Abstract: To study the influence of pipe length on the coupled relationship between the flow velocity of detonation front and peak overpressure caused by gas deflagration, the propagation characteristics of overpressure and velocity in a closed end pipe was studied by numerical simulation in this paper. The results show that all of the last explosion overpressure attenuate to 0.7~0.9 MPa in the pipes with different lengths. For the short pipes, the peak value of velocity is relatively small, and the decline trend of the peak velocity value is relatively gentle, while the oscillation frequency of velocity is relatively fast in the positive and negative interval. For the relatively long pipes, the peak value of velocity is relatively large, and the decline of peak value is fast, while the oscillation frequency is small. In addition, there exists a critical length between 15 m and 20 m. When the pipe length is larger than the critical length, two minimum overpressure peaks will appear, and when the pipe length is shorter than the critical length, only one minimum overpressure peak appears. Moreover, the first peak value of velocity is in good proportion to the overpressure. The coupled relation between the first peak value of velocity and overpressure was obtained by the numerical data fitting. The results can provide reference to explosion prevention and control in the limited space.

Key words: gas explosion, length, velocity, overpressure, oscillation