A fuel tank made entirely of plastic, and thought to be the first of its kind, has been developed jointly by fuel systems expert TI Automotive and French petrochemical company Atofina.
The tank, dubbed the Permblok AS6 and due to make its debut on the 2005 Ford GT, is made from a combination of six layers designed to reduce the loss of fuel and exceed rigorous crash-test standards.
However, it is the tank’s ingenious ‘ship in a bottle’ (SIB) design that’s really making people sit up and take notice.
In order to limit fuel evaporation, and spurred on by stringent new evaporative emissions requirements, the designers of the system have used the blow moulding technique so that the fuel pumps, level sensors and other components can be enclosed inside the tank.
Explaining the decision, Manouchehr Kambakhsh, vice-president of advanced technology at TI Automotive, claimed that while hydrocarbon emissions for a typical 70 litre, six-layer co-extruded, saddle-shaped fuel tank run at around 200mg for a 24-hour test cycle, the same tank redesigned as an SIB has a permeation rate of less than 40mg.
Brian Lindsay, TI’s managing director for global fuel system sales, explained how these fuel savings are made.
‘The basic SIB design requires only one or two openings in the fuel tank shell, whereas past tanks often had up to six or seven. This dramatically reduces the potential permeation paths from the fuel tank system, compared to conventional tanks with components such as valves, lines and filters attached to the exterior of the tank.’
An added advantage of the system is its proven ability to increase the volume of fuel stored. By putting components inside, the tank can be enlarged to use space previously needed for external components and the tank shell.
Indeed, Kambakhsh claimed that in the Ford application the volume of the tank is over 8 per cent greater than a traditional alternative.
‘To accommodate mounting of various fuel delivery and vapour management components in and on to the fuel tank, the upper surface of the tank has to be contoured to provide the appropriate interface and attachment mechanisms,’ explained Kambaksh.
‘Invariably the contouring exercise compromises the maximum volume geometry of the tank.
‘By mounting the fuel delivery and vapour management components (pump, module, fuel level sensor, filter, valves, jet pumps and so on) on a carrier which is then to be inserted into the fuel tank during the blow moulding operation, we practically eliminate all externally-mounted components of the tank, the need for contouring and thus the associated volume compromise.’
A further space-saving innovation within the tank is the use of a piezoelectric ceramic element. This is used to judge the fuel-level.
A pressure wave is initiated by electronics sitting at the bottom of the tank next to a piezoelectric ceramic. The wave travels through the fuel to the surface and, when it hits the surface, it is reflected on to the bottom of the tank. When it hits the piezoelectric element, an electrical signal is generated, which is used by the processor to calculate the fuel level.
The Ford SIB systems will be built at TI Automotive’s plant in Ossian, Indiana.