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为研究地震避难所结构设计及力学特性,本文开发一种可折叠正四面体结构地震避难所,采用新型动态支点铰链结构设计,结合有限元分析,获取空间正四面体内部应力分布。结果表明:顶部承压时,正四面结构中上部区域应力较大,可适当增加此部分结构厚度保证安全;楼板冲击荷载作用楼层越多,正四面体所受应力越大,但其超过4层作用后结构所承受应力值增长幅度有限,进而从侧面体现正四面结构对超荷载作用缓冲能力强,结构安全稳定。 相似文献
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对四冲程柴油机(4-85)的排气噪声的机理和特性进行了研究;利用波形合成的原理,控制高速信号处理芯片TMS320C25合成次级声源的声波,可以实现宽带消声。对柴油机的排气噪声进行了有源消声的初步设计。 相似文献
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杨世柏 《理化检验(物理分册)》2007,43(12):636-638
某远洋轮主柴油机排气门发生漏气。采用扫描电镜对排气门基体、堆焊层的显微组织和裂纹形态进行了观察,同时检测了气门材料和腐蚀产物的化学成分。结果表明,排气门的材质合格,主要由于燃烧产物中硫和钒的氧化物等粘附在气门受热面上,在组织应力和热应力作用下产生了应力腐蚀,同时在高温燃气冲刷及冲击载荷的作用下加速了该气门的失效。 相似文献
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为提升某乘用车急加速工况下排气噪声的运动感,通过控制排气噪声主要阶次声压级和能量配比从而达到改善排气声品质的目标。从典型消声器结构单元消声频率与阶次对应关系入手,推导典型消声单元传递损失与排气噪声的阶次相关性;基于某乘用车排气系统消声器模型设计四组正交组合方案,采用CAE方法研究抗性消声器结构对阶次噪声的影响规律,总结出排气噪声中四阶成分与六阶成分对扩张腔结构参数、四阶成分对共振腔结构参数、二阶成分对赫尔姆兹谐振腔结构参数变化敏感的规律。以此为依据正向设计消声器,实现排气噪声阶次成分调整。加工样件并进行排气噪声尾管试验,证明排气噪声阶次成分分布满足设计要求,主观感受声品质满足运动感目标。该研究可为消声器正向开发及声品质目标实现提供借鉴。 相似文献
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针对柴油机排气噪声设计了一套有源消声系统,并对高速数字信号处理芯片为基础的控制单元进行了仿真试验,该系统采用了转速信号作为次级声源输入,并以自适应同源谐波滤波为控制模型,保证了系统的有效性和稳定性,仿真结果表明,本系统有很好的消声效果。 相似文献
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本文介绍最新的隔震技术在核电站中的应用。通过在一个结构的不同地点,组合使用钢制螺旋弹簧隔振器与粘滞阻尼器,就可以在降低系统频率的同时,增加阻尼比,减小地震引起的结构响应。所以与无保护结构的地震响应比较,极大地减小了地震响应的应变与应力,从而可以在一次强烈地震发生后极大地降低可能产生的危害,而且结构构件的性能可以保持在弹性范围内。可以发现,与没有任何抗震措施的建筑结构比较,抗地簏的建筑结构相应的设计力将大大减小,因此在相似的安全水平下,将降低抗横向力系统的造价。此外,如果考虑在一个中等强度至强烈地震后必要的检修,抗地震系统的安全性增加,而投资更经济。核设施的安全特别重要,新近的地震事件对这些设施造成的损害被再次提出来讨论。其中一件是2007年发生在日本Chuetsu的地震,可以在几个报告中找到Kashiwazaki Kafiwa核电站中造成的损害。在其余的事件中有汽轮机受到损害的,有观察到燃料储存池溢流(Fukushima,2007与Yamashita,2008)的。 相似文献
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The vibratory torque of a diesel engine caused by the reciprocating motion of the mass and gas pressure force of a cylinder is one of the main causes of the failure of the driving shaft of the diesel engine and the connecting shaft to the reduction gear. Because high cycle torsional fatigue can occur in the reduction gear shaft connecting the engine under vibratory torsional stress, the US Navy restricts it under the MIL G 17859D(SH) standard and suggests a procedure for evaluating the safety of the shaft for the reduction gear. In this study, the structural safety of the reduction gear input shaft in which fatigue failure occurs in typical naval vessels is investigated in accordance with the VDI 3822 RCA (root cause analysis) procedure based on the MIL G 17859D(SH) standard. When evaluating the safety factor in accordance with the MIL G 17859D(SH) standard, the alternating bending moment from the lateral vibration and the stress concentration factor under static load are considered. In addition, an improved design is suggested by CAE to satisfy the safety factor suggested by the MIL G 17859D(SH) standard. 相似文献
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《发动机故障诊断系统设计》 总被引:1,自引:0,他引:1
