手工自蔓延焊接燃烧机理研究

利用燃烧型焊条对Q235钢板进行手工自蔓延焊接试验,对焊条的燃烧机理进行了研究,分析了焊条的燃烧类型、燃烧模式和燃烧波结构,对不同成分焊条的绝热燃烧温度进行了理论计算,测定了燃烧速度.试验发现,手工自蔓延焊接的燃烧过程是典型的非均匀体系燃烧,燃烧反应类型为液体火焰和准固体火焰,表现为非稳态混沌燃烧,燃烧波实际温度分布图...     

Ti-B4C-C系在火焰喷涂时的SHS过程

以Ti—B4C—C为反应喷涂体系，依托SHS反应火焰喷涂制备TiC—TiB2复相陶瓷涂层技术，通过水淬熄实验，截取了喷涂过程中飞行不同距离的粒子，观测了不同飞行距离下，中间状态反应产物的宏观特征、成分和组织结构及其变化过程，理论探讨了复合粉体在氧．乙炔火焰焰流中的飞行燃烧过程与反应机理。研究表明，中间状态的反应产物按其宏观特征出现了完全熔融的实心陶瓷液滴、完全熔融的空心陶瓷液滴、表面熔融芯部未熔的陶瓷颗粒和完全未熔的陶瓷颗粒4种。其飞行燃烧过程机理是：SHS反应始于钛粉的熔化，对位于火焰焰流芯部的中小尺寸喷涂团聚颗粒，其燃烧合成受扩散和毛细管机制控制，以爆燃方式进行；对位于火焰焰流外围的较大尺寸喷涂团聚颗粒，其燃烧合成受组元熔解析出机制控制。     

套筒式陶瓷燃烧器内燃烧过程数学模型

应用湍流扩散火焰燃烧模型，对套筒式陶瓷燃烧器燃烧室内的燃烧过程进行了计算机模拟研究，确定了燃烧过程中煤气空气及燃烧产物的速度分布，温度２和各组分的浓度分布，得到了燃烧过程中火焰的形状和长度。     

火焰喷涂合成TiC-Fe涂层的热力学分析

火焰喷涂合成技术是自蔓延高温合成（ＳＨＳ）与氧乙炔火焰喷涂技术结合而发展起来的,已成功制备了ＴｉＣ－Ｆｅ复合涂层,利用计算相图技术,确定Ｆｅ－Ｔｉ－Ｃ系的平衡相组成,并结合火焰喷涂合成工艺,重点讨论了原材料配比对体系熔化,凝固行为及涂层形成的影响,并讨论了燃烧合成ＴｉＣ－Ｆｅ的反应机理。     

燃气燃烧特性对火焰切割性能的影响

根据燃气物理化学性质的分析,比较燃气燃烧速度,火焰质量分布,温度的高低,阐述了乙炔,丙烷,等燃气燃烧特性对火焰切割性能的影响。最后对燃气的选用进行了讨论。     

活化燃烧合成氮化硅陶瓷粉体

研究了机械活化和加入活性剂对于燃烧合成氮化硅粉体的影响.结果表明,随着机械活化强度的提高,反应的燃烧温度升高,同时α相氮化硅含量降低;在选定的活化强度下,提高稀释剂以及活性剂的含量,有利于降低燃烧反应温度,并可以提高α相氮化硅含量.活性剂的加入对于燃烧合成反应也有重要的影响,活性剂的加入可以起到引入固体氮化剂的作用,这种固体氮化剂与N2相比具有较低的键能,利于反应进行.     

甘氨酸-硝酸盐法合成高烧结活性氧化铈电解质粉体

用甘氨酸-硝酸盐法合成了适用于中低温固体氧化物燃料电池的电解质材料Ce0.8Gd0.05Y0.15O1.9，主要分析了甘氨酸，硝酸根比值对燃烧合成过程、制得粉体结构、粒度和形貌的影响，并对其烧结性能作了评价。     

四种燃气的基本特性及火焰加工性能对比试验

针对我国火焰加工方面形成的单一能源结构方式，选用丙烷，丙烯、液化石油气，乙炔等四种燃气进行了基本特性比较和热切割、火焰校正等加工性能的对比试验，并根据各种燃气燃烧特性的不同．选择了合理优质工具。对每种燃气的经济性和社会效益进行了分析，指出将丙烷用于上述火焰加工具有突出的经济性，安全性及较高的质量保证。     

固体发动机射线检验工艺探讨

有关文献表明,固体发动机关键区域内,当界面脱粘面积达15cm~2,间隙达0.38mm时,脱粘处推进剂的燃烧,可引起发动机壳体烧穿;药柱内缺陷能增大火焰燃烧面积而引起发动机爆炸。因此,必须对发动机内的缺陷进行有效控制,以保证安全。     

基体表面类金刚石涂膜对金刚石火焰法沉积的强化作用

所谓金刚石火焰合成法,是一种使合成原料发生不完全燃烧,利用所产生火焰的内焰合成金刚石的方法。这种方法有许多优点:设备简单,操作较易,合成速度高等等。近三年来的研究发展情况表明,金刚石火焰合成法已经成为金刚石低压气相合成研究领域最受重视的方法之一。     

Experimental Study of Thermal and Flame Front Characteristics in Combustion Synthesis of Porous Ni-Ti Intermetallic Material

This article describes experimental investigation of thermal and combustion phenomena during the self-propagating combustion synthesis of Ni-Ti intermetallic materials for structural application. Ni-Ti mixture is prepared from elemental powders of Ni and Ti. The mixture is pressed into solid cylindrical samples of 1.1-cm diameter and 2-3-cm length, with initial porosity ranging from 30 to 42%. The samples are preheated to various initial temperatures and ignited from the top surface such that the flame propagates axially downward. The flame speed images are recorded with a motion camera, and the temperature profile is recorded. The flame front propagation velocity is deduced as a function of the preheat temperature and initial porosity as well as the effective thermal conductivity of the reactants.     

