Energy conversion mechanics and power evaluation of compressible fluid in pneumatic actuator systems

This work discusses the power transmitted by flowing compressed air, called air power in this study. Two processes are discussed to clarify the energy conversion in pneumatic systems. One is air compression where mechanical work is required for compressing air, and another is actuation of an actuator where compressed air is supplied and mechanical work is outputted. It is concluded that air power can be represented by the work-producing potential of compressed air. Furthermore, it is clear that air power consists of two parts. One is transmission power which represents pushing power from the upstream to the downstream of flowing air, and another is expansion power from the work ability of air expansion. It can be seen that expansion power should exist in any compressible fluid. With the success in determining air power, an energy consumption comparison between pneumatic and electric actuator systems is made. It is clear that a pneumatic system is not always less efficient. When holding a load for a long time, a pneumatic system is more efficient.