复合推进剂中铝粉粒度对分布燃烧响应和粒子阻尼特性影响

针对不同初始铝粉粒度的含铝复合推进剂,对其燃烧产物粒子阻尼特性和铝粒子分布燃烧响应特性进行了试验研究。试验结果表明:粒子阻尼的大小取决于流场中的凝相燃烧产物粒径分布和振荡频率,与推进剂中铝粉初始粒度基本无关;粒子阻尼预估方面,采用单一粒径预估的阻尼值与实际测量的阻尼值相比,仍存在一定的误差(>10%),需要进一步改进;分布燃烧响应方面,在同一振荡频率范围内,分布燃烧响应特性与复合推进剂中初始铝粉粒度有关,即初始铝粉粒度越大,在燃烧过程中产生的分布燃烧增益越大,这对于发动机燃烧的稳定性是十分不利的。

含铝复合推进剂分布燃烧数值模拟

为研究发动机内含铝复合推进剂以及铝的燃烧,基于FLUENT软件,应用EDC模型和颗粒表面反应模型,建立了固体火箭发动机内流场两相流分布燃烧模型,对AP/HTPB/Al复合推进剂固体火箭发动机内流场进行了数值计算。计算结果表明,与表面燃烧相比,铝的燃烧导致发动机内出现了延长的燃烧区域,铝燃烧贯穿整个发动机燃烧室,形成分布燃烧;延长的燃烧区域导致发动机内流场分布不均匀,燃烧室是非等温的,温度由燃面附近的2600 K增长到3600 K,燃烧室核心区域温度约为3200 K;铝燃烧消耗的同时生成其他产物,也导致燃烧室内燃气组分和密度的分布不均匀;铝的燃烧是一个复杂的物理化学过程,对发动机内流场有着重要影响,颗粒相始终贯穿整个发动机,最终从喷管喷出。

考虑燃烧室出口温度分布的航空发动机部件级模型

燃烧室出口温度分布不均匀会使涡轮叶片受到不均匀的热载荷,严重影响涡轮叶片的工作寿命。本文提出一种具有燃烧室出口温度分布预测功能的部件级模型建模方法,为燃烧室出口温度分布控制研究提供了仿真平台。以变循环发动机为研究对象,根据其设计点参数设计燃烧室三维模型,通过CFD数值模拟的方法,计算得到该燃烧室三维模型在地面不同工作状态下的燃烧室出口温度分布场,组成温度分布场训练数据集。提出基于Inception-反卷积网络的燃烧室出口温度分布场重建方法,基于该方法构建了燃烧室出口温度分布场预测模型。建立了适用于全包线、全状态,可以预测燃烧室出口温度分布场的部件级模型,与传统的部件级模型相比,该模型能够预测发动机在不同工作状态、不同包线点下的燃烧室出口温度分布场。结果表明:Inception-反卷积网络在训练集和测试集上的均方误差比常规反卷积降低11.83%和5.6%,比WGAN-GP降低87%和90%;部件级模型预测温度分布场和CFD仿真温度分布场的温度分布趋势基本一致;所提出的Inception-反卷积网络预测精度高于常规反卷积网络和WGAN-GP网络预测精度,在热斑处温度点误差更小,在亚声速巡航点(H=8 km,Ma=0.7),(H=8 km,Ma=0.9)和超声速巡航点(H=10 km,Ma=1.4),(H=10 km,Ma=1.6)时,Inception-反卷积网络预测温度分布场的平均温度误差分别为0.05 K,-1.38 K,-1.54 K和4.44 K,均方误差分别为6.7×10^(-4),1.9×10^(-4),3.0×10^(-4)和1.4×10-3,热斑温度误差分别为-3.91 K,-3.67 K,-5.34 K和0.85 K。

柴油机主喷提前角对燃烧过程改善的模拟

多次燃油喷射的灵活调节对改善柴油机燃烧过程具有重要影响。利用CONVERGE模拟研究不同主喷提前角对燃烧过程和产物分布的影响,表明缸内燃空当量比为0.6~1.0的稀混合气容易自燃,引起缸内混合气温度的升高,自燃混合气浓度范围扩大,促使燃空当量比为1.0~1.3的浓混合气发生燃烧。当主喷提前角为12°CA BTDC时,通过改变稀混合气、浓混合气的自燃时刻,燃烧放热更加集中在压缩上止点附近,使得平均指示压力达到最大并提升3.8%。

