Subjects -> PHYSICS (Total: 857 journals)
    - ELECTRICITY AND MAGNETISM (10 journals)
    - MECHANICS (22 journals)
    - NUCLEAR PHYSICS (53 journals)
    - OPTICS (92 journals)
    - PHYSICS (625 journals)
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    - THERMODYNAMICS (30 journals)

THERMODYNAMICS (30 journals)

Showing 1 - 28 of 28 Journals sorted alphabetically
Advances in Heat Transfer     Full-text available via subscription   (Followers: 27)
Applied Thermal Engineering     Hybrid Journal   (Followers: 38)
Araucaria. Revista Iberoamericana de FilosofĂ­a, PolĂ­tica y Humanidades     Open Access  
Archives of Thermodynamics     Open Access   (Followers: 11)
Chemical Thermodynamics and Thermal Analysis     Open Access   (Followers: 3)
Condensed Matter Physics     Open Access   (Followers: 2)
Diffusion Foundations     Full-text available via subscription   (Followers: 4)
European Journal of Mechanics - B/Fluids     Hybrid Journal   (Followers: 5)
Experimental Heat Transfer     Hybrid Journal   (Followers: 18)
Experimental Thermal and Fluid Science     Hybrid Journal   (Followers: 35)
Fluids     Open Access  
Heat and Mass Transfer     Hybrid Journal   (Followers: 28)
Heat Transfer Engineering     Hybrid Journal   (Followers: 38)
High Temperature     Hybrid Journal   (Followers: 2)
HTM Journal of Heat Treatment and Materials     Full-text available via subscription   (Followers: 3)
International Journal of Thermodynamics     Open Access   (Followers: 14)
International Journal of Thermophysics     Hybrid Journal   (Followers: 7)
Journal of Chemical Thermodynamics     Hybrid Journal   (Followers: 8)
Journal of Low Temperature Physics     Hybrid Journal   (Followers: 6)
Journal of Non-Newtonian Fluid Mechanics     Hybrid Journal   (Followers: 14)
Journal of Thermal Science     Hybrid Journal   (Followers: 22)
Journal of Thermal Spray Technology     Hybrid Journal   (Followers: 5)
Journal of Thermodynamics     Open Access   (Followers: 9)
Journal of Thermophysics and Heat Transfer     Hybrid Journal   (Followers: 95)
Low Temperature Physics     Hybrid Journal   (Followers: 6)
Metal Science and Heat Treatment     Hybrid Journal   (Followers: 36)
Quantitative InfraRed Thermography Journal     Hybrid Journal  
Thermophysics and Aeromechanics     Hybrid Journal   (Followers: 6)
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Journal Cover
Journal of Thermal Science
Journal Prestige (SJR): 0.316
Citation Impact (citeScore): 1
Number of Followers: 22  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1993-033X - ISSN (Online) 1003-2169
Published by Springer-Verlag Homepage  [2467 journals]
  • Design Optimization and Analysis of Exit Rotor with Diffuser Passage based
           on Neural Network Surrogate Model and Entropy Generation Method

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      Abstract: Abstract In this paper, a diffuser passage compressor design is introduced via optimization to improve the aerodynamic performance of the exit rotor in a multistage axial compressor. An in-house design optimization platform, based on genetic algorithm and back propagation neural network surrogate model, is constructed to perform the optimization. The optimization parameters include diffusion angle of meridian passage, diffusion length of meridian passage, change of blade camber angle and blade number. The impacts of these design parameters on efficiency and stability improvement are analyzed based on the optimization database. Two optimized diffuser passage compressor designs are selected from the optimization solution set by comprehensively considering efficiency and stability of the rotor, and the influencing mechanisms on efficiency and stability are further studied. The simulation results show that the application of diffuser passage compressor design can improve the load coefficient by 12.1% and efficiency by 1.28% at the design mass flow rate condition, and the stall margin can be improved by 12.5%. According to the local entropy generation model analysis, despite the upper and lower endwall loss of the diffuser passage rotor are increased, the profile loss is reduced compared with the original rotor. The efficiency of the diffuser passage rotor can be influenced by both loss and load. At the near stall condition, decreasing flow blockage at blade root region can improve the stall margin of the diffuser passage rotor.
      PubDate: 2023-01-21
       
  • Temperature Uniformity, Correlations and the Flow Field in Swirling
           Impinging Jets

