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Date of Award

2017

Document Type

Campus Access Master's Thesis

Degree Name

Master of Science in Mechanical Engineering (MS)

Administrative Home Department

Department of Mechanical Engineering-Engineering Mechanics

Advisor 1

Jeffrey D. Naber

Committee Member 1

Mahdi Shahbakhti

Committee Member 2

Scott A. Miers

Abstract

Dilute combustion is an effective way to increase part-load efficiencies in a Spark Ignition (SI) engine. However, dilute combustion leads to a slower combustion rate and longer burn durations, which results in higher heat transfer loss. To overcome this, some degree of charge flow enhancement exists in modern engines that improves combustion rate and shortens burn durations. This flow enhancement has an adverse effect on performance of the modern Transistorized Coil Ignition (TCI) system and hence presents a limitation on improving combustion rates. Additionally, dilute combustion has a detrimental effect on combustion stability, wherein a larger variation in engine cycle work is observed from cycle to cycle which degrades engine performance. Improving combustion stability under dilution poses a challenge for the modern single coil ignition system, which is where the motivation lies in this research.

This research details the development and instrumentation of a Configurable Dual Coil Ignition (CDCI) system that is later tested on a single cylinder metal engine. The effectiveness of different ignition profiles developed with the CDCI system in extending the dilution limit while maintaining combustion performance and lower cycle-cycle variations, thereby improving fuel conversion efficiency, is investigated. Effects of dilution by excess air and internal (exhaust) residuals on the performance of these ignition profiles are investigated under different operating conditions. In-cylinder flow is enhanced by means of tumble planks installed in the intake port of the engine. The impact of enhanced in-cylinder flow on the capabilities of the developed ignition profiles is also investigated under different conditions. Moreover, effects of different spark plug gap sizes and orientations are also investigated. Although majority of the tests are done with Direct Injection (DI) gasoline, some tests are performed with Port Fuel Injection (PFI) methane to compare the effects of fuel delivery and charge preparation.

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