What happens to the combustion rate when the fuel mixture is either fuel rich or fuel lean?

The combustion rate is influenced significantly by the composition of the fuel mixture. When a mixture is fuel-rich, there is an excess of fuel compared to the available oxygen, which can lead to incomplete combustion. This incomplete combustion produces less energy and can lower the combustion rate because the reaction is not able to proceed efficiently.

Similarly, in a fuel-lean mixture, there is an excess of oxygen compared to fuel. While this can lead to more complete combustion, it often results in a slower reaction velocity compared to an ideal stoichiometric mixture where fuel and oxygen are perfectly balanced. In both cases of being fuel-rich or fuel-lean, the efficiency of combustion is compromised, leading to a decrease in the overall combustion rate and the maximum pressure produced during the combustion process.

Therefore, when assessing how combustion behaves under different fuel mixtures, recognizing that both extremes result in a decreased combustion rate and pressure helps to clarify why this answer is the most accurate in the context of combustion dynamics.