Use of hollow core fibers, fiber lasers, and photonic crystal fibers for spark delivery and laser ignition in gases

Joshi, Sachin; Yalin, Azer P.; Galvanauskas, Almantas

doi:10.1364/ao.46.004057

Cited by 47 publications

(25 citation statements)

References 40 publications

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“…A convenient parameter to use when describing launch conditions for HCWs is fnumber; that is, the ratio of the focal length of the focussing optic to the beam diameter incident on the lens, Equation 6. The f-number is particularly useful as it incorporates key laser parameters relevant to the focussing of the beam.…”

Section: Optimal F-number For Multimode Vis-nir Transmissionmentioning

confidence: 99%

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Multimode VIS–NIR transmission through silver coated hollow optical waveguides

Griffiths

Dowding

Kirk

2016

Optik

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ABSTRACT:Multimode transmission of continuous wave 633 nm radiation and 1064 nm Q-switched Nd:YAG pulses using silver coated hollow core optical waveguides (HCWs) with bore diameters of 700 μm and 1000 μm is reported. The effect of launch conditions, input beam polarization and waveguide bore diameter on the pulse energy transmission and potential for focussing the beam effectively at the HCW exit is detailed. An optimal launch f-number range of 155-165 is identified for minimizing the exit angle.

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Section: Optimal F-number For Multimode Vis-nir Transmissionmentioning

confidence: 99%

“…Joshi et al reported delivery of high peak power radiation from a Q-switched Nd:YAG operating at 1064 nm via a 2 m long cyclic olefin polymer coated HCW [6]. An f-number of 55 was identified as suitable, producing an exit beam with a beam quality factor (M 2 ) of 15.…”

Section: Introductionmentioning

confidence: 99%

Multimode VIS–NIR transmission through silver coated hollow optical waveguides

Griffiths

Dowding

Kirk

2016

Optik

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“…They have successfully demonstrated the propagation of intense laser pulses as well as the application of laser ignition on an engine using such hollow fibers. Experimental investigations in [39] reported fiber transmissions greater than 80% using a 2 m-long and 700 µm-core diameter straight fiber and incoupling lens with an effective focal length between 135 and 315 mm. Bending of the fiber causes a drastic reduction of the fiber transmission and poor beam quality which leads to misfires.…”

Section: Fiber Delivery-based Laser Ignition Systemsmentioning

confidence: 99%

Transportation of megawatt millijoule laser pulses via optical fibers?

2010

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Abstract:Laser ignition is considered to be one of the most promising future concepts for internal combustion engines. It combines the legally required reduction of pollutant emissions and higher engine efficiencies. The igniting plasma is generated by a focused pulsed laser beam. Having pulse durations of a few nanoseconds, the pulse energy E for reliable ignition amounts to the order of 10 mJ. Different methods of laser ignition with an emphasis on fiber-based systems will be discussed and evaluated.PACS (2008)

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“…4 th row -Published results for fiber laser from reference [17]. Table 1 We have worked in collaboration with an external partner (University of Michigan) to demonstrate spark-delivery with fiber lasers [18]. This approach has not yet been tested on engine and is included in this report as Appendix A.…”

Section: Figure Of Merit and Analysis Of Fiber Delivery Challengesmentioning

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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Use of hollow core fibers, fiber lasers, and photonic crystal fibers for spark delivery and laser ignition in gases

Cited by 47 publications

References 40 publications

Multimode VIS–NIR transmission through silver coated hollow optical waveguides

Multimode VIS–NIR transmission through silver coated hollow optical waveguides

Transportation of megawatt millijoule laser pulses via optical fibers?

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

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