kW级立式氧碘化学激光器的初步实验研究

 实验考察了立式氧碘化学激光器的工作性能。在氯气流量为82 mmol/s,无主稀释气的条件下,输出功率约1.3 kW，化学效率达到16.9％。分别与以氦气和氮气为稀释气的氧碘化学激光器进行了主要参数的比较（He-COIL在氯气流量110 mmol/s时，输出功率为2.4 kW；N_{2-COIL在氯气流量115 mmol/s时，输出功率为2.6 kW；立式氧碘化学激光器在氯气流量115 mmol/s时，输出功率为1.32 kW），结果表明该COIL装置初步实验结果与传统的He-COIL和N2-COIL相比还存在很大差距。但通过对实验结果的深入分析得知，若进一步降低单重态氧发生器的pτres值，缩短超音速喷管中亚音速段的氧碘混合长度或采用超音速段氧碘混合方式，使该立式氧碘化学激光器在无主稀释气的条件下运行且达到与He-COIL和N2-COIL相当的功率水平是可以实现的。}     

稀释气对COIL输出功率的影响

 研究了稀释气进气位置、稀释比以及氮气、二氧化碳、氩气作为稀释气对kW级立式N₂-COIL输出功率的影响。结果表明：主稀释气从发生器进入,有利于输出功率的提高;从发生器出口进入,有利于激光器的稳定。采用不同的稀释气时,输出功率有很大的不同,但是随着稀释比的变化趋势几乎相同。以Ar作为稀释气可以降低超音速段的温度,提高小信号增益系数;据此优化设计激光器,可以提高激光器的输出功率和化学效率。以CO₂气体为稀释气的激光器在低温吸附方面却有着极大的吸引力。对于不同的实验目的和要求,应该选择不同的气体作为稀释气,充分利用气体自身的优势。     

以氮气为载气COIL的设计与实验

 根据以氮气为载气的特殊要求，对kW级氧碘化学激光器（COIL）装置的结构进行了有针对性的设计和实验研究。在氯气流量为140mol/s的情况下, 获得了2.6kW的功率, 相应的化学效率为20.4%, 喷管出口能流密度达到了74W/cm²。这一结果达到了以氦气为载气COIL的水平。     

副气流中He流量变化对流场混合状态的影响

 在保持主气流流量和副气流中I₂的流量不变的条件下,改变副气流中He的流量,数值模拟氧碘化学激光器拉伐尔喷管内的流场混合特性。结果表明,随着副气流中He的流量的增加,副气流垂直穿透主气流的深度逐渐变大,主、副气流混合状态也逐渐变好,直至氧碘气流混合均匀。     

碘气流穿透深度和碘流量对COIL激光输出功率的影响

 通过采用Cl₂流量250mmol/s列管射流式氧发生器的COIL出光实验，得到了激光输出功率随碘副气流相对于氧主气流混合穿透深度的变化规律。实验结果表明，穿透深度对激光功率影响较大，存在最佳穿透深度，约为3.16mm,计算的最佳穿透深度与实验得到的最佳穿透深度基本一致。通过逐步改变供碘系统的碘气流流量，测量激光的输出功率，在实验上证实并找到了COIL的最佳碘流量值，约为4.5mmol/s，这一结果比以往文献所登载的最佳碘流量值要确切。     

O2(1Δ)发生器溶液预混及反应换热系统设计

 通过采用离心泵与换热器进行的换热系统设计,缩短了溶液预混时间,增强了O₂(¹Δ)发生器的反应换热效率,同时使发生器在反应中具备了动态传质性能,改善了氧碘化学激光器的输出功率。     

以氮气为载气的千瓦级COIL的初步实验研究

 首次在氯气流量为110mmol/s、采用方列管型射流式O₂(¹Δ)发生器(SPJSOG)以及列阵式超音速氧碘混合喷管的COIL装置上，以氮气替代氦气作为载气进行出光实验研究。初步实验获得1.8kw的激光输出功率以及18%的化学效率。     

用吸收光谱法测量COIL的水汽含量

 分析了利用吸收光谱法测量氧碘化学激光器的水汽含量的原理,在氯气流量为0.1 mol/s的N₂-COIL上进行了测试实验。实验结果显示,在常规工作条件下,由于BHP温度变化所引起的水汽百分含量变化仅为0.1%,可以忽略;水汽含量随稀释气体流量增大而增加,气体流速是引起水汽含量变化的主要原因,实验中应把氯气和氧气的比例控制在4∶1之内。     

方列管型射流式O2(1Δ)发生器的COIL出光研究

 方列管型射流式O₂(¹Δ)发生器是一种新型高效的氧碘化学激光器(COIL)化学能源供给装置。描述了采用该发生器在COIL上所做的一系列出光实验,这些实验着重于考察该发生器的性能参数及相应的COIL化学效率。结果在Cl₂流量为0.25mol/s、无冷阱、稳定腔条件下获得化学效率高达26% 。     

