Experimental Flow Characterization and Geometric Selection of a Passive Pneumatic Synchronizing Element

Abstract

Passive synchronization of two pneumatic actuators is difficult because differences in external load, friction, and pneumatic resistance may cause unequal piston-rod motion. This study investigates the airflow characteristics of a passive pneumatic synchronizing element and the influence of its principal internal geometric parameters. Airflow measurements were performed at a constant supply gauge pressure of 2.4 ∙ 105 Pa. Equalizing-channel diameters of 3 ∙ 10⁻⁴ and 4 ∙ 10⁻⁴ m were tested with the annular microgap closed. The influence of the microgap height was then investigated for a constant channel diameter of 3 ∙ 10⁻⁴ m, using microgap heights from 2.5 ∙ 10⁻⁵ to 1.0 ∙ 10⁻⁴ m. Increasing the equalizing-channel diameter from 3 ∙ 10⁻⁴ m to 4 ∙ 10⁻⁴ m increased the airflow rate from 8.58 ∙ 10⁻⁵ m3/s to 1.14 · 10⁻⁴ m³/s. Increasing the microgap height from 2.5 ∙ 10⁻⁵ to 1.0 ∙ 10⁻⁴ m increased the airflow rate from 8.85 ∙ 10⁻⁵ m³/s to 2.18 ∙ 10⁻⁴m³/s . For the required airflow rate of 1.001 ∙ 10⁻⁴ m³/s, linear interpolation yielded 𝑆𝑆2,𝑖𝑖𝑖𝑖𝑖𝑖 = 3.99 ∙ 10⁻⁵m, corresponding to approximately 4.0 ∙ 10⁻⁵ m. The airflow capacity of the passive synchronizing element can be adjusted through the combined selection of the equalizing-channel diameter, investigated at 3.0 ∙ 10⁻⁴ m and 4.0 ∙ 10⁻⁴ m, and the annular microgap height, varied from 2.5 ∙ 10⁻⁵ m to 1.0 ∙ 10⁻⁴ m . The proposed procedure provides a practical basis for adapting the element to the airflow demand and piston-rod velocity limitation of a specific dual-actuator pneumatic system. The reported values are valid for the investigated geometry and operating conditions, including a supply gauge pressure of 2.4 ∙ 105 Pa, equalizing-channel diameters of 3.0 ∙ 10⁻⁴ m and 4. 0 ∙ 10⁻⁴ m, and annular microgap heights from 2.5 ∙ 10⁻⁵ m to 1. 0 ∙ 10⁻⁴ m.