Railplug Ignition System for Enhanced Engine Performance and Reduced Maintenance

Abstract

This Final Technical Report discusses the progress that was made on the experimental and numerical tasks over the duration of this project. The primary objectives of the project were to 1) develop an improved understanding of the spark ignition process, and 2) develop the railplug as an improved ignitor for large bore stationary natural gas engines.We performed fundamental experiments on the physical processes occurring during spark ignition and used the results from these experiments to aid our development of the most complete model of the spark ignition process ever devised. The elements in this model include 1) the dynamic response of the ignition circuit, 2) a chemical kinetics mechanism that is suitable for the reactions that occur in the plasma, 3) conventional flame propagation kinetics, and 4) a multi-dimensional formulation so that bulk flow through the spark gap can be incorporated. This model (i.e., a Fortran code that can be used as a subroutine within an engine modeling code such as KIVA) can be obtained from Prof. Ron Matthews at rdmatt@mail.utexas.edu or Prof. DK Ezekoye at dezekoye@mail.utexas.edu.Fundamental experiments, engine experiments, and modeling tasks were used to help develop the railplug as a new ignitor for large bore natural gas engines. As the result of these studies, we developed a railplug that could extend the Lean Stability Limit (LSL) of an engine operating at full load on natural gas from φ = 0.59 for operation on spark plugs down to φ = 0.53 using railplugs with the same delivered energy (0.7 J). However, this delivered energy would rapidly wear out the spark plug. For a conventional delivered energy (<0.05 J), the LSL is φ = 0.63 for a spark plug. Further, using a permanent magnet to aid the plasma movement, the LSL was extended to φ = 0.54 for a railplug with a delivered energy of only 0.15 J/shot, a typical discharge energy for commercial capacitive discharge ignition systems. Here, it should be noted that railplugs and the associated ignition circuit should not cost much more than a conventional spark ignition system. Additionally, it is believed that the railplug performance can be further improved via continued research and development.iii TABLE OF CONTENTS Abstract iii EXECUTIVE SUMMARYThis Final Technical Report discusses the progress that was made on the experimental and numerical tasks over the duration of this project. The primary objectives of the project were to 1) develop an improved understanding of the spark ignition process, and 2) develop the railplug as an improved ignitor for large bore stationary natural gas engines.Due to these two objectives, the experimental subtasks involved 1) detailed measurements regarding the physical processes occurring during spark ignition, and 2) measurements of the factors that affect railplug performance. Similarly, the modeling subtasks involved developing an improved model for the conventional spark ignition process and developing a model for railplug performance and ignition.The four phases of spark ignition are ...

Fractional models of selected combustion engine ignition systems

“…Generally, ignition systems can be represented as systems with energy storage in inductance and the ones with energy storage in capacitance [4,5,9,11]. Replacing the inductive element (ignition coil) with L  element we obtain two models shown in Figure 1.…”

The influence of impurities on the operation of selected fuel ignition systems in combustion engines

“…Due to the presence of anti-detonation additives in fuel, certain amounts of the combustion products may accumulate on the spark plug insulator, and consequently, reduce the discharge energy or even prevent ignition of the mixture. Research on the subject conducted in many centres all over the world aims to optimize the operation of the ignition system by eliminating mechanical elements [6][7][8][9].…”

“…The combustion of the fuel-air mixture filling the combustion chamber is largely dependent on the spark discharge parameters determined by the way the discharge is produced [5][6][7][10][11][12][13][14] This paper attempts to analyze the system by simulating the effect of fuel impurities on the value of spark discharge energy [1][2][3][11][12][13][14][15].…”