Heat Transfer Effects on the Dynamic Responses of Pneumatic Cylinder Driven by Meter-out Circuit

To identify the effect of different thermodynamic models on the dynamic responses of pneumatic cylinders, an isothermal cylinder is proposed and designed to verify the effect of temperature and heat transfer. The mathematical models of isothermal and normal cylinders were established, a test rig was built to measure the dynamic characteristics of cylinders, which includes the temperature change and heat transfer effect; then the isothermal and polytropic models were verified by experiments. This study indicates that the temperature change in a normal cylinder is up to 50K, but which is less than 3K in an isothermal cylinder. As the temperature or heat transfer coefficient increase, the equilibrium velocity increases simultaneously. However, the temperature increasing promotes the pistons motion and the heat transfer intensity impedes it. Comparing with an isothermal model, the adiabatic model is more approximate to the normal cylinder and it can be used for general analysis. This study presents an idea for avoiding condensation and helps improve the accuracy of cylinder control.