Development of an Automated Testbench for Functional Testing of Dosing Unit

Increasingly stringent emission regulations continue to be legislated around the world to signifi-cantly minimize pollutants released to the air by internal combustion engines. After Treatment Systems (ATS) meant for reducing oxides of nitrogen (NOx) in the exhaust into non-harmful species have evolved at a rapid pace over the past two decades. Stringent emissions requirements have driven complex ATS architecture through sensors to measure delta-pressure, NOx, and tem-peratures. Accurate and precise performance of individual components as well as the integrated ATS is required to ensure regulatory compliance and efficient performance. Both of which require substantial amounts of performance and validation testing. Manufacturers have been developing the ability to accurately and efficiently test the ATS components. To meet the norms for tail pipe or stack emissions of NOx in ‘as new’ condition and during the entire ‘emissions useful life (EUL)’ of the ATS, all components of an ATS must perform with high accuracy, every single time. A well designed ‘automated testbench’ ensures better accuracy in testing the functionality of many parts of the ATS, as rapidly as possible. Dosing Unit (DU), also known as the Urea Dosing Unit, in the ATS is responsible for delivering urea as needed into the exhaust airstream thereby helping in the reduction of NOx from the tail pipe or exhaust stack in the SCR (Selective Cata-lytic Reduction). This paper describes the development of an automated testbench to validate the performance of the dosing unit. The test bench is designed such that both new and used (returned from field) ATS can be tested or evaluated for performance. The automated testbench for urea dosing has been developed at the Cummins Technical Center in India (CTCI) keeping in mind the needs for similar testbenches for Cum-mins use in other parts of the world. The test bench design, build, and test process and protocol have been formulated such that the same test bench can be used to test urea dosing units to meet emission standards defined by EPA, CARB, EURO, NS, and other international standards.