热催化蜂窝降解室内VOCs实验研究

使用热催化材料降解挥发性有机化合物(VOC)是一种新型的空气净化方式。本文采用陶瓷蜂窝(负载含1%Pt的热催化剂)组成催化装置,研究了其在密闭环境舱中降解空气中甲醛和甲苯的特性。结果表明,在25℃条件下,热催化蜂窝装置对甲醛的降解效果显著,对甲苯无明显降解效果;在170℃条件下,装置对甲醛降解效果明显增强,对甲苯也表现一定降解效果。分析表明,提高温度对降解性能的影响主要表现为催化反应速率的增强。     

吸附-热催化复合材料的净化能力研究

针对室内空气中常见的有机挥发性污染物,制作了低能耗且无二次污染的吸附-热催化复合空气净化材料。实验结果表明;(1)原料用量为1∶1的0.25%Pt热催化-硅胶复合材料对空气中的甲醛、苯、甲苯净化效果最好;(2)复合材料对甲醛、苯、甲苯的净化能力都有时效性。上述结果对该材料在实际空气净化中的有效应用具有指导意义。     

光谱法测定室内空气中甲醛浓度

为了对甲醛的浓度进行快速而有效的检测，设计了一套光栅式光谱检测系统。该系统主要包括光学系统、光电信号采集系统和计算机处理系统。系统硬件电路包括前置放大滤波电路、A/D转换电路及单片机的数据采集和发送电路。对酚试剂分光光度法测定空气中甲醛浓度的实验条件进行了研究，分析了影响实验结果的因素，得出了光谱检测实验的实验结果，并对相关结论进行了分析和论证。通过所设计的系统，可直接测出甲醛分析液的透射光光谱，从而得出相应的甲醛浓度。     

空气制水装置的性能研究

空气制水装置能够解决饮用水短缺问题,满足人们对健康饮用水的需求。国内关于空气制水装置的研究处于起步阶段,制水装置存在能耗高、出水量小等问题。针对这些问题,对提高出水量方法进行了研究,搭建了变风量空气制水装置实验台,介绍了实验过程和实验原理。通过对实验研究和模拟计算结果的分析讨论,论述了影响空气制水装置性能的主要因素之间的关系,建立了预测空气制水装置实际出水量的理论模型。它可以作为空气制水装置设计和性能优化的依据。     

具有公自转运动模式的高效轮式抛光工具设计

为了提高光学加工效率,缩短大口径光学元件制造周期,本文提出了一种具有公自转运动模式的新型高效抛光方式,对其结构、工作原理以及去除特性进行了研究。首先,介绍了公自转抛光装置机械结构及工作原理。接着,根据Hertz接触理论和Preston方程进行了去除函数建模,讨论了不同转速比情况下的去除函数形状。然后,根据理论模型进行了去除函数实验、工艺参数实验以及稳定性实验,研究了压入深度、转速等工艺参数对去除结果的影响。最后,进行了200 mm口径SiC工件的仿真加工。实验结果表明:在2 mm压入深度、200 rpm转速情况下,去除区域直径为19.23 mm,体去除率达到0.197 mm~3/min,去除效率高于同等去除区域大小的传统小磨头加工方式;仿真加工结果表明:SiC仿真镜经过3.7 h加工,面形从3.008λPV,0.553λRMS提高到0.065λPV,0.005λRMS,收敛效率为达到98.18%。     

光学镜面离子束加工去除函数工艺可控性分析

实验分析了离子束加工去除函数的工艺可控性问题并进行了初步修形实验。从工艺实现的角度分析光学镜面离子束加工技术对去除函数的要求,以去除函数环半峰全宽、体积去除率和峰值去除率为评价指标研究去除函数的长时稳定性、线性性、小扰动鲁棒性以及大参数调节变化等特征,以此分析结果为依据,对Φ100mm K4平面样件进行了修形,经过三次迭代面形RMS误差从0.149λ收敛到0.013λ。实验结果表明:离子束加工中的去除函数具有较长时稳定性,去除量对时间具有线性关系,对工艺参数小扰动的鲁棒性,可以通过调节离子源电源参数优化选取去除函数的宽度和幅值;利用离子束可以对镜面进行高效地修形。     

不同温度下空气比热容比测量装置的研究

针对大学物理实验现有测量空气比热容比装置存在的不足,研制了可测量不同温度下空气的比热容比的装置,包括贮气瓶、压力传感器、温度传感器及水浴系统.该装置可使贮气瓶内空气保持在30～90℃之间的任一温度.每隔10℃测量空气的比热容比值,实验结果表明空气比热容比随温度上升而下降.     

