scholarly journals Numerical Simulation of the Effects of Oil Gun Location and Oil Feed Rate on Coal Ignition and Burner Wall Temperature in a Tiny Oil Ignition Burner

Energies ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 7597
Author(s):  
Qilei Ma ◽  
Wenqi Zhong ◽  
Xi Chen ◽  
Jianhua Li ◽  
Hui Zhang
Keyword(s):  
Wall Temperature ◽  
Feed Rate ◽  
Side Wall ◽  
Flame Length ◽  
Pulverized Coal ◽  
Combustion Gas ◽  
Flow And Heat Transfer ◽  
Actual Operation ◽  
Temperature Monitor ◽  
Good Agreement

To solve the overheating problem of tiny oil ignition burners’ walls during the firing-up process in a 330 MWe tangentially pulverized coal-fired boiler, a numerical model of a tiny oil ignition burner was carefully built considering combustion, gas–solid flow, and heat transfer. Then, the burner location and oil feed rate were optimized based on the model to prevent the burner’s walls from overheating. The effects of the oil gun extension distance (100, 200, 300, 400, 500 mm) and oil feed rate (160, 140, 120, 100, 80, 70, 60 kg/h) on coal ignition performance and burner wall temperature were carefully investigated. The simulation results showed good agreement with the measured results. The results indicated that decreasing the oil gun distance within the burner diminished the flame length of the co-combustion of oil and pulverized coal, thus lowering the burner wall temperature. Decreasing the oil feed rate appropriately could also reduce the burner wall temperature without influencing the ignition performance. Considering both ignition performance and burner wall temperature, an extension of 400 mm of the oil gun location and an oil feed rate of 160 kg/h were successfully applied to the actual operation without adverse effects. Moreover, it is suggested to move the temperature monitor points from the burner upper wall to the burner side wall.

scholarly journals Large-Eddy Simulation Study of Flow and Heat Transfer in Swirling and Non-Swirling Impinging Jets on a Semi-Cylinder Concave Target

2021 ◽  
Vol 11 (15) ◽  
pp. 7167
Author(s):  
Liang Xu ◽  
Xu Zhao ◽  
Lei Xi ◽  
Yonghao Ma ◽  
Jianmin Gao ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Large Eddy Simulation ◽  
Wall Temperature ◽  
Target Surface ◽  
Impinging Jets ◽  
Small Scale ◽  
Complex Flow ◽  
Eddy Simulation ◽  
Flow And Heat Transfer ◽  
Large Eddy

Swirling impinging jet (SIJ) is considered as an effective means to achieve uniform cooling at high heat transfer rates, and the complex flow structure and its mechanism of enhancing heat transfer have attracted much attention in recent years. The large eddy simulation (LES) technique is employed to analyze the flow fields of swirling and non-swirling impinging jet emanating from a hole with four spiral and straight grooves, respectively, at a relatively high Reynolds number (Re) of 16,000 and a small jet spacing of H/D = 2 on a concave surface with uniform heat flux. Firstly, this work analyzes two different sub-grid stress models, and LES with the wall-adapting local eddy-viscosity model (WALEM) is established for accurately predicting flow and heat transfer performance of SIJ on a flat surface. The complex flow field structures, spectral characteristics, time-averaged flow characteristics and heat transfer on the target surface for the swirling and non-swirling impinging jets are compared in detail using the established method. The results show that small-scale recirculation vortices near the wall change the nearby flow into an unstable microwave state, resulting in small-scale fluctuation of the local Nusselt number (Nu) of the wall. There is a stable recirculation vortex at the stagnation point of the target surface, and the axial and radial fluctuating speeds are consistent with the fluctuating wall temperature. With the increase in the radial radius away from the stagnation point, the main frequency of the fluctuation of wall temperature coincides with the main frequency of the fluctuation of radial fluctuating velocity at x/D = 0.5. Compared with 0° straight hole, 45° spiral hole has a larger fluctuating speed because of speed deflection, resulting in a larger turbulence intensity and a stronger air transport capacity. The heat transfer intensity of the 45° spiral hole on the target surface is slightly improved within 5–10%.

Examination of flame length for burning pulverized coal in laminar flow reactor

2010 ◽  
Vol 24 (12) ◽  
pp. 2567-2575 ◽  
Author(s):  
Jae-Dong Kim ◽  
Gyu-Bo Kim ◽  
Young-June Chang ◽  
Ju-Hun Song ◽  
Chung-Hwan Jeon
Keyword(s):  
Laminar Flow ◽  
Flow Reactor ◽  
Flame Length ◽  
Pulverized Coal

Numerical Prediction of Combustor Heatshield Flow and Heat Transfer With Sub-Grid-Scale Modelling of Pedestals

2001 ◽  
Author(s):  
John K. Luff ◽  
James J. McGuirk
Keyword(s):  
Heat Transfer ◽  
Life Prediction ◽  
Conjugate Heat Transfer ◽  
Energy Equation ◽  
Flow And Heat Transfer ◽  
Extra Energy ◽  
Scale Modelling ◽  
Heat Transfer Calculation ◽  
Proper Account ◽  
Good Agreement

