The means by which the control of very low flows in the region of 0.1-400ml/hr using valves with microchannels (<250μm) is not well defined. This work presents a review of existing literature that contributes to the understanding of controlling very low flows. Mechatronic principles are used to bring new understanding to the field of very low flow control using needle valves. Flow rate experiments were conducted using a mechatronically controlled needle valve and a novel flow measurement device constructed for the purpose, from which an analytical flow model is developed. Details of a linear actuated needle valve are given along with open loop and closed loop control systems developed for the purpose of accurately controlling very low flows. The open loop system is derived from the valve operating principles enabling an efficient method of modelling the valve flow characteristics for the purpose of control. The closed loop method, incorporating gain scheduling is capable of controlling flows to within 0.0016ml/hr at low flows. A prototype lubricant dispensing system using a low flow needle valve was tested in an industrial environment. A design synthesis is developed by consolidating the knowledge gained from these studies is presented. This discusses the all main factors affecting the design and operation of needle valves for the control of very low flows while describing practical solutions to the problems commonly encountered.
|Publication status||Published - Jun 2008|
- low flow