Optimization of urea SCR deNOx systems for HD diesel engines

摘要: In the past decade, SCR deNOx technology with urea injection has grown to maturity. European OEMs will apply meet future heavy-duty emissions legislation starting EURO-4 (2005/2006). Numerous research programs in Europe and US have shown a variety of system layouts control strategies. The main differences are formed by: engine-out NOx calibration; application an NO NO2 catalyst; open-loop or closed-loop dosage control. This paper gives overview possible configurations that required for different stages emission legislation. Engine-out is strongly influenced by ambient conditions. Projections this study show combination cold climate wintergrade fuel most severe: it may lead 30% lower respect laboratory varying requires safety margin case open-loop-controlled order avoid excessive NH3 slip. Calculations Euro 4 limits can be met dosage; catalyst not even required. For other (Euro 5, 2007 2010), becomes difficult safely achieve 2010 require because low average load consequently exhaust gas temperatures. Engines developed need special measures increase temperature reduce below 2 g/kWh. all cases, optimal hydrolysis mixing conditions major importance. High-speed photography droplet size measurements presented as methods characterizing modelling aqueous spray patterns. information from these used input parameters simulation tools. These consist 2D/3D CFD program analysis 1D model development optimization dimension. Finally, simulations compared on engine test bench.