Results of small-signal gain measurements on a supersonic chemical oxygen iodine laser with an advanced nozzle bank

Николаев, В. Д.; Загидуллин, М. В.; Svistun, M I; Anderson, B.; Tate, Ralph F.; Hager, Gordon D.

doi:10.1109/3.998612

Cited by 30 publications

(12 citation statements)

References 8 publications

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“…Figs. 16 and 17 show the temperatures for the fits for the 10 species, 13 reaction and 13 species, 52 reaction simulation extracted lineshapes in which the bulk gas velocity was not included in the functional evaluation of equations [1] and [8]. The agreement between the Doppler, Lorentzian, and thermodynamic temperatures shown in Figs.…”

Section: I( P ) I( P )mentioning

confidence: 66%

“…While the effect of the bulk gas velocity was not taken into account in these investigations, the diagnostics developed by these investigations provided the means to due so. Nikolaev et al, 8 applied the same type of continuously tunable diode laser to the I 2 P 1/2 2 P 3/2 transition to investigate the influence of mean gas velocity through a COIL device upon the laser gain. They showed that by varying the angle at which the diode laser beam passes through the COIL flowfield, the line center gain can be varied.…”

Section: Problem and Methodologymentioning

confidence: 99%

“…With the values for the Doppler and Lorentzian widths D and L determined, separate values for the temperature can be found using equations [6] and [7] and an independent determination of the pressure and the mole fractions. Here, the simulation data were spatially and temporally averaged using the same procedure as for the gain expressed mathematically in equation [8] to determine average pressures and species mole fractions. When performing this analysis with experimentally measured lineshapes, wall pressures and mean mole fractions based upon the measured molar flow rates may be the only values available and may lead to errors in the extracted temperatures.…”

Section: I( P ) I( P )mentioning

confidence: 99%

“…The degree of agreement between the Doppler and Lorentzian determined temperatures and the average thermodynamic temperature from the simulation provides a means to assess the lineshape fit and the interpretation of the fit. To perform this comparison, the thermodynamic temperatures were averaged from the simulation data using the same integration procedure as used for the gain in equation [8]. Figs.…”

Section: I( P ) I( P )mentioning

confidence: 99%

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Prediction of I²P 1/2 →²P 3/2 transition lineshapes from 3-D, time dependent simulations of chemical oxygen-iodine laser (COIL) flowfields

Madden

2008

SPIE Proceedings

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Keywords: Laser gain, Doppler Broadening, Lorentzian Broadening, lineshape, computational fluid dynamics, flow unsteadiness. IntroductionThe lineshape of the I 2 P 1/2 2 P 3/2 transition provides a means to ascertain a variety of useful information regarding the performance of the chemical oxygen-iodine laser (COIL). The value at the center of the lineshape, commonly referred to as the 'line center,' is proportional to the laser amplification on the I 2 P 1/2 2 P 3/2 transition. The infinite integral of the lineshape is proportional to the number density of the ground and excited states of atomic iodine in the gas, indicating the degree of I 2 dissociation. And the width of the lineshape indicates the amount of broadening of the transition, both due to collisional and Doppler shift effects. As the Doppler shift is proportional to velocity, the width of the transition can be used to estimate the degree of random molecular motion in the gas, expressed in macroscopic terms as temperature. A Doppler shift to the frequencies in the transition can also occur through the straight-line, bulk motion of the gas, and this can be used to examine the velocity field of the gas. However, the flow may experience rotation through the presence of eddies carried within the gas, and these too may contribute to the Doppler shift of the lineshape frequencies. Given that eddies by virtue of their positive and negative velocity components can induce positive and negative Doppler shift, the widening of the lineshape is similar to thermal motion which also includes positive and negative velocities. Thus, when interpreting transition lineshapes, if some account is not made for both thermal and rotational motion, the effect of either physical process will be over-estimated.The work discussed here is oriented toward examining the interplay between the gas dynamics and the lineshape of the I 2 P 1/2 2 P 3/2 transition, and in turn determine the ramifications for the use of spectroscopic lineshape based diagnostics and interpretation of their data. These efforts in turn are directly linked to efforts improve the understanding of the physical processes underlying chemical lasers, as excursions outside the traditional operational parameter space become increasingly necessary. Problem and MethodologyThe objective of this work is to generate a greater physical understanding of the physical processes underlying COILs through use of the models employed in simulation of these devices. This objective is achieved through 3-D, time accurate numerical simulation of the COIL flowfield using the Navier-Stokes equations coupled to species continuity equations. Previous work by Madden and Miller 1 presented computational data for COIL simulation indicating that the flowfield should be marked by substantial flow unsteadiness, as documented in the experiments of Fric and Roshko 2 for incompressible, air-air jet-in-crossflows at Reynolds numbers similar to those found in COILs. Building on the earlier results, this work further elucidates the flow unsteadiness,...

