Drivers will now know exactly if their vehicle meets the mandatory emission levels.
Exhaust gas post-treatment is of paramount importance to reduce harmful emissions from vehicles.
Along with reducing carbon dioxide (CO2) emissions, reducing harmful nitrogen oxides is one of the biggest challenges for the automotive industry. This is why in 2011 the German tire manufacturer and technology provider to the automotive industry, Continental, is working on the development of a Selective Catalytic Reduction (SCR) system.
Many passenger cars and commercial vehicles with diesel engines are already equipped with this SCR system. In this technology, an aqueous solution of urea reacts with nitrogen oxides in engine exhaust gases, and thus harmful nitrogen oxides are converted into harmless nitrogen and water. The effectiveness of this process depends on accurate measurement of urea level and concentration. It is because of the importance of these metrics that Continental is launching a dedicated sensor for the first time to help further improve the performance of SCR systems and measure their effectiveness. The urea sensor can measure the quality, level and temperature of the urea solution in the tank. A number of car manufacturers are planning to use this new Continental technology in their models.
“Our urea sensor technology complements SCR systems. The sensor provides data that helps to clarify the amount of urea injected in accordance with the current engine load. This data is needed to diagnose exhaust aftertreatment and urea levels in the engine to help the driver fill the AdBlue on time, ”explains Kallus Howe, director of sensors and propulsion systems at Continental. The new Euro 6 e emission standard requires diesel vehicles to have a urea-injected SCR catalytic converter, and the integration of a new Continental sensor into the system will increase driver confidence in the vehicle's exhaust aftertreatment functions.
The innovative sensor uses supersonic signals to measure the concentration of urea in the water and the fuel level in the tank. For this, the urea sensor can be welded either into the tank or into the pump unit.
The amount of solution injected should be calculated based on the instantaneous engine load. To calculate the exact injection quantity, the actual urea content of the AdBlue solution (its quality) must be known. Also, the urea solution should not be too cold. Therefore, to ensure the constant readiness of the system, it is necessary to control the temperature in the urea tank, if necessary, activating the heating system. Last but not least, there must be a sufficient amount of urea in the tank as the supersonic sensor allows the liquid level in the tank to be measured from the outside. It is not only a key element of frost resistance, but also prevents corrosion of sensor elements or electronics.
The measuring cell in the sensor contains two piezoceramic elements that emit and receive supersonic signals. The level and quality of the solution can be calculated by measuring the vertical travel time of supersonic waves to the surface of the liquid and their horizontal velocity. The sensor uses the ability of supersonic waves to travel faster in a solution with a higher urea content.
To improve the measurement even when the vehicle is in an inclined position, a second level measurement is provided to provide a reliable signal on high slopes.