四气门汽油机低速低负荷燃烧过程的试验研究

在发动机试验台上,用CB-466燃烧分析仪对四气门汽油机低速低负荷燃烧压力循环变动进行了试验研究。试验结果表明,转速不变时,随着负荷的增加,指示热效率逐渐增加,达到最大值后又逐渐减小,最高燃烧压力及其标准偏差和平均指示压力逐渐增加,最高燃烧压力循环变动率和平均指示压力循环变动率则随之减小;中等负荷与小负荷相比,最高燃烧压力循环变动率减少了28.3%,平均指示压力循环变动率减少了47.6%。在负荷不变的条件下,随着转速的增加,指示热效率逐渐增加,低转速时的指示热效率仅为中等转速时的指示热效率的57.4%,最高燃烧压力随之减小,最高燃烧压力循环变动率、平均指示压力及其标准偏差和平均指示压力循环变动率逐渐增加。平均指示压力循环变动率与最高燃烧压力循环变动率相比较小,平均指示压力循环变动率仅为最高燃烧压力循环变动率的37.1%。     

四角对冲燃烧技术的探讨与应用

针对四角切向燃烧方式的锅炉运行中存在的烟温偏差、结焦等人们关心的问题 ,分析了几种四角燃烧方式的特点和缺陷以及成功事例 ,指出用四角对冲燃烧方式对老锅炉进行改造是解决烟温偏差、结焦等问题的好方法     

四角切圆锅炉同轴燃烧系统空气动力特性的研究

对300MW四角切圆煤粉锅炉采用低NOx同轴燃烧系统时炉内流场及燃烧器区域浓度场进行了冷态模化试验研究。分析了当二次风偏置角度、二次风与一次风动压比、燃尽风比率及燃尽风布置方式变化时，对炉内气流相对切圆直径、旋转动量流率矩、湍动度、一二次风混合、燃尽风穿透力等的影响，进而分析了对锅炉工作的影响。图7表4参6     

燃气镁合金熔化炉内气相燃烧过程的三维数值模拟

对燃气镁合金熔化炉内的三维湍流气相燃烧场特性进行了数值模拟,湍流模型采用了标准k-ε双方程模型,湍流燃烧采用有限速率/涡耗散模型,辐射换热P1模型,数值方法采用SIMPLE算法,实现了燃烧过程的数值再现,特别考察了烧嘴位置和入口流量速度因素对炉内温度场和流动场的影响,并为熔化炉的结构设计提供了一些合理化建议,为其实际运行提供了有益的参考价值。     

四气门发动机可变滚流结构稀薄燃烧特性的研究

研究了可变滚流结构的稀薄燃烧特性。主要讨论了可变滚流结构对发动机稀薄燃烧时燃油经济性和排放特性的影响。结果表明 :在稀薄燃烧情况下 ,发动机负荷大小对 CO排放的影响不大 ,CO排放始终保持在 0 .5 %以下 ;HC排放则具有相似的变化趋势 ,但排放量随负荷增加而略有增加 ;负荷对 NOx 排放的影响主要表现在空燃比为 13～ 18的范围内 ,负荷越大 ,NOx 排放越大 ;对空燃比小于 13或大于 18的 NOx 排放影响较小。阀片位置 (或滚流比 )对发动机稀燃状态 CO排放的影响很小 ,而对 HC和 NOx排放则存在一定影响。在稀薄燃烧条件下 ,滚流运动更有利于改善低速高负荷时的燃油经济性。     

低压气相辅助溶液法制备无铅铋基钙钛矿太阳电池的研究

采用低压气相辅助溶液法制备MA3Bi2I9钙钛矿太阳电池,制备了晶粒大小为300 nm,表面致密且粗糙低的MA3Bi2I9钙钛矿薄膜,其吸收边位置在598 nm,光学吸收带隙为2.07 eV.还通过对一步溶液法、两步溶液法和低压气相辅助溶液法3种方法制备的MA3Bi2I9钙钛矿太阳电池进行对比发现,与其他2种方法制备的...     

