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1.
This paper presents the results of the calculation of the parameters of the active medium of a fast-axial-flow CO2 laser using numerical methods in the framework of a one-dimensional approximation of the set of continuity equations, Bernoulli equation, equation of gas state, energy equation and multi-temperature rate equations with regard to diffusion for the gas flow in the cylindrical discharge tube. The spatial distribution of the small-signal gain and gas temperature along the gas flow direction have been calculated for a given set of initial conditions, namely, gas flow velocity, gas pressure and the tube diameter. In addition, the dependence of small-signal gain, the asymmetric stretch vibrational temperature of CO2 (T3) and the gas temperature on the discharge current were studied.  相似文献   

2.
Transverse flow transversely excited (TFTE) CO2 lasers are easily scalable to multikilowatt level. The laser power can be scaled up by increasing the volumetric gas flow and discharge volume. It was observed in a TFTE CW CO2 laser having single row of pins as an anode and tubular cathode that the laser power was not increasing when the discharge volume and the gas volumetric flow were increased by increasing the electrode separation keeping the gas flow velocity constant. The discharge voltage too remained almost constant with the change of electrode separation at the same gas flow velocity. This necessitated revision of the scaling laws for designing this type of high power CO2 laser. Experimental results of laser performance for different electrode separations are discussed and the modifications in the scaling laws are presented.  相似文献   

3.
In a research of fast axial flow CO2 laser sustained by 150 kHz silent discharge, we found the optimized gas mixing ratio was CO2:N2:He=1:22:5 or the content of helium was only about 18%. This result upset the situation of common CO2 lasers in which the most important laser gas is helium. An explanation of our particular results and supporting experimental evidence are given.  相似文献   

4.
An inductively coupled plasma etching process to fabricate notched long-period fiber gratings for CO2 gas sensing is proposed in this article. In the gas sensing test, the 15% mixed CO2 gas was used for characterization of CO2 adsorption by the amine-modified nanoporous silica foams of the notched long-period fiber grating sensor. The results shows the spectra were changed with the CO2 gas flow within 13 min. During the absorption process, the transmission of the resonant dip was decreased by 2.884?dB. Therefore, the proposed notched long-period fiber grating gas sensor shows good performance and is suitable as a gas sensor for monitoring the CO2 adsorption process.  相似文献   

5.
A supersonic gas flow having a Mach number of 2 has been realized in a closed-cycle radio-frequency (RF)-discharge-excited supersonic CO2 laser system. Stable RF discharge at a high CO2 gas concentration has become possible using supersonic gas flow and RF discharge generated between dielectric electrodes. As a result, high RF input power density has been obtained. In addition, a high small-signal gain has been obtained in the supersonic section through decreases in gas pressure and gas temperature due to supersonic gas flow.This revised version was published online in August 2005 with a corrected cover date.  相似文献   

6.
The repetition rate capability of self-switched transversely excited atmosphere (TEA) CO2 laser was studied for different gas flow configurations. For an optimized gas flow configuration, repetitive operation was achieved at a much smaller gas replenishment factor between two successive pulses when compared with repetitive systems energized by conventional pulsers.  相似文献   

7.
CO2 lasers with transverse discharge and convective gas cooling find ever-increasing application. On strategy in making such lasers more efficient radiators is increasing the rate of the gas flow through the discharge zone with the help of diametral disk fans-heat exchangers. The application of such fans-heat exchangers, however, entails serious difficulties related to the glow discharge-gas flow interaction. In the present study, we investigate the stability problem for volume discharge in the gas loop of a CO2 laser with diametral dis fans-heat exchangers.  相似文献   

8.
Summary The gas flow rate has resulted very important to get high power in a CO2 diffusion-cooled laser. Some measurements suggest that the power dependence on the flow is connected with the chemical dissociation of the components of the gas mixture. Four different gas circuits have been experimented. To speed up publication, the authors of this paper have agreed to not receive the proofs for correction.  相似文献   

