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Laser Spark Distribution and Ignition System

Date Posted
USPN 7,421,166


The Department of Energy’s National Energy Technology Laboratory (NETL) is seeking licensing partners interested in implementing United States Patent Number 7,421,166 titled "Laser Spark Distribution and Ignition System."

Disclosed in this patent is NETL’s laser spark distribution and ignition system, which reduces the high-power optical requirements normally needed for such a system by using optical fibers to deliver low-peak-energy pumping pulses to a laser amplifier or laser oscillator. Laser spark generators then produce a high-peak-power laser spark from a single low power pulse. The system has applications in natural gas fueled reciprocating engines, turbine combustors, explosives, and laser induced breakdown spectroscopy diagnostic sensors.


Current emission regulations relating to NOx require reciprocating engines to operate at very lean fuel/air mixtures. The excess air keeps the combusting gases cooler and limits thermal NOx development. At the same time, the lean mixture requires much more energy to be delivered to the spark plug for successful ignition, which leads to rapid erosion of spark plug electrodes and short spark plug lifetimes (only hundreds of hours). The resulting maintenance costs are thus very high, especially for natural gas fueled energy generation engines which must run continuously for thousands of hours.

Many researchers have explored the possibility of substituting a fiber optics system capable of transmitting a laser-induced plasma spark to an ignition chamber, thereby eliminating the need for spark plugs. But the high energies needed to produce a plasma spark usually destroy the optical fiber. A fiber of sufficient diameter to handle the energy and resist destruction produces a laser spot so diffuse that is incapable of generating a spark.

NETL scientists and engineers have met this challenge by combining a low power optical pumping source, an optical distributor, and a number of distinct spark generators. The optical pumping source, having a peak optical power less than 1,000 Watts so as not to destroy the optical fibers, is coupled to the optical distributor. The distributor is connected to a number of spark generators, which can produce a high energy spark from the original low power laser pulse. The laser spark generators can be either laser amplifiers or laser oscillators. The sparking sequence is directed by the optical distributor.


This technology provides:

  • A method of creating sparks in lean fuel/air mixtures without expensive, short-lifetime spark plugs
  • A means of meeting low NOx emissions requirements in engines and combustors
  • A novel, optical-based method of operating natural gas fueled reciprocating engines, turbine combustors, explosives, and laser induced breakdown spectroscopy diagnostic sensors

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