Gas dynamic pipe flow effects in controlled pneumatic systems - A simulation study

Electro-pneumatic modulators (EPMs) are widely used in controlled pneumatic systems. Their aim is to ensure a controlled operating pressure modulated at a high accuracy and high temporal resolution. This paper reports a computational case study representing the influence of gas dynamic pipe flow effects on the operation of a pneumatic system to be controlled by means of an EPM. The simulation has been carried out with use of simulation software AMESim version 3.01. Given that no standard gas dynamic pipe model and electro-dynamically-relevant solenoid valve model are included in the present version of the simulation software, such models had to be elaborated by the authors. The simulation studies reveal that the self-developed gas dynamic pipe model resolves properly the wave effects and flow fluctuations expected from a realistic pneumatic pipe performing high velocity flow. The simulation must accurately resolve such phenomena if the computational study aims to provide an aid to the design of a proper pressure control loop. It has been concluded that a gas dynamic pipe model, covering reliably the physically possible entire Mach number range, is essential in simulation of pneumatic systems.