RESUMEN
Exhaust gas recirculation (EGR) and selective catalytic reduction (SCR) are crucial technologies for mitigating nitrogen oxide (NOx) emissions in diesel engines. Although EGR reduces engine outlet NOx emissions, it simultaneously increases diesel consumption, leading to a poor economic performance. SCR requires AdBlue consumption; thus, striking the right balance for overall engine economy is of utmost importance. This study aims to evaluate NOx emission control and fluid cost in diesel engines. The total fluid cost of the diesel engine includes diesel and AdBlue. The engine is equipped with an aftertreatment system comprising a diesel oxidation catalyst (DOC), diesel particulate filter (DPF), selective catalytic reduction (SCR), and ammonia slip catalyst (ASC). The study was carried out at 1600 and 2100 rpm (25, 50, 75, and 100% load). The results show that with the increase of EGR valve opening, the exhaust temperature increased, the brake-specific fuel consumption (BSFC) increased, and the NOx emission decreased. With the increased AdBlue dosage, the NOx conversion efficiency gradually improved, ultimately approaching near-zero NOx emissions. However, as NOx emissions decreased, the equivalent diesel fluid cost rose. At 1600 r/min (100% load), when the NOx emissions were reduced by zero, the maximum fluid costs were 235, 223, and 218g/(kW·h) under the AdBlue/diesel price ratios of 1/1, 1/2, and 1/3, respectively. As the AdBlue/diesel price ratio decreases, the influence of EGR on the fluid cost diminishes. Coordinated control of EGR and AdBlue allows for reduced NOx emissions while mitigating the overall cost of diesel engines and aftertreatment systems. This research provides valuable guidance for EGR and urea control in diesel engines and contributes to the field of diesel engine emission control.
RESUMEN
Nitrogen oxides (NO x ) are the main emissions of diesel engines. Selective catalytic reduction (SCR) is the main technology used to reduce NO x emissions from diesel engines. NO x conversion efficiency and ammonia (NH3) escape are the main indicators to evaluate SCR performance. In this work, the effects of diesel engine exhaust temperature and exhaust mass flow rate on the SCR performance under different atmospheric pressures were studied by the combination method of experiment and one-dimensional numerical simulation. At the same time, the response surface method (RSM) was used to analyze the interaction of atmospheric pressure, exhaust temperature, and exhaust mass flow rate on the SCR performance. The results show that the lower the atmospheric pressure, the lower the NO x conversion efficiency and ammonia escape. Under the same exhaust temperature, the lower the atmospheric pressure, the smaller the impact of exhaust mass flow rate on NO x conversion efficiency. According to the RSM results, the optimal NO x conversion efficiency is 78.6% under the combination working conditions of an atmospheric pressure of 100 kPa, exhaust temperature of 395 °C, and exhaust mass flow rate of 250 kg/h, and the NH3 escape is also at a low level of 1.7 g/cycle.