共查询到19条相似文献,搜索用时 187 毫秒
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GDI发动机喷雾特性的数值模拟和试验 总被引:3,自引:0,他引:3
汽油直喷发动机高压燃油喷射系统与燃油经济性和废气排放等密切相关,通过试验和数值模拟对高压喷油系统和旋流喷油器的喷雾特性进行了研究.在不同喷射压力、背压压力条件下,利用高速摄像机对喷入定体积容器的喷雾进行了喷雾贯穿距离和喷雾锥角参数的测量.结果表明:在低背压压力下,喷雾呈现出空锥、较大范围的分布形态,有利于实现燃油与空气的均质混合;在高背压条件下,喷雾呈现出紧凑密集的分布形态,有利于实现燃油与空气的分层混合.获得的贯穿距离经验公式与试验测量值在一定范围内是一致的.基于AVL HYDSIM环境建立了一维高压喷油系统模型,模拟得到的针阀升程与试验获得的图像在时间上具有一致性. 相似文献
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基于Matlab数字图像处理的多片喷雾特性研究 总被引:1,自引:0,他引:1
从提高直喷柴油机缸內油气分布均匀性及减少燃油附壁来降低排放的角度出发,开发了利用多孔油嘴喷出的油束近距离撞击导向平面的多片喷雾系统.应用高速摄影对自由喷雾和多片喷雾的喷雾过程进行了试验研究,使用Matlab软件对数字图片进行后处理,测取了投影喷雾贯穿距、喷雾锥角、喷雾面积等宏观喷雾特性参数.试验结果表明:与自由喷雾相比,在相同背压条件下,多片喷雾的投影贯穿距明显缩短,投影喷雾扩散角、投影喷雾面积增大;碰撞后油滴细化,雾化改善,油束液核区减小;多片喷雾具有扩散度高、液核区小、空间分布均匀等特点,有利于缸內均匀混合气的形成. 相似文献
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脂肪酸甲酯/柴油喷雾特性的对比试验 总被引:1,自引:0,他引:1
采用高速摄影和粒子图像分析技术对脂肪酸甲酯(FAME)/柴油的高压共轨喷雾的宏观和微观特性,包括喷雾贯穿距离、喷雾锥角及索特平均直径(SMD)进行了试验.结果表明:两种燃料喷雾均为两阶段模式,并得到其喷雾贯穿距离与喷射压力、背压和燃料密度等的关系式;相同工况下脂肪酸甲酯的贯穿距离比柴油略大,喷雾锥角比柴油略小;柴油的索特平均直径比脂肪酸甲酯的小,但差距不超过3,μm,且两者的粒径分布相似;发动机不做太大改动就可以使用脂肪酸甲酯或脂肪酸甲酯/柴油的混合燃料. 相似文献
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液化石油气喷雾特性的试验与计算研究 总被引:1,自引:0,他引:1
采用高速摄影技术对液化石油气(LPG)喷雾特性进行试验研究,并利用准维气相射流模型模拟计算LPG喷雾的发展过程,计算结果与试验结果吻合较好。研究结果表明:在喷孔直径、背压等参数相同的条件下,LPG喷雾锥角和喷雾轴心浓度的衰减率随启喷压力升高而增大,而启喷压力对喷雾轴心速度的衰减率和喷雾贯穿距离则影响较小;在喷孔直径、启喷压力等参数相同的条件下,喷雾锥角、喷雾轴心速度和浓度的衰减率均随背压的升高而增大,而喷雾贯穿距离则随背压的升高而减小;背压对贯穿距离、喷雾锥角、喷雾轴心速度和浓度衰减率的影响均大于启喷压力。 相似文献
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柴油机SCR系统尿素溶液喷雾特性的试验研究 总被引:1,自引:0,他引:1
应用多普勒粒子动态分析仪(PDA)研究了SCR系统尿素溶液喷雾的粒径及其分布特征。试验对比了有、无空气辅助喷射系统的喷雾粒径分布特征;测量了空气辅助喷射系统尿素溶液喷雾在垂直喷雾轴线不同截面上的粒径分布;研究了空气压力及喷嘴的喷孔结构对喷雾粒径的影响。通过高速摄影得到空气辅助喷射系统尿素溶液喷雾的发展过程。试验结果表明:空气辅助喷射系统沿喷雾轴向喷雾粒径的大小及粒径分布变化不大,大直径液滴所占比例随着辅助空气压力的减小而增大,有倒角喷孔较无倒角喷孔更有利于喷雾雾化;无空气辅助喷射系统喷雾雾化效果较差,大直径液滴所占的比例明显增大。 相似文献
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《Applied Thermal Engineering》2007,27(14-15):2618-2625
To properly determine the oil charge to the compressor of a closed-loop vapor compression system, it is important to be able to accurately estimate how much oil is held-up in refrigeration cycle components other than the compressor. To provide such information, this paper reports the results of an experimental investigation of the oil distribution behavior in a specific transcritical CO2 air-conditioning system. To experimentally measure the oil retention at each individual cycle component, a novel oil injection–extraction method was applied and a new test facility was developed. Experimental results show that as the oil concentration of the working fluids discharged from the compressor increases the oil retention volume in the heat exchangers and suction line also increases. Thirty-two percent and 24% of the total oil amount charged initially is retained in heat exchangers and suction line at 5 wt.