Core components and functions of urea post-treatment
2025-08-20
urea tank
Function: Store urea solution for vehicles (usually 32.5% urea aqueous solution) and provide reaction materials for SCR systems.
Structure: including box shell, liquid level sensor, temperature sensor, suction tube, return tube, and heating pipeline (for low-temperature thawing).
Key points: It is necessary to have corrosion resistance and reserve expansion space (the volume expands by about 9% when urea freezes).
urea pump
Function: Accurately transport urea solution from the urea tank to the nozzle and control the injection pressure.
Type:
Gas assisted urea pump: Assisted by compressed air injection, an electrically controlled nozzle is required to prevent premature urea injection (such as when the pressure reaches 700kPa).
Non gas assisted: direct injection controlled by pump body pressure.
Structure: Integrated metering pump, compressed air solenoid valve, heater and controller, with fault self diagnosis function.
urea nozzle
Function: Atomize urea solution and spray it into the exhaust pipe to undergo catalytic reduction reaction with NOx in the exhaust gas.
Installation requirements:
Angle: The recommended installation angle for the exhaust pipe diameter is 45 °~85 °, with an axial angle of 275 °~315 °, to avoid direct injection or deposition of urea onto the pipe wall.
Cooling: It is necessary to connect the engine cooling water pipeline to prevent high temperature damage.
SCR catalytic converter
Function: Provide a reaction site to convert the ammonia gas (NH3) produced by urea decomposition and NOx into harmless nitrogen gas (N ₂) and water (H ₂ O) under the action of a catalyst.
Condition: The reaction requires the presence of a catalyst and a temperature above 200 ℃.
Types: Bucket type (suitable for limited space scenarios such as buses) and box type (suitable for different vehicle configurations).
Sensors and controllers
Nitrogen oxygen sensor (NOx sensor): monitors the concentration of NOx after catalytic reaction, and feeds back the signal to the DCU (Dosing Control Unit) for closed-loop control.
Liquid level/temperature sensor: Real time monitoring of urea tank liquid level and temperature to prevent system failure caused by low-temperature crystallization or low liquid level.
DCU controller: calculates urea injection quantity, coordinates engine ECU data, and ensures accurate reduction of NOx.
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Core components and functions of urea post-treatment
