A study of optimization NOx reduction quality with different types of urea injectors in an SCR system

The heavy-duty diesel engines have created effective method to reduce nitrogen oxide (NOx) pollutions with selective catalytic reduction (SCR) system. This study deals with problems in the urea evaporation and decomposition process, the ammonia gas distribution in SCR system and ammonia pattern at inlet of catalyst. The test system used a 12,000 cc heavy-duty diesel engine for parameter and two types of urea injectors, an L-type and an I-type. The uniformity of the ammonia was sampled at the catalyst inlet using a gas sensor, and samples of NOx from each urea injector were compared by experiments and simulations using STAR-CCM+ software. The results elucidate the saturation phenomena, vaporization phenomena, urea distribution patterns, and NOx reduction efficiency value from the two types of urea injectors. The study on the extent of NOx reduction at the catalyst inlet demonstrate the different chemical mechanisms governing the ammonia concentration distribution and the mixing process quality with NOx.