Acoustic resonance in the combustion conduits of a steam locomotive

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Acoustic resonance in the combustion conduits of a steam locomotive

Ziada, S. / Oengören, A. / Vogel, H.H.

The sound emission of a modern, oil-fired steam rack locomotive increased when the locomotive speed exceeded the design value of 12 km/h. The results of pressure and noise measurements, together with an acoustical model of the combustion conduits, indicated that the acoustic resonance modes of the combustion conduits are excited by the pressure pulsations generated by the exhaust from the steam cylinders at multiples of the piston frequency. Additionally, when the acoustic resonance is initiated, the resulting pulsations trigger the flame instability of the oil burners which, in turn, enhances the resonance. By means of the acoustical model, a Helmholtz resonator has been designed and optimized to reduce the acoustic response such that it does not excite the flame instability. A second set of measurements, after installing the resonator, has shown a reduction in the noise level by an amount exceeding 21 dB. The paper focuses upon the identification of the excitation source and the implementation of the counter-measure, which are of interest to other applications in solving combustion oscillations.