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Date of Award

2017

Document Type

Campus Access Dissertation

Degree Name

Doctor of Philosophy in Mechanical Engineering-Engineering Mechanics (PhD)

Administrative Home Department

Department of Mechanical Engineering-Engineering Mechanics

Advisor 1

Jeffrey Naber

Committee Member 1

Mahdi Shahbakhti

Committee Member 2

Scott Miers

Committee Member 3

Mohsen Azizi

Abstract

Diesel-NG fuel blends are increasingly being used in Reactivity Controlled Compression Ignition (RCCI) applications due to high Brake Thermal Efficiency (BTE), low NOx and PM emissions. But it also has a few disadvantages such as high HC and CO emission and relatively low Exhaust Gas Temperature (EGT). This leads to find out the optimum tradeoff between emissions to meet the regulation and also investigate the cost of operation and find out the minimum liquid consumption (fuel + urea) in RCCI mode. A Cost Function (CF) including Brake Specific Fuel Consumption (BSFC) and Brake Specific Urea Consumption (BSUC) is considered and minimized in this study. This optimization helped to investigate the optimum input parameters between 3 to 12 bar IMEP at 1500 RPM engine speed. This study has been done while all the population in optimization process meet the Tier 3 Bin 20 emission regulations. To increase the number of data points in this optimization, a mathematical (numerical) model is developed to predict (or assess) the Diesel-NG RCCI data. Single fuel diesel only mode is also considered in this optimization, since high BTE of RCCI is limited to medium and high load operating conditions and due to the high HC and low EGT, RCCI may not be an ideal combustion mode at low loads. Parametric models have been developed and validated using experimental data on a light duty 1.9L inline 4 cylinder Compression Ignition (CI) engine as a function of independent input variables including, first and second Start of Injection (SOI1 and SOI2), Manifold Absolute Pressure (MAP), lambda, Exhaust Gas Recirculation (EGR) and Blending Ratio (BR), and validated using RCCI experimental data. In these models, selected emissions – including HC, CO, PM and NOx–, Exhaust Gas Temperature (EGT) and BSFC were computed using correlations as functions of independent input variables. The computed EGT were then used to estimate the Selective Catalyst Reduction (SCR) and Diesel Oxidation Catalyst (DOC) efficiencies to assess the emission data for different input variables by considering after-treatment system to see if they meet the tailpipe emission regulation. Running the engine with this calibrated input parameters not only meet the Tier 3 Bin 20 EPA standard, but also minimized the cost of operation in RCCI mode within 3 to 12 bar IMEP engine load at 1500 RPM engine speed.

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