Fuels are a lot more complex than most people realize. Not only is each fuel made up of many different ingredients but also each of these ingredients is made up of a mix of components. This is why blending fuel involves so many possible permutations and why choosing the right components is such a key part of expert fuel design.
It is important to understand what is meant by a reference fuel. These are fuels that have standard components and act as a yardstick, or reference, against which other fuels can be measured. In particular, reference fuels are often used to determine the octane of other fuels. There are primary and secondary reference fuels, with the secondary fuels calibrated against the primary ones so that they can be used to give accurate measurements of other fuels.
Fuel design for a reference fuel
Fuel development experts know that they need to produce a fuel that uses available components, fulfills the functions required, and can be produced consistently time after time. It also has to interact reliably with the other components in the fuel, remains stable, and have a reasonably extended keeping time.
Within the fuel, each component has to meet this requirements checklist. The fuel is tested in the lab and by using mathematical modeling. If it appears promising, the fuel design process moves on to full-scale testing. The fuel may be tested both in the lab and in engine tests.
If the fuel design passes this test, fulfilling its requirements, production can begin, starting with producing the components that will be blended into the final fuel mix. These are stored separately so that they do not affect each other. A pilot batch of the fuel is blended and re-tested before a full-scale production blend is attempted. The first production blend may also be tested again in the lab as a final check.
One of the challenges for experts developing a reference fuel is logistical. All those components and the various batches need a lot of different tanks. Some of the components need to be stored under pressure before blending so that their quality profile does not change. Even the infrastructure of pipes has to be specially designed so that each storage tank has a separate pipe to deliver its component into the blend to prevent the mixing of components with each other.
Distributing the fuel
When a larger batch has been blended, it needs to be delivered. The delivery method depends on the size of the batch and the location of the customer. Sometimes, the fuel is simply a few liters and the storage is an ordinary fuel can; other times, multiple tankers or ships are needed to deliver the fuel to the customer or an agreed storage location.
If the fuel is going to be stored for some time, it will be monitored and lab tests will be used to check periodically that its quality has not been affected.