Pressure and force behaviors in a closed pipe with a holed piston

A mathematical model for a closed pipe with a holed piston was established to investigate the operational characteristics of a gas spring. Working fluid as an ideal gas and adiabatic process were assumed in the model. Results of simulation show good agreement with those of experiment. The model was then used to investigate the effects of the orifice diameter, the filling pressure and the velocity of piston on the applied force and operating pressures of two chambers in the gas spring. The results showed that the effects of the orifice diameter and the piston velocity on the pressure difference between two chambers were remarkable. 0.05 mm reduction of the orifice diameter leads to about twice increase in the pressure difference. 10% increases in the piston velocity results in about 25% increases in the pressure difference. The orifice diameter and the piston velocity have effect on larger pressure change in the chamber with lower pressure than in the chamber with higher pressure. Force applied to the piston also varies with the piston velocity, the orifice diameter, and the filling pressure due to irreversibilities including throttling process through the orifice and friction between the wall and the piston. Present results are expected to supply useful information about new gas spring design.