Combined Silencers and Urea-SCR Systems for Heavy-Duty Diesel Vehicles for OEM and Retrofit Markets

One OEM UREA-SCR SILENCER, comprising a silencer with built-in catalyst. The system was tested on a Scania DC1205 320 kW diesel engine, which was calibrated for the Euro II emission standard. The test results showed that it is possible to reduce more than 85% of the NOx emission with an insignificant NH₃ slip in the ETC transient test cycle. The pressure-drop of the system was measured at 80% of that of the engine's original silencer and the silencing performance was improved for low frequencies below 125 Hz.

One RETROFIT UREA-SCR SYSTEM for HD engines, comprising a silencer with built-in catalyst, an electronic urea injection control system, urea injection and a urea tank. The importance of injection strategy and the relation between urea/NOx ratio, ammonia slip and obtained NOx-removal was elucidated by transient tests with a 10 liter 190 kW Volvo HD excavator engine on test rig. NOx-removals of 77 to 88% were demonstrated in ETC and the European ISO 8178C1 off road test cycles with essentially no ammonia slip. 99.7% NOx reduction was obtained with a high NH₃-slip of about 100 ppm, illustrating the potential of the urea SCR technology. The silencer contained 29 liter catalyst.