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      Abstract: Abstract Infrared thermography, velocity and impingement pressure measurements alongside numerical modelling are used in this study to resolve (heated) surface temperature distributions of turbulent swirling impinging jets for two Reynolds numbers (Re=11 600 and 24 600). Whilst building upon earlier discoveries for this same geometry, this paper provides three new contributions: (1) identifying the role of impingement distance (H/D) as a deciding factor in the trade-off between more efficient heat transfer (at high swirl numbers) and achieving better substrate temperature uniformity (lower gradients), (2) developing correlations to predict Nusselt number for swirling and non-swirling cooling jets, and (3) predicting the underlying mixing field in these jets and its interplay with the thermal distributions resolved. Results indicate substrate temperature uniformity varies based on H/D and swirl intensity (S) with a significant level of thermal non-uniformity occurring in near-field impingement (H/D=1) at stronger swirl (S=0.59 and 0.74). Four correlations describing the effects of S, Re, and H on the average heat transfer and stagnation heat transfer are developed and yield accuracies of 8% and 12%, respectively. Flow recirculation near the impingement surface is predicted at H/D=1 for stronger swirl jets which disappears at other substrate distances. The peak wall shear stress reduces and the flow impingement becomes radially wider at higher H/D and S. Stronger turbulence or eddy viscosity regions for non-swirling jets (S=0) are predicted in the shear layer and entrainment regions at H/D=1, but such turbulence is confined to the impingement and wall jet regions for strongly swirling flows.
      PubDate: 2023-01-21
       
  • Numerical Study of New-Type Receiver with Axially-Hollow Spiral Deflector
           for Parabolic Trough Direct-Steam-Generation Loop of Concentrating Solar
           Power System

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      Abstract: Abstract The thermal stress-induced deformation issue of receiver is crucial to the performance and reliability of a parabolic-trough (PT) concentrating solar power (CSP) system with the promising direct steam generation (DSG) technology. The objective of the present study is to propose a new-type receiver with axially-hollow spiral deflector and optimize the geometric structure to solve the above issue. To this end, optical-flow-thermal multi-physics coupling models have been established for the preheating, boiling and superheating sections of a typical PT-DSG loop. The simulation results show that our proposed new-type receiver demonstrates outstanding comprehensive performance. It can minimize the circumferential temperature difference through the spiral deflector while lower the flow resistance cost through the axially hollow structure at the same time. As quantitatively evaluated by the temperature uniformity improvement (εΔT) and the performance evaluation criteria (PEC), different designs are achieved based on different optimal schemes. When εΔT is of primary importance, the optimal design with torsional ratio of 1 is achieved, with εΔT=25.4%, 25.7%, 41.5% and PEC=0.486, 0.878, 0.596 corresponding to preheating, boiling, superheating sections, respectively. When PEC is of primary importance, the optimal design with torsional ratio of 6–6.5 is achieved, with PEC=0.950, 2.070, 0.993 and εΔT=18.2%, 13.3%, 19.4% corresponding to preheating, boiling, superheating sections, respectively.
      PubDate: 2023-01-21
       
  • Thermal Performance of Mini Cooling Channels for High-Power Servo Motor
           with Non-Uniform Heat Dissipation

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      Abstract: Abstract High-power servo motor is widely employed as a necessary actuator in flight vehicles. The urgent problem to be solved restraining the working performance of servo motor is no longer the torque and power, but the heat dissipation capability under high-power working conditions, which may cause the overheat, even burn down of motor or other potential safety hazards. Therefore, a structure of mini cooling channels with appropriate channel density is designed in accordance with the non-uniform heat flux of servo motor in this paper. Combined with the regenerative cooling method, the cryogenic fuel supercritical methane is served as the coolant, which is easy to be obtained from the propulsion system, and the heat from the servo motor can be transported to the combustion for reusing. According to the actual working cases of servo motor, a numerical model is built to predict the thermal performance of cooling channels. In order to better represent the secondary flow of coolant in the cooling channels, especially the turbulent mixed flow in the manifold, the k-ε RNG model with enhanced wall treatment is employed resulting from its precise capacity to simulate the secondary and wall shear flow. On this basis, the heat transfer mechanism and thermal performance of cooling channels, as well as the influence of various heat flux ratios are investigated, which can offer an in-depth understanding of restraining excessive temperature rise and non-uniformity distribution of the servo motor. By the calculation results, it can be concluded that under the adjustment of the channel density according to the corresponding heat flux, the positive role of the appropriate channel density and the manifolds on heat transfer is manifested. Moreover, the maximum temperature difference of heating wall can be kept within an acceptable range of the servo motor. The heat transfer coefficient in the manifold is nearly 2–4 times higher compared with that in the straight cooling channels. The effect of buoyancy force cannot be neglected even in the manifold with turbulent mixed flow, and the pattern of heat transfer is mixed convection one in all the flow regions. The thermal resistance R and overall Nusselt number Nu are affected remarkably by all the operation parameters studied in the paper, except the pressure, while the overall thermal performance coefficient η demonstrates differently. The strong impact of heat flux ratio is implied on thermal performance of the cooling channels. Higher heat flux ratio results in the stronger non-uniform temperature distribution. Meanwhile, only tiny temperature differences of the fluid and inner wall in manifolds among various heat flux ratios are demonstrated, resulting from the positive effect of mixture flow on heat transfer.
      PubDate: 2023-01-21
       
