柴油机生物柴油-甲醇混合燃料燃烧与排放特性

分别在100mL生物柴油（M0燃料）中添加10mL甲醇、20mL甲醇与12mL油酸,经过相关处理后形成新的微乳化燃料M10燃料与M20燃料。以台架试验与排放分析法为基础,当发动机转速点为1 500r/min、平均有效压力分别为0.088 9、0.177 0、0.266 0、0.354 0、0.443 0、0.531 0MPa时,分别对3种燃料的燃烧特性与排放特性进行了试验研究。试验结果表明：与M0燃料相比,M10燃料与M20燃料的滞燃期延长,燃烧持续期缩短,3种燃料的最大滞燃期分别为6°、7°、8°;M10燃料与M20燃料的峰值压力、峰值压力升高率以及峰值燃烧放热率均增大,3种燃料的最大峰值压力升高率分别为1.236、1.377、1.280MPa/（°）,3种燃料的最大峰值燃烧放热率分别为0.280、0.281、0.297kJ/（°）;M10燃料与M20燃料的HC、CO与碳烟排放均降低;NOx排放没有明显变化。     

高浓度有机污染土壤自燃修复技术的影响因素

自燃修复(self-sustaining treatment for active remediation,STAR)技术是一种新近发展起来的并对修复非水相液体(NAPLs)污染包气带具有较好应用前景的修复方法。该技术与固体物质的阴燃类似,是没有火焰的缓慢燃烧。有机污染物附着在土壤含水层介质固体表面,依靠异相氧化燃烧,产生的热量可以维持污染物的持续燃烧,不需要热量的持续输入。为了探讨高浓度有机污染土壤STAR修复技术的影响因素,缩短煤焦油加热时间,减少二次污染的产生。通过一维模拟柱分别开展了污染物浓度、空气流速、含水率对煤焦油维持阴燃的影响。研究表明:当污染物浓度在80 000～110 000 mg·kg~(-1)时,煤焦油可以维持阴燃;当浓度低于80 000 mg·kg~(-1)时,煤焦油不能维持阴燃;随着煤焦油浓度的增大峰值温度出现所需时间越来越短,平均峰值温度越来越大,平均燃烧传播速度越来越小;空气流速在2～10 cm·s~(-1)范围内时煤焦油均可维持阴燃,且随着空气流速的增大峰值温度出现所需时间越来越短,平均燃烧传播速度与空气流速间近似呈线性增长关系;含水率的增大对煤焦油维持阴燃没有影响,且随着含水率的增大峰值温度出现所需时间越来越长,平均峰值温度和平均燃烧传播速度均有所降低。与污染物浓度和空气流速相比,含水率对加热时间的影响最大。因此,在含水率变化的情况下,应重点关注煤焦油副产物苯、甲苯、二甲苯、萘等有毒有害气体的产生。     

小缸径直喷式柴油机燃烧与NOx排放物仿真

利用FLUENT对柴油机在标定工况下的燃烧过程与NOx排放进行数值模拟研究.通过实验确定多维计算的边界条件,然后利用FLUENT中的燃烧模型定制边界条件、定义物理模型,完成缸内燃烧模拟.模拟结果与实验结果相吻合,标定工况下,误差不超过6 %.研究结果表明,采用柴油机燃烧多维计算模型模拟缸内燃烧过程与NOx排放是一种有效的研究策略,为柴油机燃烧性能的研究提供一种可靠的手段     

The effects of coal blending on the formation and properties of particulate matter during combustion