设计出一套适合实车不解体的发动机故障诊断新系统,它利用PC声卡配合LabVIEW采集排气噪声,然后对发动机不同状态下排气噪声信号进行矢量量化分析,从而完成系统的设计。实验结果表明该系统方案切实可行,诊断准确,为发动机故障诊断系统设计提供了一条新途径。 相似文献
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《Engineering Failure Analysis》2007,14(1):196-208
The failure analysis of a four-stroke 3000 kW off-shore operating diesel engine is presented. The failure occurred during engine normal operation period in the leak-off oil pipe from the injection valves, which experienced a fracture through the pipe wall and a diesel engine fire as a result. A detailed analysis of all elements which had an influence on the failure initiation was carried out, namely leak-off oil pipe vibration level, pipe stress level, presence of corrosion pits on the pipe external surface under the zinc coating and engine components temperature distribution in the failure zone. It was found that the crack initiation and propagation of the leak-off oil pipe from injection valves was driven by a fatigue mechanism, which was facilitated by loose pipe supports (excessive pipe vibration) and corrosion pits on the pipe surface that acted as stress concentrators. The contact of leak-off atomized oil due to the pipe through wall fracture with the hot engine exhaust muff (390 °C approximately) caused local fire of the diesel engine. 相似文献
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分析了柴油机排气噪声的特征,利用自适应有源前馈系统对噪声进行控制;对间歇性噪声的控制进行了建模分析;对柴油机的排气噪声进行了有源消声的初步设计;参考柴油机实际工况,利用高速信号处理芯片TMS320F2812进行了编程及调试;通过实测数据和DSP仿真实验验证了所采用方法的有效性。 相似文献
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在某型防爆柴油机加装DOC+DPF后处理装置上进行台架实验,结果表明,PY03型装置不会增大防爆柴油机系统的排气背压,对CO平均转化效率达96%,对颗粒物有较高的捕集和再生效率,不透光烟度平均转化效率为82.7%;PY02型装置因尺寸较小,热负荷较高,与该排放状况不匹配。为提高装置的利用率和使用寿命,通过对耦合的DOC+DPF孔道进行可燃性气体CO组分输运和颗粒物离散相数值模拟。结果表明:随着废气流速的增大,DOC+DPF出口废气中CO浓度升高,转化效率下降;15 m/s的气流速度是发动机该排放水平下转化效率最高的最大速度;孔道入口速度增大,颗粒物向孔道后端壁面沉积;DOC+DPF装置在防爆柴油机上实用可行。 相似文献
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D. Sakthivadivel Stephil Stephen V. S. Vigneswaran S. Iniyan 《Fullerenes, Nanotubes and Carbon Nanostructures》2019,27(4):358-366
This article deals with an experimental work that aims to examine the effects of MWCNTs dispersed into diesel fuels. Nano diesel fuels were prepared by dispersing multi-walled carbon nanotubes into base liquid. The MWCNT nanomaterial was mixed in the fuel blend along with a surfactant by means of an ultrasonicator, to attain stable dispersion. Physicochemical properties of nano-additive based diesel were measured and compared with pure diesel fuel. Physicochemical properties of nano-additive based diesel were measured and compared with pure diesel fuel. An experimental investigation was performed at a constant speed of 1500 revolution per minutes at different engine load conditions. The engine performance and exhaust emissions of a diesel engine burning MWCNTs were compared with pure diesel fuel. MWCNTs to diesel oil is effectively enhancing the performance and decreasing exhaust emissions in a diesel engine. The properties of N80?+?JB20 with MWCNT fuel blend are changed owing to the mixing of biodiesel and the combination of the MWCNT nanomaterials. 相似文献