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在柴油机燃烧室内的残余废气中和壁面上,存在固态微小碳粒,使喷雾两相流变成了喷雾三相流。本文探讨了碳粒对燃油喷雾、油滴破碎与聚合、油滴着壁特性等可能产生的影响。 相似文献
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小缸径直喷式柴油机喷雾,燃烧和碳粒生成过程试验研究 总被引:4,自引:2,他引:4
本介绍了作采用同步高速摄影技术和图象分析技术研究柴油机缸内碳粒生成和氧化过程的研究结果。研究结果表明:在柴油机燃烧过程中碳粒最早出现在燃烧室内有空气渗混的富油区;速燃期内高温富碳燃烧区的形状与着火前一时刻喷雾场的形状相吻合;富油区大直径油滴的燃烧裂解和活塞顶隙处外溢燃气的低温燃烧是柴油机产生碳烟微粒排放的主要原因。 相似文献
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直喷式柴油机燃烧室形状对碳粒形成过程影响的试验研究 总被引:8,自引:2,他引:8
本文介绍了作者采用可视化技术和图象分析技术研究直喷式柴油机燃烧室形状对燃烧室内喷雾场和燃烧碳粒场影响的研究结果。分析了四角形燃烧室和盆形燃烧室喷雾发展历程和燃烧碳粒场发展历程,找出了四角形燃烧室碳粒排放量较低的原因。 相似文献
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柴油喷雾燃烧发光机理分析 总被引:2,自引:0,他引:2
为探讨柴油机燃烧光的性质,在容弹上采用光强传感器,并应用双色法在不同温度、压力、氧浓度与二氧化碳浓度的条件下,对柴油喷雾的燃烧光强波进行了测量分析。结果表明:在柴油机燃烧过程中,同时存在碳粒的氧化与还原两种反应,其中以氧化反应占优势,碳粒与其附面层温度基本一致。碳粒的附面层反应与柴油中其它气体成分的氧化反应形成火焰,所以可认为碳粒与火焰处于热平衡状态,碳粒的表面反应热以热辐射的方式向外界传递。表面反应热与辐射传热的平衡确定了碳粒的体积与密度。因此柴油喷雾的燃烧光强反映的是碳粒的辐射热强度,燃烧光强波反映的是碳粒的氧化过程。燃烧光强与火焰内的总碳量、氧的分压力、碳粒温度有关,同时还受二氧化碳等还原性气体浓度的影响 相似文献
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高压旋流中空燃油喷雾日益广泛地应用于缸内直喷(GDI)汽油机中,为此发展了一种适合于模拟这种燃油喷雾雾化过程的薄膜喷雾模型.燃油薄膜的破碎过程采用表面波破碎理论来模拟.对Spalding蒸发模型和油滴阻力模型进行了改进,用来计算油滴的蒸发和阻力变形过程,同时引入初始喷雾液团的计算模块.在多维内燃机计算程序KIVA3的基础上建立了改进的数值计算模型,并对不同喷射条件下的定容压力容器中空旋流燃油喷雾过程进行了数值计算,对计算和实验所得的喷雾特性包括油束外形结构,油束喷雾贯穿度和油滴粒径进行了详细的比较,同时对单液滴的蒸发过程也进行了数值计算,油束模型的计算结果与实验结果吻合良好。 相似文献
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为加深对多孔介质发动机中均匀混合气形成的了解,用改进的KIVA-3V详细模拟了空心喷雾油滴碰撞热多孔介质的过程。在KIVA-3V中增加了油滴碰撞热多孔介质壁面的碰撞模型、传热模型及空心喷雾的线性不稳定性液膜破碎(LISA)模型。油滴与热壁的碰撞模型和传热模型经检验证明了其合理性。在简化多孔介质结构的基础上,在不同的环境压力及喷雾锥角下,模拟了空心喷雾与热多孔介质的相互作用。计算结果表明:油雾在碰撞到热多孔介质后,发生分裂的油束和多孔介质区域的高温,促使油滴实现快速蒸发并为油蒸汽与空气充分混合创造了前提。不同的空间压力及喷雾锥角直接影响到油滴在多孔介质中的分布。 相似文献
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柴油机喷雾蒸发过程的模拟计算与分析 总被引:1,自引:0,他引:1
本文以单滴蒸发为基础建立了一个燃料单元的蒸发计算模型,对各种温度条件下燃油喷雾蒸发过程进行了模拟计算。计算结果表明,在高温条件下,喷雾中油滴尺寸分布与油滴蒸发过程密切相关。计算结果与作者运用Malvern粒度分析仪结合截断修正法得到的实验结果进行了比较,取得了良好的一致性,从而验证了计算模型的有效性。并且,运用模拟计算结果对一些高温条件下的喷雾实验现象提出了合理的解释。 相似文献
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作者应用STAR—CD软件对有限流沿燃烧室内喷雾撞壁过程进行了数值研究,发现在活塞接近上止点时,因为缸内温度较高,所以在喷雾到达燃烧室壁面时,大部分液滴已经蒸发,这样基本上没有液滴与壁面的相互作用,所以撞壁模型的选取对计算结果的影响不大。同时也验证了限流沿可以使燃油从壁面剥离。 相似文献
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Aiming at improving efficiency in combustion systems, the study on droplet behavior and its trajectory is of crucial importance.