9.
A. K. Nath  V. S. Golubev 《Pramana》1998,51(3-4):463-479
Various criteria for designing high power convective cooled CO2 lasers have been discussed. Considering the saturation intensity, optical damage threshold of the optical resonator components and the small-signal gain, the scaling laws for designing high power CW CO2 lasers have been established. In transverse flow CO2 lasers having discharge of square cross-section, the discharge lengthL and its widthW for a specific laser powerP (Watt) and gas flow velocityV (cm/s) can be given byL = 1.4 x 104 p 1/2 V -1 cms andW = 0.04P 1/2 cms. The optimum transmitivity of the output coupler is found to be almost constant (about 60%), independent of the small signal gain and laser power. In fast axial flow CO2 lasers the gas flow should be divided into several discharge tubes to maintain the flow velocity within sonic limit. The discharge length in this type of laser does not depend explicitly on the laser power, instead it depends on the input power density in the discharge and the gas flow velocity. Various considerations for ensuring better laser beam quality are also discussed.  相似文献   

10.
《Solid State Ionics》2006,177(37-38):3323-3331
A performance of an anode-supported tubular Ni–8YSZ/Ni–ScSZ/ScSZ/GDC/LSC cell was investigated at 650–750 °C by feeding model kerosene reformate gas (H2, H2O, CO, CO2, and CH4) to a Ni–8YSZ/Ni–ScSZ anode. Variations of gas composition were observed not only between inlet and outlet of anode to estimate the degree of internal reforming, but also during current input by online quadrupole mass spectrometry and Fourier-transform infrared spectrometry.The electrochemical performance of the cell was independent of reforming temperature of kerosene, i.e. gas composition (in particular CH4 concentration) at moderate anode gas flow rates. At open-circuit states, 10% or less methane in the kerosene-reformed gas was readily converted by steam or CO2 over the Ni–8YSZ/Ni–ScSZ electrode so that gas compositions could almost follow the thermodynamic equilibrium at 650–750 °C. This suggests that the internal reforming should proceed almost completely over the Ni anode. Consumption of H2 and CO and production of CO2 were observed during current input. I–V characteristics remained constant at 650 °C as long as anodic W/F was more than 0.2 kg mmol 1 s. It was demonstrated that a catalytic activity of an anode electrode for hydrocarbons will be important for SOFCs with liquid fuels such as kerosene in order not to deteriorate cell performance.  相似文献   

11.
The fractal dimension of three samples of activated carbon has been determined according to two different experimental methods. The first method is based on the vaporization of gas species from the sample into a CO2 flow up to a constant temperature of 573 K, and the adsorption of CO2 from the CO2 flow onto the surface of the sample under cooling. The second method is based on the application of the equation proposed by Frankel, Halsey and Hill. The degree of concordance between both methods is excellent.  相似文献   

12.
S. Jelvani  A.M. Koushki 《Optik》2012,123(16):1421-1424
In this paper, the laser output power of a fast-axial flow CO2 laser was optimized with gas pressures ratio of CO2:N2:He using a genetic algorithm technique. The power of laser was increased from 500 W (un-optimized case) to 2200 W (simulated case), also experimentally the power has achieved the value of 700 W (optimized case).  相似文献   

13.
This paper concerns the influence of a direct current (dc) corona discharge on production and reduction of NO, NO2 and N2O in N2:O2:CO2 and N2:O2:CO2:NO2 mixtures. The corona discharge was generated in a needle-to-plate reactor. The positively polarized electrode consisted of 7 needles. The grounded electrode was a stainless steel plate. The gas flow rate through the reactor was varied from 28 to 110 cm3/s. The time-averaged discharge current ranged from 0 to 6 mA. It was found that in the N2:O2:CO2 mixture the corona discharge produced NO, NO2 and N2O. In the N2:O2:CO2:NO2 mixture the reduction of NO2 was between 6–56%, depending on the concentration of O2, gas flow rate and corona discharge current. The NO2 reduction was accompanied by production of NO and N2O. The results show that efficient reduction of nitrogen oxides by a corona discharge cannot be expected in the mixtures containing N2 and O2 if reducing additives are not employed.  相似文献   

14.
A transverse flow, transverse discharge cw CO2 laser in which de discharge is sustained by employing high repetition rate high voltage pulses has been developed. Pulser sustained discharge through electrodes of innovative design provided uniform excitation at electrical input power densities more than 10 W/cc. Laser output power more than 2.5 kW was obtained in a laser gas mixture consisting of 0.5 mbar of CO2, 16 mbar of N2 and 38.5 mbar of He. Design details and operational characteristics of this laser are presented.  相似文献   

