Implementation of an acoustic stall detection system using near-field DIY pressure sensors

Abstract

In this paper, the use of DIY transducers is proposed to detect the pressure instabilities in a low-speed industrial axial fan. The authors aim is to detect rotating stall, a well-studied aerodynamic instability with a typical frequency that can be even lower than 10 Hz in low-speed industrial fans. Pressure transducers and piezoelectric sensors, such as microphones, in turbomachinery are used respectively in the near and far field as standard methods to perform time-resolved pressure measurements. Other classes of sensors, such as electret microphones, may be not suited for pressure measurements, especially in the ultrasound region because their cutoff frequency is about 20 Hz. In this study, the authors use a lowcost DIY technology, as alternative technology to stall detection, in comparison with a high precision piezoelectric sensor. The authors performed the pressure measurements using a dynamic transducer, a piezoresistive transducer, and a piezoelectric high sensitivity sensor that provides the measurement baseline. They implemented and setup a measurement chain to identify the typical rotating stall pattern in low-speed axial fans. The results have been validated with respect to the state-of-the-art acoustic control techniques described in literature. The signals acquired using the two technologies are discussed using a combination of spectral and time-domain space reconstruction. The acoustic patterns obtained through the phase space reconstruction show that the DIY dynamic sensor is a good candidate solution for the rotating stall acoustic analysis.

Acoustic Noise-Based Detection of Ferroresonance Events in Isolated Neutral Power Systems with Inductive Voltage Transformers

“…From the frequency and sensitivity requirements, infra-sound microphones, e.g., Brüel & Kjær Type 4964 microphones [ 36 ], are the most suitable ones, but the prices can be relatively high, i.e., hundreds of USD. Both low-cost dynamic and condenser microphones will exhibit issues around 20 , despite the available solutions to extend the frequency range below this value, e.g., [ 37 , 38 ]. Neglecting the frequency response, the robustness of dynamic ones, both the moving coil and the ribbon, the absence of polarization or self-noise would make piezoelectric microphones [ 39 ] valuable candidates for this application.…”

Editorial for Special Issue on Air Movement Fan Technology

“…Corsini et al. 7 studied the practicality of using low-cost pressure sensors in an acoustic stall detection system. The study compared measurements taken using a low-cost dynamic transducer and a precision piezoelectric sensor costing approximately 100 times more than the dynamic transducer.…”