易自燃煤层放顶煤开采工作面合理长度分析

以采空区自然发火危险为约束条件,用采空区场流方法(数值模拟)和自燃三带理论,结合实例,研究放顶煤开采工作面合理长度问题.得到工作面长度安全临界值与煤的最短自然发火期成正比关系.通过现场测定风量和采空区气体浓度分布,得到在当前工作面特定采空区流场环境下的自燃氧化带宽度和模型基础参数,数值模拟出不同工作面长度的采空区自燃氧化区宽度的变化关系;回归得到,在理论上,工作面长度与自燃氧化带宽度近似服从二次曲线关系.分析中给出了自燃安全判别量和自燃安全区间.     

Investigation on extremal and critical characteristics of ignition time for H<Subscript>2</Subscript>/O<Subscript>2</Subscript> combustion system and their applications

The L, H and C curves in P-T phase are proposed to describe the minimal, maximal and critical characteristics of ignition time of H₂/O₂ combustion system, respectively. The features of H₂/O₂(Air) combustion system, including explosion or not as well as the time delay to achieve its explosion status, can be well shown by explosion limits and these proposed curves. These curves can be described by 1.2k ₁=k _s [M_s], (k ₁₁/k ₁₀+1)k ₁=k _s [M_s], and 2k ₁=k _s [M_s], respectively, which provide a physical explanation for these curves and give another way to establish them. Based on the contour of ignition time, the Z-type explosion limits can be explained by thermal explosion theory. Furthermore, the ignition distance of supersonic combustion is predicted according to the ignition time obtained in a Semenov system, which is very reasonable.     

煤尘爆炸特征参数影响因素研究

采用20L球形爆炸装置研究了煤尘粒径、浓度、点火能量对煤尘爆炸最大压力、爆炸最大压力上升速率的影响。研究结果表明,在煤尘粒径一定的条件下,随着煤尘浓度的增大,爆炸最大压力及爆炸最大压力上升速率先增大后减小,煤尘浓度在400~480g/m3之间取得爆炸最大压力最大值0.94MPa、爆炸最大压力上升速率最大值28.79MPa/s;在煤尘浓度一定的条件下,爆炸最大压力不随煤尘粒径的减小而单调变化,爆炸最大压力上升速率随煤尘粒径的减小而逐渐增大;随着点火能量的增大,爆炸最大压力及爆炸最大压力上升速率明显增加。     

稠油火驱二次点火主控因素及点火策略

为了实现火驱开发过程中熄火油层再次燃烧,保障火驱开发效果,通过一系列室内物理模拟实验和油藏数值模拟计算,开展包括点火温度、通风强度、地下含油饱和度分布、结焦带等影响二次点火的主控因素的研究,给出了合理的二次点火温度和通风强度的范围,同时结合注气井地下空气腔规模给出了不同条件下启动油层二次燃烧的点火策略.结果表明,电点火温度应控制在450 ℃以上,点火期间通风强度应维持在10 m³/(m²·h)以上,对于需要注燃料油进行二次点火的注气井,燃料油的用量不低于已燃区空气腔体积的2/7.     

Trajectory Simulation for Underwater Vehicle with Power-Lunched

The motion of combustion gas bubble produced by underwater ignition was developed based on Rayleigh-Plesset equation. Combining the bubble motion equation with the underwater launched vehicle motion equation in the longitudinal plane, a trajectory simulation model with power-launched was established. The hydrodynamic characteristics of underwater ignition at different depths and the trajectory analysis of the underwater vehicle with power-launched were given by simulation. The simulation results have a good agreement with experimental results, and show that the thrust peak caused by underwater ignition and the stable thrust both decrease slightly with the increase of the water depth, and the thrust peak will decline obviously by enlarging the initial radius of gas bubble; the thrust peak generated at the instant of ignition and the low-frequency oscillation of the stable thrust have no significant influence on the trajectory of underwater vehicle.     

