非均匀温度场的可调谐激光吸收光谱诊断分析及其算法研究

高超声速燃烧问题中因为大量湍流及激波的存在,温度,组分的分布存在着极大的不均匀性。如何准确而可靠地诊断这些不均匀参数的分布对诊断超燃发动机燃烧工况具有重要意义。传统的热电偶测温技术由于热电偶的介入会对超声速流场产生重大干扰,且热电偶的电阻丝可能会被超声速燃烧下的高温流场烧毁或破坏,因此在超燃流场温度诊断时效果欠佳。而目前诊断超燃流场时使用最多的单通道吸收光谱技术由于检测的是激光路径上的平均值,其测量结果并不能有效反应流场中的不均匀性。本文中根据可调谐激光器的吸收光谱特性,尝试采用多组多波长激光器在二维平面组成激光网格,通过全局优化算法尝试求得全局不均匀温度场与浓度场的分布。和传统CT扫描实验方..

基于量子级联激光器的ADN基液体发动机稳态燃烧CO特征浓度的实验测量

二硝酰胺铵(AND)作为一种绿色无毒推进剂已在固体推进剂以及液体推进剂领域得到一定程度的应用,是未来化学推进技术的一个新方向.目前我国正处于ADN基液体推进剂研究的起始阶段,对于其燃烧反应过程的研究是当前的一个研究重点.由于ADN基液体推进剂催化分解及燃烧反应过程复杂,相关的实验结果国内外公开文献发表较少,因此有必要开展ADN基液体发动机催化分解及燃烧反应的实验研究.本实验采用基于量子级联激光器的吸收光谱诊断技术,对ADN基液体发动机燃烧室内燃烧过程进行探究.CO是ADN基液体推进剂催化分解及燃烧反应的特征产物之一,通过测量ADN基液体发动机典型工况下CO的特征浓度,可以定量获得ADN基发动机...</p

An Optical High Temperature Thermometer for Plume Measurement of Solid Propellant Rocket Motor

利用辐射光谱测量温度的原理,设计并制造了一种新型的非接触式光学辐射高温计.详细介绍该温度计的基本原理和标定方法,并将该温度计应用于火箭发动机喷管出口羽流的温度测量中,初步的实验结果和数值模拟结果相一致

Near-diffraction-limited, 35.4 W laser-diode end-pumped Nd:YVO4 slab laser operating at 1342 nm

A diode stack end-pumped Nd:YVO4 slab laser at 1342 nm with near-diffraction-limited beam quality by using a hybrid resonator was presented. At a pump power of 139.5 W, laser power of 35.4 W was obtained with a conversion efficiency of 25.4% of the laser diode to laser output. The beam quality M-2 factors were measured to be 1.2 in the unstable direction and 1.3 in the stable direction at the output power of 29 W. (C) 2009 Optical Society of Americ

Measurement of multispecies concentration and gas temperature in an ammonium-dinitramide-based thruster by tunable diode lasers

In this paper, quantitative experiments were made to measure the concentration of key intermediate products (CO, N2O, and NO) and the gas temperature for combustion flow based on near-infrared and mid-infrared laser absorption spectroscopy. This paper used the developed diagnostic system to study two main ignition modes of a real 1-Newton thruster based on ammonium dinitramide (ADN): steady-state firing and pulse-mode firing over a feed pressure of 5-12 bar. The steady-state firing experiments distinguished the whole process into catalytic decomposition stage and combustion stage, experimentally demonstrating the combustion kinetics mechanism of an ADN monopropellant. Experiments for pulse-mode firing showed the measured multispecies concentration and temperature were consistent with pulse trains, verifying good performance for the thruster pulse-mode firing operation. The performance of the thruster was given based on the optical measurements, and characteristic velocity for the ADN-based thruster standard operation was higher than the corresponding 1-Newton hydrazine thruster. (C) 2018 Optical Society of America</p

Transmission characteristics of EM wave in a finite thickness plasma

One of the key factors for solving the problems of re-entry communication interruption is electromagnetic (EM) wave transmission characteristics in a plasma. Theoretical and experimental studies were carried out on specific transmission characteristics for different plasma sheath characteristic under thin sheath condition in re-entry state. The paper presents systematic studies on the variations of wave attenuation characteristics versus plasma sheath thickness L, collision frequency &nu;, electron density ne and wave working frequency f in a &phi; 800mm high temperature shock tube. In experiments, L is set to 4 cm and 38 cm. &nu; is 2 GHz and 15 GHz. ne is from 1&times;10^10 cm&minus;3 to 1&times;10^13 cm&minus;3, and f is set to 2, 5, 10, 14.6 GHz, respectively. Meanwhile, Wentzel&ndash;Kramers&ndash;Brillouin (WKB) and finite-difference time-domain (FDTD) methods are adopted to carry out theoretical simulation for comparison with experimental results. It is found that when L is much larger than EM wavelength &lambda; (thick sheath) and &nu; is large, the theoretical result is in good agreement with experimental one, when sheath thickness L is much larger than &lambda;, while &nu; is relatively small, two theoretical results are obviously different from the experimental ones. It means that the existing theoretical model can not fully describe the contribution of &nu;. Furthermore, when L and &lambda; are of the same order of magnitude (thin sheath), the experimental result is much smaller than the theoretical values, which indicates that the current model can not properly describe the thin sheath effect on EM attenuation characteristics

Measurement of temperature, velocity and water vapor concentration in a scramjet combustor based on nearinfrared diode laser absorption