Effect of fuel and its concentration on the nature of Mn in Mn/CeO2 solid solutions prepared by solution combustion synthesis

Nano and microcrystalline, Mn/CeO₂ solid solutions (5 mol.% Mn) have been prepared by solution combustion synthesis using urea, glycine or polyethylene glycol (PEG) as fuel. The nature of the fuel and its concentration (fuel to metal mole ratio, F/M) have a strong influence on the physical and chemical characteristics of the resulting Mn/CeO₂ solid solutions. The variations in the physicochemical properties are attributed to differences in (i) the adiabatic/real flame temperature realized with these fuels at different F/M ratios; (ii) the sustenance of the temperature or the quenching effect of the fuel at higher F/M ratios; (iii) combustion or decomposition of the precursors as the main course of the reaction; and (iv) the generation of gaseous products during combustion. Since the addition of the fuel to the initial precursor solution does not change the pH of the medium, the differences in the type of Mn species formed are mainly attributed to the combustion process.     

气相燃烧法制备纳米材料的研究进展

纳米材料的气相燃烧合成一般是指利用气体燃料燃烧提供高温,通过物理或者化学过程从气溶胶中获得纳米材料的过程。气相燃烧法可以制备不同结构的纳米材料,具有过程连续、易于规模化、无后处理、低成本等优点,是纳米材料制备最具工业化潜力的方法之一。气相燃烧制备纳米材料涉及快速高温反应和产物单体成核、生长、凝并、团聚等过程,这些过程互相关联、交互影响;纳米材料制备过程中材料结构调控及材料生长机理成为近年来国内外的研究重点。主要介绍了气相燃烧反应器结构、材料制备、结构调控、应用性能和工业生产等方面的研究进展,并对其前景进行了展望。     

Electrical structure of the jet of a gas mixture flame

The combustion of the open flame of an air-domestic gas mixture in air is considered. The concept of the stoichiometric ratio for such a system is specified. The combustion of an enriched mixture, a stoichiometric mixture, and a depleted mixture are singled out. For each case, the structure of the flame and its variations under the condition of the transition of the combustion into the pulsating mode are found by electric and optic measurements. A significant role of the secondary (ambient, atmospheric) air for the stoichiometric flame combustion is noted.     

Computational simulation of liquid-fuelled HVOF thermal spraying

Liquid-fuelled high-velocity oxygen–fuel (HVOF) thermal spraying systems are gaining more attentions due to their advantage of producing denser coatings in comparison to their gas-fuelled counterparts. The flow through a HVOF gun is characterized by a complex array of thermodynamic phenomena involving combustion, turbulence and compressible flow. Advanced computational models have been developed to gain insight to the thermochemical processes of thermal spraying, however little work has been reported for the liquid-fuelled systems. This investigation employs a commercial finite volume CFD code to simulate the flow field through the most widely used liquid-fuel HVOF gun, JP5000 (Praxair, US). By combining numerical combustion and discrete phase models the turbulent spray flame is captured and the development of supersonic gas flow is revealed. The flow field is thoroughly examined by adjusting the nozzle throat diameter and combustion chamber size. The influence of fuel droplet size on the flame shame shape and combusting gas flow is also examined.     

自身预热式燃气辐射管的数值研究

采用 FLUENT商用软件对自身预热式辐射管内的流动、传热和燃烧过程进行了二维数值模拟.研究了内套管与燃烧室出口的相对位置以及助燃空气的一次风与二次风的比例对火焰长度、辐射管温度的影响.结果表明,当增加套管和燃烧室出口的距离时,火焰长度有所增加,辐射管外壁温度、套管平均温度和烟气平均温度有所增加.当增大二次风比例时,火焰长度增加,辐射管外壁温度却减小.计算结果为自身预热式辐射管的开发与优化提供了参考数据.     

Simulation and application of a HVOF process for MCrAIY thermal spraying

This work deals with numerical simulation and application of a high velocity oxygen fuel (HVOF) process for MCrAlY thermal spraying. The main objective of this study was to observe the correlations between coating oxidation and oxygen content in combustion products or flame temperature. Spray parameters were selected on the basis of the numerical simulation of combustion and particle behavior in the flame. The results of experiments revealed that the oxygen content is not the main key factor concerning the oxidation rate of MCrAlY coatings. On the contrary, the flame temperature has a decisive influence on oxidation. Combustion conditions corresponding to stoichiometric factors between 0.82 and 1.2 appeared not to be favorable for MCrAlY thermal spraying. Outside this range, it appeared preferable to use a combustion system on the fuel-rich side.     

氧生物柴油火焰温度计算及火焰切割分析

从理论上分析生物柴油用于金属火焰切割的可行性,根据热力学理论计算生物柴油中性焰和氧化焰的理论温度,分析生物柴油燃烧过程中氧气的消耗量;并根据燃烧学对比分析生物柴油与汽油在空气中完全燃烧的火焰长度。计算结果表明:虽然生物柴油火焰温度比乙炔燃烧温度低,但能达到2436℃以上,火焰长度将近是汽油火焰长度的0.92倍,长度基本相当,说明生物柴油可用于金属火焰切割,只是预热时间应比乙炔长。这在理论上说明生物柴油可作为金属切割的燃料,为进一步进行氧生物柴油火焰切割技术研究奠定了理论基础。