15.
A four-temperature model has been applied on a fast axial flow, longitudinal discharge CO2 laser. Using Runge–Kutta method, a set of differential equations of the model is numericaly solved. These equations describe the operation of the laser with certain ratio 1:3:6 of the mixture CO2:N2: He and average output power of 550 W.The temporal behaviour of the output power and photon density was obtained. The effects of kinetic temperature, coupled mirror reflectivity, gas flow speed, and cavity loss on the output power were studied.Calculated output power was compared with its measured value taken from experiment and a good agreement was observed.  相似文献   

16.
The paper presents the results obtained in determining the accommodation coefficients for the translational and rotational energy of gas molecules in a Knudsen flow past a thin wire. The method used was based on numerically solving the complete heat balance equation for a wire probe. The accommodation coefficients were determined for H2, N2, CH4, and CO2 on a gilded tungsten surface. For hydrogen with a quenched rotational energy, a negative accommodation coefficient of rotational energy was obtained due to the conversion of the rotational energy of incident molecules into the translational energy of reflected molecules.  相似文献   

17.
《Applied Surface Science》1987,29(4):427-432
The amount of carbon adsorbed on the surface of Ni in contact with carbonaceous gas mixtures such as CH4/H2 and CO/CO2, is estimated from equilibrium segregation data. The results are displayed on “gas composition versus temperature” plots for the above two gas mixtures. These plots provide basic thermodynamic information relevant to reactions such as steam reforming of hydrocarbons on supported Ni catalysts. For example, the plot for CO/CO2 gas mixtures represents the Boudouard equilibrium on a single crystal Ni catalyst, whilst the plot for CH4/H2 gas mixtures provides information relevant to the equilibrium hydrogenation of adsorbed C to CH4.  相似文献   

18.
The gas-liquid upward flow was studied in a rectangular minichannel of 1.75×3.8 mm and length of 0.7 m. The experiments were carried out within the range of the gas superficial velocity from 0.1 to 10 m/s and the liquid superficial velocity from 0.07 to 0.7 m/s for the co-current H2O/CO2 flow under the conditions of saturation. The method for the two-beam laser scanning of structure and determination of statistic characteristics of the two-phase flow was worked through. The slug-bubble, slug, transitional, churn, and annular flows were distinguished. The statistics characteristics of liquid and gas phases motion in a minichannel were obtained for the first time including the velocities of phase motion.  相似文献   

19.
The objective of this study was to understand fluid flow in porous media. Understanding of fluid flow process in porous media is important for the geological storage of CO2. The high-resolution magnetic resonance imaging (MRI) technique was used to measure fluid flow in a porous medium (glass beads BZ-02). First, the permeability was obtained from velocity images. Next, CO2–water immiscible displacement experiments using different flow rates were investigated. Three stages were obtained from the MR intensity plot. With increasing CO2 flow rate, a relatively uniform CO2 distribution and a uniform CO2 front were observed. Subsequently, the final water saturation decreased. Using core analysis methods, the CO2 velocities were obtained during the CO2–water immiscible displacement process, which were applied to evaluate the capillary dispersion rate, viscous dominated fractional flow, and gravity flow function. The capillary dispersion rate dominated the effects of capillary, which was largest at water saturations of 0.5 and 0.6. The viscous-dominant fractional flow function varied with the saturation of water. The gravity fractional flow reached peak values at the saturation of 0.6. The gravity forces played a positive role in the downward displacements because they thus tended to stabilize the displacement process, thereby producing increased breakthrough times and correspondingly high recoveries. Finally, the relative permeability was also reconstructed. The study provides useful data regarding the transport processes in the geological storage of CO2.  相似文献   

20.
The paper presents the results of a long-term measurement series using hermetic containers to make more precise quantitative estimation of the generation rates and radioactivity of the gas in a drum of low and intermediate level radioactive waste (L/ILW) packages. Development of special preparation lines and isotope-analytical measurements of the headspace gas samples were performed in the ATOMKI. Stable isotope measurements were executed from the CO2 and CH4 fractions by stable isotope ratio mass spectrometer. Noble gas (He) measurements were done by noble gas mass spectrometer. The tritium content of the vapour, H2 and CH4 fractions was measured in H2O chemical form by a low background liquid scintillation counter. The 14C content of the CO2 and CH4 fractions of the headspace gas samples was measured by a low background gas proportional counter system.  相似文献   

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