Laser versus conventional ignition of flames

Ronney, Paul D.

doi:10.1117/12.152237

Cited by 280 publications

(88 citation statements)

References 30 publications

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“…It is worth noting that the use of laser radiation for affecting combustion has been widely discussed during the past decades [5][6][7][8][9]. Until now, only three methods of laser-assisted combustion initiation, such as laser-induced thermal ignition, laser-induced photochemical ignition, and laser-induced spark ignition, have been realized in experiments.…”

Section: Introductionmentioning

confidence: 99%

Initiation of combustion by laser-induced excitation of molecular vibrations of reactants

2006

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The features of combustion initiation in H 2 /air and CH 4 (C 2 H 2 )/air mixtures under laser-induced excitation of the asymmetric mode of ozone molecules added in a small amount to the mixture are analyzed. It was shown that such an approach to supply radiation energy to the combustible mixtures reduces the induction time and decreases the ignition temperature at a small energy of laser radiation delivered to the mixture. These effects are explained mostly by two factors -the intensification of chain reactions due to acceleration of O-atom formation during dissociation of vibrationally excited O 3 molecules and the heating of the mixture due to a faster decomposition of O 3 molecules. The considered method of ignition/combustion control is much more effective (by a factor of 10-100) than the method based on heating the gas by resonance laser radiation in the case where the characteristic time of highly reactive radical and atom formation does not exceed significantly the relaxation time of the asymmetric mode of the O 3 molecule.

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Section: Introductionmentioning

confidence: 99%

Initiation of combustion by laser-induced excitation of molecular vibrations of reactants

2006

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“…These include high altitude relight of gas turbines and cyclic variations in spark ignition reciprocating engines. Laser ignition has been proposed as a potential ignition source that can offer some advantages over conventional systems such as the ability to position the ignition source optimally for ignition, rather than for mounting or durability reasons (Ronney, 1994 andEl-Rabii et al, 2004). A variety of laser ignition strategies are available and these include the use of: a high flux density from a focused pulsed laser to breakdown the fuel-air premixture (Spiglanin, 1995); a wavelength tuned laser to excite a specific species within a mixture (Lucas, 1987;Forch and Miziolek, 1991) or a laser beam that is focused onto a target thereby reducing the energy flux density required (Bach et al, 1969).…”

Section: Introductionmentioning

confidence: 99%

Laser Ignition of Iso-Octane Air Aerosols

Lawes

Lee

Mokhtar

et al. 2007

Combustion Science and Technology

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Iso-octane aerosols in air have been ignited with a focused Nd:YAG laser at pressures and temperatures of 100 kPa and 270 K and imaged using schlieren photography. The aerosol was generated using the Wilson cloud chamber technique. The droplet diameter, gas phase equivalence ratio and droplet number density were determined. The input laser energy and overall equivalence ratio were varied. For 270 mJ pulse energies initial breakdown occurred at a number of sites along the laser beam axis. From measurements of the shock wave velocity it was found that energy was not deposited into the sites evenly. At pulse energies of 32 mJ a single ignition site was observed. Overall fuel lean flames were observed to locally extinguish, however both stoichiometric and fuel rich flames were ignited. The minimum ignition energy was found to depend on the likelihood of a droplet existing at the focus of the laser beam.3

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“…By focusing a laser beam into a small region in a volume of gas, very high electrical fields can be produced to ionize the gas. Initial demonstrations of the use of laser sparks to ignite combustible mixtures were performed in the late 1960s [1], and in recent years a relatively large number of studies have been performed [2][3][4]. By tightly focusing the beam from a high-power pulsed laser in a flammable mixture, a combustion-initiating spark can be created.…”

Section: Introductionmentioning

confidence: 99%

Fundamental Studies of Ignition Process in Large Natural Gas Engines Using Laser Spark Ignition

Yalin¹,

Willson²

2008

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Past research has shown that laser ignition provides a potential means to reduce emissions and improve engine efficiency of gas-fired engines to meet longer-term DOE ARES (Advanced Reciprocating Engine Systems) targets. Despite the potential advantages of laser ignition, the technology is not seeing practical or commercial use. A major impediment in this regard has been the "open-path" beam delivery used in much of the past research. This mode of delivery is not considered industrially practical owing to safety factors, as well as susceptibility to vibrations, thermal effects etc. The overall goal of our project has been to develop technologies and approaches for practical laser ignition systems. To this end, we are pursuing fiber optically coupled laser ignition system and multiplexing methods for multiple cylinder engine operation. This report summarizes our progress in this regard. A partial summary of our progress includes: development of a figure of merit to guide fiber selection, identification of hollow-core fibers as a potential means of fiber delivery, demonstration of bench-top sparking through hollow-core fibers, single-cylinder engine operation with fiber delivered laser ignition, demonstration of bench-top multiplexing, dual-cylinder engine operation via multiplexed fiber delivered laser ignition, and sparking with fiber lasers. To the best of our knowledge, each of these accomplishments was a first. 3 List of Tables Executive SummaryPast research has shown that laser ignition is a potential means to reduce emissions and improve engine efficiency of gas-fired engines to meet longer-term DOE ARES (Advanced Reciprocating Engine Systems) targets. From a fundamental point of view, the benefits of laser ignition (over conventional ignition) are due to: 1) the freedom to locate the laser spark in the middle of the combustion volume away from electrodes and walls which act as heat sinks; and 2) the higher power density of laser sparks, which lead to faster early flame growth and more robust early flame kernels. Additionally, laser ignition avoids limitations of conventional spark including erosion and dielectric breakdown, both of which become increasingly problematic as engine motored pressures increase. Past laser ignition efforts have generally employed "open-path" beam delivery, which is not considered industrially practical owing to safety factors, as well as susceptibility to vibrations, thermal effects etc. The overall goal of our project has been to develop technologies and approaches for practical laser ignition systems. (The project goal is inconsistent with the title of the project; however, very early in the life of the project the goals and milestones were re-scoped by DOE and the research team.) To enable practical systems we have pursued fiber optically coupled laser ignition systems and multiplexing methods for multiplecylinder engine operation. The approaches are selected in order to be compact, rugged, reliable and with the potential for low-cost. For multi-cylinder operation w...

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Laser versus conventional ignition of flames

Cited by 280 publications

References 30 publications

Initiation of combustion by laser-induced excitation of molecular vibrations of reactants

Initiation of combustion by laser-induced excitation of molecular vibrations of reactants

Laser Ignition of Iso-Octane Air Aerosols

Fundamental Studies of Ignition Process in Large Natural Gas Engines Using Laser Spark Ignition

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