玻璃钢转板单重态氧发生器的研究

 研究了作为化学氧碘激光器能源的转板式O₂(¹Δ)发生器非金属化的可行性。实验结果表明, 采用玻璃钢转板代替不锈钢转板是可行的, 有助于COIL小型化和实用化。     

无稀释气立式氧碘化学激光器的设计与实验

 分析了氧碘化学激光器（COIL）在无稀释气条件下工作所带来的一系列问题和对其性能的影响，并提出了相应的解决方法，进而对COIL结构和相关参数进行了有针对性的设计和实验研究。在氯气流量为117.6 mmol/s时,平均输出功率2.25 kW，化学效率达到21.1%，比功率0.22 J/g；分别以氦气和氮气为稀释气，对COIL进行了参数和实验数据比较。     

Effects of dissolved gases and an echo contrast agent on ultrasound mediated in vitro gene transfection

The effects of acoustic cavitation on in vitro transfection by ultrasound were investigated. HeLa cells were exposed to 1.0 MHz continuous ultrasound in culture media containing the luciferase gene. Transfection efficiency was elevated when an echo contrast agent, Levovist was added or air was dissolved in the medium. When cells were sonicated in medium saturated with Ar, N2 or N2O which have different gamma values (Cp/Cv), or were saturated with He, Ar or Ne with different thermal conductivities, the effectiveness for the dissolved gases in the ultrasound mediated transfection was Ar > N2 > N2O or Ar > Ne > He, respectively. When free radical formation in water by ultrasound was monitored as a measure of inertial cavitation, it was similarly affected by dissolved gases. These results indicate that the efficiency of ultrasound mediated transfection was significantly affected either by occurrence of or by modification of inertial cavitation due to various gases.     

Performance Analysis and Optimization for Irreversible Combined Carnot Heat Engine Working with Ideal Quantum Gases

An irreversible combined Carnot cycle model using ideal quantum gases as a working medium was studied by using finite-time thermodynamics. The combined cycle consisted of two Carnot sub-cycles in a cascade mode. Considering thermal resistance, internal irreversibility, and heat leakage losses, the power output and thermal efficiency of the irreversible combined Carnot cycle were derived by utilizing the quantum gas state equation. The temperature effect of the working medium on power output and thermal efficiency is analyzed by numerical method, the optimal relationship between power output and thermal efficiency is solved by the Euler-Lagrange equation, and the effects of different working mediums on the optimal power and thermal efficiency performance are also focused. The results show that there is a set of working medium temperatures that makes the power output of the combined cycle be maximum. When there is no heat leakage loss in the combined cycle, all the characteristic curves of optimal power versus thermal efficiency are parabolic-like ones, and the internal irreversibility makes both power output and efficiency decrease. When there is heat leakage loss in the combined cycle, all the characteristic curves of optimal power versus thermal efficiency are loop-shaped ones, and the heat leakage loss only affects the thermal efficiency of the combined Carnot cycle. Comparing the power output of combined heat engines with four types of working mediums, the two-stage combined Carnot cycle using ideal Fermi-Bose gas as working medium obtains the highest power output.     

Frequency dependence of amplifying parameters of a copper vapor laser using air as a buffer gas

We use a pair of copper vapor lasers in an oscillator–amplifier configuration to investigate amplifying parameters such as the small signal gain and the saturation intensity versus the pulse repetition frequency when two different types of buffer gases are employed. We show that the values of these parameters are not the same if different gas mixtures are used in the gain medium. We show that the values of the parameters are estimated to be higher if a He–Ne buffer gas is used than in the case of air. The laser output power is relatively high and has fairly good stability at some special pulse repetition frequencies when air is used as a buffer gas.     

Analysis of the effect of foreign gases in the production of hyperpolarized 129Xe gas on a simple system working under atmospheric pressure

Experimental conditions that affect the degree of polarization of 129Xe gas were tested for a higher degree of polarization to facilitate a laboratory use of 129Xe NMR, primarily on the effect of addition of foreign gases. When He, N(2), or D(2) gas was added separately to pure Xe gas with natural isotope abundance, D(2) gas gave better results than the others in enhancing the degree of polarization in 129Xe atom. When these gases were added in mixture, however, N(2) plus He was proved to be more efficient than D(2) or He in enhancing the degree of polarization. As a result, the degree of polarization was found to be increased by more than an order, when diluent gases were properly mixed; polarization as high as 35% was reached at gas composition of 5% Xe, 10% N(2), and 85% He, whereas only a few percent was attainable when Xe gas was polarized without mixing any foreign gases [J. Magn. Reson. 150 (2), 156-160 (2001)]. These results were discussed on a basis of quenching and buffer effects of foreign gases. Polarization was also measured after separating the pure Xe gas from the mixture; value of 22% was obtained for the Xe gas isolated after solidification in liquid nitrogen trap. Build-up time of the polarization was also tested, which did not change remarkably depending on the gas composition.     

Power enhancement of the cw 12.08 μm NH3 Raman laser with the addition of H2/He buffer gases

The effects of H₂, He, and N₂ buffer gases on the efficiency of the cw 12.08 μm NH₃ Raman laser are studied experimentally. The laser output power is increased by nearly 60% with the addition of H₂ or He, which we essentially attribute to the high thermal conductivity of these buffer gases. In the optimum conditions (NH₃/H₂:1/1 mixture with 0.35 Torr partial pressure of NH₃) 3.3 W output power at 12.08 μm is obtained which corresponds to 11% power conversion efficiency.