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四气门柴油机进气道的三维实体造型及流场数值模拟 总被引:5,自引:1,他引:5
本文介绍了四气门柴油机双进气道设计的一种现代方法,即应用反向工程技术实现气道三维造型,并应用CFD软件FIRE对其实现气道一气门一气缸内气体三维数值模拟,计算结果与试验结果吻合较好。对气道内气流流动特性进行评价及对比,得出对于单进气道布置以切向布置最佳,因这样能产生相对大的涡流,双进气道因两气流产生干涉,造成少量的流量损失,但却会增强缸内的涡流。 相似文献
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用稳流气道试验和计算流体动力学(CFD)流动模拟两种手段对柴油机进气道进行了流动特性参数的测量和计算.对两气门柴油机的单个螺旋气道的试验和模拟数据进行了对比,对四气门柴油机两气道同时开启情况进行了模拟.根据流场信息对模型进行了修改,修改前后模拟结果的比较说明YZ495的气门与气道匹配良好,YZ4102的单螺旋气道多余截面削除后显著提高了涡流比. 相似文献
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By performing gas flow field numerical simulations for several inlet Reynolds numbers Re (from 2 × 105 to 9 × 105) and byflow ratios x (from 10% to 20%), the present study has proposed to improve the flow passage of an inlet particle separator. An adjacent objective of the study is to lower pressure losses of the inlet particle separator (IPS). No particle has been included in the gas flow for a k -epsilon turbulence model. The velocity distribution in different sections and the pressure coefficient C p along the duct have been analyzed, which indicates that there exist important low-velocity regions and vortices in the separation area. Therefore, the profile of streamlines along the original passage has been considered. This profile illustrated a vacuum region in the same area. All investigations suggest that the separation area is the most critical one for fulfilling the objective on pressure losses limitation. Then the flow passage improvement method has focused on the separation area. An improved shape has been designed in order to suit smoothly to the streamlines in this region. Similar numerical studies as those for the original shape have been conducted on this improved shape, confirming some considerable enhancements compared with the original shape. The significant vortices which appear in the original shape reduce in amount and size. Besides, pressure losses are greatly decreased in both outlets (up to 30% for high Reynolds number) and the flow is uniform at the main outlet. Subsequent engineering surveys could rely on expressions obtained for C p in both outlets which extend the pressure losses for a wide range of inlet Reynolds numbers. As a result, the numerical calculations demonstrate that the flow passage improvement method applied in this study has succeeded in designing a shape which enhances the flow behavior. 相似文献
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为了有效缓解电网突然出现的电力不平衡现象,同一个抽水蓄能电站不同水力单元机组同时分别发电及抽水运行,是对抽水蓄能运行及调度方式的一个重大创新措施。以某抽水蓄能电站上库为例,通过数学模型研究上库进/出水口在同发同抽工况下的库区水流流态、流道的水力特性、库区漩涡特性等水力参数的变化规律。结果表明,VOF方法可很好地模拟抽水蓄能同发同抽过程;同发同抽工况下,库区内进出水口附近局部水流流态与单向运行工况基本一致,但是两进/出水口之间形成连通的水流通道,库区内形成大范围横向流动,致使抽水单元大部分水流再次进入发电单元。 相似文献
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The inlet recirculation characteristics of double suction centrifugal compressor with unsymmetrical inlet structures were studied in numerical method, mainly focused on three issues including the amounts and differences of the inlet recirculation in different working conditions, the circumferential non-uniform distributions of the inlet recirculation, the recirculation velocity distributions of the upstream slot of the rear impeller. The results show that there are some differences between the recirculation of the front impeller and that of the rear impeller in whole working conditions. In design speed, the recirculation flow rate of the rear impeller is larger than that of the front impeller in the large flow range, but in the small flow range, the recirculation flow rate of the rear impeller is smaller than that of the front impeller. In different working conditions, the recirculation velocity distributions of the front and rear impeller are non-uniform along the circumferential direction and their non-uniform extents are quite different. The circumferential non-uniform extent of the recirculation velocity varies with the working conditions