Experimental tests for the after treatment system validation of an offroad diesel engine

This Master Thesis deals with experimental tests performed to validate the after treatment system of a Kohler KDI 3404 diesel engine used on off-road applications, such us agricultural or earth-moving machines. In the first chapter is given an overview on the main characteristics of Diesel engines, with an analysis of pollutant substances emitted by these systems. The emission limits adopted, over the course of the years, in Europe and USA is presented in chapter 2. The experimental tests performed on the after treatment system are presented in chapters 3, 4, 5. In particular in the third chapter the fine-tuning of the DeSOx strategy acting on the SCR system of a Tier4 KDI 3404 engine is analyzed. This model was already defined inside the control unit software, but it has been important to refine the temperature thresholds at which the DeSOx strategy is activated and the SOx model desorption rates, in order to reach a better alignement with experimental data and to ensure the best regeneration on the working field. Tests presented in the fourth chapter has been done to study how the DOC and DPF systems works together, on a KDI 3404 Stage V, with the aim of understanding the soot accumulation behaviour on the DPF filter. Different working cycles, such as NRTC transient and low load, has been used at the dyno-brake to obtain soot accumulation results. Finally the fifth chapter is focused on the analys and characterisation of possible urea deposits inside SCR of a KDI 3404 Stage V engine. In the last part of the work the conclusions about the usefulness of these activities, with respect to after treatment system development, is explained.