Semester

Fall

Date of Graduation

2010

Document Type

Dissertation

Degree Type

PhD

College

Statler College of Engineering and Mineral Resources

Department

Mechanical and Aerospace Engineering

Committee Chair

Nigel N. Clark.

Abstract

West Virginia University's Center for Alternative Fuels, Engines, and Emissions (CAFEE) has designed and constructed, with support from the U.S. Department of Energy (DOE), the 'next level' transportable dual-primary full-flow dilution tunnel emissions-measurement laboratory. As one of the major contributors, the author participated in the design and the fabrication processes of this laboratory. A systematic SimulinkRTM model was built for the Particulate Matter (PM) sampling system and a parametric study of the PM system was performed. Modeling of gas chemical composition, mass and heat transfer, as well as modeling of the primary and the secondary tunnels, were conducted with this SimulinkRTM model. This model simulated the tunnel flow and wall temperature, the PM filter face temperature, and the system's estimated theoretical PM diffusion losses. A computational fluid dynamic (CFD) model was also set up to help the selection of the location and sizes of the mixing orifice plates, as well as the configurations of the high efficient particulate air (HEPA) filter and the exhaust pipe housing plenum box. This dissertation describes the modeling processes and results from this SimulinkRTM model and this CFD model. Each sub-system of this transportable laboratory and results of the qualification tests on the laboratory as the outcomes of the CAFFE teamwork are also described. Size distributions of ultra-fine particles in the diesel exhaust from a naturally aspirated, 2.4-liter, 40-kW ISUZU C240 diesel engine equipped with a diesel particulate filter (DPF) were studied. Tunnel dilution in the standard primary and secondary-dilution tunnels on the transportable laboratory, instrument dilution with one Portable Particulate Measurement Device (PPMD), and ambient dilution at post-tailpipe centerline of the engine were studied as three dilution methods with different dilution ratios. Particle size distribution data, during steady-state engine operation, were collected using a Cambustion DMS500 Fast Particulate Spectrometer. The CFD models were employed to predict the exhaust mixing in the primary tunnel and at the engine post-tailpipe centerline. The dilution ratios obtained from the CFD models were verified with measured dilution ratios. The CFD models then were used to provide auxiliary information on the exhaust dilution processes.;The tunnel test results indicated varying size distributions across the tunnel cross sections where the flow was still developing. Homogenous particle-size distributions were observed across the sections at locations where the primary flow was fully mixed. However, the profile of particle-size distributions continued to evolve, due to residence time, even for fully mixed primary flow conditions. Variability of size distributions at the end of the secondary dilution tunnel was also observed with varied secondary-dilution ratios. The effects of dilution ratios, dilution speeds, and residence times on the diesel particulate matter (DPM) size distributions and particle mass concentration levels were analyzed and discussed. For example, the increased residence time of particles in the primary tunnel resulted in lower total particle count but higher mass concentration level. The particle-size distributions of the post-tailpipe and the PPMD test results were also analyzed and compared to the tunnel test results. The results from the post-tailpipe study show that the particle-number-concentration levels increased along the post-tailpipe centerline, with increasing dilution ratios. It indicates that nucleation was the dominant process when the exhaust plume was diluted along the post-tailpipe centerline. The measurement results from the PPMD dilution indicate that change of particle-size-distribution curves, number and mass concentration levels were not as strongly correlated to the dilution ratios as other two tests indicated. Finally, the analyzed results showed that stack corrected and uncorrected particle-size-distributions obtained from one dilution method could be remapped to particle-size distributions obtained from another dilution method. The particle-size distributions measured inside tunnels could mimic the freshly emitted exhaust immediately post-tailpipe. For example, when the engine was running at 122 Nm and 1800 rpm, the stack-corrected particle-size-distribution measurement at 38 cm of post-tailpipe centerline was found to be identical to the stack-corrected particle-size-distribution measured at the secondary dilution tunnel outlet with the primary-dilution ratio of 12.5 and the secondary-dilution ratio of 8.

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