Why should diesel vehicles add urea?

Diesel vehicles are rare in China. Few car factories produce diesel cars. Only SUVs, pickups, MPVs, buses and other vehicles use diesel engines. Why do diesel vehicles need urea?

Diesel vehicles need urea to reduce vehicle exhaust emissions and protect the atmospheric environment. Because diesel vehicles use urea to purify nitrogen oxides in engine exhaust.

The composition of diesel exhaust gas is basically the same as that of gasoline vehicle, but diesel engine does not use three-way catalytic converter, because diesel engine adopts diffusion combustion, which is different from premixed combustion of gasoline engine. The intake system of diesel engine has no throttle, and the power is adjusted by fuel injection. The larger the intake air, the better, which leads to the diesel engine being in oxygen-enriched combustion state most of the time, and the oxygen concentration in the exhaust gas is too high.

In the past, diesel engine exhaust could meet the standard directly, so there was no exhaust purification device. However, with the increasingly stringent emission standards, diesel engines generally adopt urea injection technology (SCR) to control exhaust emissions.

In addition to the fuel tank, there is also a urea box on the diesel car. As long as the diesel engine is started, urea will be consumed, so urea on diesel vehicles is a consumable. Generally speaking, every 100 liter of gasoline consumes 4 liters of urea, and the specific consumption is related to road conditions, load and engine displacement.