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Sökning: WFRF:(Wang Jian) > Teknik

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1.
  • Fenstermacher, M.E., et al. (författare)
  • DIII-D research advancing the physics basis for optimizing the tokamak approach to fusion energy
  • 2022
  • Ingår i: Nuclear Fusion. - : IOP Publishing. - 0029-5515 .- 1741-4326. ; 62:4
  • Tidskriftsartikel (refereegranskat)abstract
    • DIII-D physics research addresses critical challenges for the operation of ITER and the next generation of fusion energy devices. This is done through a focus on innovations to provide solutions for high performance long pulse operation, coupled with fundamental plasma physics understanding and model validation, to drive scenario development by integrating high performance core and boundary plasmas. Substantial increases in off-axis current drive efficiency from an innovative top launch system for EC power, and in pressure broadening for Alfven eigenmode control from a co-/counter-I p steerable off-axis neutral beam, all improve the prospects for optimization of future long pulse/steady state high performance tokamak operation. Fundamental studies into the modes that drive the evolution of the pedestal pressure profile and electron vs ion heat flux validate predictive models of pedestal recovery after ELMs. Understanding the physics mechanisms of ELM control and density pumpout by 3D magnetic perturbation fields leads to confident predictions for ITER and future devices. Validated modeling of high-Z shattered pellet injection for disruption mitigation, runaway electron dissipation, and techniques for disruption prediction and avoidance including machine learning, give confidence in handling disruptivity for future devices. For the non-nuclear phase of ITER, two actuators are identified to lower the L-H threshold power in hydrogen plasmas. With this physics understanding and suite of capabilities, a high poloidal beta optimized-core scenario with an internal transport barrier that projects nearly to Q = 10 in ITER at ∼8 MA was coupled to a detached divertor, and a near super H-mode optimized-pedestal scenario with co-I p beam injection was coupled to a radiative divertor. The hybrid core scenario was achieved directly, without the need for anomalous current diffusion, using off-axis current drive actuators. Also, a controller to assess proximity to stability limits and regulate β N in the ITER baseline scenario, based on plasma response to probing 3D fields, was demonstrated. Finally, innovative tokamak operation using a negative triangularity shape showed many attractive features for future pilot plant operation.
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2.
  • Wang, Jin, et al. (författare)
  • Conjugated heat transfer analysis of a film cooling passage with turbulator ribs
  • 2016
  • Ingår i: Heat Transfer Research. - 1064-2285. ; 47:2, s. 89-103
  • Tidskriftsartikel (refereegranskat)abstract
    • In this study, the adiabatic film cooling effectiveness and conjugate heat transfer characteristics for a circular hole are investigated numerically. Seven turbulator ribs are located on the internal wall, and a film cooling hole between two adjacent ribs has an inclination angle of 30°. The secondary flow rate is affected by the internal channel flow velocity, and the external film cooling is combined with the internal channel flow conditions. In the conjugate heat transfer research, two different plate materials are considered to analyze the heat conduction characteristics. The results show that the turbulator ribs enhance the downstream heat transfer and provide a more extensive coverage area and effective cooling protection. More blade-wall heat is transferred by heat conduction, which makes the area-average wall temperature for the high thermal conductivity case to decrease along the secondary flow direction. The wall temperature distribution and film cooling effectiveness are affected significantly by heat conduction.
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3.
  • Wang, Jinsheng, et al. (författare)
  • Conjugated heat transfer investigation with racetrack-shaped jet hole and double swirling chamber in rotating jet impingement
  • 2018
  • Ingår i: Numerical Heat Transfer; Part A: Applications. - : Informa UK Limited. - 1040-7782 .- 1521-0634. ; 73:11, s. 768-787
  • Tidskriftsartikel (refereegranskat)abstract
    • A numerical study is performed to investigate the effects of jet hole shape and channel geometry on impingement cooling for both stationary and rotating condition. Two hole shapes and two channel geometries are introduced to counteract the adverse effects of centrifugal force and Coriolis force which are induced by rotation. Both the fluid and solid part are considered for realizing the conjugate heat transfer simulation. The unsteady k-ω SST turbulence model was employed to obtain the time-averaged Nusselt number distributions, time-averaged temperature and temperature gradient fields and the turbulent flow structure. The results show that the cooling jet from the racetrack-shaped hole can effectively withstand the intensive streamwise crossflow to enhance the heat transfer. The double swirling chamber (DSC) channel significantly improves the heat transfer characteristics on the cambered surface and diminishes the adverse effects of the Coriolis force. The high Nu number region is expanded while the temperature uniformity is improved. The combination of the racetrack-shaped hole and DSC channel provides the highest heat transfer among the four cases. The averaged Nu numbers on both the leading and trailing sides for all tested cases show obvious downtrend as rotation number increases, especially at high Reynolds number.
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4.
