Transmission, Distribution, & Refining
Laser-Spark Ignition for Natural Gas Fueled Reciprocating Engines

NETL In-house

Goal: The goal is to enhance the efficiency of the nation's natural gas transmission and distribution infrastructure, while reducing emissions.

Objectives The objective of this project is to develop laser ignition technology that can facilitate the development of high-efficiency, low-emission stationary natural gas fueled reciprocating engines for gas compression. 
 


Close-up of a laser-spark plug with window lens pressure barrier

Performer:
NETL in-house research with support from West Virginia University – project management and research product

Accomplishments:

  • Performed tests of spark plug and laser-spark ignition systems to compare misfire limits, ignition timing, and knock limits,
  • Performed lab-scale testing to evaluate how the ignition process proceeds under laser-spark ignition.

Laser-spark plug with and without engine adaptor

A demand for higher engine efficiency combined with lower emissions in reciprocating gas compressor engines has driven engine combustion towards leaner air/fuel operating conditions. This requires increased spark energy to maintain stable combustion with low emissions. Unfortunately, increased spark energy negatively impacts spark plug durability and performance as an ignition source. An alternative is laser-spark ignition, where high-energy photons are focused to create a plasma breakdown at a point inside a compressor cylinder. One of the most promising aspects of laser-spark ignition is its ability to ignite lean mixtures that would be un-ignitable by a typical spark ignition system.

NETL is undertaking in-house research to study the performance, combustion and emission behavior of laser-induced spark ignition in high-pressure, fuel-lean, and large-bore natural gas engines. This effort will identify optimum ignition location configurations and quantify potential benefits (emissions, efficiency, combustion stability, reliability and durability). It will also identify the specific technical difficulties that challenge an eventual commercial system for a reciprocating engine.

NETL's approach includes:

  • Tests of laser system and conventional spark components using single cylinder engines,
  • Evaluation of the suitability of different laser sources,
  • Investigation of fiber optic laser beam delivery systems, and
  • Demonstration of the technology and collection of performance data for a multi-cylinder, natural-gas-fueled engine in a commercial configuration.
Tests of both spark plug and laser-spark systems showed that the misfire limit is significantly extended for laser ignition. Also, ignition delay was found to be approximately 7 percent shorter for laser ignition over the conventional spark plug system. The engine knock limit exhibits a slight decrease, probably due to small differences in combustion phasing and remaining differences in start-of-combustion. Multipoint ignition via laser delivery offers potential for engine applications to further extend misfire and knock limits. Combustion testing where a laser was used to initiate combustion in a pressurized test vessel revealed that the laser-spark ignition process seems to be dominated by a hot ball of gas remaining after the laser spark has dissipated.

Current Status and Remaining Tasks
Experimentation continues on the development of a working end-pumped laser ignition system which will be engine-tested if time permits during FY2007. At that point, work on this project will be completed.

Contact Information:
NETL – John Ontko (John.Ontko@NETL.DOE.GOV or 304-285-4930)

 
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