Prediction model of moisture content of dead fine fuel in forest plantations on Maoer Mountain,Northeast China

Preventing and suppressing forest fires is one of the main tasks of forestry agencies to reduce resource loss and requires a thorough understanding of the importance of factors affecting their occurrence.This study was carried out in forest plantations on Maoer Mountain in order to develop models for predicting the moisture content of dead fine fuel using meteorological and soil variables.Models by Nelson(Can J For Res 14:597-600,1984)and Van Wagner and Pickett(Can For Service 33,1985)describing the equilibrium moisture content as a function of relative humidity and temperature were evaluated.A random forest and generalized additive models were built to select the most important meteorological variables affecting fuel moisture content.Nelson’s(Can J For Res 14:597-600,1984)model was accurate for Pinus koraiensis,Pinus sylvestris,Larix gmelinii and mixed Larix gmelinii—Ulmus propinqua fuels.The random forest model showed that temperature and relative humidity were the most important factors affecting fuel moisture content.The generalized additive regression model showed that temperature,relative humidity and rain were the main drivers affecting fuel moisture content.In addition to the combined effects of temperature,rainfall and relative humidity,solar radiation or wind speed were also significant on some sites.In P.koraiensis and P.sylvestris plantations,where soil parameters were measured,rain,soil moisture and temperature were the main factors of fuel moisture content.The accuracies of the random forest model and generalized additive model were similar,however,the random forest model was more accurate but underestimated the effect of rain on fuel moisture.

Modelling the dead fuel moisture content in a grassland of Ergun City,China

The dead fuel moisture content(DFMC)is the key driver leading to fire occurrence.Accurately estimating the DFMC could help identify locations facing fire risks,prioritise areas for fire monitoring,and facilitate timely deployment of fire-suppression resources.In this study,the DFMC and environmental variables,including air temperature,relative humidity,wind speed,solar radiation,rainfall,atmospheric pressure,soil temperature,and soil humidity,were simultaneously measured in a grassland of Ergun City,Inner Mongolia Autonomous Region of China in 2021.We chose three regression models,i.e.,random forest(RF)model,extreme gradient boosting(XGB)model,and boosted regression tree(BRT)model,to model the seasonal DFMC according to the data collected.To ensure accuracy,we added time-lag variables of 3 d to the models.The results showed that the RF model had the best fitting effect with an R2value of 0.847 and a prediction accuracy with a mean absolute error score of 4.764%among the three models.The accuracies of the models in spring and autumn were higher than those in the other two seasons.In addition,different seasons had different key influencing factors,and the degree of influence of these factors on the DFMC changed with time lags.Moreover,time-lag variables within 44 h clearly improved the fitting effect and prediction accuracy,indicating that environmental conditions within approximately 48 h greatly influence the DFMC.This study highlights the importance of considering 48 h time-lagged variables when predicting the DFMC of grassland fuels and mapping grassland fire risks based on the DFMC to help locate high-priority areas for grassland fire monitoring and prevention.

DYNAMIC MODELS OF AQUIFEROUS CONTENT OF LIVING FUELS

Forest fire occurrence is closely relative with fuel water content. There are a lot of research about dead fuels. but forest fuels consist of both dead fuels and living fuels. Each large fire occurrence has a good relationship with living fuels. Especially living fuels can influence the production and development of big forest fire, so, we selected Tahe, in Daxingan Mountains, as observation site. According to actual data,we can establish a set of models of different living fuel water content variation with linear -regression method.

Effect of Emulsified Diesel Fuel on Performance and Emissions Characteristics

Diesel fuel has been known as the most effective fuel but it is known as a fuel which produces harmful emissions. Later, emulsified diesel fuel was introduced as a better solution but there is no sufficient research data concerning combustion of emulsified fuel. The present work carried out a simulation of non-surfactant emulsified diesel fuel where composition of water in emulsion varied from 0% to 20% to determine the ratio of water to diesel which is more effective in reducing the exhaust emissions especially NOx. For this simulation,5% of water in diesel without surfactant was able to reduce NOx?up to 35%. It was shown that as the percentage of water increases, the power from that fuel combustion reduces.