  • Wang, Jinsheng, et al. (författare)
  • Numerical investigation of heat transfer and fluid flow in a rotating rectangular channel with variously-shaped discrete ribs
  • 2018
  • Ingår i: Applied Thermal Engineering. - : Elsevier BV. - 1359-4311. ; 129, s. 1369-1381
  • Tidskriftsartikel (refereegranskat)abstract
    • A numerical study is performed to investigate the effects of various discrete rib configurations on the heat transfer and fluid flow characteristics of a rotating rectangular straight channel (aspect ratio of 2:1) with 45° orientation. Three parameters of the discrete rib configuration - rib streamwise distance, rib widthwise distance, and inner-half-rib angle - are examined based on a continuous inclined rib. The blockage ratio (e/Dh) is 0.1 and the pitch ratio (P/e) is 10. The Reynolds number is fixed at 10,000 in each case, while the rotation number is varied from 0 to 0.7. Details of the turbulent flow structure, turbulence kinetic energies, temperature fields, normalized Nusselt numbers, friction penalties and thermal performance factors were obtained by Computation of Fluid Dynamics (CFD) with the k-ω SST turbulence model. The results show that a small streamwise rib gap can effectively enhance the leading wall heat transfer. The heat transfer decreases gradually as the streamwise rib gap is enlarged. The inner-half-rib angle β provides the most conspicuous effects on heat transfer and friction loss, and the best heat transfer appears at β = 60° or 75° for different rotating conditions. The case with a rib streamwise gap normalized distance of 0.2 and inner-half-rib angle of 45° provides best thermal performance. A widthwise rib gap is favorable in reducing pressure drop, but its heat transfer augmentation is limited.
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5.
  • Cao, Jianyin, et al. (författare)
  • W-band high-gain low profile circularly polarized magneto-electric dipole antenna array with gap waveguide feeding technology
  • 2018
  • Ingår i: IET Conference Publications. ; 2018:CP741
  • Konferensbidrag (refereegranskat)abstract
    • In this paper, a high gain circularly polarized (CP) aperture-coupled magneto-electric (ME) dipole antenna array excited by the air cavity in gap waveguide (GWG) feeding technology in W-band is proposed. This antenna array is composed of two layers, upper CP ME-dipole antenna subarrays and lower metallic GWG feeding networks. The planar antenna array structure is realized by the high mode air cavity feeding network, which is realized by extending the 1×2 cavity to 3×2 cavity using more shorted pins to split the electromagnetic field. The whole single-layer GWG feeding network is composed of a ridge gap waveguide (RGWG) transmission structure and short-ended vertical polarized groove gap waveguide (VP-GGWG) high mode air cavities. The transmission loss caused by the coupling and the fabrication tolerance can be reduced by combining the RGWG and GGWG in the same layer. In addition, the feeding network is fabricated all in metal with no substrate loss. Transverse slots are etched at the right position of the printed circuit board (PCB) backside to excite the CP ME-dipoles. The antenna element has stable radiation patterns and wide axial-ratio (AR) bandwidth. The proposed 3×8 planner antenna array has a maximum boresight gain of 22 dBi and an AR bandwidth of 10.8% for AR < 3 dB. In the frequency band from 87.7 to 97.7 GHz, a boresight gain above 20 dBi is achieved.
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6.
  • Jinzhi, Lu, 1988-, et al. (författare)
  • A Domain-specific Modeling Approach Supporting Tool-chain Development with Bayesian Network Models
  • 2019
  • Ingår i: Integrated Computer-Aided Engineering. - : IOS Press. - 1069-2509 .- 1875-8835. ; 27:2, s. 153-171
  • Tidskriftsartikel (refereegranskat)abstract
    • Constructing and evaluating a comprehensive tool-chain with commercial off-the-shelf and proprietary tools for the deployment of model-based systems engineering (MBSE) is a challenging and complex task. Specifically, the lack of early assessment during tool-chain development has led to increased research and development costs when unexpected features are developed or poor decisions are made. In this paper, a domain-specific modeling (DSM) approach is proposed to support decision-makings during tool-chain design and to facilitate quantitative assessment of tool-chain features at early-phases. Using this approach, different views of tool-chains are first formalized under a DSM framework. Then the DSM models are transformed to Bayesian network models for supporting the quantitative assessment of related tools in order to analyze the whole tool-chains’ features. In the case study, the approach is verified by comparing two MBSE tool-chains for an auto-braking system design. The results indicate that the DSM approach enhances the understanding of tool-chain concepts, promotes the efficiency of MBSE tool-chain development, and verifies the tool-chain in early development phases using a quantitative approach.
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7.
  • Yuan, Bo, et al. (författare)
  • Preparation and properties of porous silicon carbide based ceramic filter
  • 2016
  • Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 684, s. 613-615
  • Tidskriftsartikel (refereegranskat)abstract
    • Porous silicon carbide ceramics with high open porosity and large pore size are usually applied as filters for the cleaning of hot dust gases. However, the large porosity and large pore size will decrease the mechanical properties. In the present study, porous SiC ceramics were prepared using bentonite as bonding phase. The effects of sintering temperature on the microstructure and the compressive strength were studied. Bentonite could melt and spread on the surface of silicon carbide particles at all the sintering temperatures. However, the bonding effects were very different at different temperatures.
