Multifunctional Cleaning Additives. Modern oil refining cannot directly produce diesel fuel which can also clean the engine and the fuel system in the process of operation. Engine operation can be disrupted even by a small amount of desposits, degrading its efficiency and economy.
That is why mutifunction cleaning additives were developed. They improve performance and environmental parameters of diesel fuel. This type of additive reduces fuel consumption by 3-5%, while decreasing exhaust toxicity by 10-15%. In combination, this reduces the risk of premature replacement of post-combustion catalysts and soot filters. However, this is not the primary objective of using the cleaning additives. Their main purpose is to ensure even spraying of fuel by preventing deposits on the spraying nozzles.
Although the deposits in diesel engines are similar in composition and structure to those formed in gasoline engines, they are far more dangerous. This is due to the possible disruption of the entire high pressure fuel system operation.
The modern diesel vehicles are mostly equipped with the Common-rail injection system. It improves the efficiency of the multifunctional cleaning additives. The main features of the Common-rail engines are:
- fuel supply pressure is 2500 atm, compared to just 100-400 atm in a regular engine;
- fuel is injected into the combustion chamber in two portions. The small portion initiates combustion. This makes the combustion even, and fuel economy reaches 20%.
The main component of cleaning additives is cyclic amines, with the molecular weight of the alkyl radical above 1000. They have high thermal stability and therefore are well suited for diesel fuel. The solvents are volatile hydrocarbon fractions which easily solve the active components of the additives, improving dosage.
A cleaning additive is usually a package of components, including the main component (thermally stable surfactant), corrosion inhibitor, antioxidant, demulsifier and anti-foaming additive. If necessary, the additive may also contain solvent, friction modifier and anti-wear components.
The efficiency of the cleaning is evaluated by the nozzle gumming rate.
Thus, the test is run by BASF. The cleaning performance of basic fuel and fuel with additives is compared on a Peugeot XUD9 A/L engine (1.9 l, 4 tacts, 4 cylinders) according to the most commonly used 10 hour test method according to the CEC-F23-A-01 standard on the motor bench in Ludwigshafen, Germany. The standard minimum, according to the world fuel charter, is 85% (limitation of the flow with fuel needle raised 0.1 mm).
Cleaning additives operate just as any other surfactant: the bind the molecules on the surface to their hydrophilic part. The polar part of the molecules are oriented towards the fuel.