This article proposes a fault diagnosis method based on an adaptive sliding mode observer (SMO) for current sensors (CSs) in the charging modules of DC charging piles. Firstly, we establish a model of the phase-shift full-bridge (PSFB) converter with CS faults. Secondly, the fault of the CS is reconstructed through system augmentation and non-singular coordinate transformation. Then, an adaptive SMO is designed to estimate the reconstructed state, and the residual between the actual value of the reconstructed state and the observed value is used as the fault detection variable. Finally, by using norms to design adaptive thresholds and comparing them with fault detection variables, the diagnosis of incipient faults, significant faults, and failure faults in CSs can be achieved. The experimental results verify the effectiveness of the proposed method in this paper; the robustness of the method has been verified under the conditions of DC voltage fluctuations and load fluctuations.

The sediment erosion of Pelton turbine components is a major challenge in the operation and development of high-head water resources, especially in mountainous areas with high sediment yield. In this paper, a study using numerical simulation was conducted with different sediment particle sizes in the fine sand range. And the erosion mechanism of the Pelton turbine injector was analyzed. The Eulerian Lagrange method was adopted to simulate the gas–liquid–solid flow. The Mansouri’s model was applied to estimate the injector erosion. The predicted erosion results were in accord with field erosion photographs. In particular, the asymmetrical erosion distribution on the needle surface was physically reproduced. With the sediment particle size increasing from 0.05 mm, the needle erosion rate decreased, while the nozzle casing erosion rate increased dramatically. In order to clarify this tendency, the characteristics of the three-phase flow were analyzed. Interestingly, the results show that with the rise in particle size, the separation of particles and water streamlines became more serious in the contraction section of the nozzle mouth. Consequently, it caused the enhancement of erosion of the nozzle surfaces and weakened the erosion of the needle surfaces. Significant engineering insights may be provided for weakening Pelton injector erosion with needle guides in the current study.

The microstructure evolution of a low-carbon 13Cr4Ni martensitic stainless steel during two-stage intercritical tempering at 630 °C and 590 °C has been investigated by X-ray diffraction, thermodilatometry, and transmission electron microscopy. It was found that the amount and size of reversed austenite increase remarkably after second-stage tempering at 590 °C. However, there is no remarkable variation in the chemical composition and nucleation site of the reversed austenite during the first- and second-stage tempering. The dynamics of the phase transformation and elements distribution imply that the martensite-to-austenite phase transformation during second-stage tempering is controlled by diffusion. The unstable austenite transformation into martensite during the cooling process of the first-stage tempering induces high density dislocations and inhomogeneous element distribution, which facilitate the nucleation and growth of the reversed austenite in the second-stage intercritical tempering. Additionally, some lathy reversed austenite spheroidizes to granular during second-stage tempering.