Effect of Turbulent Flow Field on Flame Developing in Fuel Gradient Field in a Constant-Volume Vessel

在直喷式火花点火发动机中，低负荷时热效率可提高约20-30%，从而减少二氧化碳排放。然而，在实际发动机中，模具现象非常复杂和困难。因此，为了从根本上研究每种现象，有必要使场易于分析。在这项研究中，产生的旋流在一个定容容器的盘型和火焰轴对称发展的中心点火与供应燃料的丙烷在燃烧室的中心。在各种湍流和浓度场中进行了实验。采用激光多普勒测速仪测量湍流流场，采用激光诱导荧光法测量燃油浓度场。用高速摄像机拍摄了火焰的发展过程，用波长为3.39 μ m的激光吸收法测量了燃烧后的碳氢化合物含量，得到了如下结果：（1）在本实验中，湍流场和浓度场都发生了变化。然而，它被发现，平均燃料浓度几乎相同，但湍流絮体是不同的，因此，只有湍流强度的影响进行了研究。(2)当总当量比大于0.7时，燃烧效率可达97%以上，而当总当量比小于0.7时，燃烧效率仅为0.3。(3)当燃烧室中心附近存在较浓的燃料时，火焰中有大量的发光部分。对于初始燃烧，主要结果如下：（4）由于不均匀混合气中含有大量的处于可燃极限（包括化学计量条件）内的较浓和较稀的部分，混合气在可燃极限外也能着火并传播。

In direct injection spark-ignition engine, thermal efficiency can increase about 20-30% in low load, leading to decrease in carbon dioxide. However, die phenomena are very complicated and difficult in actual engines. Therefore, in order to investigate each phenomenon fundamentally, it is necessary to make the fields easy to analyze. In this study, a swirl flow was produced in a constant-volume vessel of disk type and a flame developed axisymmetrically by igniting at the center with supplying fuel of propane at the center of the combustion chamber. Experiments were done in various turbulent flow and concentration fields. Turbulent flow was measured with a laser Doppler anemometer and fuel concentration field was measured with a laser induced fluorescence method. A high-speed video camera was used to capture the flame development Hydrocarbon after the combustion was measured with absorption method using a laser of 3.39 micrometer wavelength.Main results for overall combustion are as follows: (1) In this experiment, both turbulent flow and concentration fields were changed. However, it was found that average fuel concentration is almost the same but the turbulent floe is different Therefore, only the effect of turbulence intensity was investigated. (2) The combustion efficiency was over 97% when overall equivalence ratio is larger man 0.7 while the combustion efficiency presented lower value of 0.3 in some cases at lower equivalence ratio less than 0.7. (3) When richer fuel existed near the center of The combustion chamber, it was observed that the flame developed with a lot of luminous parts in it As for initial combustion, main result is summarized as follows: (4) The mixture can ignite and flame propagates even outside the flammable limits because inhomogeneous mixture includes a lot of richer and leaner parts that are within the flammable limits including stoichiometric condition.