Improving fuel economy during high load diesel engine system operation through valve train flexibility
Abstract
As emission regulations getting more stringent and the demand for fossil fuel growing, it is crucial to develop advanced technologies for internal combustion engine to lower emissions and fuel. Strategies such as diesel oxidation catalysts (DOC) for UHC, diesel particulate filters (DPF) for PM, and selective catalytic reduction (SCR) for NOx have been developed and implemented to convert harmful emissions to innocuous species. However, the efficiencies of these after-treatment systems are heavily temperature dependent. Heavy-duty over-the-road trucks require periodic active diesel particulate filter regeneration to clean the filter of stored particulate matter. These events require sustained temperatures between 500 and 600 °C to complete the regeneration process. Engine operation during typical 65 mile/hour highway cruise conditions (1200 rpm/7.6 bar) results in temperatures of approximately 350 °C, and can reach approximately 420 °C with late fuel injection. This necessitates hydrocarbon fueling of a diesel oxidation catalyst or burner located upstream of the diesel particulate filter to reach the required regeneration temperatures. These strategies require increased fuel consumption, and the presence of a fuel-dosed oxidation catalyst (or burner) between the engine and particulate filter. This work experimentally demonstrates that, at the highway cruise condition, deactivation of valve motions and fuel injection for two or three (of six) cylinders can instead be used to reach engine outlet temperatures of 520 - 570 °C, a 170 - 220 °C increase compared to normal operation. This is primarily a result of a reduction in the air-to-fuel ratio realized by reducing the displaced cylinder volume through cylinder deactivation. HDFTP drive cycle has more than half of the fuel consumed at high speed/high load conditions. Strategies using valve train flexibility were investigated experimentally to improve fuel economy at high speed/high load conditions. IVC modulation at high speed is an effective way of achieving higher volumetric efficiency from dynamic charging in turn help fuel efficiency. Intake valve closure from nominal 565 CAD to 595 CAD at high speed enables dynamic charging and thus increases EGR fraction with air-to-fuel ratio maintained. The strategy of "dynamic charging" helps get fuel economy benefit by around 1.25% without sacrificing BSNOx.
Degree
M.S.M.E.
Advisors
Shaver, Purdue University.
Subject Area
Engineering
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