Analysis of Knock Phenomenon and Proposal of the Solution

通过定容燃烧室的实验研究，发现负温度系数（NTC）对爆震现象有影响。然而，由于压力、燃料、不稳定性、温度和湍流等条件与生产发动机有很大的不同，因此设计并建造了一台能够模拟实际发动机条件的快速压缩机。由于这台机器是基于九州大学开发的机器，它具有结构紧凑、活塞运动轮廓可变、振动适中等特点。使用该机器，可以实现气体温度和压力的测量，可视化和气体分析。由于局部气体温度测量被认为是爆震的最重要因素，因此使用双线热电偶进行测量，即使在壁附近也可以进行测量。因此，尽管精度取决于流动方向，密度和速度，但测量误差在2%以内。同时，对定容室的实验数据进行了0维数值分析。通过研究，获得了爆震分析的有用信息，特别是爆震是否发生的条件。NTC被认为是有效的，这取决于实验条件。为避免爆震，降低燃气温度、缩短高温持续时间和降低爆震发生时的未燃燃料是有效的。

Knock phenomenon was found affected by Negative Temperature Coefficient(NTC), examined by experiments using a constant volume chamber. However, as the conditions such as pressure, fuel, unsteadiness, temperature and turbulence are quite different from production engines, a rapid compression machine, which can simulate the conditions in actual engines, was designed and built. As this machine is based on a machine developed at Kyusyu Univ., it has features such as compact, variable piston-motion profile, moderate vibration. Using this machine, measurements of gas temperature and pressure, visualization, and gas analysis can be achieved. Because the local gas temperature measurement is considered as the most important factor for knock, it was made by using two-wired thermocouples, allowable the measurement even in the vicinity of wall As a result, although the accuracy depends on the flow direction, density, and velocity, measurement was made within 2% error. Meanwhile, 0-dimensional numerical analyses were carried out for data taken with the constant volume chamber. Through this study, useful information for knock analysis was obtained, especially conditions whether knock occurs or not. NTC was found affective, depending on experimental conditions. To avoid knock, reductions in the gas temperature, the duration in high temperature and unbumed fuel at the moment of knock initiation are affective.