射频聚焦离子源熔石英高确定去除特性研究

在离子束抛光工艺过程中，材料确定性去除特性对预测光学元件的各工位材料去除量和驻留时间具有极其重要的作用。采用射频离子源对熔石英光学元件的离子束刻蚀特性进行了研究，利用ZYGO激光干涉仪获得准确的去除函数，系统分析了气体流量、屏栅电压、离子束入射角和工作距离等因素对熔石英去除函数的影响，并分析了各单一工艺因素微小扰动时，材料峰值去除率、半高宽和体积去除率的相对变化率。实验结果表明，相同工作真空条件下，工作气体质量流量的微小变化对去除函数影响极小，在典型的工艺条件下，屏栅电压在±5 V、离子束入射角±1°、工作距离在±0.5 mm范围内变化时，熔石英峰值去除率、体积去除率和峰值半高宽的相对变化均小于5%，去除函数具有较好的确定性和稳定性。     

OH自由基启动甲苯光氧化产物的质谱

在烟雾腔系统内,辐照甲苯/CH₃ONO/NO/空气混合系统,启动甲苯的光氧化反应. 利用同步辐射光电离质谱在线检测甲苯光氧化气相产物,并用气溶胶飞行时间质谱实时测量甲苯光氧化形成的二次有机气溶胶粒子. 实验结果表明,呋喃、甲基乙二醛,2-甲基呋喃、苯甲醛、甲基酚和苯甲酸是甲苯光氧化反应形成的气体相和粒子相的主要产物,而乙二醛、2-羟基-3-氧代-丁醛、硝基甲苯和甲基硝基酚只存在粒子相.     

以地下土壤为冷源的空气取水实验研究

随着水资源的日益缺乏,如何获取更多的淡水资源越来越得到重视,尤其体现在一些严重干旱地区。为解决干旱地区淡水资源短缺的问题,研究并探索了一种利用沙漠中土壤与大气环境温差来实现空气取水装置。空气中含有大量的水蒸气可以利用,本文为此设计了一种新型空气取水系统,利用温度较为恒定的土壤作为冷源,整个系统使用极低的能耗,通过降温的方式达到空气取水的效果。搭建试验台进行了相关实验,发现系统的取水能力主要受空气温度的影响,通过模型实验与计算的方法确定了空气取水过程中送风速度与冷凝水量的关系式,得出最优风量为11.37 m/s,此时取水系统的取水效率最高。     

IR spectroscopic study of the chemical composition of epiphytic lichens

Changes in the chemical composition of lichens exposed to pollutants are investigated by means of FTIR spectroscopy. According to model experiments, alkyl nitrates, ammonium salts, amines, and sulfones develop in the lichen thallus through the action of ammonia and nitric and sulfuric acids. Spectroscopic data of modeling experiments enabled nitrogen- and sulfur-containing substances to be identified as the main air pollutants in the vicinity of a pig-breeding complex and information to be obtained on the content of the pollutants and their impact on the lichens.     

光催化反应器性能参数及其简便测试方法

本文分析了光催化反应器降解有机挥发化合物(VOCs)的特性,提出了反应器总降解常数的概念,提出了一种测量光催化反应器性能参数-传质单元数、反应有效度和总降解常数的方法。管状光催化反应器降解空气中微量甲醛的实验验证了该方法的可行性。实验表明:在空气温度22-24℃,空气湿度40％附近,甲醛的光催化反应在不同浓度区间近似为一次反应,在1.6-12.4 mg/m3浓度区间内其总降解常数最大。     

