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In exhaust systems with selective catalytic reduction (SCR) a fast conversion of liquid urea to gaseous ammonia and a uniform distribution of the ammonia vapor upstream of the SCR catalyst are essential to reduce the nitric oxides efficiently. For the prediction of the mixing process and the transport of ammonia vapor with the CFD method an accurate description of the turbulent flow field is a basic requirement. This paper presents the comparison of simulation results using three different turbulence models (high-Re kε-RNG model, low-Re kω-SST model, Reynolds stress model) with measurements of the turbulent velocity field using Laser Doppler Anemometry (LDA). The investigations were carried out for a SCR system with a swirl mixer on a cold flow test bench for two different volume flows. From the measured velocity signals different components of the Reynolds-tensor were derived.

A higher level of atomization of the fuel leads to a more homogeneous mixture with the air in internal combustion engines, whether they are equipped with direct injection or port fuel injected systems. The further break-up of the atomized fuel drops by the interaction of two fuel sprays is described in this paper. In the present research, a simulation of the collision and swirl of two fuel sprays in a double-injector engine concept is carried out through a qualitative comparison with the images obtained from the recorded video of the sprays and the results of the simulation. Previous work simulated and tested the spray interaction of fuel injectors on the top of the combustion chamber; while this research proposes a new approach to reduce the diameter of the atomized fuel drops through the direct collision of the sprays with injectors located oppositely and fully horizontally to get advantage of the flow’s momentum.