Heat Transfer Characteristic for Premixed Flame Jet from Swirl Chamber

The objective of this research is to study flame structure and heat transfer characteristics for the premixed flame jet from the swirling chamber. In this study, LPG and air was utilized as gas fuel and oxidizer for a premixed flame. The equivalence ratios () of LPG and air were considered at 0.8, 1.0, and 1.2 under a Reynolds number Re = 4,000. The swirl flame was generated by double tangential inlets in cylindrical chamber. The diameter of chamber was fixed at D = 20 mm and the hydraulic diameter of the inlet was Dh = 5 mm. In this study, the effect of chamber geometry on flame structure was investigated by varying the chamber from H = 2.2Dh to 7.0Dh. The structures and temperature of the free flame jet was recorded with camera and measured with a thermocouple. The heat transfer rate of impinging flame jet was also measured at distance from chamber outlet to flame impingement surface varying from L = 4Dh to 10Dh. The results show that the maximum of flame temperature occurs at =1.2. Impinging flame jet for case of chamber height at H = 4.6Dh and impingement distance at L = 4Dh give the highest heat transfer for all equivalence ratios due to the reaction zone of combustion reached to approach near the heat transfer surface.

Download Full-text

Effect of Swirl Intensity on the Heat Performance of a Premixed Circular Impinging Flame Jet With Swirl Induced

Heat Transfer: Volume 1 ◽

10.1115/ht2005-72750 ◽

2005 ◽

Author(s):

X. Q. Huang ◽

C. W. Leung ◽

C. K. Chan

Keyword(s):

Heat Transfer ◽

Flame Temperature ◽

Small Scale ◽

Uniform Heat Flux ◽

Swirl Ratio ◽

Heat Transfer Characteristics ◽

Flow And Heat Transfer ◽

Swirl Angle ◽

Swirl Intensity ◽

Impinging Flame

Swirl has been successfully introduced to a small scale premixed circular impinging flame jet under low Reynolds number. The study on the flow and heat transfer characteristics of such a swirling impinging flame found that it could provide a more uniform heat flux and flame temperature distribution around the stagnation point. The swirl ratio, which is indicated by swirl angle and axial velocity at the exit of the nozzle is changed to investigate the effect of swirling intensity on the heat performance of the flame jet.

Download Full-text

Porosity and Permeability Effects on Centerline Temperature Distributions, Peak Flame Temperature, Flame Structure, and Preheating Mechanism for Combustion in Porous Media

Journal of Energy Resources Technology ◽

10.1115/1.2424964 ◽

2006 ◽

Vol 129 (1) ◽

pp. 54-65 ◽

Cited By ~ 10

Author(s):

S. R. Khatami F. ◽

B. Safavisohi ◽

E. Sharbati

Keyword(s):

Heat Transfer ◽

Porous Medium ◽

Porous Media ◽

Flame Structure ◽

Flame Temperature ◽

Geometrical Parameters ◽

Temperature Distributions ◽

Porosity And Permeability ◽

Porous Zone ◽

Centerline Temperature

The applicability and usefulness of combustion in porous media is of much interest due to its competitive combustion efficiency and lower pollutants formation. In the previous works, the focus has been on the effects of combustion and heat transfer parameters such as excess air ratio, thermal power, solid conductivity, convective heat transfer coefficient, and radiation properties on centerline temperature and pollutant formations. A premixed combustion scheme and a fixed porous medium with constant geometrical parameters have been used in these works; therefore, the effects of porous material parameters have been less considered. In this research, the effects of geometrical parameters of porous medium, namely porosity and permeability, on centerline temperature distributions, peak flame temperature, flame structure, and gas mixture preheating have been investigated by numerical methods. To this, a two-dimensional axis-symmetric physical model of porous burner is considered. As the most typical porous burners, a two stage one which has preheating porous zone (PPZ) and combustion porous zone (CPZ) is studied. The continuity, momentum, energy, turbulence, and species transport equations are solved employing a one-step chemical reaction mechanism with an eddy-dissipation model for rate of reactions. The turbulence is modeled with two transport equations which are not considered in similar works. The combustion regime is assumed to be diffusion and combustion parameters are fixed in all cases. Porosity effects on the structure and temperature characteristic of the flame are probed in a wide range for PPZ and CPZ. Critical permeability is defined and permeability effects on flame characters in both of the preheating and combustion regions are studied thoroughly.

Download Full-text