Effect of Humidity Content and Morphology on the Properties of Proton Exchange Membrane from Sulfonated Poly (arylene ether sulfone) s Containing Fluorophenyl Pendant Groups

The characters of proton exchange membranes from sulfonated poly( aryl ether sulfone) s( SPAESs) containing fluorophenyl pendant groups are studied in this paper.Both the water uptake and the water content parameter( λ) of all SPAES membranes increase almost linearly with sulfonation degree( SD)and temperature.After being equilibrated in deionized water,the dimensional change in plane is much less affected by temperature than that in vertical direction.Under all the humidity condition the proton conductivities of these SPAES membranes increase with SD and temperature.A maximus proton conductivity of 0.38 S/cm is attained at 90 ℃ for SPAES-5 with a SD of 99.3% when the membrane is fully hydrated,higher than that of Nafion 115.But the proton conductivities of SPAES membranes decrease dramatically with the relative humidity and all of them are lower and more affected by relative humidity than that of Nafion 115 at relative humidity lower than 100%,which may be due to the cumulative effects of narrower channels with spherical clusters for proton migration,more rigid chains and larger tortuosity of SPAESs.

基于D-D中子源的乏燃料组件钚含量测量装置设计

为了满足国际社会上对于乏燃料组件内特种可裂变材料钚的保障监督需求,以持续提供核材料信息,研究乏燃料组件内钚含量测量的非破坏性分析技术显得尤为重要。本文采用主动法,以压水堆乏燃料组件作为测量对象,D-D中子作为质询中子源,开展了乏燃料组件钚含量测量装置的设计研究。采用MCNPX软件,基于最大化探测器计数率和使各探测器计数率尽量一致的目的,对测量装置中的中子管与探测器组件距离、中子管慢化材料及其厚度、探测器组件与中子管高度差、探测器组件中慢化体厚度等关键参数进行了模拟计算。此研究为中子质询乏燃料组件钚含量测量技术研究及实验验证打下了基础。

SOME ANALYTIC PROBLEMS FOR CLEAN FUEL PRODUCTION

Sulfur contents olefins, aromatics, octane number and cetane number are very important indicators of clean fuel. The analytical methods of these indicators proposed by Research Institute of Petroleum Processing (RIPP) were introduced in this article. These methods possess the advantages of fast, convenient and precise, and have been used in R&D work and production process control as well.

温湿度变化对车用燃料电池输出性能的影响

研究温湿度变化对车用燃料电池输出性能(输出电压和功率)的影响可为高精度进气控制策略提供有效的依据。本工作提出了一个温湿度-电流(temperature and relative humidity-current,TRH-C)模型,该模型考虑了电池内部电化学反应、电渗迁移和加湿冷凝三部分水来源,揭示了电流随温湿度变化规律和由水活度表征的电渗迁移系数计算式。根据电池流道实物在计算软件COMSOL中建立网格,将TRH-C模型导入并应用有限体积法进行计算;搭建了燃料电池测试系统,在工作温度60℃和70℃、相对湿度分别为50%和100%条件下进行了实验并进行数据处理;并对通过TRH-C模型得到的极化曲线与实验数据进行比较,分析了电流密度和膜水含量分布云图。结果表明,TRH-C模型能预测燃料电池的性能,在工作温度为60℃、相对湿度为50%时,电压和功率密度的相对误差最大(电流密度为0.018 A/cm^(2)),分别为3.674%和3.696%。工作温度升高会导致膜水含量降低,但相对湿度增大会导致膜水含量升高。

压水堆乏燃料组件中主要同位素含量分析计算

绝大多数的特种可裂变材料钚均存在于商用乏燃料组件中,在核保障领域,对于乏燃料组件中钚含量的核实显得尤为重要。为分析计算乏燃料组件中易裂变核素钚的含量,以31组AFA-2G典型压水堆乏燃料组件为研究对象,通过分析核燃料在反应堆运行过程中的U-Pu循环燃耗链的特点,分析计算了乏燃料组件中主要同位素的含量和固有中子本底,同时利用蒙特卡罗模拟方法计算了239Pu等效质量的等效系数。本文工作为中子质询乏燃料组件易裂变核素含量非破坏性测量的方法研究及测量装置的设计打下了基础。

