基于可调谐二极管激光吸收光谱技术的炉内燃烧场参数在线监测系统设计

基于可调谐二极管激光吸收光谱(tunable diode laser absorption spectroscopy,TDLAS)技术,设计了炉内多燃烧场参数(温度,CO、CO₂和NO浓度等)同时在线监测技术方案,包括一维燃烧参数监测系统和多维燃烧参数监测系统。在一维燃烧参数监测系统中,引入光开关技术实现多个燃烧参数的同时测量。在二维燃烧参数监测系统中,引入分光器技术和代数迭代算法(algebraic reconstruction technique,ART)实现平面内二维燃烧参数的反演和测量。在此基础上,设计了三维燃烧参数监测系统,三维燃烧参数测量步骤为：先将炉内燃烧区域划分为多层二维切片;再基于ART法重建二维燃烧参数;最后基于多层二维燃烧参数数据重构三维燃烧参数。本文所设计的炉内燃烧场参数监测系统有利于未来锅炉精细化调整。     

新能源车用CO2空调系统泄漏特性仿真研究

CO₂作为一种安全、高效且环境友好的自然工质,是未来汽车空调制冷剂替代方案的重要选择。考虑到CO₂系统制冷剂泄漏导致乘员舱气体体积分数超标的舒适及安全问题,本文使用三维仿真软件STAR-CCM+搭建乘员舱CO₂制冷剂泄漏仿真模型,仿真分析两种不同泄漏速率和泄漏圆孔孔径下乘员舱乘客面部测点CO₂体积分数的动态变化情况。在50 g/s的高CO₂泄漏速率下,面部CO₂体积分数在泄漏完成时能够达到9%以上,需要切换送风模式提供新风来降低乘员舱内CO₂体积分数;在0.1 g/s的低CO₂泄漏速率下,泄漏完成时面部CO₂体积分数不超过3%,处于呼吸安全区范围。     

CO2聚能剂燃烧与冲压实验研究

为进一步地揭示CO₂相变膨胀的热力学机理,通过CO₂爆燃冲压实验,对起爆温度、CO₂与CO₂聚能剂(一种高能复合材料)质量比对CO₂爆燃冲压过程、CO₂聚能混相流体燃烧速率、燃烧热和峰值压强的影响规律进行了研究。最终得到了不同工况下实验组的压强时程。结果表明：爆燃筒内反应能否发生对CO₂密度和起爆温度有一定的要求;在实验研究范围内,CO₂密度、CO₂与CO₂聚能剂质量比、起始温度与爆燃实验的化学反应速率、压强增长速率呈正相关。     

利用发射光谱探究CO2对MPCVD法生长单晶金刚石质量的影响

等离子体发射光谱作为一种非侵入性等离子体诊断手段能有效探测等离子体内部基团的变化信息,对这些信息的分析可以反映等离子体的特性,从而有助于探究影响单晶金刚石生长结果的原因和机理。CO₂是一种比O2更安全的气体,近年来在源气体引入CO₂生长高质量单晶金刚石的研究日渐增多。本文利用微波等离子体化学气相沉积法在4.2 kW的微波功率下进行单晶金刚石同质外延生长实验,对生长过程中的CH4/H2/CO₂等离子体进行了发射光谱诊断,最后结合光谱信息和拉曼光谱表征研究了CO₂体积分数对单晶金刚石生长质量的影响,结果发现CO₂浓度增加对C2和CH基团强度抑制作用明显,对C2抑制作用最强,这也是导致生长速率下降的主要原因。I(CH)/I(Hα)比值略有增加,说明CO₂增加对金刚石前驱物的沉积有促进作用,这在一定程度上减弱了对生长速率的不利影响。拉曼表征结果说明0～5%CO₂浓度下的单晶金刚石质量随CO₂浓度上升变好,且浓度为5%时,...     