  • Numerical Investigation on Flow and Cooling Characteristics of a
           Micro-Ribbed Vane Endwall

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      Abstract: Abstract The secondary flow originated from the inherent pressure gradient inside the vane cascade has a strong impact on the endwall cooling performance as the crossflow sweeps the upstream coolant jet towards the suction side, resulting in intensifying thermal load near the pressure side endwall. Hence a novel ribbed-endwall is introduced to suppress passage crossflow. The effects of the mass flow ratio and the rib layout were examined using numerical simulations by solving the three-dimensional Reynolds-averaged Navier-Stokes (RANS) equations with the shear stress transport (SST) k-ω turbulence model. The results indicate that the ribs effectively prevent the coolant migrating from the pressure side to the suction side, helping the coolant jet to spread along the lateral orientation. Therefore, the endwall adiabatic film cooling effectiveness is substantially improved. The maximum cooling effectiveness is achieved for the case with three-ribs when the height of the rib equals one hole diameter among all cases. The area-averaged adiabatic cooling effectiveness is enhanced by 31.6% relative to the flat endwall when the mass flow ratio of coolant to mainstream equals to 0.52%. More importantly, the ribbed-endwall obtains a relatively lower level of aerodynamic loss owing to the reduced lateral migration inside the vane cascade.
      PubDate: 2023-01-21
       
  • Effects of Ribbed-Cavity Tip on the Blade Tip Aerothermal Performance in a
           High Pressure Turbine Stage

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      Abstract: Abstract For unshrouded blade tip, the high-temperature gas flows through the tip clearance by force of the lateral pressure difference. Thereby, the blade tip endures increasing thermal load. Furthermore, the conventional blade tip treatment cannot continuously provide protection for the deteriorating service environment. In the present study, aerothermal characteristics of the squealer blade tip with staggered ribs, partial squealer rim and different partial squealer rim thickness were investigated to explore the influences of ribbed-cavity tip on the tip heat transfer, leakage flow and turbine stage efficiency. The numerical results indicate that the ribbed-cavity tips are beneficial for the reduction of the blade tip thermal load and leakage flow. Among the present six blade tip designs, the minimal area-averaged heat transfer coefficient is obtained by the case with the staggered ribs and a deeper squealer rim, which is reduced by 31.41% relative to the squealer tip. Plus, the blade tip modification closer to leading edge or tip mid-chord region performs better than trailing edge in reducing the tip leakage flow.
      PubDate: 2023-01-21
       
  • Effect of Disturbances on the Operation Process of a Methane-Fueled
           Free-Piston Engine Generator

