Pressure recovery in chemical lasers

Abstract

A one-dimensional flow model of the chemical laser, from combustor to subsonic diffuser, is developed for the study of laser pressure recovery. Combustor and flow chemistry effects, nozzle and cavity boundary-layer losses, laser cavity combustion, and nozzle, cavity, and diffuser geometry influences are included in the analysis. The results from experimental tests on a laser nozzle array with a constant area diffuser are presented. Diffuser exit pressures as high as 263 Torr were measured during these experiments. The one-dimensional flow model is shown to be in agreement with the measured diffuser exit pressures over the full range of test conditions. A AR C D Hpp Nomenclature = area = nozzle area ratio =yth station molar heat capcity, 2J XjiC pi -cavity exit hydraulic diameter = ith specie heat of formation =yth station sensible enthalpy, 2y \ C pi dT =yth station stagnation enthalpy, h } + 1/2 M wj U 2 j =yth station enthalpy, H 0j ; + £j X^hî =yth station total enthalpy, nfij = mass flow = Mach number, U/(yRT) l/2 =yth stream molecular weight,2j XjiM wi -molar flow ' = fluorine available in cavity as F 2 , 1/2 n p ? + n p¥l = pressure = cavity heat release = normalized heat release, Q/n p p 2 = gas constant = cavity mixture ratio, n sr>2 /n p p 2 = temperature = velocity = mole fraction, /i_////i/; X p = n p /n 3 , X s = n s /n 3 = mass fraction, myjmj -fluorine dissociation, 1/2 n pP /n p p 2 = deuterium dissociation, n 4D /n pF = specific heat ratio = laser specific power, (9^/m 3 =yth stream dilution level,^ ^/ 5 T = secondary, fuel stream = second throat diffuser m M M n n P Q q R R L T U y a \l/j Subscripts 0= stagnation state 1-7 = flow stations; Fig. 1

Flowfield experiments on a DF chemical laser

“…Using HF(3) as an example, the energy emitted by HF(3) during time t at wavelength X is E=K (A x t/\) [HF (3)] where A x is the transition probability (Einstein coefficient) for the X transition under consideration, and K is a constant which depends on the experimental configuration. The ability to detect this concentration of HF(3) requires that E be greater than the minimum energy deposition required to expose the particular film being used.…”

“…While ry c decreases with increasing pressure, the pressure recovery potential of the flow increases with pressure. 3 When high pressure recovery is an essential requirement, the simultaneous achievement of a high laser efficiency can only be obtained using nozzle designs which yield mixing rates faster than those achievable in the laminar mode. It was to satisfy the joint requirements of high efficiency and pressure recovery that the so-called "trip" nozzle was developed.…”

Choice of working parameters of pressure recovery systems for high-power gas flow chemical lasers

“…The data demonstrate how it is important to select the shape of cavity correctly. The analysis[9] shows a considerable degree _____ of influence of the cavity extension and parameters in the generator of atomic fluorine (GAF) on parameters of flow before SD. In the CCL case the S selection of SD performances…”

Pressure recovery systems for high-power gas flow chemical lasers

“…HPGCL are understood here as open cycle machines. At this rate it is important to take into account such feature of the laser PRS operation, as a heat generation by exhaust laser gas mixtures in diffuser channels [2,5]. Exhaust gas products after resonator cavity cannot be evacuated directly to atmosphere.…”