Date of Award

8-1-2021

Publication Type

Thesis

Degree Name

M.A.Sc.

Department

Mechanical, Automotive, and Materials Engineering

Keywords

Spark plugs, Gap resistance, Elevated background pressures, Breakdown voltage

Supervisor

X. Nie

Supervisor

J. Tjong

Rights

info:eu-repo/semantics/openAccess

Abstract

The ever-growing demands to meet the exhaust emission regulations and fuel economy requirements, drive the development of modern spark ignition (SI) engines towards lean or diluted conditions at boosted intake pressure and with intensified charge motions. Boosted in-cylinder pressure conditions require additional energy to initiate the spark discharge, thereby challenging the ignition system. Additionally, the geometry of the spark plug has a profound influence on the spark discharge characteristics. The main objective of this research is to study the impact of high voltage electrode diameter on breakdown voltage and equivalent spark gap resistance at elevated background pressures (1-25 bar abs.). During spark discharge process, the plasma channel can be assumed as a conductor. Resistance of the plasma is one of the important factors that can have a significant impact on the spark energy, which is delivered to the spark gap. Three different types of spark plugs with different high voltage electrode diameters are used for the study. Empirical study is conducted using an inductive ignition system with a boosted-current ignition module at elevated background pressures. By controlling different parameters, the effect of high voltage electrode diameter on breakdown voltage is characterized under various test conditions, including different spark gap sizes and background pressures. Subsequently, the effect of high voltage electrode diameter on equivalent spark gap resistance is studied, with varied spark discharge current levels, spark gap sizes and background pressures. Within the tested conditions, the increase in high voltage electrode diameter (0.81-1.74 mm) results in a lower breakdown voltage. The equivalent spark gap resistance is not sensitive to the high voltage electrode diameter.

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