Fuel Filling Without Flowbacks

Plot showing filling angle v maximum flow rate

Market research has shown that most drivers dislike having to stop to refill the fuel tanks of their cars, treating it as a chore to be finished as quickly as possible. Consequently, car makers are anxious to design fuel filler pipes which can cope with the high rates encountered at the filling stations. On the other hand, the design of the pipe has to ensure that pumping fuel into the tank at this rate does not cause surges or flowbacks to occur. In cases like these, fuel travels back up the pipe and out of the neck of the filler pipe.

Preventing this involves the installation of a sensing pipe in parallel with the filler pipe proper, to allow the air displaced by the incoming fuel to be safely vented.

Pump nozzles on the garage forecourt also have a safety cut-off designed to be triggered by indications that the vehicle tank is nearly full. This means that an acceptable fuel filler pipe design must avoid operating this cut-off prematurely, and preventing the customer from being able to fill the tank to its full capacity.

Until now, design of fuel filler systems has involved a costly and time-consuming process of testing and modification, to make sure a particular layout of pipes, filler outlet and fuel tank shape can perform as required. A major project undertaken by Stoneman Solutions examined the fluid dynamics involved in the transfer of fuel from the forecourt pump to the tank of the vehicle. The project achieved it’s objective of setting basic design guidelines which can allow the design of the fuel filler system to be incorporated into the design of the system at a much earlier stage.