Flowfield experiments on a DF chemical laser

Abstract

Diagnostic experiments were conducted on a DF chemical laser to obtain data on the reaction zone structure for laminar mixing and when the mixing has been augmented by gas jet injection at the reactant interface. DF and HF emission from the reaction zones was recorded using infrared sensitive film and an IR scanner with an InSb detector; DF small-signal gain experiments were also conducted. The IR scanner and gain measurements were used to verify the photographic data which showed a decrease in the axial mixing length from 5 cm to 0.5-1.0 cm in going from the laminar to the augmented mixing mode.

Mixing enhancement in chemical lasers. II - Theory

“…The conditions in Table 1 were obtained from detailed combustor and nozzle calculations on the CL-XI trip nozzle array. 2 The results indicate that the transverse flow angle, surface stretching distance, and strain rate are a r = 9 deg, x r = Q.6 cm, and 5 r = 4xl0 5 s" 1 , respectively. This value for x r falls between the values of X F = OA cm and X O =O.S cm given by the CL-XI data.…”

“…9 the extent of surface stretching for the two-zone strain rate model can be written as (4a) (4b) t>t r : \l/ 2 (t) = 1 + (2s r t r ) =t 2 = (1 + /*) -const s r = v r /(2L r ) is the reference strain rate, v r = v F + v 0 and L r is the trip jet spacing. Since /*= (w c /L r ) 2 , the extent of surface stretching \[/ r is a function of only the nozzle centerline and trip jet spacing. Substituting Eqs.…”

“…8, the flame location is given by: B } is a stoichiometry-dependent parameter and D is the laser fuel diffusion coefficient. For laminar mixing, s(t)=Q and y f (t)=2B l (Dt) l/2 ; the oxidizer is fully-reacted when 2 . Z>(cm 2 /s) scales 11 as D = ET 5/3 /p; E is a composition-dependent coefficient ap-AIAA JOURNAL proximately equal to 0.05 for D 2 fuel and 0.07 for H 2 .…”

“…This value for x r falls between the values of X F = OA cm and X O =O.S cm given by the CL-XI data. 2 Typical lasing zone lengths for trip nozzles are x e = 3-5 cm; since x r <x e , the laser is expected to operate as in regions 3 and 4. Table 1 also shows how the parameters vary with flow temperature.…”