中子成像技术在元素分析中的应用

中子成像作为一种快速、直观的无损检测技术,在核工业、航空航天、新能源、地质、考古、先进制造等多个领域得到广泛应用。中子成像利用中子不带电、穿透能力强、对轻元素敏感、可区分同位素和近邻元素等特性,非常适合开展含氢元素、近邻元素和同位素等材料的无损检测。通过概述中子成像技术的基本原理及特点,并结合中国先进研究堆(CARR)中子成像装置上的应用案例,重点综述了国内外中子成像技术在储氢材料、燃料电池、岩石、核燃料元件、古代文物等领域的典型应用。随着中子成像技术的不断发展和广泛应用,有望为我国更多领域研究提供更强有力的技术支撑。

北京西山林场侧柏林可燃物含水率及林火预测

以北京西山林场侧柏林为研究对象,对选择林分的特征进行调查,经内业试验对侧柏林地表细小可燃物含水率进行测定,选择通过Pearson相关性分析呈显著的气象因子为拟合变量建立细小可燃物含水率模型,根据引燃试验建立地表火发生概率模型,同时结合Cruz树冠火发生模型,利用实际气象条件对地表火与树冠火发生概率的动态变化进行分析。结果表明:侧柏林细小可燃物含水率模型预测效果较好;防火期内,侧柏林发生地表火的概率较大,而不同样地发生树冠火的概率差别较大,在风速较大时发生树冠火的概率较大。

水分对喷气燃料质量性能的影响研究

较高品质的喷气燃料能有效避免航空发动机发生故障。燃料中水分因为高空低温环境下结冰或储罐中滋生微生物而对燃料品质与性能造成影响,为探究在油轮空载时向货油舱内灌注压舱水是否会对喷气燃料含水量造成影响,在不同油水比例、不同油水接触时间和不同品质水分条件下,对高闪点喷气燃料含水量进行考察,并定量分析水分对于高闪点喷气燃料外观及理化性质的影响。另进行海水对高闪点喷气燃料其他理化性质影响探究。得出结论:油水比例、不同品质水和接触时间对高闪点喷气燃料中的含水量影响较小,但在海水环境下会影响喷气燃料硫含量、总酸值等性质。在油库中,可以考虑用水代替喷气燃料作为冲洗、试压介质,减少油料浪费,提高冲洗操作的安全性。

蜡油加氢裂化装置航煤产品物理性状优化研究

介绍了某石化公司220万t·a^(-1)蜡油加氢裂化装置生产过程中航煤产品合格率低于公司指标的情况,装置频繁出现航煤产品浑浊现象。航煤出现浑浊后需进行二次加工处理,增加了生产能耗,严重影响公司经济效益。针对上述问题,通过成立QC小组对其产生问题的症结进行追踪溯源和多角度分析,找到影响航煤产品外观的症结原因并提出有效解决措施。措施实施后取得良好效果,对比上周期航煤产品质量合格率由89.82%提高至100%,避免经济损失502.7万元,取得巨大经济效益和社会效益。

船舶尾气监测无人机系统设计与应用

为监测珠江水域在航船舶的燃油合规性,设计了一套用于监测船舶尾气的微型嗅探无人机系统,该系统利用无人机搭载微型嗅探传感器,可实时监测在航船舶尾气中的二氧化硫(SO_(2))和二氧化碳(CO_(2))浓度,进而监管船用燃油硫含量的合规情况,筛查违规使用高硫油的船舶。经过现场测试与应用,成功查实多艘违规使用高硫燃油的船舶。通过对比分析船舶燃油硫含量的监测值和实际值,验证了船舶尾气嗅探无人机技术的可靠性。船舶尾气嗅探无人机监测系统的应用可以为海事执法提供便捷手段和技术支撑,提高海事执法效率。

