A Combined Experimental and Numerical Study of Heat Transfer Characteristics for Methane/Air Flame Impinging Normally on a Flat Surface

2008 ◽  
Author(s):  
Subhash Chander ◽  
Anjan Ray
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Flat Surface ◽  
Numerical Study ◽  
Combustion Process ◽  
Sharp Peak ◽  
Numerical Code ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Simulation Results

An experimental and numerical study has been conducted to determine the heat transfer characteristics for laminar methane/air flame impinging on a flat surface. A commercial numerical code (FLUENT) was used to simulate the laminar premixed flame. Simulation results were compared with the experimental results and there was good agreement between the results. The purpose of simulation is to understand the impinging flame structure and the chemical physical combustion process. Further, simulation results are presented to define the reasons for a sharp peak in radial heat flux distribution when the inner reaction zone was intercepted by the plate. Here, it has been observed that the resultant effect of peak in radial velocity, axial velocity and velocity magnitude along with peak in the temperature and temperature gradient caused that sharp peak in heat flux value in the radial direction.

Heat Transfer Characteristics of a Radial Jet Reattachment Flame

1997 ◽  
Vol 119 (2) ◽  
pp. 258-264 ◽  
Author(s):  
J. W. Mohr ◽  
J. Seyed-Yagoobi ◽  
R. H. Page
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Combustion Process ◽  
Local Heat ◽  
Operating Conditions ◽  
Recirculation Region ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Impingement Surface

A Radial Jet Reattachment Combustion (RJRC) nozzle forces primary combustion air to exit radially from the combustion nozzle and to mix with gaseous fuel in a highly turbulent recirculation region generated between the combustion nozzle and impingement surface. High convective heat transfer properties and improved fuel/ air mixing characterize this external mixing combustor for use in impingement flame heating processes. To understand the heat transfer characteristics of this new innovative practical RJRC nozzle, statistical design and analysis of experiments was utilized. A regression model was developed which allowed for determination of the total heat transfer to the impingement surface as well as the NOx emission index over a wide variety of operating conditions. In addition, spatially resolved flame temperatures and impingement surface temperature and heat flux profiles enabled determination of the extent of the combustion process with regards to the impingement surface. Specifically, the relative sizes of the reaction envelope, high temperature reaction zone, and low temperature recirculation zone were all determined. At the impingement surface in the reattachment zone very high local heat flux values were measured. This study provides the first detailed local heat transfer characteristics for the RJRC nozzle.

Numerical Study on Aero-Thermal Performance of HP Turbine Endwalls Under Influence of Hot Streak and High Mainstream Turbulence

2016 ◽  
Author(s):  
Zhiduo Wang ◽  
Wenhao Zhang ◽  
Zhaofang Liu ◽  
Chen Zhang ◽  
Zhenping Feng
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Turbulence Intensity ◽  
Wall Temperature ◽  
Numerical Study ◽  
Leading Edge ◽  
Heat Transfer Characteristics ◽  
Adiabatic Wall ◽  
Transfer Characteristics ◽  
Hot Streak

In this paper, unsteady RANS simulations were performed at two hot streak (HS) circumferential positions with inlet turbulence intensity of 5% and 20%. The interacted HS and high mainstream turbulence effects on endwall heat transfer characteristics of a high-pressure (HP) turbine were discussed by analyzing the flow structures and presenting the endwall adiabatic wall temperature, heat transfer coefficient (HTC) and heat flux distributions. The results indicate that both the wall temperature and HTC increase with the turbulence intensity at most stator endwall regions. In addition, the increase of wall temperature plays a greater role than HTC of influencing the wall heat flux. However, higher turbulence intensity decreases the intensity of the stator passage horse-shoe vortex, also the corresponding region HTC and heat flux are reduced. In rotor passage, the variation of HS circumferential position would alter the hub and casing endwall temperature, however, the discrepancy is weakened at higher turbulence. The elevated HS attenuation at higher turbulence results in temperature augmentation at the leading edge of rotor hub and casing endwalls, while temperature decrease after 50% axial chord, thus obtains more uniform temperature distributions on the endwalls. However, the rotor endwall HTC is only augmented significantly at the leading edge on hub endwall, and pressure side and downstream of trailing edge on casing endwall. Variation of HTC and adiabatic wall temperature jointly determines the rotor hub and casing endwall heat flux, and the temperature variation has dominant effects in the most regions. In general, the variation of adiabatic wall temperature and HTC should be considered simultaneously when analyzing the turbine endwall heat transfer characteristics.

scholarly journals Numerical Study on the Flow and Heat Transfer Characteristics of a Second Throat Exhaust Diffuser According to Variations in Operating Pressure and Geometric Shape

