Fiber Coupled Optical Spark Delivery System

Towards an Optical Ignition Engine

At a Glance

Researchers in the Department of Mechanical Engineering at Colorado State University have developed ignition systems based on state-of-the-art optical fibers and sophisticated new delivery strategies.  It is generally challenging to use optical fibers to deliver laser pulses in a way that allows one to focus the exit (output) pulse to form a spark in the gas-phase.  The typical required breakdown intensity is approximately 100-300 GW/cm2.   Light intensities of this magnitude require an exit pulse with a sufficient combination of optical power and beam quality (the latter in order to focus the light to a small spatial dimension).  To meet this challenge, researchers at Colorado State University are employing state-of-the-art optical fibers and creative new delivery strategies.

Background

Due to the large cylinder pressure and mixture density desired in modern engines, traditional spark ignition systems must operate at high voltage levels. As a result, dielectric breakdown (unwanted sparking) and electrode erosion frequently plague modern gas engines and are a limiting factor in the operational envelope of modern gas engines.

Optical sparks suffer from neither of these shortcomings and thus may have significant advantages for improved engine operation. In certain cases, optical sparks can also afford performance benefits associated with extension of maintenance intervals as well as changes in the lean limit, coefficient of variation of pressure, pollutant emissions and other parameters. Laser ignition has been shown to be a particularly effective way of igniting lean mixtures. In fact, it is fairly easy to create a spark by using “open path” laser delivery. The open path method implies that the laser beam propagates through the ambient air and is steered to the desired location by mirrors. Although simple and effective, this system is not practical for most industrial applications. Thus, there is a need for the development of an alternative optical delivery system.

Overview

This technology includes a spark delivery system for generating a spark using a laser beam. The spark delivery system is a laser light source and a laser delivery assembly, which utilizes launch focusing optics to input the laser beam, and exit focusing optics to demagnify an exit beam of laser light. This method increases the intensity of the laser beam, thus creating a spark. The described system may be used to create a spark in a combustion engine.

Figure 1 (below) is an example spark plug.

Benefits

  • Optical ignition systems offer performance benefits over traditional sparking systems
  • Enhanced delivery strategy allows for tuning of laser beam intensity and fiber choice
  •  Performance benefits, such as lean limit reduction of fuel source and reduced pollutant emission
  • No dielectric breakdown and electrode erosion due to high voltages
    • Leads to lower cost of maintenance
    • Enhanced delivery strategy allows for tuning of laser beam intensity and fiber choice
  • Performance benefits, such as lean limit reduction of fuel source and reduced pollutant emission

Applications

  • Optical ignition engines
Last Updated: December 2022
Spark plugs
Opportunity

Available for Licensing
TRL: 7

Inventors

Bryan Willson
Azer Yalin
Morgan Defoort

Reference Number
04-002
Licensing Manager

Jessy McGowan
Jessy.McGowan@colostate.edu
970-491-7100