共查询到19条相似文献,搜索用时 83 毫秒
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介绍一种消声器综合性能指标的测量评价方法.利用噪声和压力测量装置对某型全液压挖掘机实际设计消声器的插入损失和压力损失进行测量,检验该消声器的综合性能指标.在额定转速2 200 r/min时,通过对设计消声器的消声性能和空气动力性能进行测量,发现此转速下消声器的插入损失为21.8dB(A).经过对设计消声器内部进行去毛刺,对焊痕及穿孔管穿孔等部位进行光滑处理后,压力损失达到了国家规定的合格限值,消声器的综合性能符合设计要求.该测量方法简单,经济适用,对消声器的研究有一定的指导意义. 相似文献
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《Planning》2016,(23)
针对1种基于气体分流对冲降低排气速度的新型结构排气消声器,使用计算流体力学的方法对其空气动力学性能进行分析。首先建立了消声器的仿真模型,并利用计算流体力学CFD技术对分流对冲排气消声器设定入口流速下的流场进行了仿真,分析了分流对冲排气消声器内部气体的流动特性和压力分布特性,并对新型消声器在不同入口气体速度下的压力损失进行模拟分析以及试验验证,并以CG25型单缸柴油机为样机,对新型消声器的声学性能进行了现场测试。结果表明:分流对冲排气消声器具有很好的空气动力性能,在柴油机标定转速下(2 200rad/min),新型消声器的插入损失为8.7dB,在柴油机不同工况下,新型消声器的插入损失高于原装消声器,证明了新型消声器具有良好的消声性能。 相似文献
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汽车发动机进排气噪声是汽车主要噪声源之一,汽车尾气的排放会导致PM2.5浓度的升高,造成环境污染问题.在进排气系统上使用净化消声器可以有效地降低汽车进排气噪声和尾气浓度.传统的净化消声器设计都是将催化转化载体与消声器作为2个独立的部分进行设计,加大了生产成本,增加了安装空间.由于催化转化载体的蜂窝结构可以视为多孔介质,具有一定的消声作用,因此,设计出一种改进之后的新型净化消声器,通过将载体放入消声器内部,形成一个统一的结构,在假定消声器的净化作用的情况下,运用声学及流场的数值仿真分析消声器的传递损失和压力损失,结果证明新型净化消声器既节省了空间,又达到了消除噪声的目的. 相似文献
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《Planning》2015,(15)
传递损失作为消声器的固有特性,通常用作消声器设计和仿真分析的评价标准,提出一种适用于进出口非规则截面改进的管道模态方法代替效率较低的传统方法来估算传递损失,并扩展了现有管道模态方法仅适用于进出口截面规则的限制,对规则截面进行计算和验证,三种方法吻合较好,而对于非规则截面,通过与传统方法比较,结果吻合较好,而现有管道模态方法则失效,因此可以采用改进的管道模态方法快速估算传递损失。 相似文献
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The present research work focuses on the influence of exhaust gas recirculation (EGR) on the characteristics of the diesel engine operated with 20% tamarind seed methyl ester (TSME 20) as the renewable fuel. The use of TSME 20 as biodiesel results in closer performance characteristics with diesel fuel. However, TSME 20 biodiesel blend generated higher oxides of nitrogen (NOX) emissions at all operating conditions. Firstly, tests are performed using diesel and TSME 20 biodiesel blend at constant speed under different loads. Thereafter, experiments are conducted on TSME 20 with EGR rates at different concentrations. The test results revealed that with TSME 20 with 20% EGR rate, NOX emissions are reduced by 45.67% and 52.69% when compared to diesel and TSME 20. However, there is a slight reduction in brake thermal efficiency. Hence, the use of 20% EGR rate to TSME 20 is an optimum approach for better control of NOX emissions.Abbreviations BDC: bottom dead centre; BMEP: brake mean effective pressure; BSFC: brake-specific fuel consumption; BTE: brake thermal efficiency; CO: carbon monoxide; CO2: carbon dioxide; EGR: exhaust gas recirculation; FSN: filter smoke number; HC: hydrocarbon; kWh: kilo Watt hour; NOX: oxides of nitrogen; ppm: parts per million; SO: smoke opacity; TDC: top dead centre; TSME: tamarind seed methyl ester; TSME 20: 20% tamarind seed methyl ester; TSME 20–20%: tamarind seed methyl ester with 80% diesel; TSME 10% EGR: TSME 20 with 10% exhaust gas recirculation; TSME 20% EGR: TSME 20 with 20% exhaust gas recirculation; TSME 30% EGR: TSME 20 with 30% exhaust gas recirculation 相似文献
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《Journal of Wind Engineering & Industrial Aerodynamics》1988,31(1):87-104
The influence of changing wind direction on the dilution of exhaust gases around buildings was investigated in a simulated, neutrally stable atmospheric boundary layer using a low speed, open circuit wind tunnel. Mean concentration measurements were made on six flat-roofed model buildings at 2–5 wind incidence angles of between 0 and 45°.When vertical exhaust momentum was low, dilution levels 2–8 times lower (depending on building shapes and vent location) were observed for wind incidence angles >30°. However, at high exhaust momentum, the minimum dilution lost its sensitivity to wind direction. A semi-empirical model was devised to quantify, within a factor of 2, the dependence of minimum dilution on wind incidence angle and exhaust momentum. 相似文献
