Flow analysis and uniformity evaluation of the exhaust pipeline of a marine diesel engine

  Objectives  In a marine diesel engine, the SCR reactor's NOx conversion efficiency is effected by the flow field uniformity at the inlet. In order to optimize the design of the exhaust pipeline of the diesel engine and the improve the SCR reactor's conversion efficiency, the establishment of a reasonable evaluation system for the flow field uniformity at the inlet has great significance.

  Methods  Based on the exhaust pipeline of a marine diesel engine, the flow properties of the exhaust pipeline were analyzed under the rated condition. Based on these results, the flow field uniformity at the inlet of the SCR reactor was evaluated by different evaluation indicators. Then, the otherness and applicability of different evaluation indicators were analyzed and compared.

  Results  The results show that, the pressure loss at the bending and abrupt parts of the pipeline accounts for about 20% of that of the exhaust system, and the bending in front of the entrance of the SCR reactor has a great influence on the flow field uniformity of the entrance with the local maximum non-uniformity as high as 19.96%.

  Conclusions  It can be concluded that, the inlet face of the SCR reactor should be kept at a distance from the bending and abrupt parts to improve the flow field uniformity at the inlet, and the uniformity index γ and the local maximum non-uniformity δ can more effectively evaluate the flow field uniformity at the inlet of the SCR reactor in the exhaust system of the marine diesel engine. The study in this paper provides an important reference for the reasonable evaluation of the uniformity of the flow field.