Combustion Process Overview Quiz

Study Notes

Combustion Overview

Combustion is the chemical reaction between a fuel and oxidant — most commonly oxygen from air — that produces heat, light, and other forms of energy release. This fundamental process has been supporting human civilization since prehistoric times by powering heating systems, cooking meals, transportation vehicles, and various industrial applications.

Types of Combustion

There are several classifications of combustion based on factors such as pressure, temperature, fuel type, and presence of compounds like catalysts and flames.

Homogeneous: Fuel and oxidizer mix together before ignition, resulting in rapid, complete burning with minimal pollution in well-controlled environments like jet engines.
Heterogeneous: Occurs when solid fuels burn directly without being mixed with the oxidizing agent first, creating visible flame zones on objects' surfaces, like candles or charcoal grills.
Premixed: Fuels and oxidants are thoroughly blended before ignition, promoting uniform burning rates and improved efficiency across many internal combustion engine applications.
Nonpremixed: Mixture formation occurs within the flame zone itself, leading to complex interactions among different fuel species, increasing pollutant emissions and limiting fuel flexibility compared to premixed combustion systems.

Reproduction Process of Combustion

The three primary steps involved in any combustion process are known collectively as the Five Ts:

Temperature rise: As fuel meets oxidizer, their combined molecular kinetic energies increase due to thermal excitation.
Triple point contact: Collisions between gas molecules result in physical impacts, forming temporary bonds called van der Waals forces that weaken the structure of both fuel and oxidizing agents.
Triggered reactions: Vibrations caused by van der Waals force contacts facilitate bond breaking, allowing electrons from broken covalent bonds to participate in new chemical reactions.
Transition state formation: Newly formed reactive intermediates converge into transition states where unstable structures temporarily store excess energy required to reach final products.
Terminal product formation: Energetically favorable pathways deliver stable end products (like CO2, H2O, N2) while releasing unused energy in the form of heat, sound waves, or light.

Despite its complexity, understanding these basic principles offers valuable insights into optimizing combustion processes to minimize unwanted side effects and maximize overall performance.