Numerical Investigation of Transient Leakage in Labyrinth Seals for Low-pressure Pistons of Liquid Hydrogen Booster Pumps

Hydrogen is recognized as an ideal energy carrier with extensive applications in energy storage, power generation, transportation, and industrial production. In the transportation sector, hydrogen refueling stations serve as critical infrastructure connecting upstream hydrogen production and downstream hydrogen utilization terminals, fulfilling essential functions of hydrogen storage and dispensing. Compared to high-pressure gaseous hydrogen storage refueling stations, liquid hydrogen refueling stations demonstrate significant advantages across multiple parameters including operational safety, hydrogen purity, initial construction costs, system compatibility, and energy consumption efficiency. The liquid hydrogen booster pump serves as a core component in hydrogen refueling stations. To maintain its efficient operation, effective sealing of pistons and plungers is crucial. During the operation of liquid hydrogen booster pumps, heat leakage from the environment and frictional heating from piston seal rings constitute significant thermal inputs. These heat sources induce phase transformation of liquid hydrogen into gas hydrogen, resulting in evaporation losses that substantially reduce operational efficiency. In contrast to piston seal rings, labyrinth seals as non-contact sealing mechanism demonstrate notable advantages including simplified structural configuration, reduced wear characteristics, and minimal frictional heating generation. This innovative sealing approach effectively mitigates internal heat accumulation during pump operation. This study proposes a novel low-pressure piston configuration that integrates conventional low pressure piston components, low pressure inlet valves, and piston labyrinth seals into a unified structure. Building upon this innovative design, we developed a transient leakage model for labyrinth seals in the low-pressure section of liquid hydrogen booster pumps using dynamic mesh technology. Through theoretical analysis, we systematically investigated the effects of piston reciprocation, labyrinth seal length, and intermediate pressure on leakage coefficients. The results demonstrate that: the coupling effect between near-wall shear flow and piston squeezing action during reciprocation increases the overall leakage through labyrinth seals,while extending labyrinth seal length reduces leakage, the optimization effect becomes limited beyond certain thresholds,higher intermediate pressure in two stage liquid hydrogen booster pumps significantly exacerbates leakage through labyrinth seals.