A multi-channel Tunable Diode Laser Absorption Spectroscopy (TDLAS) system was designed and constructed for flow parameters diagnostics in a scramjet combustor. Two fiber coupled distributed feedback (DFB) lasers with narrow line width were used to probe two H2O absorption features (7185.597cm-1,7444.35cm-1+7444.37cm-1(c ombined)) by using direct absorption Time-Division-Multiplexing (TDM) strategy at a 4-kHz repetition rate. Laser light was split into five beams and transmitted across the test region. Two motorized precision translation stages were used to move the collimators during the test, so that the three beams located near the cavity and at the exit of the combustor can scan the cross sections respectively. Flow parameters could be obtained simultaneous which included average temperature, water vapor concentration and velocity at the entrance of the combustor, the distribution of temperature, water vapor concentration at a cross section near the cavity, the distribution of temperature, water vapor concentration and velocity at the exit cross section of the combustor. The parameters of the flow entering and exiting the combustor could be used to evaluate the performance of the direct-connected scramjet facility and the combustion efficiency of the combustor. The parameters at the cross section in the combustor could also be used to analysis combustion characteristics in the combustor

CO concentration and temperature measurements in a shock tube for Martian mixtures by coupling OES and TDLAS

CO concentration and gas temperature distribution are diagnosed behind a strong shock wave simulating the Martian atmosphere entry processes by coupling optical emission spectroscopy (OES) and tunable diode laser absorption spectroscopy (TDLAS). The strong shock wave (6.31 +/- A 0.11 km/s) is established in a shock tube driven by combustion of hydrogen and oxygen. Temperature of the shock-heated gas is inferred through a precise analysis of the high temporal and spatial resolution experimental spectral of CN violet system (B (2) I pound (+) -> X (2) I pound (+), Delta v = 0 sequence) using OES. A CO absorption line near 2,335.778 nm is utilized for detecting the CO concentration using scanned-wavelength direct absorption mode with 50 kHz repetition rate. Combined with temperature results from OES, CO concentration in the thermal equilibrium region is derived. The current experimental results are complementary for determining an accurate rate coefficient of CO2 dissociation and validation relevant chemical kinetics models in Mars atmosphere entry processes

Effects of alkaline-earth strontium on the performance of Co/Al_2O_3 catalyst for methane partial oxidation

联系作者: 余长林( 1974-) ，湖南炎陵人，男，博士，副教授。主要从事纳米催化新材料研究。Tel: 0797-8312334; E-mail: [email protected]。 本文的英文电子版由Elsevier 出版社在ScienceDirect 上出版( http: / /www.sciencedirect． com /science /journal /18725813) 。[中文文摘]以γ-Al2O3为载体,采用共浸渍法制备了Sr-Co/Al2O3系列催化剂,研究了助剂Sr对Co/Al2O3催化剂上甲烷部分氧化(POM)制合成气反应的影响,并利用N2物理吸附、X射线衍射、H2-程序升温还原和热重等技术对催化剂的理化性质进行了表征。结果表明,未添加助剂的Co/Al2O3和800℃焙烧的Sr-Co/Al2O3催化剂在POM反应初期催化活性很低,然而,当添加Sr的质量分数高于2%时,催化剂表现出很好的催化活性和稳定性。焙烧后的新鲜催化剂上主要存在两类Co物种,一类是与载体相互作用较弱、易被H2还原为单质的Co3O4;另一类是与载体相互作用较强、难还原、无催化活性的CoAl2O4尖晶石。在焙烧过程中,Sr易形成Sr4Al14O25,从而削弱Co与Al2O3之间的相互作用,能在一定程度上抑制CoAl2O4物种的形成,提高催化剂的稳定性和活性。未添加Sr的Co/Al2O3在反应时易发生物相改变生成尖晶石,导致催化剂迅速失活;但当焙烧温度达到800℃时,添加有限量的Sr还是无法阻止CoAl2O4的产生。[英文文摘]A series of Sr-Co/Al2O3 catalysts were prepared by co-impregnation method using γ-Al2O3 as the support.The effect of strontium promoter on the catalytic performance of Co/Al2O3 catalyst for partial oxidation of methane(POM) to synthesis gas was studied.The catalysts were characterized by some physicochemical characterizations such as N2 physical adsorption,X-ray diffraction(XRD),H2-temperature programmed reduction(H2-TPR) and thermogravimetry(TG).The results show that both Co/Al2O3 calcined at 700 ℃ and Sr-Co /Al2O3 calcined at 800 ℃ exhibit low activity and deactivate at the initial stage of POM reaction.The addition of above 2% mass fraction of strontium will greatly enhance the activity and stability of Co /Al2O3.Two types of Co species were identified on the fresh calcined catalysts.One is Co3O4 which weakly interacts with Al2O3 (easily reduced by H2) and the other is the spinel CoAl2O4 ( non-catalytic performance) which strongly interacts with the support.During the course of calcination，strontium can react with Al2O3 to form Sr4Al14O25 which will restrain the generation of the CoAl2O4 species and promote the stability and activity of catalysts．Without strontium promoter，CoAl2O4 is easy to be formed over Co /Al2O3 in the POM reaction.However，the formation of CoAl2O4 cannot be avoided with the addition of limited strontium when the calcination temperature is over 800 ℃．国家自然科学基金(21067004,21263005); 厦门大学固体表面物理化学国家重点实验室开放基金(200906);; 江西省自然科学基金(2010-GZH0048); 江西省教育厅科技项目(GJJ12344); 江西省青年科学家培养对象资助(20122BCB23015