Sealing performance evaluation criteria and profile optimization of the volumetric cavities of positive displacement motors for directional drilling

Authors

• KUANG Yuchun, School of Mechanical Engineering, Southwest Petroleum University, Chengdu 610500, ChinaFollow
• HU Xin, School of Mechanical Engineering, Southwest Petroleum University, Chengdu 610500, China
• ZHOU Jingpei, School of Mechanical Engineering, Southwest Petroleum University, Chengdu 610500, China
• LUO Jinwu, School of Mechanical Engineering, Southwest Petroleum University, Chengdu 610500, China; School of Intelligent Manufacturing, Chengdu Institute of Technology, Chengdu 611730, China
• LIU Yihui, School of Mechanical Engineering, Southwest Petroleum University, Chengdu 610500, China
• HAN Yiwei, School of Mechanical Engineering, Southwest Petroleum University, Chengdu 610500, China

Abstract

Objective Constrained by complex stratigraphic conditions in underground coal mines, directional drilling faces challenges such as low efficiency when encountering medium-hard and hard formations. Positive displacement motors (PDMs) with a diameter of 89 mm are commonly used for directional drilling. Their efficiency is primarily influenced by the sealing performance of their volumetric cavities, which further significantly affects the drilling efficiency. Methods Based on the structural characteristics of the three-dimensional (3D) volumetric cavities of PDMs and the simulation method of two-way fluid-structure interactions, this study proposed the criteria for quantitatively evaluating the efficiency and volumetric cavity performance of PDMs, followed by the analysis of the dynamic sealing performance of the 3D volumetric cavities during motor operation. Targeting the sealing characteristics of the 3D volumetric cavities of hypocycloidal PDMs, this study proposed two improvement schemes: an optimized hypocycloidal profile and an irregular stator profile. The feasibility of the improvement schemes was verified through numerical simulations and whole-machine tests. Results and Conclusions During the operation of a PDM, its volumetric cavities underwent severe leakage in the suction stage, when the rotor meshed with the upper side of the stator inner diameter, but exhibited high sealing performance in the extruding stage, when the rotor meshed with the lower side of the stator inner diameter. Compared to the PDM with the original structure, those with the optimized hypocycloidal profile and irregular stator profile demonstrated significantly improved sealing performance of volumetric cavities, with total efficiency increasing by 7.9% and 15.15%, respectively. The whole-machine tests confirm the rationality of the improvement schemes. Overall, the results of this study provide a reference for enhancing the efficiency and equipment performance of directional drilling in underground coal mines.

Keywords

underground coal mine, positive displacement motor (PDM), sealing performance of a volumetric cavity, two-way fluid-structure interaction (FSI), profile optimization, directional drilling

DOI

10.12363/issn.1001-1986.25.09.0663

Recommended Citation

KUANG Yuchun, HU Xin, ZHOU Jingpei, et al. (2026) "Sealing performance evaluation criteria and profile optimization of the volumetric cavities of positive displacement motors for directional drilling," Coal Geology & Exploration: Vol. 54: Iss. 5, Article 24.
DOI: 10.12363/issn.1001-1986.25.09.0663
Available at: https://cge.researchcommons.org/journal/vol54/iss5/24

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