CO2制冷压缩机性能检测装置与试验研究

根据CO₂制冷压缩机的运行特点,设计了一套适用于跨临界循环的压缩机性能检测装置,该装置适用于制冷量为14 kW⁷0 kW的冷冻冷藏及热泵系统用CO₂压缩机的测试,试验方法为制冷剂气体流量计法和跨临界气体冷却器法;在此基础上开展了CO₂制冷压缩机的性能测试,结果表明,该压缩机的主侧制冷量、辅侧制冷量及主辅侧平均值的测量结果重复性偏差均在±1%以内。     

CO2高温电解技术助力化工产业碳中和(英文)OA

化学工业是我国主要的CO₂排放源,为了实现我国的碳中和目标,必须重点关注化学工业的碳排放情况。基于固体氧化物电解池(SOEC)的CO₂高温电解技术,对于中国实现碳减排、碳达峰和碳中和目标具有重要意义。此外,该技术可以实现CO₂的资源化利用,从而产生可观的环境效益和潜在的经济效益。目前,CO₂高温电解技术已经在实验室和中试阶段取得了很大进展,但该技术的大规模工业应用还需要进一步探索。本文综述了高温CO₂电解池材料的最新研究进展,讨论了SOEC技术的未来发展方向,并提出了SOEC技术与化工合成耦合实现碳中和目标的方法。     

介孔碳/聚酰亚胺杂化膜原位聚合法制备及其气体分离性能

通过原位聚合法分别将无序介孔碳（DOMC）、有序介孔碳（OMC）掺杂到聚酰亚胺（PI）中制备DOMC/PI、OMC/PI杂化膜。利用FTIR、TEM、SEM和XRD等分析表征两种介孔碳材料的结构及其掺杂对杂化膜形貌和结构的影响,结合CO₂和N₂的渗透实验考评杂化膜的气体渗透性能。DOMC、OMC均具有孔隙结构,且与CO₂分子之间存在相互作用,通过掺杂DOMC、OMC既能提高杂化膜的自由体积,又可促进杂化膜对CO₂的优先选择吸附。表现为掺杂DOMC、OMC可有效改善PI膜的CO₂、N₂渗透性能和CO₂/N₂渗透选择性。随掺杂量的增加,杂化膜的CO₂、N₂渗透性能和CO₂/N₂渗透选择性均先增大后减小。另外,相较于OMC,DOMC具有更多孔隙结构和更大的比表面积,使DOMC/PI杂化膜的CO₂、N₂渗透性能优于OMC/PI杂化膜,但两种杂化膜的CO₂/N₂渗透选择性相近。     

紫外吸收光谱法在线测量SO3的实验研究

基于紫外吸收光谱法对SO₃的在线测量进行了实验研究,搭建了SO3气体发生系统。为提高检测精度,探究了去除测量过程中的各种干扰因素。SO₃与SO₂的特征吸收波段重叠严重,通过合理选择特征吸收波段和光谱反演策略最大程度地去除SO₂对SO₃测量的影响。研究中采用标准曲线法结合单波长法、双波长法和积分光谱法建立了标准曲线。结果表明:积分光谱法的测量误差最小,可优先应用于SO3排放的在线光谱计量分析。     

CO2/O2环境下L320钢在不同流速下的腐蚀行为研究

为了确定L320钢在CO₂/O₂环境中不同流速下的腐蚀行为,通过多相流瞬态模拟仿真软件,模拟目标管道的流动状态,确定室内模拟试验的流速范围,选择L320钢进行CO₂/O₂共存体系下不同流速的高温高压动态反应釜试验,采用扫描电镜、X射线衍射仪对腐蚀产物进行微观形貌表征和成分分析。结果表明:温度和压力随着里程的增加呈现下降的趋势;管道气体流速和壁面剪切力随着里程的增加呈现逐渐上升的趋势。基于Pearson相关系数法,确定了流速是影响腐蚀速率的主控因素。随着流速的增加,L320在CO₂/O₂共存条件下的均匀腐蚀速率逐渐增大。CO₂/O₂共存体系的腐蚀产物为Fe 2 O₃、FeOOH、Fe(OH)3、Fe 3 O 4、FeCO₃等。研究结论可为不同流速下的L320钢在CO₂/O₂共存环境中的防护提供借鉴。     

跨临界CO2制冷技术发展现状及其改进途径综述

跨临界CO₂制冷是一种以CO₂作为制冷剂气体冷却过程在临界点以上的新型制冷技术。对近年来CO₂制冷技术的发展进行了概括及分析。针对传统制冷剂与CO₂制冷剂的特点,重点分析了二者在物理性质上的区别,说明了CO₂作为新型制冷剂的可取性;针对提升制冷系数的目标,讨论了两级压缩、膨胀机、回热器的工作原理以及对系统性能的影响。综述了新型双级压缩CO₂制冷循环的研究现状,归纳了CO₂制冷循环进一步改善性能的技术途径。     

Geometrical factors affecting the CO2 laser chemical vapour deposition of silicon oxide films in parallel configuration