The control of particulate matter (PM) emissions from coal combustion becomes an urgent work due to their adverse effects on human health. Coal blending is a promising option for submicron particulate (PM1) reduction. This study addressed the effects of coal blending on the formation and properties of particulate matter in combustion process. Coal blends from lignite and bituminous coal, with different blend ratios (9:1, 7:3, 5:5, 3:7 and 1:9), were combusted in a drop tube furnace. The mass size distribution, concentration, elemental composition and morphology of the particulate matter generated under O₂/N₂ and O₂/CO₂ conditions were characterized. Particulate matter was collected by a low pressure impactor (LPI), which aerodynamically segregated particulates into thirteen fractions with sizes ranging from 0.03 to 9.8 μm. The results showed that coal blending reduced PM1 generation, compared with the calculated average values from the combustion of constituent coals. This indicated that the mineral interactions had a great effect on PM₁ reduction. The blend ratio also played an important role in the suppression of PM1 generation. In this experimental study, PM1 generation suffered a maximum suppression at the blend ratio of 7:3. The O₂/CO₂ atmosphere affected the formation and properties of the PM1 during coal blends combustion. Compared with the O₂/N₂ combustion, the interaction of minerals was weakened under O2/CO2 combustion, thus the suppression of PM₁ generation decreased after coal blending. Compared with the calculated values, the concentrations and percentages of Ca, Fe in PM₁ decreased, but the concentrations of Ca, Fe, Si and Al in coarse particulates (PM₁₀₊) increased after coal blends combustion. The interactions between the aluminosilicates in the bituminous coal and volatile elements Ca, Fe in the lignite were thought to contribute to the suppression of PM₁ generation during the com-bustion of coal blends.     

胜利油田含油污泥的燃烧特性分析

依据胜利油田含油污泥的自身性质,以含油污泥的热重试验为基础,对比分析了含油污泥燃烧与热解的热重曲线,采用热重-微商热重(TG-DTG)法确定了不同升温速率条件下的着火温度和燃尽温度,利用Coats-Redfern积分法求解含油污泥的指前因子和表观活化能,并进一步分析升温速率对含油污泥燃烧特性的影响.结果表明:随着升温速率增加,燃烧速率、着火温度和燃尽温度不断提高,含油污泥的指前因子和表观活化能有所增大.     

车用内燃机气门弹簧优化设计

本文阐述了车用内燃机气门弹簧的作用和对其进行优化设计的重要性,提出了车用内燃机气门弹簧优化设计的数学模型,通过分析车用内燃机气门弹簧优的设计变量、目标函数和约束条件,得出结论。     

Web database sampling approach based on attribute correlation

In this paper,we present a novel approach utilizing attributes correlation for the sampling task on nonuniform hidden databases. We propose the method of calculating the attributes dependency and construct the sampling template according to the attributes dependency. Then,we use the sampling template to gen-erate initial sampling queries and propose a bottom-up algorithm to search the sampling template. We also conduct extensive ex-periments over real deep Web sites and controlled databases to illustrate that our sampling method has good performance both on the quality and efficiency.     

基于模糊渗流理论的采场上隅角瓦斯治理

为了防止由于煤层开采深度、强度及瓦斯涌出量的增大而造成的上隅角瓦斯积聚。通过建立模糊微分方程对采空区风流移动进行描绘,并利用相似材料模拟实验对上隅角瓦斯进行研究,针对性的提出了防止工作面上价值。     

高浓度CO2对柴油着火延迟特性的影响

为了研究柴油在高浓度CO2下环境中的着火延迟特性,提出了适用于该环境下的着火延迟时间公式。该公式考虑了CO2的热效应和第三体效应对着火延迟的影响,分析了CO2摩尔浓度与着火延迟的关系,运用chemkin模拟了CO2对OH自由基生成速率的影响。对该环境下柴油的着火问题进行了定容燃烧弹的可视化实验研究和仿真计算。结果表明：着火延迟时间公式在CO2浓度小于60%时能够有效表达CO2对着火延迟时间的影响;CO2浓度大于60%时,反应H2O2+M→2OH+M中的第三体效率降低导致着火延迟增长变慢。     

劣质混煤的热解与燃烧特性

利用热重法研究了洗选煤矸石与洗中煤混合而成的劣质混煤的热解与燃烧特性,获得了着火温度、燃尽温度、综合燃烧特性指数、燃尽指数等特征参数,通过动力学分析得到了活化能与频率因子等参数。研究结果对优化循环流化床锅炉的运行、节约燃料减少污染排放具有重要意义。