Laser Diagnostics of Quenching Mechamisms in Microscale Combustion

S. Wan, M. Lee, T. Kwan, Y. Fan, and Y. Suzuki

Overview

Micro combustion, i.e., combustion under characteristic length smaller than the classic quenching distance, behaves much different from macroscale combustion. Short residence time with a low Reynolds number, significant wall heat losses and non-neglectful near-wall radical quenching due to increased surface-to-volume ratio lead to serious flammability and flame stability problems.

In this, planar quartz micro combustors (channel height: 0.7/1.0/1.5 mm) have been developed for the study of thermal effects on micro combustion with laser diagnostics. The combustion channel is fusion-bonded with black quartz for absorption of radiation heat from IR lamp heaters, so combustion in the channel is investigated under controllable wall temperature by tuning the external heat input to the walls. Effects of the channel height and the wall temperature on quenching distance and extinction limits are investigated. Time-resolved CH*/OH* chemiluminescence imaging, phase-locked OH-PLIF and OH 2-line method have been developed for the capturing of flame propagation with flame speed and flame temperature information. It is found that the oscillating flame observed for rich mixture is quenched by heat losses from the flame to adjacent walls, which is verified by the flame front deceleration and temperature drop during the upstream propagation.

In order to elucidate effect of wall material on chemical quenching behavior, a methane-air premixed flame formed in 5-mm-wide channel is investigated. In the present study, platinum, quartz, alumina and chromium are chosen as the wall materials. Platinum, chromium and alumina thin films ~100 nm in thickness are deposited on quartz substrates using sputtering, vacuum arc plasma gun or atomic layer deposition techniques to establish equivalent thermal boundary condition with different wall chemical reactions. OH-PLIF/micro-OH-PLIF and numerical simulation with detailed reaction mechanisms are employed to examine interaction between the gas-phase and the wall surface reactions. It is clearly shown through the PLIF measurements that OH* mole fraction in the vicinity of the wall is the highest for alumina, while it is increased in order of quartz, chromium, and platinum. On the platinum surface, the gas-phase combustion is suppressed due to fast consumption of the reactants by the catalytic reaction. On the other hand, on the other surfaces, radical quenching cause the reduction of OH* near the wall. By using a radical quenching model, the initial sticking coefficient associated with radical absorption is evaluated. It is found that radical quenching does exist on the quartz wall, while the alumina surface works as an inert surface.

In addition, pulsed arc discharge is employed to generate OH on demand, in which the spatio-temporal development of OH under wall chemical effects can be precisely studied. OH distributions over quartz plates with thin films of different materials are measured with LIF in synchronization with the pulsed discharge. The wall temperature is kept constant up to 900 °C with an external infrared lamp heater. OH development under different wall thermal/chemical conditions is examined in detail.

Collaborators:
Dr. Yu Saiki (Nagoya Institute of Technology)
Prof. Kaoru Maruta (Tohoku University)
Prof. Yiguang Ju (Princeton University)
Prof. Olaf Deutchmann (Karlsruhe Institute of Technology)

Quartz planar micro combustor (Fan et al., 2007)

a) Microscopic OH-PLIF measurement set-up,b) Quartz plate with thin-film coating of different materials for wall chemical effect investigation (Saiki et al., 2013, 2015)

OH radical concentration versus the wall distance on alumina walls with different deposition methods (Saiki et al., 2013, 2015)

OH radical concentration versus the wall distance on quartz, SUS321, and Inconel (Saiki et al., 2013, 2015)

Flexible wireless wall temperature sensor prototype(Lee et al., 2015)

