Pre-Turbo Aftertreatment Position for Large Bore Diesel Engines - Compact & amp; Cost-Effective Aftertreatment with a Fuel Consumption Advantage

Abstract

Tier 4 emissions legislation is emerging as a clear precursor for widespread adoption of exhaust aftertreatment in offhighway applications. Large bore engine manufacturers are faced with the significant challenge of packaging a multitude of catalyst technologies in essentially the same design envelope as their pre-Tier 4 manifestations, while contending with the fuel consumption consequences of the increased back pressure, as well as the incremental cost and weight associated with the aftertreatment equipment. This paper discusses the use of robust metallic catalysts upstream of the exhaust gas turbine, as an effective means to reduce catalyst volume and hence the weight and cost of the entire aftertreatment package. The primarily steady-state operation of many large bore engine applications reduces the complication of overcoming pre-turbine catalyst thermal inertia under transient operation. Upstream placement of the catalyst packages also offers potential for reducing the overall fuel consumption penalty (associated with the use of aftertreatment) in comparison to the conventional post-turbine placement. This softening of the fuel consumption penalty can be attributed to better light-off and performance of catalyst substrates, as well as a reduction in the impact of aftertreatment pressure drop on engine pumping work. The investigation involved numerical simulation of pre-turbo application of a diesel oxidation catalyst (DOC), partial-flow diesel particulate filter (DPF), and selective catalytic reduction (SCR) catalyst on a 30-35L class diesel engine. The effect of this placement over traditional downstream placement in terms of fuel consumption, package size, weight and cost was examined. The investigation revealed that the inherently higher gas density in the pre-turbine location allows a dramatic reduction in catalyst volume of up to 70%. The fuel consumption penalty associated with the addition of aftertreatment can also be reduced by approximately 1% with upstream placement of the catalyst packages.

Cu-SSZ-13 as pre-turbine NOx-removal-catalyst: Impact of pressure and catalyst poisons

“…As a further benefit, the pressure built-up from the turbocharger (typically up to 5 bar [10][11][12]) would lead to an increased residence time of the reactants at the catalyst, which would make a smaller total catalyst size possible as well as a decreased backpressure penalty [11,13]. This is also supported by numerical simulations by Subramaniam et al [13], who studied a preturbine placement of the entire aftertreatment system for a large bore diesel engine and predict a reduction of the catalyst volume > 40% and some decreased fuel consumption. Kröcher et al [11] reported that a pressure increase by a factor of two combined with half the catalyst size did not result in the same catalytic activity but a slightly lower one, probably due to diffusion limitations.…”

The Impact of Pressure and Hydrocarbons on NOx Abatement over Cu- and Fe-Zeolites at Pre-Turbocharger Position

“…In addition to temperatures of up to 180 • C higher at this location [18], the residence time is enhanced due to the higher pressure. These effects might enable a reduction of catalyst volume up to 40-70%, as shown in the case of diesel oxidations catalyst (DOC) and diesel particulate filter (DPF) applications [19,20]. However, at this location several challenges have to be faced.…”

Analysis of Regulated Pollutant Emissions and Aftertreatment Efficiency in a GTDi Engine Using Different SOI Strategies

“…In this sense, the implementation of the gasoline particle filter (GPFs) has become an alternative to reduce the particles number emitted by those engines. However, the fact of incorporating more and more aftertreatment systems in the exhaust system causes an increase in the back pressure and, therefore, an increase in the pumping losses, producing increases in fuel consumption [14,15].…”