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Section: I( P ) I( P )mentioning

confidence: 66%

Section: Problem and Methodologymentioning

confidence: 99%

Section: I( P ) I( P )mentioning

confidence: 99%

Section: I( P ) I( P )mentioning

confidence: 99%

See 2 more Smart Citations

Prediction of I²P 1/2 →²P 3/2 transition lineshapes from 3-D, time dependent simulations of chemical oxygen-iodine laser (COIL) flowfields

Madden

2008

SPIE Proceedings

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“…Since the fuel is injected downstream of the throat in supersonic COIL, flow velocity increases and the partial pressure of singlet delta oxygen is reduced, both of which reduce the rate of oxygen loss. Several designs for supersonic COIL lasers have been described in the open literature [5,6,7,8,9,10,11]. In all cases, mixing of the fuel with carrier into the primary flow is crucial to chemical laser design.…”

Section: Overview Of Validation Problemsmentioning

confidence: 99%

Prediction of Chemical Laser Flow

Vorobieff¹,

Truman²

2006

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Executive summaryThe scope of the work as proposed to the funding agency was to carry out numerical calculations of high-speed mixing flows using GASP, a computational fluid dynamics (CFD) code. The ultimate goal is to use GASP for prediction and optimization of chemical laser flows. To do it, one must have confidence in the performance of the hydrodynamic and mixing part of the code.For complex numerical simulations, it is essential to perform code validation -a quantitative comparison of numerical results with experimental results confirming that the code faithfully reproduces the physics of the real problem. Two detailed validation exercises were performed with GASP:" Simulation of a shock-accelerated mixing flow. This validation exercise compared the numerical results produced by GASP with highly-resolved experimental data on flows subject to Richtmyer-Meshkov instability (RMI), the preferred test problem for quantitative assessment of the performance of CFD codes in prediction of the properties of high-speed mixing flows. The validation problem revealed that GASP can faithfully reproduce all the large-scale quantitative properties of the flow. We also gained important additional insights into the strengths and limitations of GASP (and other numerical codes) in prediction of disordered small scales in flows transitioning to turbulence." General jet-in-crossflow problem. The problem of a supersonic jet discharging into a supersonic crossflow presents a significant computational challenge, yet provides a valuable validation exercise when the results are compared with experimental data. The conditions for this exercise were chosen to achieve two goals: -Provide comparison with best experimental data available in open literature.-Test the code in a generic configuration that can be easily modified to represent a specific chemical laser nozzle injection scheme.The agreement with the experimental data was quite good, yet subtle features of the flow that were not apparent in the experiment were revealed by the simulation.The results of our work are as follows."* We found the hydrodynamic model used in GASP to be suitable for prediction of mixing in chemical laser flows."* We found the error in prediction of the geometry of large-scale features (e.g., counter-rotating vortex pairs) not to exceed 10-15% when compared with experiment.

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Lasers

Photonics

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The LASER light source, whose name is based on "Light Amplification by Stimulated Emission of Radiation", is the most important device in almost all photonic applications. First built in 1960 [6.1-6.5] it allows the generation of light with properties not available from natural light sources. Modern commercially available laser systems allow output powers of up to 10 20 W for short times with good beam quality and of several kW in continuos operation, usually with less good beam quality. Very short pulses with durations smaller than 5 · 10 −15 s, wavelengths from a few nm in the XUV to the far IR with several 10 µm, pulse energies of up to 10 4 J and frequency stability's and resolutions of better 10 −13 can be generated. The laser prices range from $ 1 to many millions of dollars and their size from less than a cubic mm to the dimensions of large buildings.The good coherence and beam quality of laser light in combination with high powers and short pulses are the basis for many nonlinear interactions, but the laser is a highly nonlinear optical device itself, using nonlinear properties of materials as described in the previous chapters. Therefore, the fundamental laws treated in Chap. 2 for the description of light as well as the description of linear and nonlinear interactions of light with matter in Chaps. 3, 4 and 5 are the basis for the analysis of laser operation and its light properties. Therefore, the theoretical description of laser devices represents an application of these laws and can be presented in this chapter in a compact form. For details the related sections of the previous chapters should be consulted. The different lasers and their constructions, as well as the resulting relevant light and operation parameters, are described and the consequences for photonic applications are discussed. Finally, possible classifications are given and safety aspects are mentioned. For further reading see [M6, M16, M17, M23-M25, M27, M28, M30, M33, M43, M44, M49, M50, M58-M65].

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Results of small-signal gain measurements on a supersonic chemical oxygen iodine laser with an advanced nozzle bank

Cited by 30 publications

References 8 publications

Prediction of I²P 1/2 →²P 3/2 transition lineshapes from 3-D, time dependent simulations of chemical oxygen-iodine laser (COIL) flowfields

Prediction of I²P 1/2 →²P 3/2 transition lineshapes from 3-D, time dependent simulations of chemical oxygen-iodine laser (COIL) flowfields

Prediction of Chemical Laser Flow

Lasers

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Results of small-signal gain measurements on a supersonic chemical oxygen iodine laser with an advanced nozzle bank

Cited by 30 publications

References 8 publications

Prediction of I2P 1/2 →2P 3/2 transition lineshapes from 3-D, time dependent simulations of chemical oxygen-iodine laser (COIL) flowfields

Prediction of I2P 1/2 →2P 3/2 transition lineshapes from 3-D, time dependent simulations of chemical oxygen-iodine laser (COIL) flowfields

Prediction of Chemical Laser Flow

Lasers

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Prediction of I²P 1/2 →²P 3/2 transition lineshapes from 3-D, time dependent simulations of chemical oxygen-iodine laser (COIL) flowfields

Prediction of I²P 1/2 →²P 3/2 transition lineshapes from 3-D, time dependent simulations of chemical oxygen-iodine laser (COIL) flowfields