2026/07/27 by Zhongjian Kang, Yanjie Shi, Yichao Shen +1
paper · doi:10.1088/1402-4896/ae913e
Abstract The spark gap switch is the core component of plasma pulse stimulation equipment. However, existing studies have largely overlooked the thermal accumulation issue induced by the combination of downhole confined environments and high-frequency pulses. The transport properties of high-temperature air are taken into account in this study. A magnetohydrodynamic model is then used to simulate the spatiotemporal evolution of heat generated by a single discharge. This model is combined with an equivalent transient heat transfer model to simulate the thermal accumulation process under continuous pulses. The results reveal that the maximum instantaneous power of a single discharge reaches 2.4 MW, with the maximum arc temperature reaching 5.7 × 10⁴ K at a current of -4.7 kA. The steady-state temperature rise of the electrode surface increases with discharge frequency, exceeding 700 K at 25 Hz. A comparative analysis indicates that at high frequencies, the heat accumulated from repetitive discharges becomes the primary determinant of the switch's temperature profile, outweighing the impact of the initial formation temperature. More importantly, the local gas rarefaction caused by the sharp temperature rise is identified as the fundamental reason for the decrease in breakdown voltage. Based on this, an empirical formula for breakdown voltage is established, achieving a mean absolute percentage error of only 3%. This study clearly reveals the thermal evolution pattern inside the confined switch and the underlying mechanism of voltage decrease, providing critical support for determining the safety boundaries and designing cooling systems for pulsed equipment used in deep wells.