change. The circumferential non-uniform extent of the recirculation velocity of front impeller and its distribution are determined by the static pressure distribution of the front impeller, but that of the rear impeller is decided by the coupling effects of the inlet flow distortion of the rear impeller, the circumferential unsymmetrical distribution of the upstream slot and the asymmetric structure of the volute. In the design flow and small flow conditions, the recirculation velocities at different circumferential positions of the mean line of the upstream slot cross-section of the rear impeller are quite different, and the recirculation velocities distribution forms at both sides of the mean line are different. The recirculation velocity distributions in the cross-section of the upstream slot depend on the static pressure distributions in the intake duct. 相似文献
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《Journal of power sources》2006,162(2):1157-1164
In this work, the influences of various operating conditions including cathode inlet gas flow rate, cathode inlet humidification temperature, cell temperature, etc. on the performance of proton exchange membrane (PEM) fuel cells with conventional flow field and interdigitated flow field are experimentally studied. Experimental results show that the cell performance is enhanced with increases in cathode inlet gas flow rate, cathode humidification temperature and cell temperature. However, as cell temperature is higher than or equal to anode humidification temperature, the cell performance is deteriorated due to failure in humidification of the cell. Comparison between interdigitated flow field and conventional flow field shows that the former provides higher cell performance and remarkably reduces fuel consumption for efficient diffusion of the fuel gas to the diffuser layer. As air is used as the cathode inlet gas, PEM fuel cell with interdigitated flow field can obtain preferable limiting current density, and the optimal power is about 1.4 times as that of the cells with conventional flow field. Rib and shoulder areas are more advantageous to electrochemical reaction in interdigitated flow field; hence a large flow field area ratio degrades the better performance area and thus the cell performance. But too small flow field area ratio also deteriorates the cell performance due to the decrease in effective reaction area. Theoretically, the flow field area has an optimum value, i.e., 50.75% in this work, providing higher performance than 66.67%. 相似文献
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针对卧式柴油机强制冷却闭式循环系统水套结构,试验研究了不同工况下水套入口流量及关键点的温度和压力。采用计算流体动力学(CFD)三维模拟的方法建立了冷却水流动仿真模型,并进行了试验验证。设计了冷却水套结构参数正交方案,通过CFD模拟分析了水泵出水流量、公共水腔截面形状和面积、缸体及缸盖入水孔的设置和分布等水套结构参数对冷却水流动的影响关系。研究结果表明:卧式柴油机缸体入水孔截面积和布置对缸体水套冷却水流动、冷却效果和冷却均匀性有很大的影响;卧式柴油机缸盖入水孔的位置、孔数和截面积等结构参数对缸盖水套的冷却水流动、冷却效果、冷却均匀性及进/排气侧的冷却分布等均有很大的影响。 相似文献
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Takashi Fukue Masaru Ishizuka Shinji Nakagawa Tomoyuki Hatakeyama Katsuhiro Koizumi 《亚洲传热研究》2011,40(4):369-386
This study describes the performance of cooling fans in terms of the P–Q curve and the maximum flow rate under various environmental conditions. It focuses on the relationship between fan performance and configuration factors such as the electronic enclosure. The presence of an enclosure wall increased the pressure characteristic of the fan performance. The presence of a narrow inlet decreased the flow rate. When the inlet area of the enclosure became smaller than twice the fan flow area, the flow rate was decreased. The maximum flow rate depended on the ratio of the inlet area to the fan flow area. A model for predicting pressure rise and flow rates in the enclosure is proposed. The model is used in a thermal analysis of a PCB model set in an enclosure. © 2011 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library ( wileyonlinelibrary.com/journal/htj ). DOI 10.1002/htj.20347 相似文献