Modeling and Simulation of Urea Dosing System

Sammanfattning: To protect our health and environment from pollution, among others regulatory agencies in the European Union (EU) and legislation from the U.S. Environmental Protection Agency (EPA) has required that pollutants produced by diesel engines - such as nitrogen oxides (NOx), hydrocarbons (HC) and particulate matter (PM) - be reduced. The key emission reduction and control technologies available for NOx control on Diesel engines are combination of Exhaust Gas Recirculation (EGR) and Selective Catalytic Reduction (SCR). SCR addresses emission reduction through the use of Diesel Exhuast Fluid (DEF), which has a trade-name AdBlue. Which is 32.5% high purity urea and 67.5% deionized water, Adblue in the hot exhaust gas decomposes into ammonia (NH3) which then reacts with surface of the catalyst to produce harmless nitrogen(N2) and water (H20). Highest NOx conversion ratios while avoiding ammonia slip is achieved by Efficient SCR and accurate Urea Dosing System it’s therefore critical we model and simulate the UDS in order to analyze and gain holistic understanding of the UDS dynamic behavior. The process of Modeling and Simulating of Urea Dosing System is a result of a compromise between two opposing trends. Firstly, one needs to use as much mathematical models as it takes to correctly describe the fundamental principles of fluid dynamics such as, (1) mass is conserved (2), Newton’s second law and (3) energy is conserved, secondly the model needs to be as simple as possible, in order to express a simple and useful picture of real systems. Numerical model for the simulation of Urea Dosing System is implemented in GT Suite® environment, it is complete UDS Model (Hydraulic circuit and Dosing Unit) and it stands out for its ease of use and simulation fastness, The UDS model has been developed and validated using as reference Hilite Airless Dosing System at the ATC Lab, results provided by the model allow to analyze the UDS pump operation, as well the complete system, showing the trend of some important parameters which are difficult to measure such as viscosity, density, Reynolds number and giving plenty of useful information to understand the influence of the main design parameters of the pump, such as volumetric efficiency, speed and flow relations.