Date of Award

2-4-2025

Publication Type

Thesis

Degree Name

M.A.Sc.

Department

Mechanical, Automotive, and Materials Engineering

Supervisor

Ming Zheng

Rights

info:eu-repo/semantics/openAccess

Abstract

Homogeneous charge compression ignition (HCCI) and spark assisted compression ignition (SACI) can effectively achieve high efficiency and produce low emissions in an internal combustion engine. Dimethyl ether (DME) is a highly reactive fuel with potential to achieve HCCI combustion due to its low autoignition temperature and high cetane number. Sootless combustion makes DME a promising diesel replacement, however conventional high pressure direct injection fueling systems encounter sealing and lubrication issues when using DME. To alleviate these complexities, premixed DME-air mixtures can be delivered via a low pressure injection system to achieve HCCI combustion. An SACI strategy adds robust external control to the combustion phasing. A spark initiates flame propagation which releases energy and adds heat to the remaining unburned mixture and triggers the autoignition process. In this thesis an experimental study was conducted to investigate the SACI combustion process of DME fuel in a rapid compression machine (RCM). Stoichiometric DME-air mixtures diluted with various CO2 concentrations were used to determine the effect of spark timing on the combustion process at different dilution levels. In-cylinder pressure measurement was used to analyze ignition delay, flame propagation duration, combustion phasing, and pressure rise rates for the different SACI testing conditions. With increased dilution, ignition delay, flame propagation duration, and the advancement of combustion phasing increased. Pressure rise rates decreased with higher levels of dilution. With retarded spark timing, more fuel energy was released during the autoignition period.

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