Automatic Control System for Composite Fuel Station

Super-Gas™ is a mixed (composite) light hydrocarbon fuel containing a nominal 50/50 mole mixture of methane suspended in propane. The purpose of this fuel, domestically, is to improve the range of CNG-type vehicles, while improving the emissions relative to LPG-type vehicles. In other countries, other light hydrocarbons might be used to better utilize native resources [1]. The Composite Fuels Laboratory at the University of Oklahoma has designed two new fueling stations to provide the necessary fuel to vehicles converted to Super-Gas™. The design of these requires design of the fluid power system and electronic control for the different stages of the process to produce Super-Gas™.

Early experimentation using a micro controller board in a small prototype of the Super-Gas™ station showed difficulty in controlling the system, incorrect data acquisition, and poor ability to modify important variables. A programmable logic controller (PLC) has been demonstrated as a cost-effective and robust solution for distributed I/O system for this application. With the advantage of a native MS-Windows™ programming tool, RLL^plus, the system development was easier, safer and better since both manual and automatic modes can be accomplished using the same algorithm while obtaining the same fuel mixture composition. Two different models of the station have been developed: these are termed Fast Fuel and Bubbling on Board Stations. Both of them use very similar control algorithms.