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Direct Injection into the Exhaust Stream of Gaseous Ammonia: Design and Efficiency of Injection and Mixing Hardware

Navistar Inc-Brad Adelman, Navtej Singh, Paul Charintranond, Greg Griffin, Shyam Santhanam, Ed Derybowski, Adam Lack
Published 2015-04-14 by SAE International in United States
Current legislative trends regarding diesel emissions are striving to achieve two seemingly competing goals: simultaneously lowering NOx and greenhouse gas (GHG) emissions. These two goals are considered at odds since lower GHG emissions (e.g. CO2) is achieved via high combustion efficiency that result in higher engine out NOx emissions and lower exhaust gas temperatures [1, 2]. Conversely, NOx reduction technologies such as SCR require temperatures above 200°C for dosing the reductant (DEF) [3, 4, 5] as well as for high conversion efficiencies [1, 2, 6, 7, 8, 9]. Dosing DEF requires injection pressures around 5 bar to ensure proper penetration into the exhaust stream as well as generate the appropriate spray pattern and droplet sizes. Dosing DEF generally requires long mixing and/or high turbulence (high restriction) areas so that the aqueous urea solution can be converted into gaseous NH3 without deposit formation [8, 10, 11, 12, 13, 14, 15]. One alternative to dosing DEF, an aqueous solution of 32.5% wt. urea, is to inject gaseous NH3. Gaseous NH3 does not require evaporation of water nor…
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Development of the NOx Emission Model for the Heavy Duty Diesel Engine Application Using Combustion Characteristic Parameters

Navistar Inc.-Navtej Singh, Prasanna Nagabushan-Venkatesh, Eduardo Nigro, Adam Lack
Published 2013-04-08 by SAE International in United States
Tighter emission norms and fuel economy demands have prompted diesel engine manufacturers to implement Aftertreatment systems for both light-duty and heavy-duty diesel applications. After implementing Diesel Particulate Filter (DPF) technology to comply with 2007 Environmental Protection Agency (EPA) emissions regulations, OEMs have turned their attention towards NOx reductions with SCR technology. Current SCR technologies include liquid based Urea injection into the exhaust stream for NOx reductions and Solid Ammonia Storage and Delivery System (ASDS) which involves dosing gaseous Ammonia. Irrespective of the technology in use, the estimation of engine-out NOx emissions plays a vital role in reductant (Urea/Ammonia) dosing estimation via feed-back controls. The general method for determination of the engine-out NOx emissions is to use commonly available NOx emission sensors (NOx Sensors). However, NOx sensors have their own drawbacks. With On-Board Diagnostics (OBD) requirements in place for the 2013 model year, the use of additional sensors translates to additional implementation costs adding up to warranty and maintenance costs. Therefore, the necessity of the virtual engine out NOx emission estimation is very important. In this…
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Exhaust Volume Flow based Time Alignment in NOx Measurements in NOx Reduction Systems

Navistar Inc.-Vijayasarathy Subramanian, Navtej Singh, Adam Lack
Published 2012-09-24 by SAE International in United States
With the emission norms becoming more and more stringent along with the focus on reducing ownership and operating costs, the need to optimize the aftertreatment system becomes much more evident. Thus, the well monitored, optimized usage of urea or ammonia (NH₃) for the NOx reduction in an SCR system is critical to reduce the operating cost of the vehicles and to comply with emission regulations. In Ammonia Storage and Delivery System (ASDS), pure gaseous NH₃ from the NH₃ cartridges is being used for the reduction of the engine-out NOx in the exhaust stream over the NPF (NOx Particulate Filter). In almost all NOx reduction systems, NOx sensors play an important role in determining the amount of urea or NH₃ to be dosed for efficient NOx reduction with minimal NH₃ consumption and slippage for best possible fluid economy. In the NH₃ dosing strategy the NOx conversion efficiency plays a vital role as a feedback variable for calculating NH₃ dosing quantity and is based on the upstream and downstream NOx sensor measurements. Since the NOx sensors are…
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