There are many NOx removal technologies: exhaust gas recirculation (EGR), selective catalytic reduction (SCR), selective non-catalytic reduction (SNCR), miller cycle, emulsion technology and engine performance optimization. In this work, a numerical simulation investigation was conducted to explore the possibility of an alternative approach: direct aqueous urea solution injection on the reduction of NOx emissions of a biodiesel fueled diesel engine. Simulation was performed using the 3D CFD simulation software KIVA4 coupled with CHEMKIN II code for pure biodiesel combustion under realistic engine operating conditions of 2400 rpm and 100% load. To improve the overall prediction accuracy, the Kelvin-Helmholtz and Rayleigh-Taylor (KH-RT) spray break up model was implemented in the KIVA code to replace the original Taylor Analogy Breakup (TAB) model for the primary and secondary fuel breakup processes modeling. The KIVA4 code was further modified to accommodate multiple injections, different fuel types and different injection orientations. A skeletal reaction mechanism for biodiesel + urea was developed which consists of 95 species and 498 elementary reactions. The chemical behaviors of the NOx formation and Urea/NOx interaction processes were modeled by a modified extended Zeldovich mechanism and Urea/NOx interaction sub-mechanism. Developed mechanism was first validated against the experimental results conducted on a light duty 2KD FTV Toyota car engine fueled by pure biodiesel in terms of in-cylinder pressure, heat release rate. To ensure an efficient NOx reduction process, various aqueous urea injection strategies in terms of post injection timing and injection rate were carefully examined. The simulation results revealed that among all the four post injection timings (10 °ATDC, 15 °ATDC, 20 °ATDC and 25 °ATDC) that were evaluated, 15 °ATDC post injection timing consistently demonstrated a lower NO emission level. In addition, both the urea/water ratio and aqueous urea injection rate demonstrated important roles which affected the thermal decomposition of urea into ammonia and the subsequent NOx removal process, and it was suggested that 50% urea mass fraction and 40% injection rate presented the lowest NOx emission levels.
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ASME 2015 Internal Combustion Engine Division Fall Technical Conference
November 8–11, 2015
Houston, Texas, USA
Conference Sponsors:
- Internal Combustion Engine Division
ISBN:
978-0-7918-5728-1
PROCEEDINGS PAPER
Impact of Urea Direct Injection on NOx Emission Formation of Diesel Engines Fueled by Biodiesel
Wenming Yang,
Wenming Yang
National University of Singapore, Singapore
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Hui An,
Hui An
National University of Singapore, Singapore
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Jing Li,
Jing Li
National University of Singapore, Singapore
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Dezhi Zhou,
Dezhi Zhou
National University of Singapore, Singapore
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Markus Kraft
Markus Kraft
Cambridge CARES C4T, Singapore
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Wenming Yang
National University of Singapore, Singapore
Hui An
National University of Singapore, Singapore
Jing Li
National University of Singapore, Singapore
Dezhi Zhou
National University of Singapore, Singapore
Markus Kraft
Cambridge CARES C4T, Singapore
Paper No:
ICEF2015-1059, V002T04A005; 7 pages
Published Online:
January 12, 2016
Citation
Yang, W, An, H, Li, J, Zhou, D, & Kraft, M. "Impact of Urea Direct Injection on NOx Emission Formation of Diesel Engines Fueled by Biodiesel." Proceedings of the ASME 2015 Internal Combustion Engine Division Fall Technical Conference. Volume 2: Emissions Control Systems; Instrumentation, Controls, and Hybrids; Numerical Simulation; Engine Design and Mechanical Development. Houston, Texas, USA. November 8–11, 2015. V002T04A005. ASME. https://doi.org/10.1115/ICEF2015-1059
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