To ensure the continuously stable dual-tank liquid piston expansion process

this study introduces an innovative approach for near-isothermal expansion of the liquid piston. In this mode of operation

the liquid piston enters the post-expansion suction stage after the completion of the expansion stage to achieve a drop in the tank water level

thus ensuring the stability of the cycle. By establishing relevant thermodynamic models

the study explores the variations in the thermodynamic performance of high-pressure air during near-isothermal expansion and reveals the energy release patterns of the liquid piston across different operational characteristics. The study findings indicate that this operational approach enables the system's stable cyclic phase after the second cycle; the system exhibits favorable isothermal performance

with the air temperature dropping to the lowest at 282.3 K during the cycle when the expansion ratio is 5. The ratio of air-to-liquid droplet heat exchange shows notable fluctuations based on the number of nozzles

rising from 20.2% to 72.8% as the number of nozzles increases from 2 to 18. For a single-cycle lasting 4 800 s

the efficiency and increase rates of energy release during liquid piston expansion reach maximum values of 84.6% and 18.1%

respectively. Optimal spray timing under different operational conditions exhibits variations in dimensionless pressure. This study proposes a novel approach to enhance the stability of the near-isothermal expansion process of the dual-tank liquid piston.