How Is Urea Used in Diesel Engines?by Richard Rowe
Although diesel engines were once -- rightly so -- considered little more than industrial manufacturers of soot and smoke, modern advances in emissions and control technology have made the paragons of torque production a truly viable option from both an economic and emissions standpoint.
Diesel engines don't ignite the air fuel mixture with a spark. They squeeze the mixture until the air heats up and causes the fuel to explode. This process produces far more heat and pressure than is found in typical gasoline engines.
Air is composed of about 78 percent nitrogen. Under the kinds of extreme heat and pressures found inside diesel engines, this nitrogen combines with oxygen to form dangerous oxides of nitrogen -- NO and NO2, collectively referred to as NOx. NOx emissions contribute to smog, deplete oxygen in water and play a large role in the formation of acid rain.
Urea is an organic compound commonly found in the urine of mammals. The compound controls nitrogen in the blood by bonding with the NOx molecule and rendering it harmless. This compound produces the same effect when injected into the NOx-rich exhaust stream of a diesel engine, reducing harmful emissions by as much as 80 percent, as in the case of Mercedes' BlueTec system.
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