Experimental investigation of vibration characteristics in a small-scale rotating system using time- and frequency-domain analysis

Abstract

This research stems from the problem that adding unbalance mass to a rotating shaft alters system vibration characteristics, a phenomenon that remains insufficiently quantified in small-scale rotating engines. This study aims to analyze the effects of variations in mass position, radial distance, and rotational speed on the vibration characteristics of a small-scale engine using combined time-domain and frequency-domain approaches. A quantitative experimental design was conducted across 27 treatment combinations, evaluating mass distances (5-25 cm) and speeds up to 860 rpm (14.33 Hz). Data acquisition utilized an accelerometer-microcontroller setup, analyzed via peak acceleration, RMS, and FFT methods. Results show a direct proportional relationship between mass radial distance and vibration amplitude, with the highest response observed at a 25 cm load distance and 860 rpm. The y1-axis exhibited the highest acceleration and RMS values, identifying it as the most sensitive measurement axis for condition monitoring. FFT analysis revealed dominant spectral peaks at the fundamental shaft rotational frequency (approximately 14.3 Hz at 860 rpm), accompanied by sub-synchronous and harmonic components induced by mass imbalance. In conclusion, vibration response in small-scale engines is heavily governed by mass location and rotational speed, underscoring the necessity of strategic sensor orientation for accurate fault detection.