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Article
Publication date: 6 November 2017

Guozeng Wu and Quanlin Dong

The purpose of this paper is to improve the stability of high voltage DC power supply and reduce the ripple.

Abstract

Purpose

The purpose of this paper is to improve the stability of high voltage DC power supply and reduce the ripple.

Design/methodology/approach

The study was conducted using the simulation analysis model and numerical calculation.

Findings

By increasing the output arm capacitance, the expression of ripple and times of the output arm capacitance and the auxiliary arm capacitance is derived. The output ripple is determined by the value of the output arm capacitance. Finally, the correctness of the method and the formula are verified using circuit simulation.

Originality value

This paper presents a method to improve the power supply stability.

Article
Publication date: 12 October 2023

Bin Chen, Quanlin Zhou and Yuan Wang

Thermal fractures initiated under cooling at the surfaces of a 2-D or 3-D structure propagate, arrest and coalesce, leading to its structural failure and material-property…

Abstract

Purpose

Thermal fractures initiated under cooling at the surfaces of a 2-D or 3-D structure propagate, arrest and coalesce, leading to its structural failure and material-property changes, while the same processes can happen in the rock mass between parallel hydraulic fractures filled with cold fluid, leading to enhanced fracture connectivity and permeability.

Design/methodology/approach

This study used a 2-D plane strain fracture model for mixed-mode thermal fractures from two parallel cooling surfaces. Fracture propagation was governed by the theory of linear elastic fracture mechanics, while the displacement and temperature fields were discretized using the adaptive finite element method. This model was validated using two numerical benchmarks with strong fracture curvature and then used to simulate the propagation and coalescence of thermal fractures in a long rock mass.

Findings

Modeling results show two regimes: (1) thermal fractures from a cooling surface propagate and arrest by following the theoretical solutions of half-plane fractures before the unfractured portion decreases to 20% rock-mass width and (2) some pairs of fractures from the opposite cooling surfaces tend to eventually coalesce. The fracture coalescence time is in a power law with rock-mass width.

Originality/value

These findings are relevant to both subsurface engineering and material engineering: structure failure is a key concern in the latter, while fracture coalescence can enhance the connectivity of thermal and hydraulic fractures and thus reservoir permeability in the former.

Details

Engineering Computations, vol. 40 no. 9/10
Type: Research Article
ISSN: 0264-4401

Keywords

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