Abstract
The uniformity of ammonia is very crucial for reducing the NOX emissions in a selective catalytic reduction system since the uniformity highly affects the chemical reaction between the ammonia and NOX emission. However, increasing ammonia uniformity in a short time period while injecting a urea solution is not a trivial task. Therefore, in this study, the uniformity of various urea injector designs is compared and an optimal design for the urea injector angle and direction is selected. The uniformity index (UI) was calculated using numerical analysis and compared with experimental result to achieve high reliability. The boundary condition of the analysis is extracted from the dominant operating region of the non-road transient cycle (NRTC) to guarantee a realistic analysis result. The design candidates were generated from the combination of three urea injection angles and eight urea injection directions and thoroughly compared to provide an insightful analysis. The conclusion is that injecting urea in the opposite direction to the main stream of exhaust gas increases the kinetic energy and thus the uniformity is highly increased. For example, urea injection in the opposite direction and angle to the mainstream flow could increase the UI to 0.966, which is a 16.7% improvement compared to the same direction and angle injection.
Highlights
Diesel engines have the advantages of a high thermal efficiency and reliability compared to other internal combustion engines
The existing aftertreatment equipment satisfied the exhaust gas regulations by installing a diesel oxidation catalyst (DOC), diesel particulate filter (DPF), or lean NOX trap (LNT), which operate without an additional injection system
The reliability of numerical analysis was determined based on an SCRinstalled exhaust gas aftertreatment device experiment
Summary
Diesel engines have the advantages of a high thermal efficiency and reliability compared to other internal combustion engines. Despite the high thermal efficiency of compression ignition engines, these engines have the disadvantage of producing a large amount of exhaust gas compared to spark ignition engines. With increasing attention toward the environmental pollution of automobiles, strengthened emissions regulations were adopted, making the installation of additional aftertreatment equipment inevitable [2,3]. Three-way catalyst devices cannot be installed due to the low exhaust gas temperature and operating air–fuel ratio; numerous aftertreatment equipment installations are necessary [4,5]. The existing aftertreatment equipment satisfied the exhaust gas regulations by installing a diesel oxidation catalyst (DOC), diesel particulate filter (DPF), or lean NOX trap (LNT), which operate without an additional injection system
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