Diesel engines draw air only, past the intake valve into the cylinder. Fuel is injected into the cylinder at high pressure. The amount of fuel injected varies to suit load, and control engine speed.
For all diesel engines, at a fixed fuel setting, the amount of fuel delivered to the engine will increase as engine and pump speed increases. It must be controlled, or over-speeding of the engine will occur.
The cetane rating of a diesel fuel defines how easily the fuel will ignite when it is injected into the cylinder. The lower a fuel's cetane rating, the longer it takes to reach ignition point.
The primary factors that affect the performance of diesel fuel are: the cetane rating, viscosity, its cloud point, the the extent to which the fuel is contaminated.
The annoying rattle of a diesel engine has largely been subdued by a combination of engineering and fuel improvements, leading to quieter engines more suitable for use in passenger vehicles.
Clean diesel technology is a combination of better fuel delivery and control systems, better combustion chamber design, turbocharging, and other improvements including lower sulfur fuels and dual-fuel systems.