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      Abstract: Abstract In this paper, the effect of disturbances on the operation process of a methane-fueled free-piston engine generator (FPEG) was experimentally investigated. Four disturbance sources, namely step change of external load, mixture flow rate fluctuation, random misfire of a cylinder, and elastic collision, were identified and applied to the FPEG. The results showed that the FPEG successfully achieved a steady-state operation with load. The maximum instantaneous electric power of 127 W and the average effective electric power of 38.9 W were obtained. When an external load was instantaneously disconnected, the engine frequency increased from 26.7 Hz to 31.3 Hz. The fluctuation amplitudes of induced voltage, pressure and compression ratio were 18.9%, 24.7% and 52.2% respectively in the disturbance. By contrast, when the external load was instantaneously connected, the corresponding values were 42.2%, 31.3% and 64.3% respectively, indicating that the instantaneous external load connection had a greater disturbance impact on the FPEG operation stability. Despite encountering the step change of external load, the FPEG can still restore stable operation and show good anti-disturbance ability. Compared with increasing mixture flow rate, reducing the mixture flow rate has a greater disturbance impact on the engine operation stability. Although random misfire of a cylinder will cause remarkable fluctuations in piston displacement and cylinder pressure, the FPEG will not stop running, but continues to work as a single-piston engine. Minor collision event may adversely affect the stability of engine operation, but will not lead to the FPEG shutdown. However, serious collision event may lead to ignition failure and shutdown accident.
      PubDate: 2023-01-17
       
  • Interactive Effects of Wind Tunnel Sidewalls on Flow Structures around 2D
           Airfoil Model

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      Abstract: Abstract This paper presents the effect of wind tunnel sidewalls on the wind turbine airfoils with experimental and numerical methods. The test is carried out in a low-speed wind tunnel at Re=2.62×105. Pressures acting on the airfoil surface are measured by a multiport pressure device. And, the oil flow visualization technique is used to investigate the flow field characteristics of the airfoil surface. Then, a numerical simulation was conducted with the measurement results. As a result, it is clarified the flow structures on the airfoil surface depend strongly on the angles of attack and the sidewalls. At small angles of attack, the three-dimensional separation caused by the interaction between the sidewall boundary layer and the airfoil boundary layer is very small, and only appears near the junction of the airfoil model and the sidewall. This corner separation becomes large with the increase of the angle of attack. At the middle part of the testing model, the boundary layer flow evolves into three-dimensional separation, i.e., stall cell, when the separation develops to an appreciate extent. The stall phenomenon will further spread from the center line to sidewalls with the increase of the angle of attack; and then, its development will be limited by the sidewall boundary layer separation. Comparably, the simulation shows that the sidewall make the pressure coefficient Cp decrease, and proper boundary condition can maintain two-dimensional flow at large angles of attack by eliminating the influence of corner vortices.
      PubDate: 2023-01-16
       
  • Experimental Study of Heat Transfer and Film Cooling Performance of
           Upstream Ejected Coolant on a Turbine Endwall

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      Abstract: Abstract An upstream coolant injection that is different from the known leakage flow was introduced to protect the turbine endwall. This coolant is ejected tangentially from a row of cylindrical holes situated at the side of a backward-facing step. In this experiment, the effects of mass flow ratio and leakage slot width on the endwall heat transfer characteristics were investigated. The dimensionless heat transfer coefficient (Nu) and adiabatic film cooling effectiveness (η) on an axisymmetric turbine endwall were measured by the stable-state thermochromic liquid crystal (TLC) technique and the pressure sensitive paint (PSP) technique, respectively. Three mass flow ratios (MFR) of 0.64%, 0.85%, and 1.07%, as well as two leakage slot widths (W) of 3.93 mm, and 7.86 mm were considered. Results indicate that the injection film suppresses the strength of the passage vortex, which leads to the coolant covering almost the entire endwall. This result is more evident for the higher MFR cases, meanwhile, the corresponding averaged film cooling effectiveness is increased with the enhancement of the MFR. However, the case with a higher MFR produces a higher heat transfer coefficient distribution, especially in the region close to the leakage slot edge. Besides, when the W is lower, the endwall presents a higher η and a lower Nu for all the cases, which can guide the optimal design of the endwall.
      PubDate: 2023-01-12
       
  • A New Nonspherical Oxidation Model of Metal Particles

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      Abstract: Abstract This paper analyzes the oxidation law of metal particles and proposes a new oxidation reaction rate model, based on measurements of thermogravimetric-mass spectrometer (TG-MS), X-ray diffractometer (XRD) and scanning electron microscope (SEM). The model is named EBM (egg broken model) with a formula of exponential law. According to the model, the aluminum particles do not react in a spherical shape, but crack and the melted metal inside flows out to form a new nonspherical surface and the reaction rate is still determined by the surface area. The model is verified with heating rates of 5°C/min, 10°C/min and 25°C/min, and with particle size of 1–2 µm, 8–9 µm and 20–22 µm. Many models are based on spherical hypothesis and the new model gives a different physical illustration to explain oxidation progress of metal particles. The new model gives an exponential law, which fits the experimental data well, and it may be useful to understand oxidation mechanism of metal particles.
      PubDate: 2023-01-11
       
