Internal combustion engines produce air pollutants due to incomplete fuel combustion. The derivatives of incomplete combustion are carbon dioxide, water, and smoke, also known as particulate matter. These emissions are strictly regulated by the government. The emission of byproducts of the combustion process depends in part on the fuel-air mixture in the combustion chamber. One inefficient way, currently known, to reduce the emission of particulate matter is by increasing the amount of air used during the combustion process. However, such increase results in increased production of nitrogen oxides (NOx), which is also strictly regulated. To reduce the production of NOx, a higher level of exhaust gas recirculation (EGR) is used but unfortunately such use results in producing increased amounts of particulate matter. Other methods, like late injection timing, and high injection pressure can be used to reduce emissions of both NOx and particulate matter, but these have a high initial cost.
The internal combustion engine usually can be divided into two engine operation conditions namely: the low engine load condition and the high engine load condition. In the low load condition, emission of particulate matter is very challenging to control. However, it still has to meet strict governmental regulations. During low engine load operation, the air density in the combustion chambers is very low which offers little resistance to spray penetration of fuel from the fuel injectors. Therefore, with the current known technology, it is difficult to comply with the emissions regulations.
The nozzle of a direct injection fuel injector may have multiple holes to disperse the fuel quantity into the combustion chamber. The diameter and spray angle of the nozzle holes also have a very strong effect on combustion characteristics. Generally, all spray holes have same diameter and angle. Therefore such fuel injectors have uniform spray penetration. Large diameter nozzle holes present significant challenges in meeting emissions regulations under low engine load conditions. Due to uniform spray penetration either there is an insufficient amount of energy in the fuel spray or insufficient in-cylinder air motion to properly mix the air and fuel as needed for efficient combustion. These insufficiencies often lead to incomplete combustion and consequently, emission of higher quantities of particulate matter.
Thus, there remains a need in the art for apparatuses, methods, and systems of various nozzle holes and piston bowl shapes that when used together or separately produce less particulate matter and permit the engine to meet emissions regulations without sacrificing the performance of after treatment systems and service life.
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