Evaluation of Indrio’s Ammonia Sensor using a Diesel Fuel Based Burner Platform

This program involved the detailed evaluation of a novel laser-based in-exhaust ammonia sensor using a diesel fuel-based burner platform integrated with an ammonia injection system. Test matrix included both steady-state modes and transient operation of the burner platform. Steady-state performance evaluation included tests that examined impact of exhaust gas temperature, gas velocity and ammonia levels on sensor response. Furthermore, cross sensitivity of the sensor was examined at different levels of NO_X and water vapor. Transient tests included simulation of the FTP test cycles at different ammonia and NO_X levels. A Fourier transform infrared (FTIR) spectrometer as well as NIST traceable ammonia gas bottles (introduced into the exhaust stream via a calibrated flow controller) served as references for ammonia measurement. Results suggested that Indrio’s sensor exhibits a strong linear relationship with reference ammonia measurement across the tested range of 0 ppm to 200 ppm with a regression factor (R²) ~ 0.99. Exhaust flowrate did not have a significant impact on sensor performance. With no temperature compensation applied, Indrio’s sensor performance was not impacted by temperatures of the order of 300°C to 400°C, however, it slightly overestimated ammonia levels at lower temperatures (~200°C). Cross-sensitivity experiments indicated that the presence of 200 ppm NO_X resulted in less than 2.5% change in slope (Indrio sensor vs reference). Transient sensor response indicated that the sensor tracked reference ammonia concentration reasonably well. Overall, the sensor exhibited tremendous potential to serve as an accurate onboard ammonia sensor that could be used for real-time SCR control strategy optimization which will be invaluable for future low NO_X platforms.