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《Journal of Building Performance Simulation》2013,6(4):239-252
The vestibules in high-rise buildings are specified zones for fire safety. In Taiwan, the designs of the structures and smoke exhaust systems of the vestibules are supervised by different government agencies. The design principles of these smoke exhaust systems take into consideration the flow rates and the impact of the flow momentum. Unfortunately, the current regulations in Taiwan only consider the former. Some small vestibules legally exist in high-rise buildings as they are in compliance with building regulations. This study uses the Fire Dynamics Simulator to analyse 20 modes of smoke exhaust systems under 1.0 MW of the fire load in small vestibules (2 m2 in area). The results indicate that the performance of different smoke exhaust systems significantly varies with different airflow momentums. Some improvement measures are discussed for the worst cases. 相似文献
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通过试验研究了蜗舌与叶轮距离对抽油烟机噪声和性能的影响,表明蜗舌与叶轮距离适当增大时,噪声明显降低,风量和风压有所降低,建议按t/D2=0.05-0.08选择蜗舌与叶轮距离。 相似文献
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Oxidative stress risk analysis for exposure to diesel exhaust particle-induced reactive oxygen species 总被引:1,自引:0,他引:1
Chio CP Chen SC Chiang KC Chou WC Liao CM 《The Science of the total environment》2007,387(1-3):113-127
We constructed a probabilistic risk-based framework to assess the human oxidative stress (OS) risk from diesel exhaust particle (DEP)-induced reactive oxygen species. A human respiratory tract model was used to estimate DEP concentration and cumulative doses in lung regions for three occupational groupings (driver, homeworker and student) in northern, central, and southern Taiwan. Dose-response profiles were reconstructed in terms of the specific ratio of the reduced and oxidized forms of glutathione (GSH/GSSG ratio) for the human macrophage cell (THP-1) and human bronchial epithelial cell (BEAS-2B). The highest estimated median daily cumulative dose of DEP with 95% CI was for driver in northern Taiwan (DEP(2.5): 0.716 (0.443-1.197) mg and DEP(0.18): 0.584 (0.417-0.822) mg), significantly higher than that of the other settings. The driver in northern Taiwan setting had the highest cumulative dose-response calculated over a 2-year exposure period: 0.57 (0.41-0.76) and 0.70 (0.53-0.87) for DEP(2.5) and 0.40 (0.25-0.70) and 0.47 (0.34-0.80) for DEP(0.18), respectively, in THP-1 and BEAS-2B cells. Our results implicate that potential risks of OS from above-critical exposure to DEP(2.5) in all settings are found, whereas from DEP(0.18) in the driver in northern Taiwan setting is also alarming. 相似文献
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《青岛理工大学学报》2015,(4)
活性粉末混凝土具有优异的抗冻融、抗渗、抗腐蚀、抗碳化等性能.通过试验,研究了水胶比、石英砂、粉煤灰、硅粉以及钢纤维掺量对活性粉末混凝土的影响,并分析了其强度及流动性的影响规律.试验结果表明:通过优选组分,在常压80℃热水养护下,可配制出抗压强度超过200 MPa、抗折强度近60 MPa的活性粉末混凝土. 相似文献
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通过水泥相容性及抗压强度试验,确定了合适的减水剂和硅灰品种,考察了水胶比和硅灰掺量对胶凝材料流动性的影响,研究了水胶比、粉煤灰、硅灰、石英粉、纳米硅以及钢纤维掺量、养护制度对RPC流动性及抗压强度的影响规律.试验结果表明,采用适当比例的硅灰、粉煤灰和纳米硅,可以提高RPC的流动性及强度;RPC中加人缓凝剂,延缓了拌合物的凝结时间,提高了试件浇筑的密实度,从而提高了RPC的强度;特别是纳米硅的加入,明显改善了RPC的流动性,在蒸压养护制度下,得到了立方体抗压强度为167 MPa的活性粉末混凝土. 相似文献