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 532
Author(s):  
Seonghwi Jo ◽  
Sanghyeon Han ◽  
Hong Jip Kim ◽  
Kyung Jin Yim
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Numerical Study ◽  
Geometric Shape ◽  
Oblique Shock Wave ◽  
Flow Section ◽  
Operating Pressure ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer

A numerical study was conducted to investigate the flow and heat transfer characteristics of a supersonic second throat exhaust diffuser for high-altitude simulations. The numerical results were satisfactorily validated by the experimental results. A subscale diffuser using nitrogen was utilized to investigate starting pressure and pressure variation in the diffuser wall. Based on the validated numerical method, the flow and heat transfer characteristics of the diffuser using burnt gas were evaluated by changing operating pressure and geometric shape. During normal diffuser operation without cooling, high-temperature regions of over 3000 K appeared, particularly near the wall and in the diffuser diverging section. After cooling, the flow and pressure distribution characteristics did not differ significantly from those of the adiabatic condition, but the temperature in the subsonic flow section decreased by more than 1000 K. Furthermore, the tendency of the heat flux from the diffuser internal flow to the wall was similar to that of the pressure variations, and it increased with operating pressure. It was confirmed that the heat fluxes of the supersonic and subsonic flows in the diffuser were proportional to the operating pressure to the 0.8 and −1.7 power, respectively. In addition, in the second throat region after separation, the heat flux could be scaled to the Mach number ratio before and after the largest oblique shock wave because the largest shock train affected the heat flux of the diffuser wall.

Effect of Swirl Intensity on Heat Transfer Characteristics of Swirling Flame Impinging on a Flat Surface

2013 ◽  
Author(s):  
Gurpreet Singh ◽  
Subhash Chander
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Stagnation Point ◽  
Flat Surface ◽  
Operating Conditions ◽  
Uniform Heat Flux ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Swirl Intensity ◽  
Swirling Flame

An experimental investigation has been carried out to determine the effect of swirl intensity on heat transfer characteristics of swirling flame impinging on a flat surface. The swirl intensity was varied by using helical vane swirlers having angles of 15°, 30° and 60° (low, medium and high swirl). Qualitative flame structures were studied by taking direct photographs of impinging flames. Experiments were conducted for different helical vane swirlers at different dimensionless separation distances (H/d = 1–6) for fixed value of Reynolds number (Re = 5000) and equivalence ratio (ϕ = 1.0). A dip in heat flux was observed at stagnation point for all levels of swirl. Peak heat flux was observed slightly away from the stagnation point due to centrifugal effect. A comparison of stagnation point heat flux has been done for different swirl intensities and for fixed operating conditions. Most uniform heat flux distribution was obtained corresponds to 30° helical vane swirler (medium swirl) at all separation distances.

Effect of Helical Vane Swirler Geometry on Heat Transfer Characteristics for Compressed Natural Gas/Air Swirling Flame Impinging on a Flat Surface

2013 ◽  
Author(s):  
Subhash Chander ◽  
Gurpreet Singh
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Natural Gas ◽  
Flat Surface ◽  
Geometric Parameters ◽  
Heat Transfer Characteristics ◽  
Compressed Natural Gas ◽  
Transfer Characteristics ◽  
Swirl Intensity ◽  
Swirling Flame

An experimental study has been conducted to investigate the effect of helical vane swirler geometry on heat transfer characteristics for compressed natural gas (CNG)/air swirling flame impinging on a flat surface. Effects of helical vane swirler geometric parameters like, length of helical insert (25 mm, 45 mm and 65 mm), depth of groove on the helical insert (2.5 mm, 3.5 mm and 4.5 mm) and number of helical vanes (8, 10 and 12), on heat transfer characteristics have been studied. All the inserts were having fixed helical vane angle of 45°. Also, the burner exit diameter was kept constant (d = 20 mm). Experiments were conducted at different dimensionless separation distances (6, 4, 3 and 2) for fixed values of Reynolds number (6000) and equivalence ratio (1.3). Significant variation in the heat flux profiles has been observed for different swirler inserts till the radial hump in heat flux. After the radial hump, almost in all cases, the heat flux lines merged together. These variations in the heat flux profiles were due to different level of swirling intensities produced by different swirlers at fixed value of the helical vane swirler angle. It was observed that the heating was comparatively more uniform at larger separation distances (H/d = 6). It has been concluded that defining swirl intensity only with the helical vane swirler angle would be incorrect for such type of swirlers. Other geometric parameters of the swirler like, number of vanes, length of the swirler and the depth of the groove should also be included in swirl intensity definition.

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