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Title: Control of Early Flame Kernel Growth by Multi-Wavelength Laser Pulses for Enhanced Ignition

Journal Article · · Scientific Reports
 [1];  [2];  [1];  [1]
  1. Colorado State Univ., Fort Collins, CO (United States). Dept. of Mechanical Engineering
  2. Colorado State Univ., Fort Collins, CO (United States). Dept. of Chemistry
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The present contribution examines the impact of plasma dynamics and plasma-driven fluid dynamics on the flame growth of laser ignited mixtures and shows that a new dual-pulse scheme can be used to control the kernel formation process in ways that extend the lean ignition limit. We do this by performing a comparative study between (conventional) single-pulse laser ignition (λ = 1064 nm) and a novel dual-pulse method based on combining an ultraviolet (UV) pre-ionization pulse (λ = 266 nm) with an overlapped near-infrared (NIR) energy addition pulse (λ = 1064 nm). We employ OH* chemiluminescence to visualize the evolution of the early flame kernel. For single-pulse laser ignition at lean conditions, the flame kernel separates through third lobe detachment, corresponding to high strain rates that extinguish the flame. In this work, we investigate the capabilities of the dual-pulse to control the plasma-driven fluid dynamics by adjusting the axial offset of the two focal points. In particular, we find there exists a beam waist offset whereby the resulting vorticity suppresses formation of the third lobe, consequently reducing flame stretch. With this approach, we demonstrate that the dual-pulse method enables reduced flame speeds (at early times), an extended lean limit, increased combustion efficiency, and decreased laser energy requirements.

Research Organization:
Colorado State Univ., Fort Collins, CO (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Fusion Energy Sciences (FES); National Science Foundation (NSF)
Grant/Contract Number:
SC0012454; PHY-1418845; CHE-1461040
OSTI ID:
1425381
Journal Information:
Scientific Reports, Vol. 7, Issue 1; ISSN 2045-2322
Publisher:
Nature Publishing GroupCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 26 works
Citation information provided by
Web of Science

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Cited By (7)

Laser-Induced Plasma Formation in Ar, N 2 , and CH 4 at Low Pressure: Energy Deposition and Flow Dynamics conference June 2019
Dual-pulse laser ignition model journal October 2018
Hydrodynamic regimes induced by nanosecond pulsed discharges in air: mechanism of vorticity generation journal July 2019
A study of velocity, temperature, and density in the plasma generated by laser-induced breakdowns journal December 2019
Plasma and flow induced by single- and dual-pulse laser-induced breakdown in stationary air journal May 2019
Hydrodynamic ejection caused by laser-induced optical breakdown journal February 2020
Single and Dual-Pulse Laser Ignition of Methane-Air and Hydrogen-Air Mixtures conference January 2020

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