液环式航空燃油离心泵自吸性能

基于Mixture模型对液环式航空燃油泵进行自吸阶段的非稳态数值计算,研究自吸过程中燃油泵内气液两相分布的变化过程,对不同时刻下燃油泵内部含气率、气液两相分布、压力及速度流线、熵产率和湍动能变化规律进行分析.结果表明:燃油泵的吸气和排气主要集中在自吸过程的前期和中期;随着自吸时间的增加,各监测面的含气率逐渐降低,当自吸时间为3.00 s时,蜗壳出口含气率接近于0,自吸过程结束;泵内压力随相对距离的增加而增大,泵内同一相对距离平面压力随自吸时间的增加而增大;在气液混合时,高速区域主要集中在叶轮中间流道和蜗壳壁面处,低速区域则集中分布在隔舌附近和导叶出口;随着自吸过程的进行,泵内湍动能和熵产率也随之增大,泵内能量损失增大,主要集中在叶轮叶片、导叶叶片和蜗壳出口处.

基于WDXRF法的动力用煤成分含量快速分析方法研究

本文对WDXRF法测定动力用煤中各成分含量进行了试验研究,分析了煤样粒度影响和黏结剂选择,通过基体效应确定了测试条件,进行了精度密试验,开展了标准样品测试和国标方法对比。试验结果表明:WDXRF法测定动力用煤中各成分含量具备良好的精密度和准确度,测定结果与国标方法一致,可应用于动力用煤中各成分含量的快速测定。

罩式炉加热罩空燃比优化

罩式炉加热罩燃烧使用的焦炉煤气为混合气体,其热值不稳定,易受多种因素的影响,难以精准控制空燃比。空燃比设置偏高,排出的废气增多,热量损失大,降低了热效率。空燃比设置偏低,加热能力不足,退火时间长,导致产量降低。基于此,提出采用排烟系统中废气氧含量反馈法对空燃比进行优化。经过测算,最终确定出空燃比的最优值和调节范围,实现了在退火过程中对空燃比的闭环控制,解决了煤气热值不稳定带来的问题,达到了预期效果。

燃油硫含量对尾气颗粒物理化特征的影响分析

文章以一台排量为4.5L的柴油机为试验对象,使用三种不同硫含量的柴油,探究了燃油中硫含量对颗粒物的微观形态、纳米结构、颗粒尺寸、石墨化程度、表面化学特性,以及化学组成等物理化学特性的影响。使用透射电子显微镜分析颗粒物的微观形貌和纳米结构,利用拉曼光谱仪对颗粒物的石墨化程度进行表征,运用傅里叶红外光谱仪分析颗粒物的表面官能团,同时运用热重分析仪和等离子体发射光谱仪进行颗粒物组分和元素组成的分析。基于低倍电镜图像发现,颗粒物表现为不规则的团聚体结构,由几十甚至上百个球形或近球形的基元颗粒团聚而成,且随着燃油硫含量的增加,基元颗粒堆叠更加明显,颗粒物微观形貌从链状结构转变为团状。基于高倍电镜图像发现,颗粒物基元颗粒物表现为典型的核-壳结构,且随着燃油硫含量的增加,基元颗粒外缘非晶态物质的厚度和基元颗粒粒径也随之增加。此外,随着燃油硫含量的增加,研究发现:形态方面,基元颗粒微晶平均曲率增加,但平均长度变短;石墨化程度方面,颗粒物石墨化程度降低;成分组成方面,有机组分及S元素占比增加。

一般工业固废源替代燃料制备工艺现状分析

经过近几年的快速发展,替代燃料制备行业迎来了爆发式增长。但发展的过程也产生了因市场原因导致的原料价格不断上升、品质不断下降的问题,以及后端需求量不断上升导致的单一废纺来源已不能满足要求的问题。物料的变化使原有替代燃料制备工艺运行过程投资及运行成本过大、系统故障率升高等问题更加突出。本文分析了原料变化、替代燃料制备工艺流程及设备选型在运行过程中存在的问题,提出了适合我国替代燃料制备行业发展的方向及建议。

SCR熔炉系统天然气燃烧节能分析及应用

因连铸连轧生产线熔炉系统天然气能源消耗较大,对熔炉投料、燃烧原理、燃烧控制、天然气能源组分等熔化工艺中影响燃气消耗的因素进行了分析,采取了天然气燃烧热能利用、燃烧CO值及铜液氧含量等关键点优化控制,使天然气燃烧余热利用率≥55%,天然气使用单耗下降至37.27 m^(3)/t。