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Selective Catalytic Reduction (SCR) operation depends strongly on both heat and ammonia availability (stored or incoming). These requirements make high efficiency SCR challenging in lower temperature cycles where SCR is relatively cold, and Diesel Exhaust Fluid (DEF) injection is largely absent due to deposit risks. Examples include low temperature cycles such as low-idling, stop-and-go or low-load cycles such as city driving or local delivery cycles. An Electrically Heated Mixer/ EHM™ is utilized to address these challenges in a single component. EHM simultaneously provides heat for rapid SCR heat-up during the cold phase or in other low-temperature operations, steady or transient. Second, its heating mechanism makes deposit risks nearly non-existent. Third, EHM enables DEF injection at 130 °C, markedly enhancing the low temperature SCR impact. It is shown that these capabilities collectively make EHM a promising pathway for meeting ultra-stringent NOx targets including California 2027 (0.02 gr/hp.hr). Via rapidly heating the SCR catalyst during cold-start, EHM enables substantially lowering the cold-phase NOx. For instance, it is shown this lowers the cold FTP and cold WHTC NOx emission by 2 – 2.5 fold and in Low-Load Cycle by 22-fold. EHM also allows DEF injection in low exhaust temperatures such as in 70 - 80 °C, for instance for rapidly filling the SCR catalyst with ammonia, if needed. Unlike adding other exhaust flow heating devices where an additional component is ultimately integrated in the aftertreatment architecture, EHM is a mixer, already present in emission control systems. These flexibilities, along with its lower cost and ease in fitting, make EHM an enabling pathway for Diesel emission control systems meeting very low NOx regulations.
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A New Electrically Heated Mixer (EHM) for Efficient SCR of NOx in Low Load Cycles
Low temperature Diesel exhaust operations such as during low-load cycles are some of the most difficult conditions for SCR of NOx. This, along with newer regulations targeting substantial reduction of the tailpipe NOx such as California-2024/2027 NOx regulations, adds to challenges of high efficiency SCR of NOx in low temperature operations. A novel design, low-cost, low-energy Electrically Heated Mixer (EHM™), energized via the 12, 24 or 48 V vehicle electrical system, is used to accelerate formation of reductants (ammonia, isocyanic acid) in low temperature exhaust (low load cycles), so to enable high efficiency SCR of NOx in most challenging SCR conditions, while also mitigating urea deposit formation. EHM™ is also used to heat the cooler exhaust flow during engine cold-start. It easily fits common exhaust configurations and can be utilized on light, medium or heavy duty Diesel aftertreatment systems, on- or non-road or in stationary systems.
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- Award ID(s):
- 1831231
- PAR ID:
- 10471323
- Editor(s):
- N/A
- Publisher / Repository:
- Society of Automotive Engineers
- Date Published:
- Journal Name:
- Frontiers in Mechanical Engineering
- ISSN:
- 26883627, 01487191
- Subject(s) / Keyword(s):
- NOx, Elkectrically Heated Mixer, Urea, Ammonia, SCR
- Format(s):
- Medium: X
- Location:
- Commercial Vehicle Conference, Indianapolis, IN, USA
- Sponsoring Org:
- National Science Foundation
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Selective Catalytic Reduction (SCR) operation depends strongly on both heat and ammonia availability (stored or incoming). These requirements make high efficiency SCR challenging in lower temperature cycles where SCR is relatively cold, and Diesel Exhaust Fluid (DEF) injection is largely absent due to deposit risks. Examples include low temperature cycles such as low-idling, stop-and-go or low-load cycles such as city driving or local delivery cycles. An Electrically Heated Mixer/ EHM™ is utilized to address these challenges in a single component. EHM simultaneously provides heat for rapid SCR heat-up during the cold phase or in other low-temperature operations, steady or transient. Second, its heating mechanism makes deposit risks nearly non-existent. Third, EHM enables DEF injection at 130 °C, markedly enhancing the low temperature SCR impact. It is shown that these capabilities collectively make EHM a promising pathway for meeting ultra-stringent NOx targets including California 2027 (0.02 gr/hp.hr). Via rapidly heating the SCR catalyst during cold-start, EHM enables substantially lowering the cold-phase NOx. For instance, it is shown this lowers the cold FTP and cold WHTC NOx emission by 2 – 2.5 fold and in Low-Load Cycle by 22-fold. EHM also allows DEF injection in low exhaust temperatures such as in 70 - 80 °C, for instance for rapidly filling the SCR catalyst with ammonia, if needed. Unlike adding other exhaust flow heating devices where an additional component is ultimately integrated in the aftertreatment architecture, EHM is a mixer, already present in emission control systems. These flexibilities, along with its lower cost and ease in fitting, make EHM an enabling pathway for Diesel emission control systems meeting very low NOx regulations.more » « less
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.4271/2022-01-1153
