Air Coolers After Turbochargers: Importance and Effects
(a) Why Air Coolers are Fitted After Turbochargers:
Air coolers, also known as charge air coolers (CACs), are installed after the turbocharger in diesel engines for a critical reason:
- Denser Air for More Power: During compression by the turbocharger, air temperature rises significantly. Denser air contains more oxygen molecules per unit volume. The intercooler cools this hot compressed air before it enters the engine cylinders. This allows for:
- Increased Power Output: Denser, cooler air allows for a larger and more efficient fuel burn, resulting in increased engine power output.
- Improved Efficiency: Denser air promotes more complete combustion, leading to better fuel efficiency.
(b) Effects of Undercooling the Charge Air:
If the charge air is not adequately cooled before entering the engine, several negative consequences can occur:
- Reduced Power Output: Hotter air entering the cylinders is less dense, containing fewer oxygen molecules. This leads to a leaner air-fuel mixture, resulting in reduced power output compared to what would be achieved with cooler, denser air.
- Increased Exhaust Gas Temperatures: With less air for cooling during combustion, the overall temperature within the cylinder rises. This leads to higher exhaust gas temperatures, putting additional stress on engine components.
- Increased Emissions: Higher combustion temperatures can promote the formation of nitrogen oxides (NOX) in the exhaust. Undercooled charge air can contribute to exceeding emission regulations.
- Increased Risk of Detonation: Detonation, also known as knocking, is a phenomenon of uncontrolled burning within the engine cylinder. Hotter intake air can increase the risk of detonation, leading to potential engine damage.
- Reduced Engine Life: The combination of higher temperatures, increased stress on components, and potential detonation can accelerate wear and tear, reducing engine lifespan.
Therefore, proper functioning of the charge air cooler is essential for maintaining optimal engine performance, efficiency, and longevity.