so an exhaust system may include several components, each having an inlet and outlet, with the outlet of one component connected to the inlet of another component. Such systems may be complex and/or difficult to integrate.
In some cases, each component may require a separate mass and/or heat injection apparatus. For example, excess diesel fuel may be injected into an exhaust stream to create combustion at a diesel oxidation reactor in order to raise an inlet temperature of a particulate filter. A NOx reactor may require injection of a reductant, (e.g., urea, ammonia, Hydrogen, and/or other fuel) in order to facilitate a reaction at a certain temperature. A diesel particulate filter may benefit from NOx injection (e.g., to oxidize soot).
In some cases, latent heat and/or chemical species exiting a first reactor may not be efficiently utilized in a second “downstream” reactor, notwithstanding that the heat and/or species might be useful in the downstream reactor. In some cases, the heat and/or species exiting a first reactor must be controlled in such a way that performance of a downstream reactor is not inhibited. Improved reactor designs might provide for such control.
Many refractory substrates (e.g., catalytic converter, diesel particulate filter, and the like) are fabricated using extrusion. Such substrates often have long channels, with the “long” direction of the channels associated with the extrusion direction. The long direction may also be aligned with the flow of fluid through the substrate. As a result, reaction kinetics, heat transfer kinetics, fluid flow properties, and the like may be constrained by the method of fabrication of the substrate (e.g., extrusion). For example, a certain minimum residence time (associated with a reaction) may require a substrate having a minimum length, which may dictate an extruded substrate whose length is impractical for a given application.
For a typical filter (e.g., a diesel particulate filter, or DPF), filtration may preferentially begin at regions having h