Document Type : Research Paper
Authors
1
Institute of Manufacturing Engineering and Industrial Technologies, Dez.C. , Islamic Azad University, Dezful, Iran
2
Department of Agricultural Science and Engineering, SR.C., Islamic Azad University, Tehran, Iran.
3
Department of Agricultural Machinery Engineering, Faculty of Agriculture,Tarbiat Modarres University, Tehran, Iran
4
Department of Agricultural Science and Engineering, SR.C., Islamic Azad University, Tehran, Iran
5
Department of Agro-Technology, College of Abouraihan, University of Tehran, Tehran, Iran,
Abstract
The noise generated by diesel engines is one of the most important harmful physical factors, causing numerous problems for both the driver and the work environment.This study investigates the effects of diesel-bioethanol fuel blends and engine speed on the sound pressure level(SPL) of a engine at the bystander position. The tests were conducted in a controlled environment in accordance with international standards. Acoustic signals were acquired using a sound level meter and analyzed within the 20 to 20,000 Hz frequency range using 1/3 octave bands. The results indicated, the dominant acoustic peak occurred in the 80 Hz center band, which corresponds to the engine's combustion frequency (85 Hz at 1700 RPM). The influence of speed on the SPL was significantly more substantial than that of fuel composition. An increase in speed resulted in a 2 to 10 dB rise across most frequencies,whereas altering the fuel blend, had a comparatively minor effect (less than 5 dB). The observed frequency variations were primarily attributed to the combustion process, valve operation, and mechanical impacts of engine components. Although the addition of bioethanol had a negligible effect on the overall noise level, detailed frequency analysis revealed alterations in the engine's acoustic profile. The analysis of variance of the overall sound level with A-weighting, showed that the main effects of fuel blend and speed, and the interaction effect of the variables speed × different fuel blends on that are significant at the 1% level, and the engine speed variable had the greatest effect.
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