Numerical simulation of the influences of catalytic wall on methane combustion characteristics in micro combustor

In order to study the effects of different catalytic walls on combustion characteristics, the premixed catalytic combustion characteristics of methane/air in micro combustor are studied. It lays the foundation for the combustion technology of hydrocarbon fuel in micro engine. Numerical simulation of flow and catalytic combustion in micro combustor was done by using laminar finite rate and second order upwind discretization methods. The results show that when wall temperature,CH4/O2 mole ratio and methane mass flow rate change, the influence of lower catalytic wall on the methane catalytic combustion efficiency is biggest, followed by side catalytic wall, the smallest is upper catalytic wall. The methane catalytic combustion efficiency unit area of lower catalytic wall is about three times of that of upper catalytic wall. The utilization of catalyst on lower catalytic wall is maximal . Therefore, when coating catalyst, the quantity of katalyst on lower catalytic wall should be appropriate more, moderate on the side catalytic wall, as little as possible on the upper catalytic wall. The influence disciplinarian and contribution rate of different catalytic wall on methane combustion have been gained. The optimized strategy of catalyst coating was put forward and reduced the cost of catalytic combustion.     

旋转修正的k-ε湍流模型在转子发动机三维流场模拟中的应用

以商业软件FLUENT为平台,采用考虑转子发动机旋转修正的k-ε湍流模型,编制并加入自定义UDF程序.通过对FLUENT软件进行二次开发,实现转子发动机工作区域网格的动态更新.考虑转子与缸体间漏气,对冷拖动工况下转子发动机内部三维湍流流动进行了数值模拟.计算结果揭示了转子发动机内部流场的分布特征和规律,为转子发动机的性能预测及优化设计提供了技术依据.     

添加剂对稻秆燃烧过程中碱金属形态分布的影响

采用化学热平衡分析方法对稻秆燃烧过程中碱金属K的化学形态及其分布,以及添加Al,Si,S,P,Ca等元素对稻秆燃烧过程中碱金属的化学形态分布的影响进行了研究.结果表明,在稻秆中加添加Al或同时添加Al和Si,可以避免稻秆燃烧过程中发生结渣和沉积问题.温度低于900℃燃烧时添加S或温度低于1 100℃添加P.可有效的缓解稻秆中碱金属引起的结渣和聚团问题.系统中Ca的增加可有效的抑制碱金属引起的结渣和聚团问题,但有可能增加其引起的沉积和腐蚀问题.而Si的增加使K以液态形式存在的摩尔百分比增加,导致底灰聚团的现象加重.     

炉灶一体式生物质气化炉灶头的结构设计及燃烧热性能测试

针对炉灶一体式生物质气化炉燃气压力小、低位热值偏低的特点,设计了与气化反应器配套使用的灶头装置,并对该灶头进行了燃烧热性能测试。试验结果表明:该灶头可保证生物质燃气稳定燃烧,二次风流量为0.0128m3/min时,热效率高达36.58%,火力强度高达2.85kW,且无回火和黄烟现象产生。     

山核桃等3类果蓬原料机制炭燃烧性能分析

利用TG-DTG-DSC热分析联用技术,对油茶Camellia oleifera,板栗Castanea mollissima和山核桃Carya cathayensis等3类果蓬制备的机制炭燃烧性能分析结果表明:3类果蓬机制炭燃烧失重开始所需的温度分别为435.4,448.1和412.3 ℃,较马尾松Pinus massoniana和杉木Cunninghamia lanceolata为原料制备的普通机制炭519.8 ℃低71.7~107.5 ℃,燃烧速率曲线峰值和峰值温度、放热曲线的峰值和相应的峰值温度均表现为普通机制炭＞油茶、板栗果蓬机制炭＞山核桃果蓬机制炭,即果蓬类机制炭可燃性优于普通机制炭;着火温度、最大释热量、最大燃烧速率和着火后最大失重速率及其相应温度5个参数大小排列均呈现为普通机制炭＞板栗果蓬机制炭＞油茶果蓬机制炭＞山核桃果蓬机制炭,其中山核桃果蓬机制炭着火温度408.6 ℃,较普通机制炭504.4 ℃低95.8 ℃,普通机制炭最大释热量95.12 Wg－1,比最大释热量分别为87.76,92.07,84.82 Wg－1的果蓬类机制炭高3.05 ~ 10.30 Wg－1,即生产中可以通过调节果蓬原料的添加量制备不同着火温度和燃烧特性的机制炭。图4表2参12     

江西常见树种抗火性研究

在对江西28种常见树种不同器官理化性状测定分析、燃烧试验和抗火性试验的基础上,应用灰色关联分析法,选择树种的含水率、燃点、热值、粗灰分、粗脂肪、木质素、粗纤维、燃烧时间、火烧强度、树皮厚度、热辐射作用下树皮的质量剩余率和内表面升温速率以及其生物生态学特性等17个指标值作为评价因素,对28种常见树种的抗火性进行综合评价....     

