Experimental thermal investigation of an ONAN distribution transformer by fiber optic sensors

Electromagnetic acoustic transducer (EMAT) is a kind of non-contact ultrasonic transducer, and during its operation, no liquid coupling is required. Despite this advantage, EMAT has low transduction efficiency and its performance depends on the tested object, thus further research of its complex multiphysics transduction mechanism involving both electromagnetic and elastodynamic phenomena is paramount. In this paper, an approach to solve directly the underlying integro-differential equations involved in the eddy current model was proposed, for both steady-state and transient analyses. Skin effect and proximity effect were observed in a generalized multi-conductor electromagnetic model, both for the complete and incomplete equations. Time-varying distributions of the Lorentz force vector were solved from the static bias magnetic field and sinusoidal current density waveforms converted from the corresponding complex phasors of the frequency-domain solution for a meander coil EMAT. For a plate model without any defect and a plate model with a slot defect, the waveforms of displacement component at two points from transient analyses were recorded. The simulated traveling velocities of the wave packets were calculated to compare with the theoretical group velocities of S0 and mode-converted A0 modes of Lamb waves.

Multiphysics Modeling of a Lorentz Force-Based Meander Coil Electromagnetic Acoustic Transducer via Steady-State and Transient Analyses

Hardfacing is done to increase the service life of structural components. Hardfacing is widely done in nuclear and petrochemical industries, mining and sugar refineries. Hardfacing is done on farming equipment to extend their service life as they are prone to impact, abrasion and corrosion. Generally, Ni-base, Co-base and Fe-base alloys are used for hardfacings. Among them, Ni-base alloys are preferred to Co-base and Fe-base alloys as these alloys can retain its hardness even at the elevated temperatures. Colmonoy alloys are predominantly used in nuclear reactor as the dose rate of these alloys is 1/265th that of Co-base alloys. Plasma Transferred Arc (PTA), Gas Tungsten Arc (GTA) and Laser are the major hardfacing processes. The hardfacing process governs the four major aspects of the coating, viz. microstructure, substrate dilution, wear and mechanical properties. This paper provides an in-depth understanding of various research works carried out on Ni alloy hardfacings by different processes on different substrates in those four domains. The outcome of this paper would be beneficial to present and future researchers on Ni alloy hardfacings and also to many hardfacing industries.

Hardfacing studies of Ni alloys: a critical review

Abstract Raman distributed optical fiber sensing has been demonstrated to be a mature and versatile scheme that presents great flexibility and effectivity for the distributed temperature measurement of a wide range of engineering applications over other established techniques. The past decades have witnessed its rapid development and extensive applicability ranging from scientific researches to industrial manufacturing. However, there are four theoretical or technical bottlenecks in traditional Raman distributed optical fiber sensing: (i) The difference in the Raman optical attenuation, a low signal-to-noise ratio (SNR) of the system and the fixed error of the Raman demodulation equation restrict the temperature measurement accuracy of the system. {ii) The sensing distance and spatial resolution cannot be reconciled. (iii) There is a contradiction between the SNR and measurement time of the system. (iv) Raman distributed optical fiber sensing cannot perform dual-parameter detection. Based on the above theoretical and technical bottlenecks, advances in performance enhancements and typical applications of Raman distributed optical fiber sensing are reviewed in this paper. Integration of this optical system technology with knowledge based, that is, demodulation technology etc. can further the performance and accuracy of these systems. 

/pdf/physics-and-applications-of-raman-distributed-optical-fiber-e0euhito.pdf

Physics and applications of Raman distributed optical fiber sensing

The ANIMMA conferences offer a unique opportunity to discover research carried out in all fields of nuclear measurements and instrumentation with applications extending from fundamental physics to fission and fusion reactors, medical imaging, environmental protection and homeland security. After four successful editions of the Conference, it was decided to prepare a review based to a large extent but not exclusively on the papers presented during the first four editions of the conference. This review is organized according to the measurement methodologies: neutronic, photonic, thermal, acoustic and optical measurements, as well as medical imaging and specific challenges linked to data acquisition and electronic hardening. The paper describes the main challenges justifying research in these different areas, and summarizes the recent progress reported. It offers researchers and engineers a way to quickly and efficiently access knowledge in highly specialized areas.

