Flowfield experiments on a tripped DF chemical laser

Driscoll, Richard; Tregay, George W.

doi:10.2514/6.1981-1271

Cited by 1 publication

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“…Ic provides a possible explanation for the short mixing length data of Driscoll and Tregay. 5 A flow element bounded by two trip jets and the nozzle centerlines is shown in Figs. Ib and Ic.…”

Section: Flow Modelmentioning

confidence: 99%

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Effect of reactant-surface stretching on chemical laser performance

Driscoll¹

1984

AIAA Journal

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High-pressure DF chemical lasers use gas trip jets to increase the laser cavity reactant mixing rate. The trip jets can improve the laser efficiency by about 100% when compared to the laminar mixing value. It is postulated that the trip jets create a secondary flow which increases the mixing rate by stretching the contact surface between the reactant streams. The surface stretching rate can be described in terms of a strain rate s 0 . A qualitative explanation for the performance characteristics of trip-nozzle lasers is provided herein by developing flow and laser models which can define the effect of strain on the reactant burning rate and laser efficiency. Strain affects laser performance via a single parameter 7 = 2s 0 /k c , where k c is a characteristic collisional deactivation rate for the lasing specie. Strain levels of 7 = 2-3 appear to be consistent with trip nozzle data. The model also indicates the efficiency of low-pressure laminar mixing (7 = 0) lasers could be increased significantly for strain rate levels in the 7 = 3-5 range. Nomenclaturefusivity fiJ 2 ~ functions in amplifier solution, Eq. (22) F = (y// w) 2 , normalized flame location 8>8o = S ain P er unit length, g 0 = o [F] 7 G = integrated gain across flow channel, Eq. (16) G* = G/(g0W), normalized integrated gain G; = -^rjr 2 )/(4NggW) 9 threshold gain / = radiation intensity k**k* = kinetic rates for collisional deactivation and pumping, cmVmole-s k c ,k p = [ ] k* 9 kinetic rate concentration product, Kj = k p /k c , (pumping/deactivation) rate ratio K 2 = 2a/(eA: c ), (stimulated emission/deactivation) rate ratio K 3 = 1+K 2 L,L 0 = fluid element length scale, see Fig. 2 M i = /'th specie molecular weight N A = Avagadro's number p = pressure P = laser power, Eq. (17) P* = ^ r/, normalized power per channel r =yf/w 9 volume fraction of oxidizer burned rj, r 2 -mirror reflectivities s(x) = dw/dz, axially varying linear strain rate 50 = characteristic constant linear strain rate t = x/ «, flow time t b = strained flow oxidizer element burnout time t d =0.25 (w/Bj) 2 /D, laminar burnout time T = temperature u -constant axial flow velocity V =(u,v,w), velocities for coordinates fixed in fluid element, see Fig. 2 w } (x), w 2 (x) = oxidizer and fuel element widths w = w ; (0), initial oxidizer element width x b ,x d =ut b ,ut d , characteristic distances X i = /th specie mole fraction y f = flame location, Eq. (9) and Fig. 2 y* = wr(x), effective flame location for strained flow Y it Yf = /th specie mass fraction, initial values 7 = 2s 0 /k c , (strain/deactivation) rate ratio e = hvN A , energy per mole of photons f =*/: c /«, normalized axial distance fj,, £ d = x b k c /u, x d k c /u, characteristic distances f,., l e = start and end of lasing region in oscillator solution f0 = axial location of flame with penetration y f $ dj = value of f rf for which r e (£ d ) = ! 9 i.e., when frf = £dj> £e ~ f 6T\ = transverse coordinate, see Eq. (3), or normalized laser efficiency (vi c /ri 0 ) 9 see Eq. (18) r] 0 = efficiency for a premixed saturated ...

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Section: Flow Modelmentioning

confidence: 99%

“…(5) only for this region. It is now appropriate to set D r = D where D is the diffusion coefficient for the fuel in stream 2.On the oxidizer side of the flame sheet, the transverse velocity and density are v= -sy f and p/, respectively, while the values on the fuel side of the flame are v f and p f .…”

mentioning

confidence: 96%

Effect of reactant-surface stretching on chemical laser performance

Driscoll¹

1984

AIAA Journal

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show abstract

Flowfield experiments on a tripped DF chemical laser

Cited by 1 publication

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Effect of reactant-surface stretching on chemical laser performance

Effect of reactant-surface stretching on chemical laser performance

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