Hydrocarbon emissions from internal combustion engines (e.g., diesel and gasoline engines) are a widely regulated pollutant. A wide variety of emissions control devices have been developed for the mitigation of such emissions. Many emissions control devices function to convert hydrocarbons within an exhaust stream (e.g., via oxidation or another mechanism) into more environmentally acceptable species. Although highly effective emissions control devices have been developed, it may be necessary to tailor the design of such a device to a particular internal combustion engine or, more particularly, to the exhaust stream produced by a particular engine.
Several characteristics of an exhaust gas stream (temperature, flow, hydrocarbon content, hydrocarbon speciation, etc.) may vary based on the operating characteristics of an engine or other hydrocarbon source. For example, an exhaust stream produced by an internal combustion engine may contain thousands of distinct hydrocarbon species. The overall concentration of hydrocarbons and the relative amount of different hydrocarbon species (i.e., different molecular weight) in an exhaust stream may differ when an engine is operated under a low load condition versus a high load condition. The various hydrocarbon species in an exhaust stream may react differently with the catalyst(s) used in an emissions control device. Design of an emissions control device therefore often involves evaluating the ability of a device design to mitigate hydrocarbon emissions at various engine operating states.
Numerous test systems and methods have been developed to test the ability of emissions control devices to treat hydrocarbons in an exhaust stream produced by internal combustion engines, such as but not limited to gasoline and diesel engines used in automobiles. Some existing test systems and methods are engine based, meaning that they utilize an actual internal combustion engine to generate a test exhaust gas that is used to test an emissions control device under consideration. Such systems can be expensive to operate, however, and can produce inconsistent results. They may also not allow the operator to dynamically control the overall amount (HC concentration) of hydrocarbon species and the composition of the hydrocarbon species in the test exhaust gas.