Simulation Study on Prediction of Urea Crystallization of a Diesel Engine Integrated after-Treatment Device

Abstract

An integrated after-treatment device model was established for our target engine based on the fluid simulation software (Converge), and simulation was performed to determine the NH 3 , temperature, and velocity uniformity at the front-end cross section of its SCR catalyst, urea deposition rate, liquid film mass of the mixer, and its positions under a low-load condition. Moreover, the structure of the mixer and injection pressure were optimized to improve the uniformity and reduce the liquid film mass. Our simulation results show the following facts: the liquid film is easily accumulated under a low-load condition and the structure of the mixer and the injection pressure significantly affect the urea deposition rate and uniformities and accumulation masses of the liquid film. As a result, our final optimization results indicate that the mass of the NH 3 and the NH 3 uniformity at the front-end cross section of the SCR catalyst increase by 2.83 times and 5.65%. The urea deposition rate and the cumulative mass of the liquid film fall by 4.82 and 10.4%, respectively. This study has certain theoretical guiding significance for the optimal design of this type of after-treatment devices.

Combination of Pilot Injection and a NH3-SCR System To Reduce NOx Emissions of a Nonroad Compression Ignition Engine

“…At present, an SCR system is generally utilized to offer high level of NOx reduction. , In the SCR system, an aqueous solution of nontoxic urea is generally used as a reductant agent for the reduction of NOx to N 2. , To accelerate the reactions concerning the NOx reduction, catalysts such as zeolite- and vanadium-based ones are required to reduce the activation energy and enable the occurrence of reactions at the exhaust gas temperature range of the engine . As reviewed by Vignesh and Ashok, with a given catalyst and the SCR configuration, the reduction degree of NOx emissions depends upon the quantity of the reductant agent and the reaction conditions generated by the engine operating conditions such as exhaust gas temperature, NOx emission level, and engine speed.…”