Large Engine Aftertreatment in a Pre-Turbine Position: A Path to Compact and Cost-Effective Emissions Reduction

With the impending implementation of the Tier 4 emissions standards in the non-road and locomotive sectors, exhaust gas aftertreatment systems will be needed on applications that previously did not require it. Based on the fact that the displacement of these engines is very large, the aftertreatment systems will also be relatively large, heavy and expensive. Additionally, even in these large engine applications, packaging space and systems cost is at a premium. Placing a robust metal aftertreatment system up-stream of the turbo-charger offers an elegant solution to these issues. The higher temperatures and faster temperature rises before the turbine yield faster light-off and better emissions performance. The higher gas density allows the total size of the aftertreatment system in the pre-turbine position to be substantially smaller for a given conversion efficiency, leading to a remarkable packaging and cost benefit of up to 64%. Additionally, by placing the flow-restriction of an aftertreatment system upstream of the turbine, a fuel consumption benefit in the pre-turbine position can be realized as pumping losses of the engine are reduced. The largely steady-state operation of these large engines negates the heat sink effect of the pre-turbine catalytic converters in transient operating conditions. This paper will investigate the benefits of placing an oxidation catalytic converter and partial-flow particulate filter up-stream of the turbo-charger on the fuel consumption of a stationary engine in the 30–35L class by simulation with GT-Power. Different locations for the aftertreatment package as well as optimized sizing for the different locations are investigated to identify the optimum solution for the engine. In addition to the fuel consumption benefits, the cost and weight advantage of the smaller pre-turbine system is emphasized. This view of both the technical and commercial side of the applications, demonstrates a clear advantage for the pre-turbine arrangement of the metal emissions reduction components on large bore engines.