73 / 2023-06-05 15:47:32

Numerical Simulation Study on the Influence of Small Tube Disturbance on the Propagation of Premixed Mixture Detonation

Small tube disturbance; Detonation behaviours; Numerical simulation;Safety Problem

Due to the wide flammability limit and low ignition energy of hydrogen, it can have extremely serious impacts in explosion accidents or extremely high combustion efficiency in propulsion system. In the integrated pipe gallery system in of cities, various obstacles such as valves, tubes, etc. may be encountered by hydrogen after leakage. Any small disturbance may promote the transition from explosion to detonation, bringing incalculable harm. So the study on the influence of disturbance on the propagation of premixed mixture detonation is helpful to achieve the safe and efficient application of hydrogen premixed mixture, thereby further ensuring ensure the urban safety.

The influence of small tube disturbance on detonation wave propagation is complex. The detonation propagation velocity and cellular structure of detonation waves obtained through conventional experimental research such as pressure sensors, smoked foils, schlieren images, etc. cannot clearly and deeply observed the microscopic phenomenon and mechanism of detonation waves. For example, the changes in frontal flow field of detonation waves under sudden boundary conditions. This paper used Fluent numerical simulation software to simulate the hydrogen premixed mixture detonation propagation process from an 80mm circular tube into an annular tube composed of small tubes of different sizes (d = 20 mm, 40 mm, 60 mm) in a two-dimensional plane. Network independence verification and time step independence verification were performed on the model. The waveform change of detonation wave at the sudden change of tube boundary was analyzed in detail. And the influence of small tube disturbance positions on detonation wave propagation was briefly discussed.

The detonation wave entered the abrupt convergent tube, which means entering the annular tube and the small tube from the 80mm circular tube. Due to the sudden reduction of the cross-section, the tube boundary produced a compression effect on the detonation wave. Therefore, the peak pressure of the detonation wave and the flame temperature in the reaction zone in the annular tube and the small tube would increase to a certain extent. The detonation wave collided with the cross-section of the small tube wall. A local high-temperature and high-pressure zone was generated, accompanied by the formation of reflected waves and diffracted waves. The reflected wave propagates backwards, while the diffracted wave propagates towards both sides of the tube wall. The small tube disturbance only hindered the local planar detonation area facing the cross-section of the tube wall. And the diffracted wave disturbed the detonation wave reaction zone on both sides of the small tube wall. Furthermore, different sizes of small tubes resulted in different disturbance positions. So the local detonation waves exhibited different shapes of reflected waves. And different disturbance positions had a significant impact on the propagation of diffracted waves. Downward diffracted waves collided and reflected at the tube axis. Under the disturbance of d = 40 mm and d = 60 mm, the upward diffraction wave collided and reflected with the outer tube wall. However, only the monitoring point at the upper part of the cross-section mutation under the disturbance of d = 40 mm small tubes can measure two adjacent pressure peaks.