Vortex engine is a kind of internal combustion engine which uses swirl flow to achieve higher combustion efficiency. One of
the important advantages of designing vortex engine is to reduce the temperature of walls by confining the combustion products
in the inner vortex. The scopes of this investigation are to study vortex engine flow field as well as effective parameters
on fuel droplet behavior such as droplet diameter, droplet initial velocity and inlet velocity of the flow field. The flow
field is simulated using Reynolds Stress Transport Model (RSM). The Eulerian-Lagrangian method and the one-way coupling approach
are employed to simulate two phase flow and dispersed phase in the chamber, respectively. A new method, based on computing
pressure force exerted on the droplet surface, is introduced to determine the distinction between using one-way and two-way
coupling approaches. The results showed that the droplets with smaller diameter are more likely to follow the flow stream
lines than bigger droplets, thus evaporate completely in the chamber. Moreover, droplets with greater initial velocity have
higher evaporation rate, yielding the existence of evaporation and combustion in the inner vortex. Additionally, the higher
inlet velocity of continuous phase results in higher centrifugal force, leads droplets in question to deviate towards the
wall faster. 相似文献
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V.E. Nakoryakov S.Ya. Misyura S.L. Elistratov 《International Journal of Heat and Mass Transfer》2012,55(23-24):6609-6617
The effect of the volume of distillate droplets and temperature of the heated wall on evaporation process was investigated. The strong influence of thermal-physical and geometrical parameters of the wall on droplet evaporation is shown. A change in the ratio of droplet diameter to the wall thickness can lead to a change in evaporation regimes. Distribution of interface temperature along the droplet length is measured. At evaporation the wall temperature under the droplet changes significantly. A new method for measurement of the droplet mass on the heated wall is presented. The regimes of droplet boiling differ significantly from pool boiling. The droplet mass is directly changed in time; evaporation is separated into several stages. 相似文献
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建立了高温高压条件下的油滴蒸发模型,并在不同的工质压力和温度下对模型进行了验证,模型计算结果和实验结果吻合良好。将此油滴蒸发模型和油膜蒸发模型相结合,应用到涡流室式柴油机的燃油蒸发过程中,通过三维数值模拟计算,研究了燃油蒸发过程中燃料蒸气浓度和工质温度场的变化历程以及燃油蒸发对涡流室平均温度和平均压力的影响。 相似文献
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Conceptual design for a kerosene fuel-rich gas-generator of a turbopump-fed liquid rocket engine 总被引:1,自引:0,他引:1
A design method for a kerosene fuel-rich gas-generator of a liquid rocket engine using turbopumps to supply propellant was performed at a conceptual level. The gas-generator creates hot gases, enabling the turbine to operate the turbopumps. A chemical non-equilibrium analysis and a droplet vaporization model were used for the estimation of the burnt gas properties and characteristic chamber length. A premixed counter-flow flame analysis was performed for the prediction of the burnt gas properties, namely the temperature, the specific heat ratio and heat capacity, and the chemical reaction time. To predict the vaporization time, the Spalding model, using a single droplet in convective condition, was used. The minimum residence time in the chamber and the characteristic length were calculated by adding the reaction time and the vaporization time. Using the characteristic length, the design methods for the fuel-rich gas-generator were established. Finally, a parametric study was achieved for the effects of the O/F ratio, mass flow rate, chamber pressure, initial droplet temperature, initial droplet diameter and initial droplet velocity. 相似文献