Flame spread and combustion characteristics of two adjacent jatropha oil droplets

• Published in: Fuel (Guildford) 2021-02, Vol.285, p.119077, Article 119077
• Main Authors: Wang, Jigang, Zhang, Hucheng, Zhang, Qibin, Qiao, Xinqi, Wang, Xiaorong, Ju, Dehao, Sun, Chunhua
• Format: Article
• Language: English
• Subjects: Boiling points; Calorimetry; Combustion; Differential scanning calorimetry; Droplets; Fatty acids; Flame spread; Jatropha oil; Liquid chromatography; Mass spectrometry; Mass spectroscopy; Oil; Pyrolysis; Room temperature; Superheating; Thermogravimetric analysis; Velocity
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/j.fuel.2020.119077

•Combustion mechanism and dynamics of jatropha oil droplets are studied.•Flame spread velocity and flame spread limit of jatropha oil droplets are determined.•The flame spread behavior of jatropha oil droplets is classified into three modes. The present study investigated the flame spread and combustion characteristics of two jatropha oil droplets, droplet A and B. Specifically, the pyrolysis characteristics of jatropha oil were studied using thermogravimetric and differential scanning calorimetry (DSC) analysis. Liquid chromatography-mass spectrometry (LC-MS) was used to analyze the components in jatropha oil. Then, the flame spread from droplet A to droplet B and combustion dynamics of two droplets were studied in a constant volume chamber under atmospheric pressure and room temperature (300 K). The effects of normalized droplets spacing S/d0 (2.7–4.9) on flame spread were also studied. The results showed that the combustion of jatropha oil droplet containing three stages: initial expansion stage, quasi-steady combustion stage and micro-explosive combustion stage. Periodic puffing and micro-explosion occurred during micro-explosive combustion stage. This is due to the superheating of low boiling-point components produced by pyrolysis of long-chain fatty acids in jatropha oil. The duration of initial expansion stage increases significantly with the increase of droplet spacing. When the normalized droplet spacing reaches 4.9, the second droplet cannot ignite and reached flame spread limit. Interestingly, the flame spread velocity increase at first and then decrease with increase droplet spacing. This is because the diffusion flame is cooled by unburned droplet when the spacing is relatively small. However, when the spacing is relatively large, the flame spread velocity mainly depends on the duration of second droplet in first stage.