With the increasingly strict government exhaust regulations, major engine manufacturers optimize SCR systems (Selective Catalytic Reduction Technology) to meet environmental requirements. SCR system is widely recognized as exhaust emission treatment system in diesel engines. And AdBlue is an essential additive for SCR system.
AdBlue is an organic compound composed of carbon, nitrogen, oxygen and hydrogen. The AdBlue solution used in the aftertreatment is a high-purity solution containing 32.5% urea and 67.5% deionized water. When heated to 160°C, it decomposes into ammonia Gas (NH3) and water. AdBlue plays a key role in vehicle power, fuel consumption and exhaust emission. The urea quality sensor is installed in the urea tank to monitor the quality of urea in real time. At present, ultrasonic measurement is a more mature scheme in the market.
How Do Ultrasonic Sensors Analyze the Quality of AdBlue?
Main working principle: Since the propagation speed of ultrasonic waves in different media is different, we can use this feature to identify urea and detect urea concentration. Within a fixed distance, the flight time of ultrasound in different media and different urea concentrations is not the same.
Figure 1 establishes the corresponding curves of propagation speed and temperature in different media (water, coolant, air, urea solution, etc.), and fits the corresponding functional relationship. The figure shows that the propagation speed of ultrasonic waves in different media is inconsistent. At a fixed distance internally, water and urea are identified by the inconsistency of flight time.
Figure 2 establishes the corresponding curves of different urea concentrations and propagation speeds, and fits the corresponding functional relations. The figure shows that the propagation speed of ultrasonic waves in different concentrations of urea is inconsistent. Within a fixed distance, different flight times can be used to identify different concentrations of urea.
The ultrasonic sensor (transceiver) is used to send out sonic pulses to the reflection baffle and then reflect back to the sensor. The average time of flight (TOF) is calculated through multiple cycles. The TOF is almost constant at a fixed temperature and a urea concentration of 32.5%.
Audiowell launched the urea quality sensor HQ0084-000, which can monitor the quality and concentration of urea by testing the flight time in the medium (urea).
-Accuracy<1% (with matching circuit)