Synthesis and Characterization of Cerium-Doped Lutetium Aluminum Garnet Phosphors by Nitrate-citrate Sol-Gel Combustion Process

Nanosized cerium-doped lutetium aluminum garnet （LuAG：Ce） phosphors were prepared by nitrate-citrate solgel combustion process using 1：1 ratio of the citrate：nitrate. The prepared LuAG：Ce phosphors were characterized by XRD, TEM, photoluminescence and radioluminescence spectra excited by UV and X-ray, respectively. The purified crystalline phase of LuAG：Ce was obtained at 900 ℃ by directly crystallizing from amorphous materials. The resultant Lu- AG：Ce phosphors were uniform and had good dispersivity with an average particle size of about 30 urn. Both photoluminescence and radioluminescence were well-known Ce^3＋ emissions located in the range of 470 -600 nm consisting of two emission bands because of the transition from the lowest 5d excited state （2D） to the 4f ground state of Ce^3＋, which matched well with the sensitivity curve of the Si-photodiode. There was a little red shift for the emission components from the UV-excited emission spectrum to the X-ray-excited emission spectrum. The fast scintillation decay component of 26 ns satisfies the requirements of fast scintillators.

The Process of a Laser-Supported Combustion Wave Induced by Millisecond Pulsed Laser on Aluminum Alloy

We study the process of a laser-supported combustion wave （LSCW） when an aluminum alloy is irradiated by a millisecond pulse laser based on the method of laser shadowgraphy. Under the condition of different laser parameters, the obtained results include the velocity, ignition threshold of LSCW and the variation law. The speed of LSCW increases with the laser energy under the same irradiation laser pulse width, and the speed of LSCW reduces with the increase of the laser pulse width under the same irradiation laser energy. Moreover, the ignition time of LSCW becomes shorter by increasing the laser number of the pulse and is not effected by changing the frequencies, when keeping the laser pulse width and energy unchanged. The results of the study can be applied in the laser propulsion technology and metal surface laser heat treatment, etc.

The Process of TiB_2-Cu Composite Phase and Structure Formation during Combustion Synthesis

The reaction process of combustion synthesis for TiB2 -Cu was investigated in detail using combustion-wave arresting experiment, X-ray diffraction （ XRD ） analysis, SEM analysis and differential thermal analysis （ DTA ）. The XRD analysis results for the different parts of the quenched specimen show that TiCux intermetallic phase firstly forms with the propagation of combustion wave, and then Ti1.87 B50 and Ti3B4 metastable phases come forth due to the diffusion of B atoms and finally the stable TiB2 phase forms because of the continuous diffusion of B atoms. The formation of TiB2 phase is uot completed by one step, but undergoes several transient processes. The process of reaction synthesis for Ti-B-Cu ternary system can be divided into three main stages： melting of Cu and Ti , and the formation of Cu- Ti melt and few TiCux , TiBx intermetallic phases ; large numbers of TiCux intermetallic phases formation and some fine TiB2 particles precipitation ; and the TiB2 particles coarsening and the stable TiB2 and Cu two phases formation in the final product.

Study of the Combustion Process inside an Ethanol-Diesel Dual Direct Injection Engine Based on a Non-Uniform Injection Approach

The use of ethanol is a promising method to reduce the emissions of diesel engines.The present study has been based on the installation of a gasoline electronic injection system in a single-cylinder diesel engine to control the amount of ethanol entering the cylinder during the compression(while diesel has been injected into the cylinder by the original pump injection system).The injection time has been controlled by crank angle signal collected by an AVL angle indicator.In the tests ethanol and diesel each accounted for half of the fuel volume,and the total heat energy supply of the fuel was equivalent to that of the diesel under the operating conditions of the original engine.A three-dimensional combustion model of the diesel engine has been implemented by using the CFD software FIRE.Simulations have been carried out assuming uniform and non-uniform injections rate for the different holes and the different results have been compared.According to these results,a non-uniform injection rate can produce early ignition and cause an increase in the maximum in-cylinder pressure and the maximum average incylinder temperature.Moreover,in such conditions NO emissions are larger while soot emission is slightly lower.

