Wei Wang and Hairui Yang
Rectangular fluidised beds are commonly used in industry, e.g. circulating fluidised bed (CFB) boilers. Apparently, no one has tried to imagine rectangular fluidised beds by…
Abstract
Purpose
Rectangular fluidised beds are commonly used in industry, e.g. circulating fluidised bed (CFB) boilers. Apparently, no one has tried to imagine rectangular fluidised beds by electrical capacitance tomography (ECT). The purpose of this paper is to design a rectangular ECT sensor to understand the behaviour of a rectangular CFB riser.
Design/methodology/approach
A rectangular sensor with eight electrodes is adopted to obtain the capacitance data. The sensitivity map is simulated to calculate the grey level of pixels for visualisation using the linear back‐projection algorithm.
Findings
Experiments showed that the position of the objects in the riser can be obviously indicated and the central region of the object(s) has significantly higher grey level than other regions in the images using the rectangular ECT sensor.
Research limitations/implications
It has a limitation in providing a higher resolution image.
Practical implications
The results obtained by the rectangular ECT sensor show that it is promising to study the characteristics of flow non‐uniformity in the fast fluidisation regime of CFB.
Originality/value
Without using square and circular ECT sensors, this is the first time a rectangular ECT sensor has been developed to study the unique problems of the characteristics of flow non‐uniformity in a rectangular CFB riser.
Details
Keywords
Hairui Jiang, Jianjun Guan, Yan Zhao, Yanhong Yang and Jinglong Qu
The purpose of this study is to investigate the corrosion resistance of superalloys subjected to ultrasonic impact treatment (UIT). The passive film growth on the superalloys’…
Abstract
Purpose
The purpose of this study is to investigate the corrosion resistance of superalloys subjected to ultrasonic impact treatment (UIT). The passive film growth on the superalloys’ surface is analyzed to illustrate the corrosion mechanism.
Design/methodology/approach
Electrochemical tests were used to investigated the corrosion resistance of GH4738 superalloys with different UIT densities. The microstructure was compared before and after the corrosion tests. The passive film characterization was described by electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS) tests.
Findings
The compressive residual stress and corrosion resistance of the specimens significantly increased after UIT. The order of corrosion resistance is related to the UIT densities, i.e. 1.96 s/mm2 > 1.71 s/mm2 > 0.98 s/mm2 > as-cast. The predominant constituents of the passive films are TiO2, Cr2O3, MoO3 and NiO. The passive film on the specimen with 1.96 s/mm2 UIT density has the highest volume fraction of Cr2O3 and MoO3, which is the main reason for its superior corrosion resistance.
Originality/value
This study provides quantitative corrosion data for GH4738 superalloys treated by ultrasonic impact. The corrosion mechanism is explained by the passive film’s characterization.
Details
Keywords
Hairui Jiang, Jianjun Guan, Yan Zhao, Jinglong Qu and Yanhong Yang
This study aims to investigate the corrosion resistance and electrochemical dissolution behavior of superalloys treated by different oxidation treatments.
Abstract
Purpose
This study aims to investigate the corrosion resistance and electrochemical dissolution behavior of superalloys treated by different oxidation treatments.
Design/methodology/approach
Ni-based superalloys were subjected to oxidation treatment at 1000 °C for 10 h, 1150 °C for 10 h and 1200 °C for 20 h. The microstructure, electrochemical dissolution behavior, elemental distribution, as well as compactness and composition of the oxide layer, were studied.
Findings
The results show that both the thickness and the granular oxide size of the oxide layer on Ni-based superalloys increase with longer oxidation times and higher temperatures. The electrochemical dissolution efficiency of Ni-based superalloys decreases with increasing oxidation time and temperature. The reduced electrochemical dissolution efficiency observed in Ni-based superalloys oxidation-treated at 1200 °C for 20 h is primarily attributed to the thicker oxide layer, which contains the highest Cr oxide content.
Originality/value
The findings contribute to the advancement of recycling and utilization of Ni-based superalloy scrap.