A goal for computational analysis of combustors is to produce a tool for life prediction. An important part of this will be the prediction of the temperature field in the combustor walls. The complex geometries of combustor components make this a formidable task. In this paper a 3D coupled numerical flow/conjugate heat transfer calculation procedure is presented for a combustor heatshield. Proper account must be taken of the blockage and heat transfer effects of pedestals. A scheme has been developed to account for these effects without resolving the pedestals in the computational grid. Extra sink terms are included in the momentum equations to account for pedestal pressure drop. An extra energy equation is solved to determine the local pedestal temperature and to account for heat transfer between pedestals and fluid. This treatment has been validated against empirical data for arrays of pedestals in ducts with good agreement for friction factor and Nusselt number. The methodology is then applied to a generic heatshield geometry to indicate that a viable computational route has been developed for combustor heatshield analysis.

An X-band gain-enhanced bidirectional antenna array using strip-loaded dielectric resonator operating in TE3δ1 mode

2020 ◽  
Vol 12 (9) ◽  
pp. 915-921
Author(s):  
Ling-Ling Yang ◽  
Yan-Hui Ke ◽  
Jian-Xin Chen
Keyword(s):  
Antenna Array ◽  
Dielectric Resonator ◽  
Side Wall ◽  
High Order Mode ◽  
Yagi Antenna ◽  
X Band ◽  
Metallic Strip ◽  
Marchand Balun ◽  
First Time ◽  
Good Agreement

AbstractA bidirectional dielectric resonator (DR) antenna array using back-to-back quasi-Yagi antenna configuration is proposed and implemented for the first time. The DR operating at higher-order TE3δ1 mode is used as a magnetic dipole, applying for the driver of quasi-Yagi antenna. Due to the high-order mode employment, the antenna gain can be enhanced. By partially loading the metallic strip on the side wall of the DR, the gain can be further enhanced. In addition, a simple dual Marchand balun is constructed for feeding the two quasi-Yagi antennas directly for bidirectional radiation. To verify the design concept, a prototype operating at the X-band is fabricated and measured. Good agreement between the simulated and measured results can be observed.

Numerical Study of Circular Tube inserted Arc Belt on Fluid Flow and Heat Transfer under Laminar Flow

2013 ◽  
Vol 561 ◽  
pp. 460-465
Author(s):  
Dong Hui Zhang ◽  
Jiao Gao
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Laminar Flow ◽  
Wall Temperature ◽  
Circular Tube ◽  
Numerical Study ◽  
Resistance Coefficient ◽  
Uniform Wall Temperature ◽  
Flow And Heat Transfer ◽  
Uniform Wall

The objective of this paper is to study the characteristic of a circular tube with a built-in arc belt on fluid flow and heat transfer in uniform wall temperature flows. Numerical simulations for hydrodynamically laminar flow was direct ran at Re between 600 and 1800. Preliminary results on velocity and temperature statistics for uniform wall temperature show that, arc belt can swirl the pipe fluid, so that the fluid at the center of the tube and the fluid of the boundary layer of the wall can mix fully, and plays the role of enhanced heat transfer, but also significantly increases the resistance of the fluid and makes the resistance coefficient of the enhanced tube greater than smooth tube. The combination property PEC is all above 1.5.

Influence of Flow Acceleration on Convection Heat Transfer of CO2 at Supercritical Pressures and Air in a Vertical Micro Tube

2010 ◽  
Author(s):  
Pei-Xue Jiang ◽  
Rui-Na Xu ◽  
Zhi-Hui Li ◽  
Chen-Ru Zhao
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Wall Temperature ◽  
Convection Heat Transfer ◽  
Heat Fluxes ◽  
Working Fluid ◽  
Convection Heat ◽  
Downward Flow ◽  
Flow Acceleration ◽  
Flow And Heat Transfer

The convection heat transfer of CO2 at supercritical pressures in a 0.0992 mm diameter vertical tube at relatively high Reynolds numbers (Rein = 6500), various heat fluxes and flow directions are investigated experimentally and numerically. The effects of buoyancy and flow acceleration resulting from the dramatic property variations are studied. The Results show that the local wall temperature varied non-linearly for both upward and downward flow when the heat flux was high. The difference in the local wall temperature between upward and downward flow is very small when the other test conditions are held the same, which indicates that for supercritical CO2 flowing in a micro tube as employed in this study, the buoyancy effect on the convection heat transfer is insignificant and the flow acceleration induced by the axial density variation with temperature is the main factor leading to the abnormal local wall temperature distribution at high heat fluxes. The predicted temperatures using the LB low Reynolds number turbulence model correspond well with the measured data. To further study the influence of flow acceleration on the convection heat transfer, air is also used as the working fluid to numerically investigate the fluid flow and heat transfer in the vertical micro tube. The results show that the effect of compressibility on the fluid flow and heat transfer of air in the vertical micro tube is significant but that the influence of thermal flow acceleration on convection heat transfer of air in a vertical micro tube is insignificant.

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