一种煤粉炉内三维燃烧温度分布优化控制方法

提出把遗传算法引入四角切圆煤粉锅炉燃烧的控制系统中,并采用了炉膛温度分布作为中间参量,以优化温度分布作为基本控制目标,在炉膛燃烧数学模型上进行仿真模拟。结果表明,采用炉膛温度分布为中间参量的遗传算法控制系统可以有效克服燃料发热量变化对炉内燃烧过程的影响,获得燃料量和风量控制指令以适应负荷的变化,并能给出个燃烧器故障情况下的识别和控制动作。

固体火箭发动机中铝粉燃烧研究概述

介绍了固体火箭发动机中单个铝颗粒燃烧模型的发展与铝颗粒的燃烧特性;阐述了铝粉分布燃烧现象、分布燃烧放热与声场的耦合关系及其对发动机稳定性的增益作用;总结了惰性颗粒的阻尼理论以及在表面旋涡脱落条件下惰性颗粒对压强振荡的放大作用;提出了应从复杂流场中全面考虑铝粉燃烧对发动机的增益与阻尼作用,建立其对发动机工作稳定性影响的综合判据的观点。

固体火箭发动机燃烧不稳定的影响因素分析和最新研究进展

总结和分析了国外对固体火箭发动机中出现的燃烧不稳定问题的理论、数值和实验研究。介绍了国外的研究思路和现状,详细阐述了固体火箭发动机中燃烧不稳定的主要影响因素,以及目前国外公认的不稳定触发机理——声/涡耦合、抑制措施及预测理论方面的进展,总结了有关发展大型分段式固体火箭发动机可能存在燃烧不稳定的相关信息,以期对国内固体火箭发动机在该方面的研究提供一定的参考。

某型多级燃烧器燃烧过程的数值模拟

有效的燃烧器结构设计可优化燃气-空气混合燃烧的燃烧效果,从而减少大气污染物的排放,实现节能减排。该文从某型多级燃烧器入手,利用计算流体动力学(CFD)技术对燃烧器内的燃烧分布进行数值模拟,得到优化结构后的燃烧器燃烧分布。结果表明:在鼓风机的作用下,气流对燃烧效果有明显的促进作用。导叶的背压作用显著,延长了火焰中心的燃烧区域。稳焰盘区域气流旋流向前,没有回流。炉膛内的燃料在火焰区域燃烧较充分,炉膛内燃烧产物NO浓度总体较低,表明燃烧效果良好。该文对多级燃烧器内燃烧分布的研究具有一定的指导意义。

镍粉对RDX-CMDB推进剂燃烧性能的影响

研究了不同粒径（1μm、3μm、5μm）与含量的镍粉对RDX-CMDB推进剂燃烧性能的影响。燃速测试结果表明：镍粉能有效提高RDX-CMDB推进剂的燃速。1~10MPa下,添加1.5%的3μm镍粉的RDX-CMDB推进剂燃速最高。火焰结构照片显示RDX-CMDB推进剂体系中加入镍粉,燃烧火焰面积大大增加,且降低了暗区厚度。1MPa下的燃烧波温度分布曲线结果显示镍粉的加入对推进剂的燃面温度无较大影响,但是绝热火焰温度大幅度地提高。

液体火箭发动机高频燃烧不稳定问题综述

高频燃烧不稳定现象诱发的大幅值压力振荡严重威胁液体火箭发动机可靠性,为此,国内外开展了大量深入的研究工作。为了提高对此类问题及相关研究的整体认识,系统阐述了液体火箭发动机高频燃烧不稳定问题的主要特点、关键物理机制、研究思路等,重点梳理了国内外在液体推进剂燃烧子过程响应机理方面的研究工作,明确指出了燃烧速率控制过程对于此类问题分析的重要意义。在此基础上,详细总结了液滴蒸发和射流掺混作为速率控制过程的高频燃烧不稳定问题数值仿真研究进展,仔细归纳了线性和非线性理论解析分析方法面临的挑战,简要介绍了基于非线性动力系统的分析方法在揭示高频燃烧不稳定非线性行为以及稳定性裕度评估方面的重要潜力。最后,针对不同工程控制措施的内在联系、应用情况等进行了分析,特别强调了燃烧释热分布控制的重要性。

