A Detailed Guide on Air-Fuel Ratio by Silverado’s Diesel Mechanics
Air-Fuel ratio, abbreviated as AFR, is the ratio of the mass of the air to the fuel (solid, liquid or gas) present during the combustion process. The air-fuel ratio is what decides if the fuel mixture is combustible or not. It also determines the amount of energy being released and the measure of unwanted pollutants created as by-products at the end of the reaction.
There is a certain AFR range outside of which ignition does not take place. Diesel mechanics demarcate this range by the upper and lower explosive limits.
Why is the Air-Fuel Ratio Important?
In internal combustion Engines, the air-fuel ratio (AFR) is an essential number that is used to decide how anti-pollution and performance optimized diesel tuning in engines. A stoichiometric mixture (also known as a stoich) is the term for the ratio where enough air is provided, and it burns away all the fuel.
Mass ratios lower the stoichiometric mixtures are known as ‘rich.’ Rich mixtures are generally less efficient, but they burn cooler and let out more power. Ratios higher than stoichiometric are considered to be ‘lean.’ Lean mixtures are way more efficient, but they are associated with higher temperatures and often the formation of nitrogen oxides.
Today, a lot of engines are designed with a lean burn feature to promote sustainable fuel usage.
Internal Combustion Engines
It seems like a stoichiometric mixture is the most ideal way to use the complete amount of the available fuel. But this is just theory, in actual practice, it is nearly impossible to achieve a stoich, primarily due to the extremely short period of the combustion cycle in an internal combustion engine.
Simultaneously, stoichiometric mixtures also burn very hot and risk damaging engine components if it is set to a high load at this AFR.
Air-Fuel Ratio Control in a Diesel Engine
In a diesel engine, the AFR control is carried out using something known as the ‘fuzzy logic methodology’. The fuzzy logic methodology is a form of control structure that imitates human decision-making, under certain circumstances. Fuzzy logic helps with control and simplifies the development process. This method tames down the complexity and eliminates lengthy mathematical derivations that are commonly associated with modern control theory.
Silverado Road Service is a family-owned, Oklahoma City-born, and bred Diesel Truck and RV Repair shop. Our mechanics offer comprehensive and quality repair work seven days a week, including diesel tuning, oil changes, and light maintenance work.
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