In motorsports, the automotive industry and throughout the chemical engineering sector, the preparation of special formulas with multiple ingredients is called ‘toll blending’. The formulation of safe and efficient fuels is particularly challenging.
The manufacturer is sometimes presented with a list of characteristics of the required product and is left to find ingredients to provide them; in other cases, permissible ingredients are pre-specified and engineers must see what can be achieved. In either case, the challenge is twofold.
Why fuel toll blending is needed?
There are many reasons why engine operators make exacting demands on fuel suppliers, not least of which in recent years has been environmental concerns. Trace waste gases – such as nitrogen and sulphur oxides, unburned benzene and particulates – have been linked to a variety of ills. Additives that promote better combustion can eliminate many impurities and improve fuel economy in the process.
According to the US Environment Protection Agency, only 17 per cent of the energy potential in gasoline moves a typical car. 16 per cent is wasted while engines idle and 62 per cent through friction and heat. With fears about future oil supplies, there is immense pressure to improve vehicle efficiencies. New engine designs are impossible to evaluate without fuels with precisely controlled characteristics.
There is little point in developing a great engine if performance rapidly drops off due to internal degradation. Fuel plays a leading part in preventing this, with a wide range of additives minimising wear, rusting, knocking, metallic corrosion, oxidation or clogging.
Why fuel toll blending is difficult?
Each addition can disturb the balance of characteristics. You may not be able to improve lubricity by simply adding a lubricant; instead, you may have to adjust several ingredients to maintain other essential qualities. The number of chemical ingredients adds to complexity exponentially. Basic ‘petrol’ contains about 15 hydrocarbons – alkanes, olefins and naphthalenes – before additives are introduced to improve shelf-life, protect engines or improve combustion.
Evaluating a formulation has to be performed across a wide range of conditions; for example, will a fuel that performs well in a warm laboratory do so in a blizzard or under heavier loads? Even altitude can affect how fuels function, with carburetted engines losing three to four per cent in power for every 1,000 feet above sea level.
These problems leave the engineer with a challenging number of interacting variables; in fact, the mathematics used to analyse test results remain a challenging field in their own right. Even big vehicle manufacturers often lack sufficient expertise to undertake toll blending alone, which is why they call in the specialists.
A certain bard once wrote: “Fillet of a fenny snake, in the caldron boil and bake; Eye of newt, and toe of frog, Wool of bat, and tongue of dog”. We have come a fair way since then; today, fuel blending plays a leading role in shaping tomorrow’s world.