  • Analysis of Spray Evaporation in a Model Evaporating Chamber: Effect of
           Air Swirl

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      Abstract: Abstract Spray evaporation of liquid fuels in a turbulent flow is a common process in various engineering applications such as combustion. Interactions between fuel droplets (discrete phase) and fluid flow (continuous phase) have a considerable effect on liquid fuel evaporation. In this paper, both the single- and two-phase modeling of liquid fuel injection into a model evaporating chamber are presented. The influences of important issues such as turbulence models, coupling between gas phase and droplets, secondary break-up and air swirling on the current spray simulation are investigated. Accordingly, the shear stress transport turbulence model, Taylor analogy break-up and two-way coupling models are applied to simulate the two-phase flow. Atomization and spray of fuel droplets in hot air are modeled employing an Eulerian-Lagrangian approach. The current results show an acceptable agreement with the experiments. Adjacent the fuel atomizer, bigger droplets are detected near the spray edge and minor droplets are situated in the middle. With increasing the droplets axial position, the droplets diameter decreases with a finite slope. The smaller droplets have a deeper penetration, but their lifetime is smaller and evaporate sooner. A linear relation between penetration and lifetime of smaller droplets is detected. Maximum droplet penetration and mean axial velocity of gas phase are observed for no air swirling case. The effect of variation of swirl number on the lifetime of droplets is almost negligible. By enhancing the swirl number, the uniformity of droplet size distribution is reduced and some large droplets are formed up in the domain.
      PubDate: 2023-01-07
       
  • Brief Information for Authors

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      PubDate: 2023-01-01
       
  • Thermodynamic Analysis of Solid Oxide Fuel Cell Based Combined Cooling,
           Heating, and Power System Integrated with Solar-Assisted Electrolytic Cell
           

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      Abstract: Abstract Syngas fuel such as hydrogen and carbon monoxide generated by solar energy is a promising method to use solar energy and overcome its fluctuation effectively. This study proposes a combined cooling, heating, and power system using the reversible solid oxide fuel cell assisted by solar energy to produce solar fuel and then supply energy products for users during the period without solar radiation. The system runs a solar-assisted solid oxide electrolysis cell mode and a solid oxide fuel cell mode. The thermodynamic models are constructed, and the energetic and exergetic performances are analyzed. Under the design work conditions, the SOEC mode’s overall system energy and exergy efficiencies are 19.0% and 20.5%, respectively. The electrical, energy and exergy efficiencies in the SOFC mode are 51.4%, 71.3%, and 45.2%, respectively. The solid oxide fuel cell accounts for 60.0% of total exergy destruction, caused by the electrochemical reactions’ thermodynamic irreversibilities. The increase of operating temperature of solid oxide fuel cell from 800 °C to 1050 °C rises the exergy and energy efficiencies by 11.3% and 12.3%, respectively. Its pressure from 0.2 to 0.7 MPa improves electrical efficiency by 13.8% while decreasing energy and exergy efficiencies by 5.2% and 6.0%, respectively.
      PubDate: 2023-01-01
       
  • Molecular Understanding of Heat Transfer in Ionic-Liquid-based Electric
           Double Layers

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      Abstract: Abstract Electric double layer capacitors (EDLCs) as promising electrical energy storage devices are faced with thermal management issues, which concern the performance and lifetime of the devices. Heat transfer at the solid-liquid interface has a crucial impact on the thermal management of EDLCs. In this work, the interfacial thermal resistance (Kapitza resistance) of the interface between ionic liquid (IL) and graphite electrode is determined, and the heat transfer resistance in the uncharged/charged system with different temperatures is investigated via molecular dynamics simulations. It is found that Kapitza resistance near the negative-charged interface decreases by 23% compared to that in the uncharged system, while the temperature effect on Kapitza resistance is little in our simulation. The unique ion layer structure of ILs formed at the interface may influence the thermal transport performance. Simulations are performed to investigate the effects of surface charge and working temperature on the heat transfer resistance of interfacial ILs from three aspects: ionic spacing, inter-ion interaction, and heat capacity. With the influence of surface charge, ionic spacing in the electric double layer is found to decrease while the inter-ion interaction and heat capacity increase, leading to the reduction in thermal resistance of interfacial ILs. However, rising temperature has small effects on the three thermal properties, with a slight tendency to increase the thermal resistance of ILs.
      PubDate: 2023-01-01
       
