Based on the thermodynamically modified Zwart cavitation model

a two-dimensional theoretical cavitation flow model of the labyrinth seal between the piston and cylinder in a liquid hydrogen piston pump is established and verified. The influence of cavitation on the pressure distribution along the clearance seal

which reduces the leakage rate

is analyzed. The influence of input pressure and degree of subcooling on the cavitation flow is discussed. Higher inlet pressure and degree of subcooling can diminish the sealing effect between cavitation and liquid-phase flows. Furthermore

the leakage rates for clearance and labyrinth seals with 20- to 60-μm sealing gap are compared. When the sealing gap is no less than 30 μm

the labyrinth sealing effect is superior to clearance seal. Finally

the leakage rates of labyrinth seals with three cavity structures—square

curve

and triangle—are simulated. The sealing effects are ordered as follows: square labyrinth cavity

curved labyrinth cavity

and triangular labyrinth cavity. The sealing effect is preferred when the optimal length-to-width ratio of the square cavity is around 5.0. The studies are further helpful to decrease the leakage rate of labyrinth seals and enhance volumetric efficiency in liquid hydrogen piston pump.