Recent Reports

PLIF Measurement of Wall Chemical Effect

  • Wan, S., Fan, Y., Maruta, K., and Suzuki, Y.,
    “HCHO-PLIF Measurement of DME Weak Flame for Investigation of Wall Chemical Effect,”
    36th Int. Symp. Combustion (Combustion 2016), Seoul, Work-in-Progress Poster, 2P138 (2016).
  • Saiki, Y., Fan, Y., and Suzuki, Y.,
    “Radical Quenching on Metal Surface in a Methane-air Premixed Flame,”
    Combust. Flame, Vol. 162, pp. 4036-4045 (2015).
    (doi:10.1016/j.combustflame.2015.07.043)
  • Wan, S., Fan, Y., Maruta, K., and Suzuki, Y.,
    “Wall Chemical Effect on DME Weak Flame in a Rectangular Micro Channel with a Streamwise Temperature Gradient,”
    10th Asia-Pacific Conference on Combustion (ASPACC), Beijing, (2015), ID.295.
  • Suzuki, Y., and Saiki, Y.,
    “Microscale Combustion: Surface Effect on Gas-phase Reaction,”
    Plenary talk, Int. Conf. Heat Trans. Fluid Flow in Microscale (HTFFM-V), Marseille, (2014).
  • Saiki, Y., and Suzuki, Y.,
    "Effect of Wall Surface Reaction on a Methane-Air Premixed Flame in Narrow Channels with Different Wall Materials,"
    Proc. Comb. Inst., Vol. 34, Issue 2, pp. 3395–3402 (2013).
    (doi: 10.1016/j.proci.2012.06.095)
  • Lin, W., and Suzuki, Y.
    "Investigation of Chemical Quenching Mechanism on Metal Surfaces based on PLIF Measurement of OH Generated with Pulsed Arc Discharge,"
    34rd Int. Symp. Combustion (Combustion 2012), Warsaw, Poland, July 29-August 3, Work-in-progress Poster, W1P058 (2012).

Methane-Air Premixed Flame in Narrow Quartz Channel

  • Fan, Y., Suzuki, Y., and Kasagi, N.,
    "Quenching Mechanism Study of Oscillating Flame in Micro Channels Using Phase-locked OH-PLIF,"
    Proc. Comb. Inst., Vol. 33, No. 2, pp. 3267-3273 (2011).
    (doi: 10.1016/j.proci.2010.05.041)
  • Fan, Y., Suzuki, Y., and Kasagi, N.,
    "Experimental Study of Micro-scale Premixed Flame in Quartz Channels,"
    Proc. Comb. Inst., Vol. 32, Issue 2, pp. 3083-3090 (2009).
    (doi: 10.1016/j.proci.2008.06.219)
  • Fan, Y., Suzuki, Y., and Kasagi, N.,
    "Ultra-Thin Quartz Combustors for TPV Power Generation,"
    8th Int. Workshop on Micro and Nanotechnology for Power Generation and Energy Conversion Applications (PowerMEMS 2008), Sendai, Japan, pp. 433-436 (2008).
  • Fan, Y., Suzuki, Y., and Kasagi, N.,
    "Flame Propagation and Quenching in Ultra-Thin Quartz Combustors,"
    7th Int. Workshop on Micro and Nanotechnology for Power Generation and Energy Conversion Applications (PowerMEMS 2007), Freiburg, pp. 265-268 (2007) .

OH 2-line Method for Flame Temperature Measurement

  • Saiki, Y., Kurimoto, N., Suzuki, Y., and Kasagi, N.,
    “Active Control of Jet Premixed Flame in a Model Combustor with Manipulation of Large-scale Vortex Structure and Mixing,”
    Comb. Flame, Vol. 158, Issue 7, pp. 1391-1403 (2011).
    (doi:10.1016/j.combustflame.2010.09.025)

Development of Wireless Wall Temperature Sensor

  • Lee, M., Morimoto, K., and Suzuki, Y.,
    Flexible Wireless Wall Temperature Sensor for Unsteady Thermal Field,”
    15th Int. Workshop on Micro and Nanotechnology for Power Generation and Energy Conversion Applications (PowerMEMS 2015), Boston, (2015). Also, J. Phys.: Conf. Ser., Vol. 660, No. 012019 (2015).
  • Lee, M., Kawahara, Y., Morimoto, K., and Suzuki, Y.,
    “MEMS Wireless Temperature Sensor for Combustion Studies,”
    14th Int. Workshop on Micro and Nanotechnology for Power Generation and Energy Conversion Applications (PowerMEMS 2014), Awaji, (2014). Also, J. Phys.: Conf. Ser., Vol. 557, No. 012077 (2014).

Last update: 2016-11-11