Browsing by Author "Sun, Youhong"

Filter results by typing the first few letters
Now showing 1 - 9 of 9
  • Effect of a Minor Sr Modifier on the Microstructures and Mechanical Properties of 7075 T6 Al Alloys
    (2017) Ma, Shaoming; Sun, Youhong; Wang, Huiyuan; Lu, Xiaoshu; Qian, Ming; Ma, Yinlong; Zhang, Chi; Liu, Baochang
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
  • The Effect of ZrO2 Nanoparticles on the Microstructure and Properties of Sintered WC–Bronze-Based Diamond Composites
    (2016) Sun, Youhong; Wu, Haidong; Li, Meng; Meng, Qingnan; Gao, Ke; Lu-Tervola, Xiaoshu; Liu, Baochang
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Metal matrix-impregnated diamond composites are widely used in diamond tool manufacturing. In order to satisfy the increasing engineering requirements, researchers have paid more and more attention to enhancing conventional metal matrices by applying novel methods. In this work, ZrO2 nanoparticles were introduced into the WC-bronze matrix with and without diamond grits via hot pressing to improve the performance of conventional diamond composites. The effects of ZrO2 nanoparticles on the microstructure, density, hardness, bending strength, and wear resistance of diamond composites were investigated. The results indicated that the hardness and relative density increased, while the bending strength decreased when the content of ZrO2 nanoparticles increased. The grinding ratio of diamond composites increased significantly by 60% as a result of nano-ZrO2 addition. The enhancement mechanism was discussed. Diamond composites showed the best overall properties with the addition of 1 wt % ZrO2 nanoparticles, thus paving the way for further applications.
  • Effects of composition and pore evolution on thermophysical properties of Huadian oil shale in retorting and oxidizing pyrolysis
    (2021-12-01) Xu, Shaotao; Sun, Youhong; Lu, Xiaoshu; Yang, Qinchuan; Li, Qiang; Wang, Zhendong; Guo, Mingyi
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    This chemical composition and pore evolution of oil shale during oxidizing pyrolysis (OP) and their influences on its thermophysical properties were investigated in this study. Various transformations of the minerals in oil shale were detected, among which montmorillonite was noted to transform into illite during anaerobic retorting (AR), and into kaolinite during OP. Variations in the quantities of residual carbon and organic matter during low-temperature AR and OP were noted to be possibly responsible for the difference in pore volumes. Remarkable increases in surface and volumes of mesopores and macropores through OP were observed even at low temperatures. The pore volume was proven to significantly affect the thermophysical properties of semi-cokes at low temperatures during OP. Higher thermal conductivity and thermal diffusivity were observed in semi-cokes obtained via OP at 350 ℃ compared to those obtained via AR at 520 ℃. These phenomena highlight the potential of OP for application in in-situ oil shale exploitation.
  • Effects of Packer Locations on Downhole Electric Heater Performance: Experimental Test and Economic Analysis
    (2020-01-13) Guo, Wei; Wang, Zhendong; Sun, Youhong; Lu-Tervola, Xiaoshu; Wang, Yuan; Deng, Sunhua; Li, Qiang
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    A downhole electric heater, which reduces heat loss along a heat insulation pipe, is a key apparatus used to ignite oil shale underground. Downhole heaters working together with packers can improve the heating efficiency of high-temperature gases, while different packer locations will directly affect the external air temperature of the heater shell and, subsequently, the performance and total cost of the downhole heaters. A device was developed to simulate the external conditions of heater shells at different packer locations. Then, the effects of external air temperature on the performance of a downhole heater with pitches of 50, 160, and 210 mm were experimentally studied. In the test, results indicated that the heater with a packer at its outlet had an accelerated heating rate in the initial stage and decreased temperature in the final stage. Additionally, the lowest heating rod surface temperature and highest comprehensive performance were achieved with minimal irreversible loss and lower total cost when using a downhole electric heater with a packer set at its outlet. In addition, the downhole electric heater with a helical pitch of 50 mm and a packer at its outlet was more effective than other schemes in the high Reynolds number region. These findings are beneficial for shortening the oil production time in oil shale in situ pyrolysis and heavy oil thermal recovery.
  • Energy consumption and product release characteristics evaluation of oil shale non-isothermal pyrolysis based on TG-DSC
    (2020-04) Zhao, Shuai; Sun, Youhong; Lu-Tervola, Xiaoshu; Li, Qiang
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Thermogravimetric-Differential Scanning Calorimetry Analysis (TG-DSC) was applied to study non-isothermal pyrolysis characteristics of oil shales, such as the starting point, stability, pyrolysis interval and product release using Fuyu and Huadian oil shale samples. Results show that with the increase of heating rate, oil shale pyrolysis moves to higher temperature zone. This trend is more noticeable at higher oil content. The pyrolysis stability of the oil shale is related to oil content and pyrolysis atmosphere. The higher the oil content, the more stable the pyrolysis of the oil shale. Under nitrogen atmosphere, the pyrolysis interval of oil shale is more concentrated, air prolongs the pyrolysis interval, and the pyrolysis stability index decreases. In addition, the increase of heating rate favours the release characteristic index of the product, which is not practically affected by oil content. The release characteristic indices of pyrolysis products from oil shale under nitrogen atmosphere are higher than those under air atmosphere. The optimum heating rate that produces the highest oil product yield for pyrolysis progress of Huadian oil shale is 20 °C/min, and Fuyu oil shale is 40 °C/min.
