Pneumatic characteristics of large-thrust heavy-load cylinder during high-speed start-up process

To implement high-speed and smooth start-up process of large-thrust heavy-load cylinders, a mathematical model based on the Van der Waals equation has been established and compared with computational fluid dynamics (CFD) simulation results. The influence of pipe diameter and load mass on the characteristics of the start-up process is analyzed. The results of the mathematical model and CFD simulation are consistent and the maximum error occurs in the gas mass flow at congested state. The average flow rate of the two models at this state is 8.161kg/s and 8.536kg/s respectively, with an error of 4.4%. The larger diameter of the tube in start-up process, the greater pressure of the rodless cavity achieved.The maximum pressure is linearly positively correlated with the diameter of the pipe in the range of 2~6mm. The maximum pressure is non-linearly positively correlated with the load mass. The smaller the load mass is, the faster the rodless cavity volume changes, which contributes to the maximum pressure of the rodless cavity decreasing. If the pneumatic cylinder is in stick-slip motion, increasing the diameter of the pipe can significantly solve the problem and improve the pneumatic characteristics during start-up process.