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内容記述 |
Although a number of papers have appeared on the qualitative spectroscopy of normal and knocking combustion in the engine cylinder, so far only a few of them have touched on the effects of the nature of fuel as well as that of engine conditions on the emission spectra. This paper is a discussion of emission spectra of combustion gases, based on photographs that were obtained by means of a four-cycle engine, provided with a fused-quartz window in the combustion chamber wall, using fuels of various compositions and of boiling points suited to the gas-line engine. The fuels tested were n-Heptane, iso-Octane, Toluol, iso-propyl-Ether, Pinacolin,-the numbers of carbon atoms of which ranged from 6 to 8,-and Methanol. In this way, the authors studied the effects of the various properties of the fuel, and that of the engine conditions, such as mixture ratio and boost pressure, on the emission spectra of explosion. Of the results obtained, two confirm data were hitherto obtained, namely, (1) that the combustion, or the oxidation reaction, is completed in the flame front, and (2) that the band spectra due to the C_2 and CH molecules are inclined to vanish when knocking occurs (See figs. 5, 6, 20, 21). In the case of normal combustion, the spectral intensity of the C_2 bands obviously depends on the nature of fuel as well as on the engine conditions. Under constant working conditions, however, it fades out in the following order: -isc-proply-Ether, iso-Octane, Toluol, Pinacolin, n-Heptane (Methanol, having only one carbon atom, barely gives C_2 and CH spectra). From the view points of fuel character, emission spectra is most intense when the strength of the mixture is adjusted to yield maximum power (see figs.7～13). The spectral intensity of a fuel containing any oxygen atom as a component of itself, however, is scarcely affected by the mixture ratio. Although the effect of boost pressure is small, its increase tends to make the band spectra obsecure. This tendency can be explained by the difference between the intensity of the band spectra of the bunsen flame and that of the engine flame. The foregoing phenomena may be attributed to the difference in the transition probability of the fuel molecules to C_2 and CH in the process of combustion. It seems that further studies in these various relations should help to solve, to a certain extent, the problems of chosing a suitable fuel and of making clear of the mechanism of knocking combustion. |
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