International Journal of Environmental Science and Development

Abstract—This paper presents the results of an experimental study on the thermal and pollutant-emission characteristics of a biogas-fired inverse diffusion flame (IDF) impinging vertically upwards on a horizontal copper plate. The IDF burner used in the experiment has a central air jet surrounded circumferentially by twelve outer fuel jets. The heat flux at the stagnation point and the radial distribution along the impingement plate were measured with a heat flux sensor while the temperatures were measured with thermocouples. The effects of Reynolds number, overall equivalence ratio, and nozzle-to-plate distance on the heat flux were investigated. The temperature and heat flux were calculated within a radial distance of 30 mm from the stagnation point of the flame, while air jet Reynolds numbers were chosen at 1000, 1500, 2000, 2500, 3000, 3500 and 4000. All the operation conditions were measured under both equivalence ratios of 2 and 3 with three different nozzle-to-plate distances of 60mm, 90mm and 120mm (corresponding to the H/d = 10, 15 and 20). Besides, four different air pollutants emitted from the flame: HC, CO₂, CO and NO₂ were measured. Heat flux and flame temperature distribution were affected by the equivalence ratio, Reynolds number and nozzle-to-plate distance. Higher equivalence ratio leads to occurrence of higher temperature and heat flux when the other conditions remain unchanged. The maximum temperature occurs at the stagnation point when the plate is above the flame, whereas the heat flux is low around the stagnation point when the flame is truncated by the plate. As for air pollutant emissions, HC is rare when the combustion is complete while CO increases with incomplete combustion. However, CO₂ emission index is quite high which should be reduced in application.

Index Terms—Inverse diffusion flame, biogas fuel, thermal characteristics.

The authors are with the Mechanical Engineering Department, The Hong Kong Polytechnic University, Hong Kong (e-mail: lei.me.lyu@connect.polyu.hk, liang.an@polyu.edu.hk, chun.wah.leung@polyu.edu.hk).

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Cite: Lei Lyu, Liang An, and Chun Wah Leung, "Thermal and Pollutant-Emission Characteristics of Inverse Diffusion Biogas/Air Flame," International Journal of Environmental Science and Development vol. 9, no. 6, pp. 162-166, 2018.