2. Experimentations
2.1. Burner and PLIF system
Fig. 1 shows the schematic of experimental apparatus. The
system consists of an OH-PLIF system, a gas delivery system
and a premixed Bunsen burner. A straight cylindrical stainless
steel tube with an inner diameter (D) of 3 mm is employed as
the Bunsen flame burner. The length of the tube is 20 mm
(>50 D) to ensure the fully developed flow. The flow rate
of each gas is precisely monitored by the delicate MKS mass
flow controllers (Models 1179A and 1559A) with an accuracy
of 1/1000 SLM to provide the desired mixture composition.
One-way valve is equipped on each gas supplying line to
prevent the reverse flow. The gases from different lines are
mixed in a mixing chamber (400 ml stainless steel) prior to
entering the burner. Total flow rate is controlled to ensure the
flow is a laminar one (Reynolds number, Re < 2000) and the
average velocity is at least five times higher than that of
laminar flame speed to get a stabilized flame.
The excitation of OH fluorescence is obtained using a 10 Hz
Nd:YAG laser (Quanta-Ray Pro-190) with power of 300 mJ per
pulse and a pulse time of 10 ns. The baseline wavelength of
the laser is 1064 nm, and it tunes to 355 nm by a harmonic
generator with THG crystal arm. The vertically polarized laser
is then pumped into a tunable dye laser (Sirah PRSC-G-3000