TESIS DOCTORAL - "Energy Efficiency of High Pressure Pneumatic Systems" a càrrec de Jose A. Trujillo (27/11/15, 11.00h)
Títol: Energy Efficiency of High Pressure Pneumatic Systems
Autor: Jose A. Trujillo
Directors: Esteve Codina i P Javier Gamez
Dia: 27 de novembre de 2015
Lloc: Sala de Conferències. Edifici TR5 ESEIAAT. c. Colom, 11. Terrassa. (antiga ETSEIAT)
The energy efficiency assessment of high-pressure pneumatic circuits is the aim of this dissertation. From a historical perspective the past and cur- rent activities with regards to the energy saving conservation in pneumatic technology were examined, and it could be concluded that high pressure pneumatic circuits have been repeatedly used for years in several industrial applications but to date no studies on that specific field are known.
After a systematic review of studies concerning energy saving in pneumatic applications, a complete dynamic model for a high-pressure air blowing machine, employed in the production of plastic bottles, was developed. A synthetic version of the real pneumatic system was considered and consisted of a valve manifold, two tanks, one that simulated the mould cavity where the plastic preform is commonly blown and the other, was intended to recycle air. The one-dimensional models were derived for the pneumatic valve, pipes and vessels. The dynamic modelling of the valve took into account the flow non-linearities through the various geometrical restrictions as well as the pressure and temperature evolution at the inner chambers. Because of the existence of flow discontinuities in the pipes, different solving methods were applied, taking as starting point the Method of Characteristics and continued delving into finite volume methods such as Riemann-solver-based schemes.
On the experimental phase a single blowing station unit was designed and built up. The pressure and temperature characteristics at different positions of the pneumatic circuit were measured in detail. In addition, the fluid flow through the valve manifold could be characterised by the sonic conductance and critical pressure ratio, which were determined by the isothermal discharge method.
Effort was also expended to study the behaviour of the pressure waves generated along the tubes. The pressure wave propagation was computationally charted, with the intention of assessing how this parameter affected the recycling process.
The examination of the experimental results proved the efficiency of the re- cycling process and demonstrated to be in close agreement with the mathematical model. The parameters governing the maximum amount of air to be recycled at each working cycle were identified, and the influence of the pipe geometry was discussed. Finally the author provides recommendations for future research and makes suggestions regarding the valve design to enhance the efficiency of the system.