  • Assessment of Flue Gas Reinjecting Operating Strategy in Performance of
           CCHP System using Energy Level Difference Analysis

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      Abstract: Abstract A proper operating strategy is helpful to improve the off-design performance of combined cooling, heating and power (CCHP) systems, providing high efficiency and low emission. The energy level difference graphic analysis method is used to identify energy level as well as exergy destruction of the part-load process. This method illustrates the energy efficiency upgrading mechanism of the flue gas reinjecting (FGR) operating strategy. It is referenced to a reducing turbine inlet temperature (TIT) operating strategy. By comparison, the FGR operating strategy leads to a 2.62% exergy distribution reduction in a gas turbine at an 85% load level due to the decrease of the energy level difference. When the output power is reduced further, the FGR operating strategy is supplanted by the TIT operating strategy with the limit of compressor inlet temperature. However, the opposite results of exergy distribution are presented in the exhaust-heat recovery devices. A heat-driven refrigeration and power cycle is introduced in a typical CCHP system as a solution. Moreover, the results suggest that the operational flexibility of the CCHP system is improved by enlarging the ratio of cooling to electricity.
      PubDate: 2023-01-01
       
  • Experimental and Numerical Research on Strengthening the Performance of
           Wave Rotor Equipment with Curved Passages

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      Abstract: Abstract The wave rotor technology is an energy exchanging approach that achieves efficient energy transfer between gases without using mechanical components. The wave rotor technology has been successfully utilized in gas turbine cycle systems, gas expansion refrigeration and a variety of other industrial domains, yielding numerous researches and application outcomes. The structure of wave rotor passages inside which the energy exchange between gases is realized has an important impact on the equipment performance. In this study, based on gas wave ejection technology, the first application trials of an expansion wave rotor with curved passages were conducted. Additionally, the performance enhancing effect and mechanism of curved passages on the energy exchanging process were studied precisely by the combination of experimental and three-dimensional numerical simulation methods. The experimental results demonstrate that the curved passage rotor (CIR rotor) employed in this research has a maximum isentropic efficiency of 61.6%, and the CIR rotor achieves higher efficiency than the straight passage rotor (STR rotor) on all working conditions in this study. Compared with the STR rotor, the maximum efficiency improving ratio of CIR rotor can exceed 14.2% at each experimental expansion ratio, and the maximum relative increments of ejection rate are more than 5%. In addition, the CIR rotor can also effectively increase the proportion of static pressure in total pressure of the medium-pressure gas, and reduce the device power consumption. The three-dimensional numerical investigations revealed the principle of gas ejection in the wave rotors and explained why the CIR rotor performed better. According to the numerical findings, the curved passages of the CIR rotor may effectively minimize various energy losses created in the processes of high-pressure gas incidence, exhausting flow in nozzle, and high-speed gas flow in the passages.
      PubDate: 2023-01-01
       
  • Modeling of Packed Bed Methanol Steam Reformer Integrated with Tubular
           High Temperature Proton Exchange Membrane Fuel Cell

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      Abstract: Abstract This work proposes a novel tubular structure of high-temperature proton exchange membrane fuel cell (PEMFC) integrated with a built-in packed-bed methanol steam reformer to provide hydrogen for power output. A two-dimensional axisymmetric non-isothermal model was developed in COMSOL Multiphysics 5.4 to simulate the performance of a tubular high temperature proton membrane fuel cell and a packed bed methanol reformer. The model considers the coupling multi-physical processes, including methanol reforming reaction, water gas shift reaction, methanol cracking reaction as well as the heat, mass and momentum transport processes. The sub-model of the tubular packed-bed methanol reformer is validated between 433 K and 493 K with the experimental data reported in the literature. The sub-model of the high temperature proton exchange fuel cell is validated between 393 K and 433 K with the published literature. Our results show that power output and temperature distribution of the integrated unit depend on methanol flow rates and working voltages. It was suggested that stable power generation performance of 0.14 W/cm2 and temperature drop in methanol steam reformer of ≤10 K could be achieved by controlling the methanol space-time ratio of ≥250 kg·s/mol with working voltage at 0.6 V, even in the absence of an external heat source.
      PubDate: 2022-12-24
       
