Experimental investigation of the effects of different parameters on NOx emissions in a selective catalytic reduction system

In this study, it is aimed to examine the NOx conversion efficiency in different parameters by installing an SCR system on a single-cylinder diesel engine. SCR systems are generally in communication with the engine electronic control unit. Depending on the current operating conditions of the engine, DEF is sprayed under the conditions determined by the manufacturer and the efficiency of the system is checked. Therefore, SCR electronic control unit and software independent of the engine have been created in our experimental system. The fact that we can intervene in the system as we wish reveals the importance of this study. For this purpose, the exhaust system suitable for the specified test engine was designed and the DEF injector characteristic was extracted. In the experimental system, the effects of DEF injection amount, exhaust gas temperature, DEF temperature, different DEF ratios and SCR mixer on NOx emissions were investigated experimentally. The best NOx conversion was achieved when the injection amount was at a flow rate of 400 mg/s and at temperatures 300 °C above the exhaust temperature. In experiments performed at different DEF temperatures, maximum NOx conversion efficiency was obtained when the DEF temperature was 40-45 °C. At different DEF ratios, it was seen that the best conversion efficiency was DEF32. At the same time, it was observed that the NOx conversion efficiency increased up to 16% when a mixer was added to the system. As a result, with the experiments carried out, data were obtained that determine the optimum conditions in SCR systems, provide the best NOx conversion, obtain the minimum DEF consumption, and increase the system efficiency by reducing the negative conditions such as urea accumulation in the system.