Selective Catalytic Reduction (SCR) revolves around the use of a urea solution that is injected into diesel engine exhaust gas to virtually eliminate all NOx emission. A mixture of 32.5% high purity urea in deionized water has been set as the standard fluid. Component development and testing of pumps and nozzles requires a high resolution meter to cover the low flow rates used.
The purpose of the SCR system is to reduce levels of NOx (oxides of nitrogen emitted from engines). Small quantities of a urea solution, DEF (diesel exhaust fluid) as it is known in the U.S. and AdBlue as it is known in Europe, are injected into the exhaust upstream of a catalytic converter where it vaporizes and decomposes to form ammonia and carbon dioxide. The ammonia in conjunction with the SCR catalyst, converts the NOx to harmless nitrogen (N2) and water (H2O).
While most engines will have a dose rate of 2% of diesel fuel consumed, the dose rate will range from 1% to 3%. To measure these low "cc per minute" rates, the Max Model P213 is often specified for its 1000 pulse/cc resolution and its +/- 0.2% linearity. With such a high resolution, small incremental flow changes can be created and maintained to verify efficiency in pumping, nozzle design, temperature gradients and injection chamber design. For even higher resolution, the Model P001 has an output of 12000 pulses/ml and can accurately measure flow profiles and sub milliliter injections. If you would like to get a quote on the meter which is becoming the industry standard, please let us know.