What is one common problem associated with combustion that can generate unwanted emissions?

Flame impingement is a significant issue in combustion processes that can lead to increased unwanted emissions. When the flame comes into direct contact with the surfaces of the combustion chamber or the burner, it can result in incomplete combustion of fuel. This incomplete combustion is problematic because it produces higher levels of carbon monoxide, unburned hydrocarbons, and other pollutants that can be harmful to both the environment and human health.

Moreover, flame impingement can also lead to thermal stresses and damage to the combustion equipment, resulting in operational inefficiencies and potential safety hazards. The design of combustion systems often aims to achieve optimal flame stability and distribution to prevent such issues, making it crucial to understand the impacts of flame interaction with surfaces.

In contrast, while excess oxygen and low fuel pressure can affect combustion efficiency, they do not typically lead to significant emission problems as can arise from flame impingement. High humidity may influence combustion efficiency and performance but is less directly associated with generating unwanted emissions compared to the implications of flame impingement.