Clean Diesel Technology

The development of clean diesel is actually a composite of three different evolved aspects working together to make diesel engines greener and more efficient; to achieve these goals, engineers have utilized clean fuels, cleaner engines, and emission controls.

Fuels

Clean fuel is the sole aspect that isn't completely controlled by the automotive industry. While it's true that researchers and engineers who work in fuel industries develop cleaner fuel options, in the end it is a governmental decision to implement regulations that require the importation and use of cleaner fuels and banning fuels which cause harmful emissions. Ultra Low Sulfur Diesel (ULSD) began arriving in the United States in 2006 ("Diesel Fuel"). The new cleaner diesel fuel has 15 parts per million of sulfur whereas its predecessor had 500 parts per million of sulfur content. ULSD allows for a reduction in sulfur emissions as well as the implementation of other emission controls that would not be possible with a high sulfur concentration ("State Legislature" 8).

Engines

Cleaner diesel engines incorporate high pressure fuel injectors and stronger materials in the engine block to make the engine more efficient. The fuel injectors spray the fuel into the cylinder to cause an explosion and move the pistons. Because there is no spark to ignite the fuel, fine fuel particulates must be introduced into the cylinder, which ignite because of the high pressure (Aoyagi 49-66). Currently the newest fuel injectors being developed inject fuel into the cylinder at around 35,000 psi; the higher the injection pressure into the cylinder, the finer the fuel mist that is injected into the cylinder. This means that more fuel is burned inside the cylinder and less is expelled as exhaust, which would raise the emissions of the engine.

The new materials and forging processes available to engineers today also allow for the construction of cleaner, more efficient engines. New composite materials and a better understanding of the mechanics behind engines have allowed engineers to develop engines which transform more of the energy in the fuel into mechanical energy. This also allows for a reduction in the amount of energy that is lost as heat (Aoyagi 49-66). Such technology actually has benefitted all types of engines, but it's more noticeable on diesel engines for which technology hasn't changed drastically since it was created.

Exhaust Control

Post-combustion filters and catalytic converters also are used in the exhaust pipe to trap particulate matter that escapes from the cylinder. The NOx and particulate matter emissions can be brought down to near the level of hybrid cars with a combination of fine filters and catalytic converter technologies. Currently, new catalytic converters are being developed that contain urea, which reacts with NOx particulates and renders them harmless (Nice), another potential future improvement in exhaust control.