基于Fluoral-P衍生物的新型甲醛探针的光谱特性研究

甲醛(HCHO)是目前室内空气主要污染物之一,长期暴露在过量甲醛环境中会对人的眼睛、皮肤、呼吸器官等产生严重危害,甚至可能导致神经系统功能的丧失[1]以及耳、鼻和喉癌[2]。因此,快速、高效、准确地实现甲醛气体的检测,对于保障人类健康具有重大的意义。当前有很多种方法可以用于甲醛气体的检测。例如,气相色谱法(GC)[3]和高效液相色谱法(HPLC)[4],色谱仪器能够提供低至μg·m-3级别的浓度检测,但是仪器较为大型笨重,并且检测非常耗时,难以实现实时连续地对甲醛气体浓度的监测;基于气敏薄膜的半导体气体传感器具备响应时间短,稳定性高以及可连续监测等优点,然而这类传感器通常检测限较高(>300 μg·m-3),并且选择性差[5];基于酶的生物传感器通常有较好的灵敏性和选择性,但是其热稳定性通常较差,这严重限制了其应用[6]。比色法和荧光法由于响应速度快,灵敏度高,检测限低,选择性好以及传感器简单便宜等特点,被广泛地应用于甲醛气体传感器的设计中去[7-9]。这种方法是利用探针分子与甲醛发生特异性结合,形成新的物质,从而引起探针吸收光谱的变化或者发出荧光,实现对甲醛的定量测量。Descamps等使用4-氨基-3-戊烯-2-酮(Fluoral-P)作为探针分子,设计了一种手提式的甲醛检测仪[10]。Fluoral-P是一种烯氨酮结构的物质,能与甲醛特异性结合形成环状化合物3,5-diacetyl-1,4-dihydrolutidine(DDL)。由于Fluoral-P自身的特征吸收带与DDL的吸收带相隔较远,同时与甲醛结合后能够产生大斯托克斯位移的荧光峰,因而被广泛应用于甲醛检测。然而,Fluoral-P在空气中有水分子存在的情况下极其不稳定,容易发生水解,形成乙酰丙酮和氨气,严重限制了Fluoral-P在甲醛检测上的应用[10]。采用紫外可见吸收光谱、稳态荧光光谱和气相色谱质谱(GC-MS)技术研究了Fluoral-P的一种衍生物,4-氨基-1,1,1-三氟-3-丁烯-2-酮(3F-FP),与甲醛溶液相互作用的光学和化学特性。实验发现,Fluoral-P的水解速率为k＝1.555 9×10-5 L2·mol-2·s-1,然而,3F-FP具有非常低(接近0)的水解速率,水溶液环境下表现出了极好的稳定性。同时,3F-FP可以与甲醛反应生成一种类似DDL的环状化合物6F-DDL,使得3F-FP在430 nm处出现了一个新的吸收带,并且在峰值489 nm处的荧光强度也得到了明显增强,增强因子为12,在峰值处的荧光增长速率为k=7.881×103 h-1。下一步我们将使用多孔玻璃作为3F-FP探针的载体,不仅可以提高3F-FP分子浓度,也可以增加探针分子与甲醛的接触表面积[11],荧光增长速率还可以得到进一步的提高,因此3F-FP分子在甲醛气体检测领域具备了良好的应用前景。     

Experimental and numerical study of product gas characteristics of ammonia/air premixed laminar flames stabilized in a stagnation flow

Ammonia has widely attracted interest as a potential candidate not only as a hydrogen energy carrier but also as a carbon free fuel for internal combustion engines, such as gas turbines. Because ammonia contains a nitrogen atom in its molecule, nitrogen oxides (NO_x) and other pollutants may be formed when it burns. Therefore, understanding the fundamental product gas characteristics of ammonia/air laminar flames is important for the design of ammonia-fueled combustors to meet stringent emission regulations. In this study, the product gas characteristics of ammonia/air premixed laminar flames for various equivalence ratios were experimentally and numerically investigated up to elevated pressure conditions. In the experiments, a stagnation flame configuration was employed because an ammonia flame can be stabilized by using such a configuration without a pilot flame. The experimental results showed that the maximum NO mole fraction was about 3,500 ppmv, at an equivalence ratio of 0.9 at 0.1 MPa. The NO mole fraction decreased as the equivalence ratio increased. In addition, the maximum value of the NO mole fraction decreased with an increase in mixture pressure. Furthermore, it was experimentally clarified that the simultaneous reduction of NO and unburnt ammonia can be achieved at an equivalence ratio of about 1.06, which is the target equivalence ratio for emission control in rich-lean two-stage ammonia combustors. Comparison of experimental and numerical results showed that even though the reaction mechanisms employed have been optimized for predicting the laminar burning velocity of ammonia/air flames, they failed to satisfactorily predict the measured species in this study. Sensitivity analysis was used to identify elementary reactions that control the species profiles but have negligible effects on the burning velocity. It is considered that these reaction models need to be updated for accurate prediction of product gas characteristics of ammonia/air flames.     

