Investigation of Urea Uniformity with Different Types of Urea Injectors in an SCR System

Abstract

Heavy-duty diesel engines in highway use account for more than 40% of total particulate and nitrogen oxide (NOx) emissions around the world. Selective catalytic reduction (SCR) is a method with effective results to reduce this problem. This research deals with problems in the urea evaporation process and ammonia gas distribution in an SCR system. The studied system used two types of urea injectors to elucidate the quality of ammonia uniformity in the SCR system, and a 12,000-cc heavy-duty diesel engine was used for experimentation to reduce NOx in the system. The uniformity of the generated quantities of ammonia was sampled at the catalyst inlet using a gas sensor. The ammonia samples from the two types of urea injectors were compared in experimental and simulation results, where the simulation conditions were based on experimental parameters and were performed using the commercial CFD (computational fluid dynamics) code of STAR-CCM+. This study produces temperatures of 371 to 374 °C to assist the vaporization phenomena of two injectors, the gas pattern informs the distributions of ammonia in the system, and the high ammonia quantity from the I-type urea injector and high quality of ammonia uniformity from the L-type urea injector can produce different results for NOx reduction efficiency quality after the catalyst process. The investigations showed the performance of two types of injectors and catalysts in the SCR system in a heavy-duty diesel engine.

Optimization of the Uniformity Index Performance in the Selective Catalytic Reduction System Using a Metamodel

“…This shows that the design parameters (D, E, and F) related to the mixer have significant contributions in improving the performance of the SCR system. The improvement of UI performance due to the optimization of the structural design parameters can also be confirmed by the experimental analysis carried out by Wardana et al [5] and Jeong et al [8]. Therefore, if optimization is focused on the design parameters of the mixer, it is estimated to be effective in reducing time and cost.…”

“…The uniformity index (UI) of ammonia is suitable for evaluating the SCR performance in a system because of its contribution to the NOx conversion efficiency and increase in the catalyst life [4]. Many factors should be considered before designing the SCR system [5,6]. In the SCR system, either the low density of NH 3 in the exhaust gas degrades the conversion efficiency of NOx or the catalyst is damaged by the excessive density of NH 3 [7].…”

Numerical and Experimental Investigation of Ammonia Uniformity in a Compact Selective Catalytic Reduction System

“…Smith et al 25 implemented a transition zone between the wall wetting and nonwall wetting regimes and showed a significantly improved correlation between simulation results and measurements of ammonia uniformity. Wardana et al 26 conducted numerical and experimental evaluation of ammonia uniformity using two different UWS dosers. Almost all studies on ammonia uniformity prediction in the literature have been conducted on systems with a relatively long mixing section.…”

Experimental Research on Distribution Characteristics of NOx Conversion Efficiency of a Diesel Engine SCR Catalyst

“…Wardana et al used two kinds of urea injection devices to study the ammonia uniformity of an SCR system . At the same time, the ammonia uniformity and urea injection time were studied to predict the NO x reduction efficiency of an SCR system. , Ehson et al realized the chromatographic measurement of ammonia concentration in a diesel engine exhaust .…”