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首页> 外文会议>ASME Internal Combustion Engine Division technical conference >EXPERIMENTAL STUDY OF FLAME STRETCH UNDER ENGINE-LIKE CONDITIONS
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EXPERIMENTAL STUDY OF FLAME STRETCH UNDER ENGINE-LIKE CONDITIONS

机译：发动机条件下火焰拉伸的实验研究

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Since fossil fuels will remain the main source of energy for power generation and transportation in next decades, their combustion processes remain an important concern for the foreseeable future. For liquid or gaseous fuels, flame velocity that propagates normal to itself and relative to the flow into the unburned mixture is one of the most important quantities to study. In a non-uniform flow, a curved flame front area changes continually which is known as flame stretch. The concept becomes more important when it is realized that the stretch affects the turbulent flame speed. The current research empirically studies flame stretch under engine-like conditions since there has not been enough experimental studies in this area. For this reason, a one-cylinder, direct-injection, spark-ignition, naturally-aspirated optical engine was utilized to image the flame propagation process inside an internal combustion engine cylinder on the tumble plane. The flame front was found by processing high speed images which were taken from the flame inside the cylinder. Flame front propagation analysis showed that after the flame kernel was developed, during flame propagation period, the stretch rate decreased until the flame front touches the piston surface. This trend was common among stoichiometric, lean, and rich mixtures. In addition, the fuel-air mixture with X= 0.85 showed lower stretch rate compared to stoichiometric or lean mixture with X= 1.2. However, based on previous studies, further enrichment may result in the flame stretch rate become greater than that of the stretch rates for stoichiometric or lean mixtures. Also, comparing the stretch rate at two different engine speeds revealed that as the speed increased the stretch rate also increased; especially during the early flame development period. Therefore, according to previous studies which discussed flame stretch as a mechanism for flame extinguishment, the probability of the flame extinction is higher when the engine speed is higher.
机译：由于化石燃料将在未来几十年中仍然是发电和运输的主要能源，因此在可预见的未来，化石燃料的燃烧过程仍然是重要的问题。对于液体或气体燃料，火焰速度垂直于其自身并且相对于流入未燃烧混合物的流传播是研究的最重要的量之一。在非均匀流动中，弯曲的火焰前部区域会连续变化，这被称为火焰拉伸。当意识到拉伸会影响湍流的火焰速度时，该概念将变得更加重要。由于在该领域没有足够的实验研究，因此当前的研究以经验的方式研究了在类似发动机的条件下的火焰拉伸。因此，利用单缸，直喷，火花点火，自然吸气的光学引擎对滚筒平面上的内燃机气缸内部的火焰传播过程进行成像。通过处理从气缸内火焰获取的高速图像可以找到火焰前缘。火焰前缘传播分析表明，在火焰核形成后，在火焰传播期间，拉伸速率降低，直到火焰前缘接触活塞表面。这种趋势在化学计量的，稀的和浓的混合物中很常见。另外，与X ＝ 1.2的化学计量或稀薄混合物相比，X ＝ 0.85的燃料-空气混合物显示出较低的拉伸速率。但是，根据以前的研究，进一步的富集可能导致火焰的拉伸速率变得大于化学计量或稀薄混合物的拉伸速率。同样，比较两种不同发动机转速下的拉伸速度，发现随着速度的增加，拉伸速度也随之增加。特别是在火焰发展初期。因此，根据讨论火焰伸展作为灭火机制的先前研究，当发动机转速较高时，熄灭的可能性较高。

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