Experimental investigation of automotive refueling system flow and emissions dynamics to support CFD development

Abstract

Government regulations restrict the evaporative emissions during refueling to 0.20 grams per gallon of dispensed fuel. This requires virtually all of the vapors generated and displaced while refueling to be stored onboard the vehicle. The refueling phenomenon of spit-back and early click-off are also important considerations in designing refueling systems. Spit-back is fuel bursting past the nozzle and into the environment and early click-off is the pump shutoff mechanism being triggered before the tank is full. Both are detrimental to customer satisfaction, and spit-back leads to failing government regulations. Development of a new refueling system design is required for each vehicle as packaging requirements change. Each new design (or redesign) must be prototyped and tested to ensure government regulations and customer satisfaction criteria are satisfied. Often designs need multiple iterations, costing money and time in prototype-based validation procedures. To conserve resources, it is desired to create a Computational Fluid Dynamics (CFD) tool to assist in design validation. To aid in creating such a model, controlled experiments were performed to inform and validate simulations. The simulations and experiments were performed on the same in-production refueling system. Test data provided characterization of non-trivial boundary conditions. Refueling experiments gave points of comparison for CFD results, especially the tank pressure. Finally, collection of emissions data during refueling experiments provided insight into the travel of gasoline vapor in the refueling system. All the information gathered provides greater understanding of the refueling process and will aid the continued development of CFD models for refueling.