Development and evaluation of a vision driven sensor for estimating fuel feeding rates in combustion and gasification processes

A machine vision driven sensor for estimating the instantaneous feeding rate of pelletized fuels was developed and tested experimentally in combustion and gasification processes.The feeding rate was determined from images of the pellets sliding on a transfer chute into the reactor.From the images the apparent area and velocity of the pellets were extracted.Area was determined by a segmentation model created using a machine learning framework and velocities by image registration of two subsequent images.The measured weight of the pelletized fuel passed through the feeding system was in good agreement with the weight estimated by the sensor.The observed variations in the fuel feeding correlated with the variations in the gaseous species concentrations measured in the reactor core and in the exhaust.Since the developed sensor measures the ingoing fuel feeding rate prior to the reactor,its signal could therefore help improve process control.

Transient flameout process of boron-magnesium agglomerates during combustion in oxygen-rich atmospheres

In this study,boron–magnesium agglomerates with varying mass ratios were prepared by drying a micron-sized boron–magnesium mixed suspension,and the combustion process of these agglomerates under different oxygen-rich concentrations were investigated using a laser ignition system.The test results showed that when the mass fraction of magnesium powder in boron-magnesium agglomerates exceeded a certain threshold(between 2%and 5%),flame extinction and reignition occurred after a significant reduction in the agglomerate volume during combustion.This process is referred to as the transient flameout process,which is affected by the magnesium content of the agglomerate and the oxygen concentration in the ambient atmosphere.An increase in the magnesium content or oxygen concentration makes this phenomenon more pronounced.During weakening of the flame intensity,a dark film gradually covered the particle surfaces.X-ray diffraction and elemental analyses of the cross-section and outer surface of the condensed combustion product suggested that the dark film is primarily composed of Mg-B-O ternary oxides.This film prevents direct contact between boron and oxygen,thereby inhibiting surface and gas-phase reactions and leading to the occurrence of the transient flameout phenomenon.

A reliable knowledge processing framework for combustion science using foundation models

This research explores the integration of large language models (LLMs) into scientific data assimilation, focusing on combustion science as a case study. Leveraging foundational models integrated with Retrieval-Augmented Generation (RAG) framework, the study introduces an approach to process diverse combustion research data, spanning experimental studies, simulations, and literature. The multifaceted nature of combustion research emphasizes the critical role of knowledge processing in navigating and extracting valuable information from a vast and diverse pool of sources. The developed approach minimizes computational and economic expenses while optimizing data privacy and accuracy. It incorporates prompt engineering and offline open-source LLMs, offering user autonomy in selecting base models. The study provides a thorough examination of text segmentation strategies, conducts comparative studies between LLMs, and explores various optimized prompts to demonstrate the effectiveness of the framework. By incorporating an external vector database, the framework outperforms a conventional LLM in generating accurate responses and constructing robust arguments. Additionally, the study delves into the investigation of optimized prompt templates for the purpose of efficient extraction of scientific literature. Furthermore, we present a targeted scaling study to quantify the algorithmic performance of the framework as the number of prompt tokens increases. The research addresses concerns related to hallucinations and false research articles by introducing a custom workflow developed with a detection algorithm to filter out inaccuracies. Despite identified areas for improvement, the framework consistently delivers accurate domain-specific responses with minimal human oversight. The prompt-agnostic approach introduced holds promise for future improvements. The study underscores the significance of integrating LLMs and knowledge processing techniques in scientific research, providing a foundation for advancements in data assimilation and utilization.

Evaluation of spontaneous combustion tendency of sulfide ore heap based on nonlinear parameters

To explore a new evaluation method for spontaneous combustion tendency of different areas in sulfide ore heap, ore samples from a pyrite mine in China were taken as experimental materials, and the temperature variations of the measuring points of simulated ore heap were measured. Combined with wavelet transform and nonlinear parameters extraction, a new method for spontaneous combustion tendency of different areas in sulfide ore heap based on nonlinear parameters was proposed and its reliability was verified by field test. The results indicate that temperature field evolution of the simulated ore heap presents significant spatial difference during self-heating process. Area with the maximum increasing extent of temperature in sulfide ore heap changes notably with the proceeding of self-heating reaction. Self-heating of sulfide ore heap is a chaotic evolution process, which means that it is feasible to evaluate spontaneous combustion tendency of different areas by nonlinear analysis method. There is a relatively strong correlation between the maximum Lyapunov exponent and spontaneous combustion tendency with the correlation coefficient of 0.9792. Furthermore, the sort of the maximum Lyapunov exponent is consistent with that of spontaneous combustion tendency. Therefore, spontaneous combustion tendency of different areas in sulfide ore heap can be evaluated by means of the maximum Lyapunov exponent method.