自由活塞汽油直线发电机燃烧过程特性

为了获得自由活塞汽油直线发电机工作过程中的燃烧特性,根据试验测得的活塞运动曲线对其燃烧过程进行了CFD仿真研究,并对比传统发动机分析了两种发动机活塞运动规律差异对燃烧过程的影响规律。研究发现:与传统发动机相比,自由活塞汽油发电机缸内最高燃烧压力和平均温度均较小,且最高燃烧压力保持时间较短,这有助于减少NO污染物;自由活塞直线发电机燃烧放热率呈现"缓和长"的特点,燃烧放热过程等容度较低;自由活塞直线发电机较少的混合气在上止点前完成燃烧,压缩行程负功较小,但由于后燃较严重,其指示效率较传统发动机低。     

瓦斯抽采下沿空留巷采空区自燃危险区域判定

由于沿空留巷工作面采空区漏风严重且对具有自然发火的煤层影响较大,所以研究沿空留巷采空区自燃危险区域具有重要意义。针对沿空留巷侧采空区瓦斯抽采及充填墙裂隙演化诱导漏风及自燃问题,以沙曲矿沿空留巷综放面为研究对象,通过SF6漏风实测及束管观测研究,研究了工作面及沿空留巷侧采空区漏风规律及氧气体积分数分布特征,并对采空区不同倾向范围内自燃氧化"三带"的分布区间进行了识别及划分,进而在理论及实测分析的基础上,结合工作面推进速度及煤层自然发火期发现在沿空留巷侧采空区倾向方向5~30 m存在自燃危险区,若改变工作面开采条件,其他非自燃区域可能转变为自燃危险区。     

Thermal efficiency characteristics of hydrogen internal combustion engine

To study the economic advantages of hydrogen internal combustion engine,an experimental study was carried out using a 2.0Lport fuel-injected(PFI)hydrogen internal combustion engine.Influences of fuel-air equivalence ratioΦ,speed,and ignition advance angle on heat efficiency were determined.Test results showed that indicated thermal efficiency(ITE)firstly increased with fuel-air equivalence ratio,achieved the maximum value of 40.4%(Φ=0.3),and then decreased whenΦ was more than 0.3.ITE increased as speed rises.Mechanical efficiency increased as fuel-air equivalence ratio increased,whereas mechanical efficiency decreased as speed increased,with maximum mechanical efficiency reaching 90%.Brake thermal efficiency(BTE)was influenced by ITE and mechanical efficiency,at the maximum value of 35%(Φ=0.5,2 000r/min).The optimal ignition advance angle of each condition resulting in the maximum BTE was also studied.With increasing fuel-air equivalence ratio,the optimal ignition angle became closer to the top dead center(TDC).The test results and the conclusions exhibited a guiding role on hydrogen internal combustion engine optimization.     

基于FDTD汽车点火系统电磁辐射的研究

电磁兼容是现代汽车设计中的关键及难点问题,点火系统是汽车内电磁辐射干扰的主要激励源,对点火系统电磁辐射计算方法的研究,是汽车电磁兼容问题研究的热点.在推导含电阻元件Yee元胞的时域有限差分法算式的基础上,构建了合理的激励源模式,借助AUTOCAD技术,建立了计算某型号汽车点火系统电磁辐射强度的时域有限差分法模型,并计算出了该型汽车点火系统高压导线在车内产生的辐射电场值.相关工作和结论对汽车电磁兼容问题的分析与预测具有一定的参考价值.     

铁电薄膜平均极化性质的研究

是在热力学唯象理论的框架下,研究由两种铁电材料组成的铁电双层膜系统的极化性质.通过引入的两个参量:参量(描述铁电双层膜系统中两种铁电体的物理性能差异)和参量(描述铁电双层膜系统两种铁电体相变温度的差异),研究了不同温度和不同界面耦合系数条件下,铁电双层膜系统平均极化随这两个参量的变化情况.研究表明:参量增大时,铁电双层膜系统的平均极化随之增大.当取固定值时,平均极化随界面耦合系数增大而增大;随着温度t、参量的增大而减小.参量增大时,铁电双层膜系统的平均极化减小.当参量取固定值时,平均极化随着温度t的增大而减小;随着参量、界面耦合系数的增大而增大.