四甲基胍单晶硅片湿法制绒工艺研究

首次采用有机碱——四甲基胍替代传统的氢氧化钠或氢氧化钾作为制绒刻蚀剂,邻苯二酚和硅酸钠作为制绒添加剂进行单晶硅片制绒,并通过实验对不同四甲基胍浓度、邻苯二酚浓度、反应温度、反应时间对单晶硅片制绒的影响进行了分析。研究结果表明：制绒后单晶硅片表面的金字塔分布密集、大小均匀;在400～1000nm的波长范围内,单晶硅片的平均反射率为9.16%,比采用传统的碱醇制绒体系制绒时获得的反射率低;同时,该制绒方法还消除了传统制绒刻蚀液中金属离子对单晶硅片的污染。     

四角切圆燃烧大容量电站锅炉烟气参数场偏置问题的研究

文章以采用四角切圆燃烧方式的３００ＭＷ以上大容量电站锅炉的大量性能反馈数据及现场试验数据为基础，通过分析和归纳，指出了该类电站锅炉会不可避免地存在上炉膛及对流烟道中的烟气流场，速度和温度场的左右侧偏置现象，并指出了该类锅炉屏式再热器和末级再热器易爆管及末级过热器出口沿炉宽方向左右侧对应点间汽温偏差过大的根本原因。文中还对原则性治理方案进行了可行性论证。并推荐了最优化方案。     

2-甲基呋喃/氧气/氩气低压预混层流火焰燃烧中间产物的鉴定

利用同步辐射真空紫外光电离质谱结合分子束取样技术,研究了燃烧当量比为0.8的2-甲基呋喃/氧气/氩气低压预混层流火焰的化学组成,得到了2-甲基呋喃火焰的光电离质谱和燃烧中间产物的光电离效率谱.从光电离效率谱得到了相应分子/自由基的电离能.将实验测量得到的电离能与文献值或者利用量子化学从头算方法得到的理论值比较,确定了2-甲基呋喃火焰中燃烧中间产物的化学结构,根据这些产物的化学结构分析了2-甲基呋喃及其初级燃烧反应产物的消耗过程.     

旋风炉内气相燃烧及两相流动的数值模拟

在有反应两相流动及煤粉燃烧的全双流体模型（ＰＴＦ模型,ｐｕｒｅ ｔｗｏ－ｆｌｕｉｄ ｍｏｄｅｌ）基础上,采用修正的ｋ－ε－ｋｐ两相湍流模型,对旋风炉内的湍流气相燃烧（甲烷和一氧化碳的燃烧）及在气相燃烧条件下的两相流动进行了数值模拟研究,模拟结果表明,在有燃烧的情况下,在旋风炉的底部存在近壁回流区,该回流区有利于火焰稳定,气粒两相切向速度分布具有类似的Ｒａｎｋｉｎｅ涡结构,该研究为煤粉燃烧的数值模拟     

生物油燃烧技术研究进展

生物油可以在锅炉中单独燃烧或者与化石燃料混合燃烧用于供热和发电,可以与乙醇、甲醇和柴油等混合燃烧以驱动柴油机发电,也可以直接应用于燃气轮机中.文章分析了由于生物油燃料特性的限制而引起的燃烧应用问题和相应的解决方法.分析表明,生物油与化石燃料在锅炉和燃气轮机中混合燃烧最具有大规模应用的可能性,在柴油机中燃烧是最有开发前景的应用技术.     

A mathematical model for exit gas composition in a 10 MW fluidized bed coal combustion power plant

A mathematical model has been developed for the oxygen mass balance for a 10 MW fluidized bed coal combustion power plant operated at Jamadoba (TISCO, India). Assuming the three phase theory of fluidization, the fluid bed is considered to consist of a number of equivalent stages in series. Within each stage, an exchange of gas takes place between the bubble, cloud-wake, and emulsion phases. An effective chemical reaction rate of char combustion has been derived considering the single film theory of char combustion for shrinking particles. The model has been used to predict the consumption of oxygen in the fluidized bed combustor, the outlet gas composition, variation of oxygen concentrations in different phases and also the variation of average oxygen concentration along the bed height. Model predictions were compared with plant data, and reasonable accuracy was obtained.     

湍流燃烧模型在燃烧室数值计算中的对比分析

对比分析了不同燃烧模型对某型回流式燃气轮机燃烧室流场的影响,建立了描述燃烧室流场的控制方程组,采用Realizablek-ε湍流模型,湍流燃烧模型分别为涡耗散模型(ED)、涡耗散概念模型(EDC)、简单概率密度模型(PDF)和稳态小火焰模型(SFM).对比分析了不同燃烧模型下燃烧室的温度场、速度分布以及NOx排放量,并...     