  • Hydrate dissociation induced by gas diffusion from pore water to drilling fluid in a cold wellbore
    (2018-08-24) Sun, Youhong; Lu, Hongfeng; Lu, Cheng; Li, Shengli; Lu-Tervola, Xiaoshu
     A2 Katsausartikkeli tieteellisessä aikakauslehdessä
    It is a common view that the high temperature of the drilling fluid can lead to the dissociation of gas hydrate during drilling through hydrate-bearing sediments. This study indicates that the hydrate dissociation in wellbore can also be induced by gas diffusion from pore water to drilling fluid even if the temperature (and the pressure if necessary) of the drilling fluid is well controlled to keep the conditions of hydrate-bearing sediments along the hydrate equilibrium boundary. The dissociation of gas hydrate was modelled based on Fick's first law. It was found that the dissociation rate mainly depended on the temperature of the sediments. The locations of dissociation front of CH4 hydrate and CO2 hydrate in wellbore were calculated as a function of time. The impacts of the hydrate dissociation on the wellbore stability and the resistivity well logging in sediments were evaluated.
  • Kinetics and thermodynamics evaluation of carbon dioxide enhanced oil shale pyrolysis
    (2021-01-12) Zhao, Shuai; Sun, Youhong; Lü, Xiaoshu; Li, Qiang
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The pyrolysis process of oil shale is significantly affected by atmospheric conditions. In this paper, the pyrolysis experiments of oil shale under non-isothermal conditions are carried out using nitrogen and carbon dioxide as heat-carrying fluids. The results show that the activation energy of the second stage of oil shale pyrolysis under carbon dioxide is less than that under nitrogen. The thermodynamic analysis of the second stage of oil shale pyrolysis shows that Gibbs free energy, activation enthalpy and activation entropy are higher under carbon dioxide than those under nitrogen, which obeys the law of carbon dioxide promoting oil shale pyrolysis. In addition, the volatile release characteristics of oil shale in the second stage of pyrolysis were analyzed, which proves that the volatile release characteristics of oil shale under carbon dioxide are higher than that under nitrogen. Therefore, carbon dioxide is helpful to promote the pyrolysis of oil shale and increases the release of volatile substances during pyrolysis.
  • Optimization of temperature parameters for the autothermic pyrolysis in-situ conversion process of oil shale
    (2023-02-01) Xu, Shaotao; Lü, Xiaoshu; Sun, Youhong; Guo, Wei; Li, Qiang; Liu, Lang; Kang, Shijie; Deng, Sunhua
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    In this study, a temperature optimization strategy for the Huadian oil shale autothermal pyrolysis in-situ conversion process (ATS) was first proposed by systematically investigating the reaction characteristics of various semi-cokes. As the pyrolysis temperature rised, the semi-coke's calorific value was found to undergo three different stages of increasing, decreasing, and flattening, peaking at around 330 °C. Additionally, the semi-cokes formed at different temperatures exhibited similar combustion characteristics, including combustion activation energy, combustion characteristic parameters, and product release characteristics. Due to the serious pore blockage caused by the substantial generation and the ignition coking of the bitumen, the reaction characteristics of semi-cokes were dramatically decreased at about 330 °C. Finally, the relationship between in-situ heat generation and demand at various stages of ATS process was discussed, and a reasonable strategy for the screening of temperature parameters was proposed. According to this strategy, the optimal control temperature for the preheating stage was determined at 350–370 °C and at Tact (defined in 4.3.2) for the retorting zone in the reaction stage. The results of this study provide a new perspective on the theoretical foundation of the ATS process and have crucial guiding implications for practical engineering applications.
  • Productivity analysis of Fuyu oil shale in-situ pyrolysis by injecting hot nitrogen
    (2021-08-02) Zhao, Shuai; Li, Qiang; Lü, Xiaoshu; Sun, Youhong
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    In this paper, the effect of heat injection on productivity of Fuyu oil shale during in-situ pyrolysis was studied by using heat flow coupling analysis method. It is found that fluid conducts heat transmission to the oil shale stratum mainly along the fissure formed by hydraulic fracturing. With the increase of heating time, the oil shale on both sides of fissures were effectively pyrolyzed, and the porosity of the formation increases and the diffusion range of the nitrogen to the oil shale stratum is also improved. After 200 days, the oil shale around the fractures first reaches the pyrolysis temperature, and 700 days later, the average temperature of the oil shale stratum reaches 500◦C; therefore, the whole oil shale can be effectively pyrolyzed. Productivity analysis shows that the best exploitation temperature is 500◦C. When the gas injection rate is in the range of 1.0~11.0 m3/min, different degrees of heat loss will occur, and the output is also different. The pyrolysis time reaches 100~150 days, showing the peak value of daily production, which is between 0.5~3.2 m3/day. The pressure of displacement fluid affects oil shale product recovery in in-situ pyrolysis. High pressure helps to improve the displacement efficiency of oil and gas products and increase the productivity of oil shale in-situ pyrolysis. The best acting pressure is 9.5 MPa.