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Selective Catalytic Reduction (SCR) catalysts are used to reduce NOx emissions from internal combustion engines in a variety of applications. Southwest Research Institute (SwRI) performed an Internal Research & Development project to study SCR catalyst thermal deactivation. The study included a V/W/TiO₂ formulation, a Cu-zeolite formulation and a Fe-zeolite formulation. This work describes NH₃ storage capacity measurement data as a function of aging time and temperature. Addressing one objective of the work, these data can be used in model-based control algorithms to calculate the current NH₃ storage capacity of an SCR catalyst operating in the field, based on time and temperature history. The model-based control then uses the calculated value for effective DEF control and prevention of excessive NH₃ slip. Addressing a second objective of the work, accelerated thermal aging of SCR catalysts may be achieved by elevating temperatures above normal operating temperatures.

A novel urea evaporation and mixing device has been developed to improve the overall performance of a urea-SCR system. The device was tested with a MY2007 Cummins ISB 6.7L diesel engine equipped with an SCR aftertreatment system. Test results show that the device effectively improved the overall NO conversion efficiency of the SCR catalyst over both steady-state and transient engine operating conditions, while NH₃ slip from the catalyst decreased.

Exhaust gas recirculation (EGR) is effective in reducing engine-out NOx emissions; however, the EGR system is subject to fouling and corrosion. Fouling is mainly due to particulate buildup on the EGR component (e.g., EGR valve and cooler) surfaces. Corrosion is primarily related to oxides of sulfur and nitrogen in the gas stream, especially problematic when condensation occurs [1]. Because cooled EGR is most effective in controlling NOx emissions, EGR cooler design and operation are important considerations in engine design in order to meet durability requirements. An approach has been developed to greatly reduce EGR system fouling. Four EGR coolers were tested simultaneously with various PM control devices installed upstream of the cooler. System configuration and on-engine test results are presented herein.

A system for injection of diesel fuel and water with real-time control, or real-time water injection (RTWI), was developed and applied to a heavy-duty diesel engine. The RTWI system featured electronic unit pumps that delivered metered volumes of water to electronic unit injectors (EUI) modified to incorporate the water addition passages. The water and diesel mixed in the injector tip such that the initial portion of the injection contained mostly diesel fuel, while the balance of the injection was a water and diesel mixture. With this hardware, real-time cycle-by-cycle control of water mass was used to mitigate soot formation during diesel combustion. Using RTWI alone, NOx emissions were reduced by 42%. Using high-pressure-loop exhaust gas recirculation (EGR) and conventional diesel combustion with RTWI, the NOx was reduced by 82%.

Diesel particulate filters (DPF) have been shown to effectively reduce particulate emissions from diesel engines. However, uncontrolled DPF regeneration can easily damage the DPF. In this paper, three different types of uncontrolled DPF regeneration are defined. They are: Type A: Uncontrolled high initial exotherm at the start of DPF regeneration, Type B: “Runaway” or uncontrolled regeneration, which takes place when the engine goes to idle during normal DPF regeneration, and Type C: Uneven soot distribution causing excess thermal stress during normal DPF regeneration. In this paper, different control strategies are developed for each of the three types of uncontrolled DPF regenerations. These control strategies include SOF control, exhaust flow pattern improvement, as well as EGR control through intake throttling and A/F ratio control.

A technique was developed for measuring the Laminar Burning Velocity (LBV) of multi-component fuel blends for use in high-performance spark-ignition engines. This technique involves the use of a centrally-ignited spherical combustion chamber, and a complementary analysis code. The technique was validated by examining several single-component fuels, and the computational procedure was extended to handle multi-component fuels without requiring detailed knowledge of their chemical composition. Experiments performed on an instrumented high-speed engine showed good agreement between the observed heat-release rates of the fuels and their predicted ranking based on the measured LBV parameters.