Development of Emission Control Systems to Enable High NO _x Conversion on Heavy Duty Diesel Engines 2014-01-1525

Selective Catalytic Reduction (SCR) systems have been demonstrated as effective solutions for controlling NO_x emissions from Heavy Duty diesel engines. Future HD diesel engines are being designed for higher engine out NO_x to improve fuel economy, which will require increasingly higher NO_x conversion to meet emission regulations. For future aftertreatment designs, advanced technologies such as SCR coated on filter (SCRF^®) and SCR coated on high porous flow through substrates can be utilized to achieve high NO_x conversion.

In this work, different options were evaluated for achieving high NO_x conversion. First, high performance NO_x control catalysts were designed by using SCRF unit followed by additional SCR on high porosity substrates. Second, different control strategies were evaluated to understand the effect of reductant dosing strategy and thermal management on NO_x conversion. Tests were carried out on a HD engine under transient test cycles. The results indicated that NO_x conversion can be significantly improved using the proposed design of SCRF component along with SCR on high porosity substrates. The conversion can be further improved by dosing NH3 rather than urea, especially at low temperatures, when urea cannot be injected. In addition, implementation of thermal management improved the NO_x conversion at lower temperature. The results of this work demonstrated that such systems along with improvement in engine control strategy can provide >95% NO_x conversion under transient FTP test cycles and will allow diesel engines to meet future emission regulations and fuel economy targets.