Manufacture, characterization and application of porous metal-fiber sintered felt used as mass-transfer-controlling medium for direct methanol fuel cells

Fabrication, characterization and performance of a porous metal-fiber sintered felt （PMFSF） based on multi-tooth cutting and solid-phase sintering were studied. The PMFSF was used as the anodic methanol barrier in a passive air-breathing direct methanol fuel cell to mitigate the effects of methanol crossover. Compared with the commercial SUS316L felt made of bundle-drawn fibers, this self-made PMFSF has larger pore diameter, polarized pore distribution, irregular fiber shape, rougher surface, lower mass flow resistance and evident hydrophobicity. The results reveal that the use of a PMFSF significantly enhances the cell performance since it helps to maintain a balance between the reactant and product management while depressing methanol crossover. The PMFSF with a porosity of 70% yields the highest cell performance at a methanol concentration of 4 mol/L.

WGI发苯乙烯新工艺

美国华盛顿国际集团公司(WGI)计划启动一套采用新工艺的苯乙烯单体生产示范装置。该新工艺采用无焰分布燃烧(FDC)蒸汽加热方式取代了现行的再加热方式。

Flame radiant image numeralization for pulverized coal combustion in BF raceway

In order to establish correlativity between pulverized coal combustion in a blast furnace raceway and its radiant image, we investigated the relationships between two dimensional radiant images and three dimensional radiant energy in a blast furnace raceway, focusing on the correlativity of the numerical simulation of combustion processes with the connection of radiant images information and space temperature distribution. We calculated the uneven radiate characteristic parameterby taking radiant images as a kind of radiative boundary for numerical simulation of combustion processes, and put fonward a method to examine three-dimensional temperatures distribution in blast furnace raceway by radiant image processing. The numeral temperature fields matching the real combustion can be got by the numeric image processing technique.

Visualization of 3-D temperature distribution in a 300 MW twin-furnace coal-fired boiler

Until now, it has been difficult to obtain on-line three-dimensional (3-D) temperature distribution information which can reflect the overall combustion condition in the furnace of a coal-fired power plant boiler. A combustion monitoring system is introduced which can solve the problem efficiently. Through this system, the 3-D temperature distribution in a coal-fired boiler furnace can be obtained using a novel flame image processing technique. Briefly, we first outline the visualization principle. Then, the hardware and software design of the system in a 300 MW twin-furnace coal-fired boiler are introduced in detail. The visualization of the 3-D temperature distribution in the twin-furnace boiler is realized with an industrial computer and the Distributed Control System (DCS) of the boiler. The practical operation of the system shows that it can provide valuable combustion information of a furnace and is useful for the combustion diagnosis and adjustment in coal-fired power plants.

Distribution of mineral species in different coal seams of Talcher coalfield and its transformation behavior at varying temperatures

Mineral phase characterization and thorough understanding of its transformation behavior during combustion are imperative to know the potential utilization of coal in the thermal industries. The primary objective of this work is to analyze the quality of Indian Coals and obtain their mineral species-specific information at different depths. The samples were obtained from Talcher Coalfield, Odisha, India. Coal from four seam sections in the Talcher coalfield, India are mainly high ash coal （〉50 %） and volatile matter deceases along with the seam depth. XRD results show that the major mineral phases present in the coal are quartz and kaolinite. Siderite, illite, and anatase were found in minor quantities. It has been observed that the clay minerals （kaolinite, silimanite, illite） decompose at higher temperature and traces of dolomite, mullite, hematite etc. are formed during the process of combustion. Among the four seams （M2, M12, M24 and M43） studied, ash of M43 has high A1203%, TIO2% and K20% content and low SIO2%, CaO% and MgO% content. High acid- to-base ratios contributed to high ash fusion temperatures （IDT 〉 1500 ℃） and low slagging potential of the coals studied. Relatively low fouling index （〈0.3） was estimated for all the coal seams studied. Furthermore, thermodynamic modeling software, FactSage, have been used to envision the mineral phase transformations that take place between 800 and 1500℃ during coal combustion.

