## 1 Introduction  
As a limiting device for blast wave and explosion products, the explosion containment vessel has wide applications in both military and civil fields. It was found that the maximum pressure of the end cover pole of the container is not the first pressure peak, but a subsequent one. [PERSON] et al. [1] used the TVD (Total Variation Diminishing) numerical method, combined with the analytical solution of a strong explosion, to analyze the internal load distribution of a cylindrical explosion container. They proposed that due to the interaction between waves, the pressure characteristics at the end cover pole were very complex, and multiple pressure peaks might be present. [PERSON] et al. [2] observed that, in the internal explosion experiment of a cuboid explosion container, the center of the cover plate at the far end of the explosion was affected by four simultaneous reflections by the chamber wall. It was suggested that the second pressure peak corresponding to the largest value appeared a few microseconds later than the first one. [PERSON] et al. [3] analyzed the internal explosion loading and the structural stability of the cylindrical reinforced concrete containment by numerical simulation. It was found that the explosion shock wave was repeatedly reflected in the vessel, and the dome of the container may have been subjected to the strongest impact. By the means of experiment and numerical simulation, [PERSON] et al. [4] studied the pressure distribution of an explosion in an irregular confined blast chamber. They found that the second pressure peak had a high intensity and even exceeded the first peak at gauges near the chamber wall or the corner. [PERSON] et al. [5] used a TNT (2,4,6-Trinitrotoluene) equivalent numerical model to analyze the explosion impact load inside the steel container, and found that due to the convergence effect of shock waves, the maximum load occurred in the pole area of the dome and all occurred in the second or third peak of the waveform. [PERSON] et al. [6], through experiments and numerical simulation, found that the second peak was much higher than the first peak, which was on the gauges at the edge and corner of the cubic explosive vessel. [PERSON] et al. [7] used numerical models with different zoom ratios to analyze the pressure load distribution of a single-layer spherical lattice shell structure, in which the maximum pressure at the pole always appeared at the second peak. [PERSON] et al. [8] experimentally measured the pressure, which was loaded on the cover plate of a cylindrical vessel, with an aspect ratio of 2:1, indicating that the pressure load on it presented multiple wave peaks, and the maximum peak of the pressure load at the center of the cover plate was three times higher than the first. In addition, [PERSON] [9], [PERSON] [10], [PERSON] [11], [PERSON] [12], [PERSON] [13; 14; 15], [PERSON] [16] and other scholars have conducted fruitful studies on the distribution of the internal load, vibration response, failure analysis and the design criteria of the explosion containment vessel.  
To explore the postposition phenomenon of the maximum pressure at the end cover pole, but also to reveal its load evolution mechanism, this paper introduced an experimental result on the pressure load of the pole of the ellipsoidal end cover and a numerical simulation on the evolution and distribution of explosive flow field over various charges and aspect ratios. This study was intended to provide references for the study of the distribution law of explosion, which loads in the container, and the design of the anti-detonation strength of the explosion containment vessel.