Effects of fractal surface on rheological behavior and combustion kinetics of modified brown coal water slurries

The paper reports the effects of surface fractal structures on the rheological behavior and combustion kinetics of raw brown coal and three modified coal water slurries （CWSs）. The results show that the fractal structures and physicochemical properties of samples are dependent on various modification processes. The apparent viscosities of the coal water slurries increase with increasing surface fractal dimensions （D）, especially with decreasing shear rates. Fur- thermore, it has been proved that the ignition temperatures and apparent activation energies of modified CWSs are lower than that of raw coal water slurry. Compared with the traditional qualitative analysis of the effect of pore structures on CWSs properties, D can more efficiently indicate the quantificational effect of pore structures on the rheological behavior and combustion kinetics of CWSs.

Presenting an engineering classification system for coal spontaneous combustion potential

The phenomenon of coal spontaneous combustion is one of the common hazards in coal mines and also one of the important reasons for the loss of coal in piles and mines. Based on previous researches, different types of coals have different spontaneous combustion characteristics. For coal loss prevention, a measure is necessary for prediction of coal spontaneous combustion. In this study, a new engineering classification system called ＂Coal Spontaneous Combustion Potential Index （CSCPI）＂ is presented based on the Fuzzy Delphi Analytic Hierarchy Process （FDAHP） approach. CSCPI classifies coals based on their spontaneous combustion capability. After recognition of the roles of the effective parameters influencing the initiation of a spontaneous combustion, a series of intrinsic, geological, and mining characteristics of coal seams are investigated. Then, the main stages of the implementation of the FDAHP method are studied and the weight of each parameter involved is calculated. A classification list of each parameter is formed, the CSCPI system is described, and the engineering classifying system is subsequently presented. In the CSCPI system, each coal seam can be rated by a number from 0 to 100; a higher number implies a greater ease for the coal spontaneous combustion capability. Based on the CSCPI system, the propensity of spontaneous combustion of coal can be classified into three potential levels： low, medium, and high. Finally, using the events of coal spontaneous combustion occurring in one of the Iranian coal mines, Eastern Alborz Coal Mines, an initial validation of the mentioned systematic approach is conducted. Comparison of the results obtained in this study illustrate a relatively good agreement.

Reaction dynamics in the combustion synthesis system of Al-CrO_3-Al_2O_3-NaF-N_2-O_2

A new material with heat-resistant and adiabatic characteristics and high strength was prepared using the combustion synthesis method by mixed powders of CrO3, Al, Al2O3, and NaF in atmospheric gas. The reaction dynamic process of the Al-CrO3-NaF-Al2O3-N2-O2 new material system by the combustion synthesis method was discussed based on the observation results by SEM, EDS, and XRD in combination with the combustion front quenching method （CFQM） and the relation curves between reaction free enthalpies and the corresponding temperatures. The combustion synthesis mechanism and the formation reasons of the phase in the combustion product were analyzed.

Absorption Property of YAG∶Sm Phosphors Prepared using Sol-Gel Combustion Method

Samarium-doped yttrium aluminum garnet (YAG∶Sm3+) phosphors were synthesized by nitrate-citrate sol-gel combustion method. Phase evolution, morphology and absorbency of the obtained materials were characterized by XRD, FESEM, reflection spectrum, respectively. The experimental results showed that single-phase cubic YAG∶Sm3+ crystalline was directly obtained at 800 ℃ from amorphous precursor, and mostly developed at 900 ℃. The prepared powders were relatively agglomerated with an average particle size of 300 nm. The reflection spectrum showed that there were several apparent characteristic absorption peaks due to the 4f→4f inner shell electron transitions from the 6H5/2 ground state to 6FJ (J=9/2, 7/2 and 5/2) excited state of Sm3+. Moreover, the intensity of the characteristic peaks was enhanced with the increasing concentration of Sm3+ ions.