Laser-induced chemical vapour deposition of SiO₂ films in a parallel configuration is a powerful technique for the growth of coatings in some special applications where other conventional low-temperature techniques cannot be applied. A CO₂ laser is more attractive than other lasers for industrial applications since it is less expensive and already widely used in the industry. Growing SiO₂ films is carried out by irradiating a gas mixture composed by SiH₄, N₂O and Ar with a continuous wave CO₂ laser. Energy absorption by the mixture causes a temperature increase in the gas phase which leads to the deposition process. Here we present a study of two important geometrical factors in our experimental set-up: the total flow rate of the reactant gases, and the distance between the laser beam and the substrate surface. Variations in gas flow cause changes in the absorption coefficient of the gas mixture and thus in the gas temperature, which mainly affects the growth rate. The beam-substrate distance influences the gas temperature owing to heat exchange between the gas and the substrate and to the collision rate of the chemical species in their diffusion path towards the substrate surface. Therefore, both the growth rate and the film properties change with this parameter.     

A wireless, passive carbon nanotube-based gas sensor

A gas sensor, comprised of a gas-responsive multiwall carbon nanotube (MWNT)-silicon dioxide (SiO₂) composite layer deposited on a planar inductor-capacitor resonant circuit is presented here for the monitoring of carbon dioxide (CO₂), oxygen (O ₂), and ammonia (NH₃). The absorption of different gases in the MWNT-SiO₂ layer changes the permittivity and conductivity of the material and consequently alters the resonant frequency of the sensor. By tracking the frequency spectrum of the sensor with a loop antenna, humidity, temperature, as well as CO₂ , O₂ and NH₃ concentrations can be determined, enabling applications such as remotely monitoring conditions inside opaque, sealed containers. Experimental results show the sensor response to CO₂ and O₂ is both linear and reversible. Both irreversible and reversible responses are observed in response to NH₃, indicating both physisorption and chemisorption of NH₃ by the carbon nanotubes. A sensor array, comprised of an uncoated, SiO₂ coated, and MWNT-SiO₂ coated sensor, enables CO₂ measurement to be automatically calibrated for operation in a variable humidity and temperature environment     

Experimental investigation of a CO2 automotive air conditioner

In this study, a CO₂ automotive air conditioner prototype was designed and constructed. The compressor was of swash plate design; the gas cooler and evaporator were made of fin-tubes; a manual expansion valve and an internal heat exchanger accumulator were used. The lubricant, the CO₂ charge, the evaporator outlet pressure, the compressor speed, the air inlet temperature and flow rate of the gas cooler and the air flow rate of the evaporator were varied and the performance of the prototype was experimentally investigated in detail. The cooling capacity, compressor power consumption, CO₂ mass flow rate, and COP value were analyzed. The experimental results showed that the CO₂ system performance was greatly affected by different lubricants; the CO₂ system performance was sensitive to the mass charge; the high side pressure affected the system performance greatly and a high side pressure controller was needed.     

Marangoni convection and weld shape variations in Ar–O2 and Ar–CO2 shielded GTA welding

Increasing the oxygen or the carbon dioxide concentration in the argon-based shielding gas leads to an increase in the weld metal oxygen content when the oxygen or carbon dioxide concentration is to be lower than 0.6 vol.% in the shielding gas. However, when the O₂ or CO₂ concentration is higher than 0.6 vol.% in the Ar-based shielding gas, the weld metal oxygen is maintained around 200 ppm–250 ppm. An inward Marangoni convection mode in the weld pool occurs when the weld metal oxygen content is more than 100 ppm. When it is lower than 100 ppm, the Marangoni convection would change to the outward direction and the weld shape varies from a deep narrow to a shallow wide shape. The effective ranges of O₂ and CO₂ concentrations for deep penetration are same. A heavy layer of oxides is formed when the O₂ or CO₂ concentration in the shielding gas is more than 0.6 vol.%. Based on the thermodynamic calculation of the equilibrium reactions of Fe, Si, Cr and Mn with oxygen in liquid iron for the oxide products, FeO, SiO₂, Cr₂O₃ and MnO and the experimental oxygen content in the weld metal, Cr₂O₃ and SiO₂ oxides are possibly formed at the periphery area of the liquid pool surface under the arc column during the welding process. One model is proposed to illustrate the role of the oxide layer on the Marangoni convection on the pool surface at elevated temperature. The heavy oxide layer inhibited the fluid flow induced by the Marangoni convection and also became a barrier for the oxygen absorption into the molten weld pool.     

