Controlling emissions with es-aftertreatment

The Expert System tool es-aftertreatment has recently been enhanced to provide even more effective numerical modeling and design of aftertreatment devices.

The continuing trend of imposing stricter emissions regulations on vehicles in order to improve air quality means that future exhaust systems are becoming increasingly complex. Most gasoline engine vehicles control emissions by using three-catalysts which simultaneously reduce CO, NOx and hydrocarbons and thereby protect the environment.

Consequently, catalyst designers are tasked with an added complexity to their already very aggressive product development cycles. Similar to other aspects of vehicle and engine design, simulation tools play a crucial role in the development and integration of exhaust components into complete systems. es-aftertreatment has therefore been developed to aid the engineer in the design and evaluation of a variety of aftertreatment devices under diverse operating conditions.


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The tool functions as a companion pre- and post- processor to STAR-CD with specific capability for modeling entire automotive aftertreatment devices. This type of analysis provides engineers with the ability for example, to examine flow distribution and associated pressure drops through flow-through catalysts and the thermal warmup behavior of non-reacting catalysts and catalytic performance of flowthrough devices. Recent enhancements include added functionality for modeling diesel particulate filters and catalyzed soot filters.

It is important to be able to understand not only the flow distribution and heat transfer, but also the chemical reactions. For this reason, included within es-aftertreatment is STAR/KINetics, which combines the multidimensional flow analysis abilities of STAR-CD with CHEMKIN, the leading software for gas-phase and surface chemistry analysis. This allows an aftertreatment analysis for the modeling of catalytic surface reactions present in typical-flow monoliths.

An example of how es-aftertreatment can be applied is to better understand the heat-up of a monolithic device. A typical item of interest for this scenario is the flow and thermal maldistribution entering the device, and indeed, inside the device as well. This is of concern as the flow and thermal distribution inside the device has a direct impact on the performance of the exhaust system in terms of emissions, power loss, and long-term durability.

Figure 1 shows how es-aftertreatment can be applied to a diesel particulate filter (DPF) with complex geometry and manifolds. In this model, 20 representative channels are distributed on a 4x5 Cartesian subdivision. Because of the sharp 90° elbow in the upstream manifold, as well as the expansion of the manifold to the DPF monolith, a very complex flow pattern develops in front of the brick. Figure 2 shows the trapped soot mass per unit volume of DPF. The trapped soot mass evaluated in the individual channels is mapped back to the large-scale grid of the DPF. For further information, contact info@cd-adapco.com or your local support office.