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Research Papers: Fuel Combustion

Simultaneous Schlieren–PLIF Studies for Ignition and Soot Luminosity Visualization With Close-Coupled High-Pressure Double Injections of n-Dodecane

[+] Author and Article Information
Ahmed Abdul Moiz

MEEM,
Michigan Technological University,
R.L. Smith Building,
1400 Townsend Drive,
Houghton, MI 49931
e-mail: amoiz@mtu.edu

Khanh D. Cung

Argonne National Laboratory,
9700 S. Cass Avenue,
Argonne, IL 60439
e-mail: kcung@anl.gov

Seong-Young Lee

MEEM,
Michigan Technological University,
917 R.L. Smith Building,
1400 Townsend Drive,
Houghton, MI 49931
e-mail: sylee@mtu.edu

Contributed by the Advanced Energy Systems Division of ASME for publication in the JOURNAL OF ENERGY RESOURCES TECHNOLOGY. Manuscript received June 28, 2016; final manuscript received October 13, 2016; published online January 9, 2017. Assoc. Editor: Reza Sheikhi.

J. Energy Resour. Technol 139(1), 012207 (Jan 09, 2017) (12 pages) Paper No: JERT-16-1272; doi: 10.1115/1.4035071 History: Received June 28, 2016; Revised October 13, 2016

Studies are performed in a constant volume preburn type combustion vessel over a range of ambient temperatures (750 K, 800 K, and 900 K) at constant density (22.8 kg/m3) with 15% O2 by volume in the ambient at 1200 bar (n-dodecane) fuel injection pressure. The influence of the pilot (first) spray flame on the ignition and combustion characteristics of the main (second) injection is investigated while varying injection pressure, dwell time, and injection strategy. Simultaneous schlieren (with soot luminosity imaging) and 355 nm planar laser-induced fluorescence (PLIF) imaging for formaldehyde (CH2O) and polycyclic aromatic hydrocarbons (PAH) visualization was performed. At both 900 K and 800 K ambient, main injection exhibits a reduction in ignition delay (ID) by a factor of 2 over their respective pilots. For the ambient temperature condition of 750 K, reducing injection pressure from 1500 bar to 1200 bar causes a significant increase in ignition delay (by ∼0.8 ms), which was attributed to the influence of injection pressure on spray-mixing and early development of cool flame. Also, at 750 K ambient condition, multiple injection schedule having two 0.5 ms injections separated by a 0.5 ms dwell was found to have a shorter ignition delay than a single 0.5 ms injection. Studies carried at an 800 K ambient show that by increasing the dwell time, main interaction with pilot reactive intermediates can be controlled to avoid an early rich ignition of the main spray and to reduce soot precursors.

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References

Figures

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Fig. 1

Optical setup for simultaneous imaging of schlieren and PLIF diagnostics. Labels are as follows: 1—LED light source, 2—pin-hole aperture, 3 and 8—parabolic reflector, 4—50/50 beam splitter, 5—combustion vessel, 6—injector, 7—reflecting mirror, 9—schlieren stop, 10—high-speed camera, 11—Nd:YAG laser, 12—dichroic mirror, 13—spherical and cylindrical lens, 14—laser sheet, 15—laser power mirror, and 16—I-CCD camera.

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Fig. 2

Rate of injection profile for 1200 bar injection for the 0.5/0.5/0.5 ms injection sequence

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Fig. 3

Nonreacting spray penetration results with single 0.5 ms injection and double 0.5/0.5/0.5 ms injection for three ambient temperature cases (900 K, 800 K, and 750 K) at injection pressure of 1500 bar

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Fig. 4

Heat-release rate profiles for the different ambient temperature cases for the 0.5/0.5/0.5 ms injection sequence at 1200 bar injection pressure. The actual injection durations are highlighted in the time axis.

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Fig. 5

Heat-release rate profiles for three individual runs for the 900 K ambient temperature case at 1200 bar injection pressure

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Fig. 6

Raw schlieren images for the 0.5/0.5/0.5 ms injection event at 900 K (left), 800 K (middle), and 750 K (right). White-dashed structures indicate schlieren softening and sold white lines indicate luminosity events.

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Fig. 7

Simultaneous PLIF imaging of the 0.5/0.5/0.5ms spray combustion event at 1200 bar for the 900 K (left) and 800 K (right) ambient case; dotted-thin contour line denotes schlieren boundaries, solid-thick contour line denotes soot luminosity, and background image is a PLIF image for formaldehyde measurement. Figure available in color online.

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Fig. 8

Soot luminosity images of 0.5/0.5/0.5 ms injection sequence for the 900 K ambient (left) and 800 K ambient (right) at 1200 bar injection pressure

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Fig. 9

Simultaneous PLIF imaging of the 0.5/0.5/0.5 ms injection spray combustion event at 1200 bar (left) and 1500 bar (right) injection pressure for a 750 K ambient. Figure available in color online.

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Fig. 10

Heat-release rate comparison of the 1200 bar and 1500 bar injection pressure cases of the 0.5/0.5/0.5 ms injection event at the 750 K ambient temperature case. The actual injection durations are highlighted in the time axis.

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Fig. 11

Schematic of PLIF shot timing in the dwell time variation tests

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Fig. 12

Heat-release rate profiles of the injection sequences with varying dwell times at 800 K. A star symbol on each curve indicates the timing of the PLIF shot acquisition.

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Fig. 13

Simultaneous PLIF imaging for a 0.5/0.3/0.5 ms injection sequence. Image is acquired at ∼880 μs ASOI. Figure available in color online.

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Fig. 14

Simultaneous PLIF imaging for a 0.5/0.6/0.5 ms injection sequence. Image is acquired at ∼1180 μs ASOI. Figure available in color online.

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Fig. 15

Simultaneous PLIF imaging for a 0.5/0.9/0.5 ms injection sequence. Image is acquired at ∼1480 μs ASOI. Figure available in color online.

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Fig. 16

Soot luminosity images for three injection sequences: 0.5/0.3/0.5 ms, 0.5/0.6/0.5 ms, and 0.5/0.9/0.5 ms, for a set of fixed after start of main injection (ASMI) times at 1800 K ambient and 1200 bar injection pressure

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Fig. 17

Heat-release profiles for limited variations in injection sequence and injection pressure at 750 K ambient temperature. Figure available in color online.

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