  • Effect of Blending Ratio on the Sodium Release Behaviors, Ash Slagging
           Characteristics and Char Gasification Performances during Co-gasification
           of Zhundong Coal with Wuhai Coal

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      Abstract: Abstract Some ash related problems, such as slagging at furnace bottom and fouling at the air pre-heater surface, are frequently encountered during circulating fluidized bed gasification (CFBG) of Zhundong coal. Low ash fusion temperatures (AFTs) and intense sodium release should be responsible for those problems. In industry, coal blending is deemed to be a feasible method to both improve AFTs and control sodium release. In this work, Wuhai coal was selected as blending coal. The ratio is varied from 0% to 40% by mass with 10% interval. The mixed samples were gasified by steam at 950°C in a lab-scale furnace. Some key indices, such as sodium release behaviors, ash slagging characteristics and char gasification performances, were investigated by ICP-OES, AFTs, XRD and TG analyzers, respectively. The results indicated that coal blending could significantly decrease sodium release behaviors. For ash slagging characteristics, it is surprised to find that three out of four AFTs (deformation temperature, softening temperature, hemispherical temperature) show an U-shaped correlation with blending ratio, indicating that a low ratio possibly causes more severe ash slagging problem. It is ascribed to the formation of substantial percentage of fusible Na-containing silicates and aluminosilicates. In addition, coal blending greatly increases ST-DT, implying that the ability of resistance to bed temperature fluctuation is markedly enhanced. Due to the high level of alkali and alkaline species, the synergistic effect is clearly observed during co-gasification. Taking all key indices into consideration, 30% blending ratio of Wuhai coal is recommended.
      PubDate: 2022-12-22
       
  • Experimental Investigation of Flame Dynamics Based on High-Speed Images in
           Swirl Combustion Systems

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      Abstract: Abstract The interaction mechanism of internally-staged-swirling stratified flame is complex, and the pilot flame has a manifest influence on flame stability. To study this, a series of experimental investigations for the pilot flame has been carried out in a model swirl combustor by only supplying the pilot fuel. The CH* chemiluminescence images of the pilot flame are acquired by a high-speed camera with a CH* bandpass filter, whose dynamic characteristics are identified by image statistical analysis and proper orthogonal decomposition (POD) analysis. And the fast algorithm based on matrix theory proposed in this paper increases the operation efficiency and operability of POD. With the pilot equivalence ratio Φ increase, the pilot flame gradually shows an unstable state, whose POD energy distribution is significantly different. In the unstable state, the flame dynamics include three modes—spiral motion mode, flame shedding mode, and axial oscillation mode, whose formation reasons have also been further analyzed in combination with the experimental characteristics. And the fast Fourier transform (FFT) analysis of the time coefficients for the first four POD modes indicates all the dominant frequency is 280 Hz, which means the model combustor is in resonance. In addition, a sensitivity analysis based on the different image resolutions further reveals the robustness of the POD method and its optimization direction. These results emphasize the important influence of the pilot fuel flow rate on the stability of the pilot flame.
      PubDate: 2022-12-22
       
  • Energy, Exergy, and Exergoeconomic Analysis of Solar-Driven Solid Oxide
           Electrolyzer System Integrated with Waste Heat Recovery for Syngas
           Production

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      Abstract: Abstract Syngas fuel generated by solar energy integrating with fuel cell technology is one of the promising methods for future green energy solutions to carbon neutrality. This paper designs a novel solar-driven solid oxide electrolyzer system integrated with waste heat for syngas production. Solar photovoltaic and parabolic trough collecter together drive the solid oxide electrolysis cell to improve system efficiency. The thermodynamic models of components are established, and the energy, exergy, and exergoeconomic analysis are conducted to evaluate the system’s performance. Under the design work conditions, the solar photovoltaic accounts for 88.46% of total exergy destruction caused by its less conversion efficiency. The exergoeconomic analysis indicates that the fuel cell component has a high exergoeconomic factor of 89.56% due to the large capital investment cost. The impacts of key parameters such as current density, operating temperature, pressure and mole fraction on system performances are discussed. The results demonstrate that the optimal energy and exergy efficiencies are achieved at 19.04% and 19.90% when the temperature, pressure, and molar fraction of H2O are 1223.15 K, 0.1 MPa, and 50%, respectively.
      PubDate: 2022-12-09
       
 
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