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8.
  • Jinzhi, Lu, 1988-, et al. (författare)
  • A Service-Oriented Tool-Chain for Model-Based Systems Engineering of Aero-Engines
  • 2018
  • Ingår i: IEEE Access. - : IEEE. - 2169-3536. ; 6, s. 50443-50458
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper proposes a service-oriented tool-chain with an emphasis on domain-specific views, simulation automation, and process management to support model-based system engineering of aero-engines. In the tool-chain, a domain-specific modeling approach is adopted to facilitate the descriptions of co-design workflows and the related development information. The relevant domain-specific models are the basis for automated creation of a Web-based process management system consolidating and controlling service-oriented technical resources (models, data, and tools). In particular, the system also provides support for automated orchestration of tool operations, model, and simulation configurations. In order to promote the model and tool interoperability, the tool-chain adopts open standards for integrations, including open services for lifecycle collaboration and functional mock-up interface. Finally, through a case study of simulation-based aero-engine performance analysis, we evaluate the flexibility and efficiency of this tool chain by comparing it with a traditional simulation process both qualitatively and quantitatively.
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9.
  • Liu, Jian, et al. (författare)
  • Application of fractal theory in the arrangement of truncated ribs in a rectangular cooling channel (4 : 1) of a turbine blade
  • 2018
  • Ingår i: Applied Thermal Engineering. - : Elsevier BV. - 1359-4311. ; 139, s. 488-505
  • Tidskriftsartikel (refereegranskat)abstract
    • Ribs are widely employed in internal cooling passages of turbine blades and other heat transfer equipment to enhance heat transfer by making cooling air flow through internal ribbed passages. From mathematics, a fractal is an abstract object used to simulate naturally occurring objects, which exhibits similar patterns and properties also at smaller scales. The evolving fractal structures of the continuous ribbed channels contains two sides truncated ribs, three sides truncated ribs, five sides truncated ribs and nine sides truncated ribs. The thermal performance of the ribbed channels is compared by taking both heat transfer and pressure drop into consideration. Steady Liquid Crystal Thermography (LCT) is employed to measure surface temperature and derive heat transfer coefficients over the ribbed surfaces in the tested channels. Turbulent flow details are presented by numerical calculations with an established turbulence model, i.e. the k-ω SST model. From the experimental results, it is found that fractal truncated ribs with smaller length scales have larger heat transfer at the low Reynolds numbers. On the other hand, the difference of Nusselt numbers for different cases can be negligible at the high Reynolds numbers. Generally, fractal truncated ribs with smaller length scales have a more uniform heat transfer distribution. The correlation between Nusselt number and Reynolds number are respectively Re0.69, Re0.64 and Re0.61 for case 2 (Two Sides Truncated ribs), case 3 (Three Sides Truncated Ribs) and case 4 (Five Sides Truncated Ribs). The distribution of the high Nusselt number regions is kept identical during the fractal truncated ribs evolving process, which is also valid for the flow field.
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10.
  • Liu, Jian, et al. (författare)
  • Effect of the relative location of a pocket cavity on heat transfer and flow structures of the downstream endwall with a symmetrical vane
  • 2019
  • Ingår i: International Journal of Thermal Sciences. - : Elsevier BV. - 1290-0729. ; 145
  • Tidskriftsartikel (refereegranskat)abstract
    • In a gas turbine engine, the low pressure turbine (LPT) and the outlet guide vane (OGV) part are connected in the rear part. The outlet nozzle is designed as a contracted part to increase the ejection velocity and a pocket cavity (PC) is formed at this location. In this research work, the effects of the locations of the PC on the downstream endwall with a symmetrical vane (SV) are investigated and evaluated. The PC is simplified as a triangular groove with a small fillet radius on the pocket edge connecting to the flat surface. The distance ratio (Ld/D) between the PC and the SV is ranging from 1.0 to 3.0 and the case with only the SV is also considered. Heat transfer and flow field characteristics over the tested surfaces are provided. Heat transfer coefficients (HTCs) are measured by steady-state Liquid Crystal Thermography (LCT) with Reynolds number (Re) ranging between 87.6 × 103 and 21.9 × 103. Two kinds of turbulence models are used to close the N-S equations for the present flow field, i.e., the unsteady DES simulation and the steady the k-ω SST model. When the PC is placed upstream of the SV, the higher Nu regions around the SV due to the horse-shoe vortices is significantly decreased compared with the SV only case. With the distance ratio between SV and PC becoming larger, the weakening effect of the PC is greatly reduced and the heat transfer distributions around the SV on the endwall are seen to approach those of the SV only case (Case 0) when the distance ratio is extremely large. The PC changes the pattern of flow impingement on the SV and the ejection flow from the PC is greatly enhanced. The ejection flow interacts with the mainstream flow and the flow separates from the endwall when it is approaching the SV. Then, the higher heat transfer around the SV is weakened.
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