受控脉动燃烧技术的研究及应用

介绍了一种成本低廉，能降低NOx排放50％-90％，提高燃烧效率，节约燃料的受控脉动燃烧技术。对受控脉动燃烧技术的原理、影响参数，以及该技术在国内外研究应用现状进行了介绍，并就脉动燃烧技术今后研究的方向提出了一些看法。     

Optimization of hydrogen production by filtration combustion of natural gas by water addition

The effect of adding steam during filtration combustion of natural gas–air mixtures was studied with the aim to evaluate the optimization of hydrogen production. Temperature, velocity, chemical products of combustion waves, and conversion from fuel to H₂ and CO were evaluated in the range of equivalence ratio (φ) from stoichiometric (φ = 1.0) to φ = 3.0 and steam content in the mixture from 0% to 39%, at filtration velocities from 12 to 25 cm/s. Numerical simulation was carried out using GRI-MECH 3.0. Results suggest that H₂ and CO concentrations, dominant for rich and ultrarich combustion, are products from partial oxidation and steam natural gas reforming processes. Experimental and numerical results show that hydrogen yield increase with an increase of steam content in the natural gas–air mixtures.     

Effects of spray characteristics on combustion performance of a liquid fuel spray in a gas turbine combustor

Spray characteristics like mean drop diameter and spray cone angle play an important role in the process of combustion within a gas turbine combustor. In order to study their effects on wall and exit temperature distributions and combustion efficiency in the combustor, a numerical model of a typical diffusion controlled spray combustion in a can‐type gas turbine combustion chamber has been made. A simple k–ϵ model with wall function treatment for near‐wall region has been adopted for the solution of conservation equations in carrier phase. The initial spray parameters are specified by a suitable PDF for size distribution and a given spray cone angle. A radiation model for the gas phase, based on modified first order moment method, and in consideration of the gas phase as a grey absorbing–emitting medium, has been adopted in the analysis. It has been recognized that an increase in mean drop diameter improves the pattern factor. However, the combustion efficiency attains its maximum at an optimum value of the mean diameter. Higher spray cone angle increases the combustion efficiency and improves the pattern factor, but at the same time, increases the wall temperature. Copyright © 1999 John Wiley & Sons, Ltd.     

燃烧流场测量的PIV应用初步研究

使用丹麦Dantec公司生产的二维PIV(Particle Image Velocimetry)系统对甲烷/空气的扩散燃烧热态速度场进行了测量,得到了燃烧状态下的速度场信息,解决了利用PIV进行热态测量的问题。     

Effects of preparation condition and particle size distribution on fumed silica gel valve-regulated lead–acid batteries performance

The effects of three types of fumed silica on the electrochemical properties of gelled electrolytes have been investigated by means of cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), transmission electron microscope (TEM) and the Brunauer, Emmett and Teller (BET) technique. The CV and EIS results show that a moderate mechanical dispersion of fumed silica in the H₂SO₄ solution has important effects on the electrochemical properties of the gelled electrolyte. The optimal mechanical dispersion time is closely related to the operating temperature during preparation of gel, as well as the silica particle size and its distribution. A high stirring rate improves the electrode capacity and decreases the viscosity of the gelled electrolyte. With moderate mechanical dispersion, gelled electrolytes prepared from different fumed silica particles exhibit equal electrode capacities.     

On the occurrence of two-stage combustion in alkali metals

Pool combustion experiments have been conducted for three alkali metals, namely, lithium (Li), sodium (Na) and potassium (K). Lithium and sodium are found to show a two-stage combustion behaviour which has been reported for a number of other metals. Here, the combustion is characterized by a sporadic rise in the flame temperature accompanied by a bright glow. Potassium is found to burn in vapour phase combustion in all cases without sporadic temperature excursions. In the present study, this different burning behaviour is attributed to the formation of thick oxide agglomerates in the case of Li and Na through the pores of which oxygen/metal vapour has to diffuse for combustion to occur. In such cases, a second stage of vapour phase combustion occurs when the oxide agglomerate is heated sufficiently so that the vapour of the liquid metal trapped in the pores breaks through to the surface. In the case of potassium, a self-cleaning mechanism, attributable to the high solubility of the metal oxides in liquid potassium and the relatively low melting point of the potassium oxides, enables a clear liquid surface to be exposed throughout for vapour phase combustion to prevail always. Recorded temperature profiles, SEM analysis of the oxide agglomerates as well as calculations of the metal–oxygen equilibrium thermo-chemistry for the three metals confirm this scenario.     

Conversion of rice husk into amorphous silica and combustible gas

Results of the studies on thermogravimetric analysis (TGA) of raw and 1(N) HCl acid treated rice husk (in still air) reveal that its thermal degradation takes place in three main stages of mass loss, namely (i) drying, (ii) devolatilization and (iii) slow oxidation of fixed carbon. Hydrochloric acid leaching of husk at 75° for 1 h prior to combustion is necessary for production of amorphous silica of complete white colour. For production of low calorie-combustible gas along with amorphous silica from the rice husks containing 5.5–7% (wb) moisture, a furnace set temperature of 450°C appears to be optimal.