Prediction of preheating conditions for inclined laser assisted machining

For laser assisted machining,shape of preheating laser heat source is changed irregularly because of complexity of material shape.So,the preheating temperature should be controlled by adjusting the feed rate or the laser power.Thermal analyses of the laser assisted machining process for inclination planes were performed.By analyzing the obtained temperature profile,a proper feed rate control method was proposed according to the inclination angles.In addition,the temperature distribution of the cross section after feed rate control was predicted.The correlation equation between inclination angles and adjusted proper feed rate was proposed.The results of this analysis can be used to predict the preheating effect on workpiece and can be applied as a preheating temperature control method in laser assisted machining processes.

pH过程控制对铁炭微电解-Fenton影响中试研究

采用铁炭微电解-Fenton联合工艺处理制药废水生化出水,探讨了初始pH对微电解过程COD降解速率、出水中Fe2+和Fe3+变化规律以及后续Fenton氧化效果的影响,为优化联合工艺提出了微电解反应pH过程控制的理论。采用pH过程控制时,微电解对COD降解速率大大提高,降解过程基本符合零级反应动力学,同时可大大提高Fe2+和Fe3+浓度及总铁析出量。试验结果表明:当初始pH=2.5,以3.0L/h连续性投加稀硫酸100 min,曝气微电解反应2 h,出水再投加1.0mL/L的H2O2进行Fenton氧化2 h,出水COD总去除率可达85.6%;采用pH过程控制可将微电解出水ρ(Fe2+)浓度从48.6 mg/L提高至149 mg/L,COD降解速率从10.9 mg/(L·h)提高至23.8 mg/(L·h)。

液体火箭发动机高频燃烧不稳定问题综述

高频燃烧不稳定现象诱发的大幅值压力振荡严重威胁液体火箭发动机可靠性,为此,国内外开展了大量深入的研究工作。为了提高对此类问题及相关研究的整体认识,系统阐述了液体火箭发动机高频燃烧不稳定问题的主要特点、关键物理机制、研究思路等,重点梳理了国内外在液体推进剂燃烧子过程响应机理方面的研究工作,明确指出了燃烧速率控制过程对于此类问题分析的重要意义。在此基础上,详细总结了液滴蒸发和射流掺混作为速率控制过程的高频燃烧不稳定问题数值仿真研究进展,仔细归纳了线性和非线性理论解析分析方法面临的挑战,简要介绍了基于非线性动力系统的分析方法在揭示高频燃烧不稳定非线性行为以及稳定性裕度评估方面的重要潜力。最后,针对不同工程控制措施的内在联系、应用情况等进行了分析,特别强调了燃烧释热分布控制的重要性。