Group 1: Mechanism of Urea Consumption in Diesel Engines - Diesel engines utilize SCR technology to meet National VI emission control requirements, with urea being an essential reagent for purifying NOx pollutants in exhaust gases [1] - The amount of urea consumed primarily depends on the total NOx in the exhaust (exhaust flow rate, NOx concentration) [1] - NOx is the main pollutant in diesel engine exhaust, and its generation is influenced by the oxygen concentration in the cylinder and combustion temperature [1] - The SCR technology works by injecting a 32.5% urea solution into the exhaust, where it hydrolyzes to form NH3, which then reacts with NOx in the SCR catalyst to produce N2 and H2O [1] Group 2: Increase in Urea Consumption for High-Efficiency Diesel Engines - Compared to engines using EGR technology, high-efficiency SCR engines have increased fresh intake air and higher oxygen concentration in the cylinder, leading to more complete combustion and reduced fuel consumption [4] - Higher combustion temperatures (above 1600°C) significantly increase NOx generation, necessitating more urea consumption to meet National VI emission regulations [4] Group 3: Reduction in Comprehensive Fuel and Urea Costs - For diesel engines using SCR technology, fuel consumption and urea consumption are interrelated; reduced fuel consumption leads to increased urea consumption [5] - The overall liquid consumption cost of high-efficiency diesel engines decreases despite the increase in urea consumption, as the cost savings from reduced fuel consumption outweigh the increased urea costs [5] - High-efficiency diesel engines show a fuel consumption reduction of 4% to 7% and a comprehensive fuel-urea cost reduction of 3% to 5% compared to EGR technology engines [5] Group 4: Factors Affecting Urea Consumption - Urea consumption is not a stable value and is influenced by driving habits and operating conditions [6] - High urea consumption can result from aggressive driving, heavy loads, poor-quality urea, or high-sulfur diesel [6] - Low or no urea consumption may occur due to SCR system failures or low-load/idle conditions [7] Group 5: Normal Urea-Fuel Ratio for National VI Diesel Engines - The urea-fuel ratio for EGR models ranges from 4% to 8%, while for non-EGR models, it ranges from 6% to 12% [8] Group 6: Recommendations for Reducing Urea Consumption - Ensure proper vehicle maintenance and use of compliant diesel and urea solutions [9] - Develop good driving habits, such as minimizing rapid acceleration and avoiding prolonged idling [10][11]