Effects of initial pressure and temperature on explosion characteristics of DME-blended LPG mixtures in obstructed confined pipeline

Global warming and the emission of carbon dioxide gases have compelled key stakeholders and policymakers to adopt stringent measures focused majorly on the development of clean, economical and environmentally friendly alternative energy sources. In particular, blended mixture of dimethyl ether and liquefied petroleum gas have showed potential applications in areas such as domestic cooking and combustion engines. Unfortunately, both dimethyl ether and liquefied petroleum gas are extremely explosive and may result in high-risk fire and explosion accidents when leaked or suddenly released. Therefore, with the increasing practical applications of the blended mixture, extensive research on the combustion and explosion characteristics of the mixture of dimethyl ether and liquefied petroleum gas is absolutely imperative both at room and elevated temperatures and pressures.

In a recent paper published in the Fuel journal, Yuying Chen (Ph.D. Student), Professor Xinming Qian, Dr. Qi Zhang, Liye Fu (Ph.D. Student), and Professor Mengqi Yuan from the Beijing Institute of Technology explored the effects of initial pressure and temperature on the explosion characteristics of dimethyl ether blended liquefied petroleum gas mixtures. A two-dimensional turbulent mathematical model for explosion of liquefied petroleum gas/dimethyl ether mixture in an obstructed confined pipeline was developed. And the mixture with 30% dimethyl ether blended was selected as the research object, which is widely used in practice. The main objective was to conduct numerical analysis on the explosion overpressure, flame temperature and flame propagation velocity of the blended mixture at different initial temperatures and pressures.

Results showed that an increase in the initial pressure resulted in a corresponding increase in the maximum explosion overpressure while an increase in the initial temperature reduced the maximum explosion overpressure. The effect of the increase in the initial pressure on the peak flame temperature was very significant at low temperatures below 150kpa and less significant after exceeding 150kpa. However, the peak flame temperature was observed to increase almost linearly with the increase in the initial temperature. Furthermore, an increase in the axial distance resulted in a gradual decrease in the the maximum explosion overpressures and peak temperatures indicating that the explosion risk in an enclosed space decreases with the increase in the distance from the ignition point.

It was worth noting that the flame front under all conditions could not propagate to the end of the pipe due to the effects of the reflected pressure wave. And a change of spherical flame-finger flame-tulip flame was experienced at all conditions. Additionally, the change of the flame velocity was divided into three stages: rapid growth, gradual decline and backward propagation. During the rapid growth stage, an increase in the initial pressure and temperature resulted in a corresponding increase both in the velocity and acceleration of the flame. The maximum flame velocity increased with the increase of initial pressure up to 200kpa after which the influence of the initial pressure became weak. However, the maximum flame velocity increased roughly linearly with the increase in the initial temperature.

In summary, the Beijing Institute of Technology research team has successfully explored the explosion characteristics of dimethyl ether blended liquefied petroleum gas mixtures at various initial pressures and temperatures. The study insights highlight the importance of explosion characteristics especially in managing and controlling fires and related accidents caused by leakages or unexpected release. Professor Mengqi Yuan explained that this approach will enhance the effective utilization of the dimethyl ether/ liquefied petroleum gas mixture as an alternative fuel source.