基于脉动燃烧技术的土壤消毒蒸汽发生装置设计与试验

为解决设施园艺土壤蒸汽消毒的蒸汽来源问题,设计了基于脉动燃烧技术的蒸汽发生装置。该装置主要由脉动燃烧发动机和锅体两部分组成,脉动燃烧发动机作为热源,其主体浸没在锅体内部水中。通过功率计算,在饱和蒸汽压力为0.6 MPa条件下满足130 kg/h蒸汽产量需要功率107.12 k W,8组脉动燃烧发动机可以满足功率需求。设计了双化油器脉动燃烧发动机,两只化油器同时进油、进气,通过"Y"型喉管连接,燃烧室呈圆柱形,尾管由3根螺旋管并联组成。试验结果表明,脉动燃烧发动机在空气中和水中均具有良好的启动性和工作稳定性,在空气中工作频率保持在90.80~90.89 Hz之间,平均频率90.86 Hz,在水中工作频率保持在87.27~87.81 Hz之间,平均频率为87.51 Hz。额定工况和非额定工况下,蒸汽发生装置热效率分别为95.5%、95.8%。额定工况下蒸汽产量150 kg/h、油耗9.7 kg/h、功率110.8 k W、尾气温度108℃、过量空气系数1.026,满足土壤蒸汽消毒蒸汽量的要求。     

生物质热解固体热载体高温烟气加热装置设计与试验

固体热载体加热生物质是生物质热解制取生物油的工艺手段之一。为解决固体热载体间接加热方式升温慢、效率低问题,设计了一种流化床生物质燃烧的热烟气直接加热固体热载体装置,分析了其结构与原理,开展了固体热载体升温性能和流化床燃烧器的燃烧特性试验研究,并对试验结果进行了热平衡分析。结果表明:流化床高温烟气加热陶瓷球热载体的平均热能利用率为66.3%,流化床燃烧生物质粉产生的高温烟气能够满足热载体加热装置对热源的需求,热载体加热器内的热量传递方式主要是对流换热。陶瓷球热载体与加热器内高温烟气的对流传热系数为475 W/(m~2·℃)。研究对结果对解决生物质热解液化技术中的固体热载体加热升温关键问题具有重要指导意义。     

Numerical simulation on multi jet diffusion combustion of low concentration coal bed methane

It is important to utilize coal bed methane to achieve the safe, environmental and economic benefits. The authors simulate the processes of multi jet diffusion combustion of low concentration coal bed methane using k ε turbulence model,non premixed combustion model and P1 radiation model. The influences of different geometrical structures and operating parameters on the combustion process are compared with each other. The results show that the distance between the gas nozzles and central axis,the angle of gas deflected from air ,the velocity ratio of air to gas have important impacts on the combustion. When the distance, the deflection angle and the velocity ratio are 30 mm,45 °and 2, respectively. The best combustion result can be achieved.     

Dendrometric and dasometric analysis of the bushy biomass in Mediterranean forests

The aim of this study was to define the dendrometric and dasometric parameters of five Mediterranean bushy plant species, to make their environmental assessment and to determine correlations with LIDAR data. The species studied were: Quercus coccifera, Rosmarinus officinalis, Ulex parviflorus, Cistus albidus, and Erica multiflora. We calculated the global form factor for each species so as to be able to determine the volume of the plants by measuring their base diameter and length. The model volume closest to the real volume was the cylinder, which had form factor values of between 0.8 and 2.33. We also studied the evolution of the moisture content of the vegetation after cutting. The initial values were from 20 to 30%, with a dry density of 1 t/m³. We defined an occupation factor to determine the relationship between the real volume occupied by the plants in an area and a model volume (hemisphere, paraboloid, cone, and cylinder). The occupation factor was similar for the five species studied in dm³ of material per m³ of (model) apparent volume: 3.5 dm³/m³ for the cylinder; 12.5 dm³/m³ for the cone; 8.5 dm³/m³ for the paraboloid; and 14.5 dm³/m³ for the hemisphere. These factors enabled us to calculate the biomass contained in an apparent volume of bushes (including materials and hollows) by density. The prediction models tested in this study will thus serve to determine the biomass of a bushy forest area when the Canopy Height Model (CHM) is calculated from LIDAR data.