Two-stage numerical simulation for temperature profile in furnace of tangentially fired pulverized coal boiler

Considering the fact that the temperature distribution in furnace of a tangential fired pulverized coal boiler is difficult to be measured and monitored, two-stage numerical simulation method was put forward. First, multi-field coupling simulation in typical work conditions was carried out off-line with the software CFX-4.3, and then the expression of temperature profile varying with operating parameter was obtained. According to real-time operating parameters, the temperature at arbitrary point of the furnace can be calculated by using this expression. Thus the temperature profile can be shown on-line and monitoring for combustion state in the furnace is realized. The simul-(ation) model was checked by the parameters measured in an operating boiler, (DG130-9.8/540.) The maximum of relative error is less than 12% and the absolute error is less than 120℃, which shows that the proposed two-stage simulation method is reliable and able to satisfy the requirement of industrial application.

船用柴油机电控高压共轨燃油喷射系统研究

为满足内河船舶发动机日益严格的排放标准,对某型高速柴油发动机配置电控高压共轨燃油喷射系统,完成共轨燃油喷射系统的关键零部件设计等基础设计工作,并通过优化油束碰撞位置等进行燃烧室优化设计,以实现柴油机的NOx和颗粒物(PM)排放指标的折中优化。借助AVL-Fire软件对发动机缸内燃烧过程、NOx排放和碳烟(Soot)排放的生成以及相关喷油策略进行仿真计算,验证优化设计的缩口-ω型燃烧室匹配6孔喷油器对燃油与空气的充分混合、改进燃油雾化和蒸发的影响,进而明确了发动机宜采取推迟喷油和较长的喷油持续期。上述经验为发动机排放标定试验提供了有益的参考。台架排放和耐久劣化试验相关研究结果表明,在有效寿命期内,配置电控高压共轨燃油喷射系统的该高速柴油发动机,其性能可达到中国内河船舶发动机第二阶段排放标准。

Distributions of rare-earth elements in two Chinese coals and their burnt products

The concentrations of two fresh Chinese coals (lignitie and fatty coal ) from dif-ferent geological origin and the corresponding fly and bottom ashes were determined us-ing inductively coupled plasma mass spectrometry(ICP-MS). The ranges and means of concentrations of these elemennts were given. Based on the combustion simulating ex-periment in the one-dismensional boiler, the contents of REE (rare-earth element) of 18 samples in lignite, fatty coal and their fly and bottom ashes in different combustion condi-tion were determined, and geochemical feature of REE were analyzed.

Effect of wall temperature and random distribution of micro organic dust particles on their combustion parameters

The effect of wall temperature on the characteristics of random combustion of micro organic particles with recirculation was investigated. The effect of recirculating in micro-combustors is noticeable, hence it is necessary to present a model to describe the combustion process in these technologies. Recirculation phenomenon is evaluated by entering the exhausted heat from the post flam zone into the preheat zone. In this work, for modeling of random situation at the flame front, the source term in the equation of energy was modeled considering random situation for volatizing of particles in preheat zone. The comparison of obtained results from the proposed model by experimental data regards that the random model has a better agreement with experimental data than non-random model. Also, according to the results obtained by this model, wall temperature affects the amount of heat recirculation directly and higher values of wall temperature will lead to higher amounts of burning velocity and flame temperature.

Experimental research on combustion fluorine retention using calcium-based sorbets during coal combustion(Ⅱ)

During the fixed bed tube furnace combustion experimental study,stimulated the calcium-based sorbent grain size and microstructured influencing factors to explain the fluorine retention effect influence law,and expounded the combustion fluorine retention agent developing principle,and probed into the high-temperature fluorine retention agent technical approach.The results show that the calcium-based sorbent particle grain size and pore structure also have the bigger influence on the combustion fluorine retention ef- fect,and reducing the calcium-based sorbent particle grain size and improving the calcium sorbent structure characteristics at very high temperature to enhance the fluorine retention effect is the important approach to the fluorine retention agent development.