1. Higher Compression Ratio: CI engines typically operate at much higher compression ratios compared to SI engines. This higher compression ratio helps in reducing the ignition delay of the fuel, ensuring that the fuel ignites before the piston reaches the top of the cylinder. As a result, CI engines are less prone to detonation, even with increased boost pressure.
2. Slower Burn Rate: Diesel fuel has a slower burn rate compared to gasoline. This means that the diesel fuel takes a longer time to burn inside the cylinder. The slower burn rate reduces the pressure rise rate during combustion, thereby mitigating the risk of detonation.
3. Fuel Injection Timing: In CI engines, fuel is injected directly into the cylinder near the end of the compression stroke. This ensures that the fuel droplets have a shorter distance to travel before reaching the hot air and igniting. This reduces the chances of auto-ignition, which can lead to detonation.
4. Fuel Quality: Diesel fuel has a higher cetane number compared to gasoline's octane number. The cetane number represents the ignition quality of diesel fuel. A higher cetane number indicates that the fuel ignites more readily. This allows for a finer control of the ignition timing, preventing premature ignition and reducing the likelihood of detonation.
In summary, the higher compression ratio, slower burn rate, precise fuel injection timing, and fuel properties of CI engines make them more suitable for pressure charging compared to SI engines, resulting in improved performance and efficiency without the risk of detonation.