Prospects for laser wakefield accelerators and colliders using CO2 laser drivers

Energy directly acquired by an electron from the laser electromagnetic field is quadratically proportional to the laser wavelength. Exploiting this feature, the emerging terawatt picosecond (TWps) CO₂ lasers, having an order of magnitude longer wavelength than the well-known table-top terawatt (T³) picosecond solid state lasers, offer new opportunities for strong-field physics research. Laser accelerators serve as an example where application of the new class of lasers will result in enhancement in gas ionization, plasma wave excitation, and relativistic self-focusing. Ponderomotively strong CO₂ laser permits a 100 times reduction in the plasma density without impeding the acceleration. The improved performance of the low-pressure laser wakefield accelerators (LWFA) is potentially due to higher electric charge per accelerated bunch and better monochromaticity. The multi-kilowatt average power, high repetition rate capability of the TWps-CO₂ laser technology opens new opportunities in development of compact, 1 m long, GeV accelerators and < 1 km long high-luminosity multi-stage LWFA colliders of the TeV scale. The first TWps-CO₂ laser is under construction at the BNL Accelerator Test Facility (ATF).     

Basic study on new cryogenic refrigeration using CO2 solid–gas two phase flow

In this paper, a cryogenic refrigeration method is described, which utilizes CO₂ solid–gas two phase flow and the dry ice. The CO₂ solid–gas two phase flow is achieved by expanding liquid CO₂ and thus refrigeration process less than CO₂ triple point −56.6 °C can be available. The experimental work is divided into two parts and two experimental set-ups were designed, constructed and tested. The interest of the first experiment test is the feasibility of expanding liquid CO₂ into CO₂ solid–gas flow in a horizontal circular tube by expansion valve. The second experiment focuses on the feasibility of the refrigeration of liquid CO₂ expanding into solid–gas two phase flows used in a prototype CO₂ heat pump system. The results show that solid–gas two phase flows can be achieved by expanding liquid CO₂ by expansion valve in a closed CO₂ heat pump system loop and low temperature refrigeration below −56.6 °C is achieved in the experiments, which give greater possibility to create a cryogenic refrigeration process below −56.6 °C for food industries, bio-medical engineering, etc.     

CO2 Laser Cutting of Calcareous Stones

Portugal is one of the major European producers of natural stones. In the last decade, transformation of stones has been privileged in most of the companies and the quantity of finished product for exportation increased with a major added value. New technologies and processes have been investigated. For example, CO₂ laser has been used for cutting, marking, and drilling. The major advantage of this tool is its flexibility, and thus, it improved the working environment significantly. This article presents a report on the use of CO₂ lasers in the cutting process of marbles and limestones. The cut quality was evaluated by adjusting the laser output power and assist gas type and pressure. The CO₂ laser can be used as a feasible tool for cutting ornamental stones. Due to the economic reasons, it is specially adequate for cutting nonlinear shapes where conventional cutting tools, such as the diamond wires and saws, have limitations on both the shape and the dimensions to be cut.     

CO2和H2O在活性炭上的吸附平衡和吸附动力学研究

活性炭是应用在变压吸附分离CO₂工艺中的常用吸附剂, 而工业废气中一般都含有一定量的饱和水蒸气. 通过吸附等温线和穿透曲线分别研究了单/双组份的CO₂和H₂O在活性炭上的吸附平衡和吸附动力学. 结果表明, 活性炭对二氧化碳具有较高的吸附量, 并具有较好的CO₂/N₂吸附选择性. 由于吸水官能团的存在, 活性炭在较高分压下表现出较大的水蒸气吸附量. 不过由于吸附机理不同, 水蒸气在活性炭上的吸附几乎不会影响活性炭对CO₂的吸附. 动力学研究表明, CO₂在活性炭上的吸附速率远大于H₂O的吸附速率.     

Microsystem With Fluidic and Optical Interface for Inline Measurement of ${rm CO}_{2}$ in Oil Fields

Motivated by the need for inline measurements in natural gas and oil exploitation, we developed a microfluidic system which is suitable for chemical measurements by optical methods. It consists of a microfluidic system allowing the separation of gas and liquid phases so that gas can be optically analyzed. This system takes advantage of surface tension effects in tiny microchannels. The application is the measurement of carbon dioxide (CO₂) concentration by evaluating absorption of infrared light at a wavelength of 4.24 mum. Measurements have been successfully performed in the 0-70 bars pressure range.