Experiments on a light duty SCR test exhaust system using ammonia gas to provide data for validation of a CFD model
Experiments on a light duty SCR test exhaust system using ammonia gas to provide data for validation of a CFD model
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使用氨气对轻型 SCR 测试排气系统进行实验，为 CFD 模型验证提供数据
DOI：
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发表时间：
2011
期刊：
影响因子：
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通讯作者：
C. A. Roberts
中科院分区：
文献类型：
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作者：
S. Benjamin;M. Gall;M. Sturgess;C. A. Roberts
SCR催化剂中反应的建模是一个具有挑战性的过程，但动力学方案在文献中可用，这些动力学方案来自于使用特定催化剂的反应器测试。本文报道了在一台轻型共轨柴油机上安装铜分子筛SCR的试验结果。实验旨在为CFD模型验证提供数据。研究了四种不同长度的SCR催化剂砖：30、45、75和91 mm。试验是在NO2：NOx比为0.05、0.46、0.62和0.82左右时进行的.研究了三种氨剂量水平。这些是缺乏氨，即NH3：NOx比约0.5，化学计量，其中该比接近1.0，以及过量氨，比大于1.0。基于已有的动力学，采用多孔介质方法建立了一维稳态CFD模型。大多数实验是在约220 °C的低排气温度下进行的，但也研究了接近300 °C的情况。计算流体力学预测与测量结果的比较表明，动力学方案给出了中等的预测与化学计量的氨供应到排气和NO 2：NOx的比例接近50%，但该模型是不适合其他条件。对于短砖和氨水平不足，NOx消耗量明显高于预测。这些数据是在真实的发动机排气中以比用于推导动力学的空速高得多的空速获得的;因此，这项研究是对动力学模型的有力检验。正在尝试修改计算流体动力学模型，以提供与实验观察更接近的协议。
Modelling of reactions in SCR catalysts is a challenging process, but kinetic schemes are available in the literature derived from reactor tests with specific catalysts. This paper reports experiments on a light duty common rail diesel engine and test exhaust fitted with copper zeolite SCR. The experiments aimed to provide data for CFD model validation. Four different lengths of SCR catalyst brick were investigated: 30, 45, 75 and 91 mm. The tests were undertaken for NO 2 :NOx ratios of 0.05, 0.46, 0.62 and 0.82 approximately. Three ammonia dosing levels were investigated. These were deficient ammonia, i.e. NH 3 :NOx ratio about 0.5, stoichiometric, where the ratio was near 1.0 and excess ammonia, ratio greater than 1.0. A 1D steady state CFD model using the porous medium approach was developed based on available kinetics. Most of the experiments were at low exhaust temperature around 220 °C but a case near 300 °C was also investigated. Comparison of CFD predictions with measurements showed that the kinetic scheme gave moderate predictions with a stoichiometric ammonia supply to the exhaust and an NO 2 :NOx ratio near 50 % but that the model was inadequate for other conditions. There was notably more NOx consumption than predicted for short bricks and for deficient ammonia levels. The data were obtained in a real engine exhaust at much higher space velocities than those used to derive the kinetics; this study is therefore a strong test of the kinetic model. Attempts to modify the CFD model to provide closer agreement with experimental observations are ongoing.