Abstract: In order to study the influence of different initial conditions on the explosion pressure of natural gas, an experimental system of a spherical vessel connecting to pressure relief pipe was built. By the pressure sensors placed in spherical vessels and pressure relief pipes, the characteristics of explosion pressure were obtained at the ignition position of 0, 2.7 and 4.7 m from spherical vessel center and the opening ratio of 0%, 25%, 60% and 100%. The results show that when the ignition position is located at 2.7 and 4.7 m, the peak pressure and pressure increase rate in spherical vessel are significantly larger than the values after ignition at 0 m, that setting the pressure relief port obviously reduces the peak pressure in spherical vessels, but with the increasing of the opening ratio, the decreasing of peak pressure is not obvious, that the peak pressure at the end of the pipe is maximum at the ignition position of 0 m without the relief port while it is maximum at the ignition position of 4.7 m with a pressure relief port, and that when the ignition position is at 0 m, the maximum pressure increase rate at the end of the pipe is less than that at the ignition position of 2.7 and 4.7 m.

Key words: spherical vessels, pressure relief pipe, ignition position, opening ratio, explosion pressure characteristics