Experimental investigation on ammonia combustion behavior in a spark-ignition engine by means of laminar and turbulent expanding flames

Ammonia combustion appears as a meaningful way to retrieve stored amounts of excess variable renewable energy, and the spark-ignition (SI) engine has been proposed as a practical conversion system. The present work aims at elucidating the combustion characteristics of ammonia blends in engine-relevant turbulent conditions. To that end, laminar and turbulent flame experiments were conducted in a constant-volume vessel at engine-relevant conditions of 445 K and 0.54 MPa to assess the combustion behavior of ammonia/hydrogen/air, ammonia/methane/air and methane/hydrogen/air mixtures observed in an all-metal single-cylinder SI engine. Results show that the respective accelerating or decelerating effects of hydrogen or methane enrichment observed in the SI engine could not be sufficiently explained by the measured laminar burning velocities of the mixtures. Since the latter are very low, the studied combustion regimes are at the boundary between the thin and broken reaction zones regimes, and thus strongly influenced by flame-turbulence interactions. The quantification of the flame response to turbulence shows much higher effects for ammonia blends, than for methane-based fuels. The aforementioned opposite effects of ammonia enrichment with hydrogen or methane are observed on the turbulent burning velocity during the turbulent flame experiments and correlated to the thermochemical properties of the reactants and the flame sensitivity to stretch. The latter may explain an unexpected bending effect on the turbulent-to-laminar velocity ratio when increasing the hydrogen fraction in the ammonia/hydrogen blend. Nevertheless, a very good correlation of the turbulent velocity was found with the Karlovitz and Damköhler numbers, that suggests that ammonia combustion in SI engines may be described following the usual turbulent combustion models. This encourages further investigations on ammonia combustion for the optimization of practical systems, by means of dedicated experiments and numerical simulations.     

有机废气处理生物膜滴滤塔操作方式研究

通过对生物膜滴滤塔降解VOC数学模型进行的因次分析,分析了操作方式对生物膜滴滤塔降解性能的影响,并通过实验研究获得了操作方式对滴滤塔降解低浓度甲苯废气的净化性能、填料床内温度分布以及气体进出口温差的影响规律。实验结果表明:相比顺流操作而言,逆流操作时系统的净化效率高,气体进出口温差大;操作方式的不同直接导致了塔内温度分布的改变,在顺流操作时塔上部温升迅速,底部温升平缓;而逆流操作时塔下部温升迅速,顶部温升较小。     

差分吸收光谱法测量大气污染的浓度反演方法研究

介绍了差分光学吸收光谱法(DOAS)测量大气污染气体浓度的基本原理,描述了对测量光谱所作的一些必要处理,对最小二乘法作了简单介绍,并将它用在DOAS方法中的浓度反演中,通过与当地监测站的数据进行对比,证明了最小二乘法非常适用于DOAS方法中的浓度反演. 关键词： 差分光学吸收光谱法 光谱处理 最小二乘法 环境监测     

Turbulent flame propagation limits of polymethylmethacrylate particle cloud–ammonia–air co-combustion

Ammonia is a highly promising energy carrier for achieving a carbon-neutral society. The co-combustion of solid particle clouds–ammonia, in particular, is considered an efficient and feasible method of reducing carbon dioxide emissions. Understanding turbulent flame stabilization and extinguishment processes during the two-phase hybrid-mixture co-combustion of solid particle clouds–ammonia is essential for the co-combustion technology to be used in combustors. To the best of our knowledge, this is the first study to describe the turbulent flame propagation limits and associated mechanism on the co-combustion of solid particle clouds–ammonia–air. Turbulent flame propagation experiments on silica particle clouds–ammonia–air mixing combustion and polymethylmethacrylate (PMMA) particle cloud–ammonia–air co-combustion were conducted in this work using a novel fan-stirred constant-volume vessel to clarify the turbulent flame propagation limits and associate mechanism of solid particle cloud–ammonia–air co-combustion. Results showed that adding inert silica particles contracted the turbulent flame propagation limits of premixed ammonia–air mixtures. However, adding PMMA particles expanded and then contracted the turbulent flame propagation limits of a premixed ammonia–air mixture as the ammonia equivalence ratio increased from lean to rich. In the solid particle cloud–ammonia–air co-combustion, reactive particles induce two types of effects on the turbulent flame propagation limits of premixed ammonia–air mixtures: The local equivalence ratio increment effect is caused by adding volatile matter from preheated particles in the preheat zone of the flame front, and the heat sink negative effect is induced by the unburned particles.     

Study of the integrated-optical concentration sensor for gaseous substances

The possibility of creating an integrated-optical chemical sensor that makes it possible to control the content of ammonia and other pollutants in air is demonstrated. A sensor of this type is experimentally studied. The limiting sensitivity of the integrated-optical ammonium sensor is estimated. The possibility of applying integrated-optical sensors in ecological monitoring is discussed.