Date of Award

2018

Document Type

Open Access Master's Thesis

Degree Name

Master of Science in Mechanical Engineering (MS)

Administrative Home Department

Department of Mechanical Engineering-Engineering Mechanics

Advisor 1

Youngchul Ra

Committee Member 1

Sajjad Bigham

Committee Member 2

Stanislaw Szwaja

Abstract

A multi-dimensional CFD study using MTU-KIVA-Geq-CHEMKIN code has been carried out for direct injection compression ignition engine combustion fueled with heavy naphtha, light naphtha, and PRF50 in low-temperature combustion (LTC) regime. At constant fueling, combustion characteristics are investigated as a function of injection timing and injection pressure. Further, operating limits of fuel confined by combustion efficiency, noise level (Maximum Pressure rise rate) and emissions at exhaust valve opening (EVO) are evaluated using parametric variation of initial gas temperature, exhaust gas recirculation fraction, boost pressure. Research conducted focuses on ability of fuel to get good combustion which is combustion efficiency > / = 90%, Pressure rise rate < / = 10 bar/deg and NOx at EVO < / = 5 g/Kg-f. It is confirmed that all three fuels display low- temperature combustion at baseline operating condition. For light naphtha due to its low cetane index, injection timings near TDC are advantageous whereas high cetane index fuel does give high efficiency with low-pressure rise rate and low emissions at EVO for injection timing early in the compression stroke. Increasing charge temperature advances injection timing operating range whereas increasing boost and EGR fraction have opposite effect. Numerical investigation helped to understand effects of air-fuel distribution on combustion characteristics and ways to manipulate it although further work is deemed necessary to understand operating of all three fuels under different load conditions.

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