The correlation between the autoignition characteristics of n-butane/di-methyl ether/air mixtures and the knock intensity in a rapid compression and expansion machine was studied. The propagation velocity was obtained from the images of propagating flames at the moment of autoignition by a high-speed camera. The dimensionless parameters, e and j, were used in the investigation, which are based on the theories of Zeldovich and Bradley. To obtain these dimensionless parameters, the numerical calculation using CHEMKIN-PRO with AramcoMech1.3 was carried out. The smaller gradient of autoignition delay time for n-butane with the higher amounts of di-methyl ether addition caused the higher flame propagation velocity and the resultant higher knock intensity, while significant differences of excitation times for autoignition heat release could not be seen. As a result, the gradient of autoignition delay time was concluded to have a strong influence on the knock intensities.

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Ludwig angina cases that could only be recognized by unmasking.

The prechamber combustion characteristics were studied using a rapid compression and expansion machine (RCEM) to improve the efficiency of cogeneration natural gas engines. The torch flames generated by a prechamber were used to investigate the effect that a prechamber has on the main combustion. In our previous study, we observed the correlation between the torch flame and the main flame (which is a so-called "prechamber combustion"). In this study, the effects of prechamber parameters such as initial pressure and nozzle diameter of injection holes, equivalence ratio on prechamber combustion characteristics were investigated in detail. Especially, by comparing the combustion characteristics of methane, which is the main component of natural gas, and propane, which is a representative of small-volume components, the effects of fuel types on the ignition and combustion characteristics of pre-chamber ignition system were investigated to elucidate of the effect of fuel property. In conclusions, regarding the mechanism of prechamber-ignition combustion, it was inferred that the jet erupted from the prechamber did not directly propagate in the main chamber but included the "ignition phenomenon" of the main chamber due to the jet. In addition, under the experimental conditions of this study, it was found that the ignition delay time and the combustion period can be predicted by simple calculation, which can lead to the important guideline for the pre-chamber design.