Modeling of propane dehydrogenation combined with chemical looping combustion of hydrogen in a fixed bed reactor

A redox process combining propane dehydrogenation(PDH)with selective hydrogen combustion(SHC)is proposed,modeled,simulated,and optimized.In this process,PDH and SHC catalysts are physically mixed in a fixed-bed reactor,so that the two reactions proceed simultaneously.The redox process can be up to 177.0%higher in propylene yield than the conventional process where only PDH catalysts are packed in the reactor.The reason is twofold:firstly,SHC reaction consumes hydrogen and then shifts PDH reaction equilibrium towards propylene;secondly,SHC reaction provides much heat to drive the highly endothermic PDH reaction.Considering propylene yield,operating time,and other factors,the preferable operating conditions for the redox process are a feed temperature of 973 K,a feed pressure of 0.1 MPa,and a mole ratio of H_(2) to C_(3)H_(8) of 0.15,and the optimal mass fraction of PDH catalyst is 0.5.This work should provide some useful guidance for the development of redox processes for propane dehydrogenation.

煤矸石自燃的关键影响因素及治理方法研究现状

煤矸石作为煤炭的伴生产物,长期堆存过程中自燃现象频发,直接或间接产生生态污染、水体污染、地质灾害等诸多问题,造成巨大经济损失和人员伤亡。煤矸石从堆积初期到燃烧状态受诸多因素影响,包括自身性质、自燃条件和外部环境等,是一个复杂的物理化学反应过程。为提高煤矿矿区矸石自燃的防治能力,分析了煤矸石自燃理论的研究现状,系统总结了现阶段国内外学者对煤矸石自燃机理和治理方法的研究进展。围绕可燃物、氧气、温度3个影响煤矸石自燃的必要因素,提出了引发自燃的主要关键影响因素和作用过程机理。较全面介绍已有煤矸石山自燃防治的主要方法,对比分析了各种常规煤矸石自燃灭火手段以及治理技术的优缺点,指出了常规简单技术治理效果的局限性。针对煤矸石作为砂、石等替代材料,回填露天矿坑、采煤塌陷区等区域进行土地整治和生态修复,提出在防治过程中要明确自燃治理的控制对象,提升防灭火材料的特定性能,通过智能化设备提高辨识准确性进行精细化监控,并运用多种监测预警技术协同自燃防治材料多手段多方法运用综合治理,并提出了煤矸石自燃防治技术的未来发展和矿用防灭火材料的研究方向,为后续开展煤矸石自燃机理研究及自燃防治工程应用提供参考和理论支持。

极寒条件下含氧燃料对柴油机冷起动特性的影响

针对柴油机存在低温冷起动困难甚至无法起动的问题,基于起动/发电机集成一体化技术柴油机,在高原低温发动机冷起动试验舱,研究-50号柴油A0(氧质量分数为0%)、A1(氧质量分数为2.05%)和A2(氧质量分数为4.40%)燃料在-43℃下对柴油机冷起动过程的影响和燃烧特性分析.结果表明:相比A0纯柴油,燃用A1、A2含氧燃料起动时间分别缩短了36.64%和42.71%;起动累计油量分别降低47.8%和60.6%;怠速运行前60 s内转速波动率分别降低25.3%和43.8%.燃用燃料氧质量分数越高,起动燃烧首循环的缸内压力、燃烧放热率、缸内燃烧温度和缸内压力升高率峰值越高,且燃烧重心前移,燃烧持续期越短;起动转速上升过程循环数越少,平均最大缸内压力越大,起动过程燃烧稳定性越好.

