Effect of Pulsating Flame Jet on Flow and Heat Transfer  Characteristics

Wongsathon Boonyopas; Nuttamas Uppatam; Chattawat Aroonrujiphan; Natthaporn  Kaewchoothong; Somchai Sae-ung; Chayut Nuntadusit

Authors

Wongsathon Boonyopas Department of Mechanical Engineering, Faculty of Engineering, Prince of Songkla University, Hatyai, Songkhla 90110, Thailand
Nuttamas Uppatam Department of Mechanical Engineering, Faculty of Engineering, Prince of Songkla University, Hatyai, Songkhla 90110, Thailand
Chattawat Aroonrujiphan Department of Mechanical Engineering, Faculty of Engineering, Prince of Songkla University, Hatyai, Songkhla 90110, Thailand
Natthaporn Kaewchoothong Department of Mechanical Engineering, Faculty of Engineering, Prince of Songkla University, Hatyai, Songkhla 90110, Thailand
Somchai Sae-ung Department of Mechanical Engineering, Faculty of Engineering, Prince of Songkla University, Hatyai, Songkhla 90110, Thailand
Chayut Nuntadusit Energy Technology Research Center (ETRC), Prince of Songkla University, Hatyai, Songkhla 90110, Thailand

Keywords:

Premixed flame jet, pulsating frequency, heat transfer enhancement, flame structure, impinging jet

Abstract

This research aims to study the effect of pulsating frequency on flame structure and heat transfer characteristics of premixed flame from a pipe nozzle. The LPG and air were used as gas fuel and oxidizer. The equivalence ratios ( ) were evaluated at 0.8, 1.0, and 1.2 under a constant Reynolds number Re = 500. The effect of nozzle-to-impingement surface distance ratio was investigated at H = 2D to 10D, here D is the nozzle diameter at 12 mm. The frequency of pulsating (f) was varied from f = 0 to 10 Hz using a solenoid valve. The flame structures of free flame jet and the impinging flame jet were recorded with a digital camera. The average heat flux on impingement surface was measured with water cooling plate and evaluated from the heat balance of the cooling water. The results show that the pulsating of flame jet become having gap on flame and the mushroom appear at the end of flame. The size of mushroom structure becomes larger when increasing the frequency. While the non-pulsating jet did not appear in this structure. Pulsating flame jet can increase the overall average heat flux on the impingement surface up to about 12% for case of = 1.2 and H = 2D and f = 10 Hz. when compared to case of f = 0 Hz.