Experimental study on the effect of airflow conditions on the combustion characteristics of methane hydrate

Abstract

Due to its large reserves and cleanliness, methane hydrate is widely regarded as a promising energy source. The study of the effect of airflow conditions on the combustion characteristics of methane hydrate can provide a theoretical basis for various engineering applications, such as realizing the method of in-situ combustion mining, improving the safety of mining and predicting the development of fire during the storage and transportation of methane hydrates. In this paper, the combustion process of methane hydrate under the conditions of natural convection, external horizontal airflow and internal vertical airflow was analyzed. This way, the effect of the form of airflow on combustion was studied, and the effect of airflow velocity on the characteristics of flame was documented. The results demonstrated that, under the conditions of natural convection and horizontal airflow, there was an “eruption phenomenon”, during which the ice layer broke and a large amount of methane gas instantly escaped, forming a high and bright flame. The vertical airflow reduced the mass transfer resistance of methane gas, whereas the combustion process was more stable, and the height of flame was more uniform. Under the condition of horizontal airflow, the tilted flame increased the heat transfer to the surface of hydrate. The flame tilt angles were different in different combustion stages. The flame tilt angle in the intensive combustion stage (61.26°) was smaller than that in the steady combustion stage (70.85°), whereas a higher combustion rate had a stronger capability to oppose the horizontal wind.