High-sensitivity Acoustic Sensor Research Articles

Study on small leaks in submarine liquid pipelines based on passive acoustic internal detection method

ABSTRACT In a submarine liquid pipeline, the timely detection of tiny amounts of leakage (less than 1 L/min) can have a critical impact on pipeline safety. Hence, a method based on a passive acoustic internal detection for pipeline small leakages was established. Firstly, the variation laws between leakage rates and sound power levels with different leakage apertures and internal pressures were simulated using Ansys Fluent 19.0 software. Furthermore, an experimental platform for pipeline small leakage detection was constructed. The acoustic experiments of small leakage detection were carried out under different leakage apertures and internal pressures using a high-sensitivity acoustic sensor placed into the pipeline. It was found that consistency between the experimental results and the finite element simulation results was established. A novel improved empirical mode decomposition (IEMD) was used to denoise the leakage signals. The characteristic parameters of different signal processing fields were extracted. A novel decision tree support vector machine (DTSVM), based on parameter optimization, was used to construct a classification model to identify small leakages through different apertures. The results show that compared with three commonly used models, the accuracy of this novel model of pipeline small leakage detection was 92.2%. This model was found to improve the small leakages detection rate of different apertures and also provided a theoretical basis for developing an acoustic internal detector for submarine liquid pipelines.

Micro-fiber-optic acoustic sensor based on high-Q resonance effect using Fabry-Pérot etalon.

A micro-fiber-optic acoustic sensor based on the high-quality-factor (high-Q) resonance effect that uses a Fabry-Pérot etalon (FPE) is presented in this study. The device has been demonstrated experimentally to be a high-sensitivity acoustic sensor with a large dynamic range over a wide frequency band. Optical contact technology was used to improve the robustness of the FPE, which consists of two parallel lenses with high reflectivity exceeding 99%. An acoustic signal detection system based on phase modulation spectrum technology was also constructed. A stable and high-Q value of 106 was measured for the FPE. As a result, high sensitivity of 177.6 mV/Pa was achieved. Because of the change in the refractive index of the air when it is modulated by the acoustic waves, a frequency response of 20 Hz-70 kHz with flatness of ±2 dB was obtained and a large dynamic range of 115.3 dB was measured simultaneously. The excellent performance of the device will be beneficial for optical acoustic sensing.

High-Priority R&D Problems of Advanced Fast Sodium Reactors

The transition to new design and circuitry requires careful validation of the efficacy of the new solutions. For the sodium-water BN-1200 macro-modular steam generator, the damage is determined by the failure of the structural material in the zone of a water leak into the sodium and the amount of water entering the coolant. The parameter that ultimately determines the magnitude of the damage is the time interval between the start of a small leak and the actuation of the steam generator’s protection system. Acoustic methods are effective for decreasing the lag of the indication system. The design is based on the use of two-frequency ranges – vibro-acoustic (0.1–40 kHz) and ultrasonic (40–500 kHz) – of high-sensitivity acoustic sensors, and fast software-hardware methods of analyzing acoustic signals in real-time. The presence of thermal insulation and protective jackets on the sodium equipment and pipelines strongly affects the character of the outflow and burning of the sodium and eliminates dispersal. Analysis shows that there are strong grounds for reducing the conservatism (safety margins) in studying emergency regimes associated with sodium leaks.

High-sensitivity acoustic sensors from nanofibre webs.

Considerable interest has been devoted to converting mechanical energy into electricity using polymer nanofibres. In particular, piezoelectric nanofibres produced by electrospinning have shown remarkable mechanical energy-to-electricity conversion ability. However, there is little data for the acoustic-to-electric conversion of electrospun nanofibres. Here we show that electrospun piezoelectric nanofibre webs have a strong acoustic-to-electric conversion ability. Using poly(vinylidene fluoride) as a model polymer and a sensor device that transfers sound directly to the nanofibre layer, we show that the sensor devices can detect low-frequency sound with a sensitivity as high as 266 mV Pa−1. They can precisely distinguish sound waves in low to middle frequency region. These features make them especially suitable for noise detection. Our nanofibre device has more than five times higher sensitivity than a commercial piezoelectric poly(vinylidene fluoride) film device. Electrospun piezoelectric nanofibres may be useful for developing high-performance acoustic sensors.