthetic gasoline, etc. In addition, there are nuclear fuels that use nuclear reactions to release huge amounts of heat. Fuel plays an important and indispensable role in industrial and agricultural production, transportation and people's lives.