/pdf/nuclear-instrumentation-and-measurement-a-review-based-on-1q7852wly7.pdf

Nuclear instrumentation and measurement: a review based on the ANIMMA conferences

Leak detection in the coolant loops of Fast Breeder Reactor (FBR) is critical for the safety of the reactors. This paper discusses the feasibility of using Raman Distributed Temperature Sensor (RDTS) for leak detection in double walled pipelines of primary sodium circuits in FBR. The leak detection is based on the resultant change in temperature due to leak. Since handling sodium is difficult, as a “proof of concept”, leak detection is demonstrated on a test loop with water as the leaking medium. Path delay multiplexing is adopted to improve the spatial resolution from 1.02 m to 0.51 m.

Monitoring Sodium Circuits Using Fiber Optic Sensors

This paper discusses finite element modeling of spiral coil electromagnetic acoustic transducer (EMAT) to generate bulk waves. First, a 2D electromagnetic model is developed for calculating the Lorentz force density, which is the driving force for sound wave generation within the material. Second, the calculated force at each point in the material is used as the driving force for generating sound wave modes. This model is used to predict the ultrasonic A-scan signals of bulk (longitudinal and shear) waves in isotropic homogeneous material. Spiral coil EMATs of two different coil spacings are developed for experimental studies. The model predicted results are validated by experimental results and for this, the ratio of amplitude of shear wave to longitudinal wave is used.

A hybrid finite element model for spiral coil electromagnetic acoustic transducer (EMAT)

Study of magnetism in Ni–Cr hardface alloy deposit on 316LN stainless steel using magnetic force microscopy

This Letter presents an ultrasonic waveguide sensor for measuring fluctuations in a liquid level using leaky longitudinal wave L(0,2) in a coolant loop system. A 20% cold-worked D9 fuel pin clad tube of 1000 mm long, 6.6 mm outer diameter and 0.45 mm wall thickness was used as a waveguide on which the L(0,2) mode was transmitted/received along the axial direction at 500 kHz. When the waveguide got introduced into a coolant loop and partially immersed in a non-viscous liquid (water/liquid sodium), the amplitude of L(0,2) mode got reduced due to leakage. The rate of leakage depends on the characteristics of the waveguide and the embedding liquid medium. By utilising this physical property of L(0,2) mode, it is possible to predict the variations in liquid level during dynamic conditions. Experimental measurements were carried out on a mock-up test loop in which water was used as embedding liquid and two artificial notches were made on the waveguide at different depths were used as reference levels. The time-amplitude signals were monitored and the reflected energies from the bottom end of the waveguide and the notches were used as the threshold and reference amplitudes respectively for identification of water level.

https://ietresearch.onlinelibrary.wiley.com/doi/pdf/10.1049/el.2020.1678

Development of ultrasonic waveguide sensor for liquid level measurement in loop system

Transformers play an important role in power distribution. Online monitoring of temperature in transformer is envisaged for hotspot detection. In this paper, we have evaluated the performance of Fiber Bragg Grating (FBG) temperature sensor by suitable encasement for hotspot monitoring in transformer. The dynamic response of the FBG encased in a transformer to hotspot was studied by introducing the defects such as partial cut and weakened insulation in the secondary coil.

B. Purna Chandra Rao

Papers

Monitoring Sodium Circuits Using Fiber Optic Sensors

A hybrid finite element model for spiral coil electromagnetic acoustic transducer (EMAT)

Study of magnetism in Ni–Cr hardface alloy deposit on 316LN stainless steel using magnetic force microscopy

Development of ultrasonic waveguide sensor for liquid level measurement in loop system

Hotspot monitoring in transformers using Fiber Bragg Grating