M.Sc Thesis

M.Sc StudentDruker Nir
SubjectStudy of Voltage-Current Characteristics across the
Ignition Gap of Internal Combustion Engines
DepartmentDepartment of Mechanical Engineering
Supervisors PROF. Eran Sher
PROF. Benveniste Natan
PROF. Gideon Goldwine
Full Thesis textFull thesis text - English Version


A preliminary examination of the voltage-current characteristics across the ignition gap of an internal combustion engine was conducted. It showed that the V-I characteristics may provide valuable information about the thermodynamic conditions inside the cylinder prior to the ignition process. At a later stage, this information can be used to monitor and optimize the engine operation online.

When two electrodes are submerged in a gas and electrical potential is applied between them, a very low electrical current flows between the electrodes through the gas. Such currents (dark discharge) can be observed prior to the breakdown event in which a high current is involved (spark discharge). The phenomenon of dark discharge was first observed by John Sealy Townsend back in 1900, and was explained as the ionization of gas molecules due to collisions with the free electrons in the gap, which are accelerated by the electric field. The dark discharge current depends on the applied voltage, the gas density and its composition. Townsend's model for dark discharge describes the phenomenon versus electric field and density conditions up to the point of the spark event. However, Townsend's model was developed for a uniform electric field (which occurs between parallel plates electrodes) in air, and cannot be applied to two thin electrodes or in the case of gas mixtures. Most past experiments have dealt with similar cases and were usually conducted at low pressures and densities. In this work, we develop a generalized model (based on Townsend's model) for the case of a non-uniform electric field and a mixture of gas components. In addition, an experimental work was conducted to measure the relevant phenomena and to examine our model under suitable conditions that exist in internal combustion engines.

This work constitutes the foundation of a project conducted in partnership with Nexus Systems LTD within the framework of the Magneton program, sponsored by the Office of the Chief Scientist in the Ministry of Economy and Industry (Israel).