点火位置对X型转子发动机燃烧过程的影响

为探究X型转子发动机独特燃烧室内复杂湍流场与点火位置的耦合作用对混合气燃烧过程的影响,建立了X型转子发动机的三维计算流体动力学模型,并与试验结果进行对比验证,数值研究了不同点火位置下X型转子发动机缸内燃烧过程,揭示了点火位置对火焰传播、燃烧特性及污染物形成的影响规律。结果表明,在压缩末期,X型转子发动机燃烧室内形成了包括涡流和单向流的复杂湍流场,这与点火位置的耦合作用显著影响火焰传播过程。为了获得较高火焰传播速度,点火位置不宜布置在漩涡区处。点火位置位于凹坑中部时,可以充分利用四周空间和涡团与单向流场过渡处形成的较高速度场加速火焰传播,从而提前燃烧重心,增加放热速率,而且峰值压力提高了25%,指示热效率超过30%;同时其也具有较低的HC和CO排放量;但是由于其缸内峰值温度较大,导致NO排放量增加。

废岩棉处理方法的实验研究

近年来废岩棉的数量越来越多,已成为工业垃圾的处理难题,且目前还没有完善的处理方案,大多数废岩棉没有得到很好的处理,故通过实验研究来获取一种废岩棉的处理方法.观察废岩棉在不同温度下的状态,对燃烧后的废岩棉进行化学成分分析和矿物分析,再对废岩棉燃烧后的体积变化量进行计算.研究结果表明:燃烧后的废岩棉主要成分为CaO、SiO_(2)、Al_(2)O_(3)、MgO和Fe_(2)O_(3),这五种主要成分对环境都是无毒无害的,不会对环境造成污染;燃烧后的废岩棉体积平均减少85.25%;通过观察不同温度下废岩棉燃烧产物的状态和XRD曲线,发现当温度为1100℃时,废岩棉燃烧得较充分,所以在1100℃下燃烧处理废岩棉很好地解决了废岩棉浪费土地资源、污染土地和环境的难题.

飞机火焰抑制器阻火测试中混合气体的适用性研究

文章对典型民用飞机油箱通气口飞机火焰抑制器火焰传播特性开展试验研究。根据SAEARP5416中规定的H_(2)、O_(2)、Ar3种混合气体的燃爆方案,借鉴ISO16852标准下的试验方法,自建燃爆试验台,并分别在不同H_(2)体积分数、阻火芯体内部孔径和芯体长度的情况下开展系列试验,并与现行商用阻火器特性进行对比,同时使用高速摄像机获得爆燃阻火现象及规律并开展仿真对比。试验结果表明,使用体积分数为5.0%~10.0%的H_(2)进行飞机火焰抑制器火焰传播试验时,试验阻火成功率极低,并得到H_(2)体积分数升高对火焰传播速度的影响规律。研究表明,H_(2)与航空煤油蒸气的特性差异是阻火失效的关键因素。该文对此次试验的混合气体局限性进行分析,试验结果也为H2类阻火器的研究提供一定的参考。

柴油机低温启动过程关键影响参数研究

为实现柴油机在极端低温环境下可以具备较好的启动性能,对相关影响柴油机启动的参数进行研究。通过正交仿真研究了环境因素(进气压力、进气温度)、设计参数(压缩比、燃烧室缩口比、喷嘴直径)、控制参数(喷油温度、预喷油量、主喷提前角、主喷持续期、主预喷间隔)对柴油机低温条件下启动过程的影响,通过极差分析提取出对柴油机启动过程影响较大的关键影响参数,并以缸内压力、缸内温度和瞬时放热率为评价指标对各因素进行参数匹配研究。结果表明,环境因素和控制参数对柴油机启动过程的影响程度更高,进气压力、进气温度、主喷提前角和主喷持续期为影响柴油机低温条件下启动的关键影响参数,并选择组合1作为最佳参数匹配组合。研究得到了柴油机低温启动过程中的关键影响参数,可为改善低温环境下柴油机的启动效果提供参考。

干熄焦放散气代替部分焦炉加热燃气的燃烧过程模拟研究

以JN-70型焦炉混合煤气加热为研究对象,利用Ansys Fluent软件对干熄焦放散气代替部分燃气的燃烧过程进行稳态模拟研究,分析了干熄焦放散气的配入对立火道内压力场、温度场、浓度场的影响。结果表明,在空气中配入5%干熄焦放散气时,立火道的最高温度不变,高向加热的均匀性有所提高,且烟气中的NO_(x)浓度变化不大。因此,焦炉燃烧室配入干熄焦放散气替代部分燃气具有一定的可行性。