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One-dimensional transient modeling techniques are adapted to analyze the thermal behavior of lean-burn after-treatment systems when active flow control schemes are applied. The active control schemes include parallel alternating flow, partial restricting flow, and periodic flow reversal (FR) that are found to be especially effective to treat engine exhausts that are difficult to cope with conventional passive flow converters. To diesel particulate filters (DPF), lean NOx traps (LNT), and oxidation converters (OC), the combined use of active flow control schemes are identified to be capable of shifting the exhaust gas temperature, flow rate, and oxygen concentration to more favorable windows for the filtration, conversion, and regeneration processes. Comparison analyses are made between active flow control and passive flow control schemes in investigating the influences of gas flow, heat transfer, chemical reaction, oxygen concentration, and converter properties.

Reversed flow converter (RFC) employs periodical reversals of exhaust gas flow through a catalyst monolith for efficient use of its heat retention properties. This paper presents the results of computer simulation of three potential applications of the RFC: destruction of hydrocarbons and CO after diesel dual fuel engines, lean-NOx reduction, and cold-start emission control. An one-dimensional two-phase reactor model was used to simulate both typical converter operation transients and standard diesel engine tests. Both catalyst support structure and catalyst activity were demonstrated to affect the converter performance. Converter configurations were suggested that comprise catalyst, inert material and/or adsorbent. Simulation results are compared with engine tests of a converter treating a diesel dual fuel engine emissions.

A novel catalytic converter technology, employing periodical reversal of gas flow through the oxidation catalyst monolith, is being developed for treatment of exhaust gas from diesel engines fueled by natural gas in combination with diesel fuel. This technology allows to trap heat energy inside the monolith and thus efficiently destroy methane at converter inlet temperature as low as ambient. This paper describes the results of the initial stage of the converter development, including development of the mathematical model, computer simulation, and prototype testing. Simulation results indicate that dual fuel engine equipped with the reverse-flow converter could exceed the required destruction standards for hydrocarbons, including methane.