% of oil circulating with the refrigerant at a mass flow rate of 14 and 27 g/s, respectively. Experimental results also show that the effect of the oil on the evaporator pressure drop increases as the oil concentration increases at constant refrigerant mass flow rate. For the refrigerant mass flow rate of 14 g/s and 27 g/s, the evaporator pressure drop increases up to 280% and 40%, respectively, when the oil concentration increases from 0 to 5 wt.% The effect of oil on pressure drop was found to be most profound at high vapor qualities where the local oil concentration is the highest. For a CO2 air-conditioning system, the oil retention in gas cooler, evaporator, and suction line is expected to be less than 20% of the initial oil charge if the oil concentration is maintained less than 1 wt.%. 相似文献
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提出了利用超短距离碰撞效应促进燃料雾化、快速形成高质量混合气的方法.据此研制了适合于直喷式柴油机的新型燃油雾化系统.并采用燃油喷雾可视化测试装置,对新型燃油雾化系统的喷雾特性进行了研究,分别获取了燃油油束的外观图像和油束断面的构成图像.结果表明,该燃油雾化系统能够快速形成分布均匀的可燃混合气.带冲击槽内壁面的碰撞喷雾,燃油喷射时间为0.6 ms时,油束中心已经有油雾存在,无油雾区域明显减少;随着喷射时间的延续,当喷射时间为1.0 ms时,油束中心基本充满较浓的油雾;在喷射后期,油束中心与周边主流已融为一体,构成更均匀的燃油油束. 相似文献
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In Taiwan, millions of tons of waste cooking oil are produced each year, and less than 20% of it, about 150,000 ton/a, is reclaimed and reused. Most waste oil is flushed down the drain. Utilizing waste cooking oil to make biodiesel not only reduces engine exhaust gas pollution, but also replaces food-derived fuels, and reduces ecologic river pollution. This study employed two-stage transesterification to lower the high viscosity of waste oil, utilized emulsion to reduce the methyl ester NOx pollution, and used methanol to enhance the stability and viscosity of emulsified fuel. To further analyze spray characteristics of fuels, this experiment built a constant volume bomb under high temperature, used high speed photography to analyze spray tip penetration, spray angle, and the Sauter mean diameter (SMD) of fuel droplets, and compared the results with fossil diesel. The experimental results suggested that, two-stage transesterification can significantly lower waste oil viscosity to that which is close to fossil diesel viscosity. At a temperature above 300 °C, waste cooking oil methyl esters had a water content of 20%, spray droplet characteristics were significantly improved, and NOx emission dropped significantly. The optimal fuel ratio suggested in this experiment was waste cooking oil methyl ester 74.5%, methanol 5%, water 20%, and composite surfactant Span–Tween 0.5%. 相似文献