TURBOCHARGER COMPONENTS HAVING A THERMAL BARRIER COATING

TURBOCHARGER COMPONENTS HAVING A THERMAL BARRIER COATING

ABSTRACT

The present disclosure relates to a method of preventing residues of non-combusted ED95 from depositing on surfaces of a turbocharger of a vehicle by coating the relevant surfaces with a coating having a reduced affinity for ED95 residues. The coating is a thermal barrier coating (TBC) having both thermal barrier properties and modified surface properties. Thus, two advantages are achieved with a single coating: thermal losses are reduced and deposition of ED95 residues is prevented. Turbocharger components coated with a TBC, such as the turbine shaft, bearing housing, turbine wheel and blades, are also disclosed.

BACKGROUND ART

The development and use of transport fuels based on renewable resources has increased over recent decades due to worries over fossil fuel depletion (“peak oil”), global warming and energy security.

ED95 is an ethanol-based fuel for use in compression ignition engines, and as such is an environmentally sustainable alternative to diesel. ED95 comprises about 95 percent ethanol, together with further additives such as ignition improver, corrosion inhibitor, surfactant, denaturant and colourant. The ignition improver is commonly a polyethylene glycol (PEG) derivative, such as Beraid 3555.

The use of ED95 in a vehicle is not without problems, however. During use, non-combusted fuel may reach the turbocharger in the exhaust system of the vehicle. This non-combusted fuel may cause sticky deposits on components of the turbo, including the turbine shaft and bearing housing. These deposits are primarily composed of the PEG ignition improver present in the ED95, which is hydrophilic and has a high molecular weight. The problem is exasperated by the formation of an oxide layer on the surface of the turbo components due to oxidation of the component by hot combustion gases. This oxide layer is also hydrophilic, meaning that it has an increased affinity for the hydrophilic PEG ignition improver, leading to increased deposits. Eventually, the build-up of such deposits may lead to the turbocharger malfunctioning and needing to be replaced, which is costly.

TECHNICAL SOLUTION

Residues may be prevented from depositing on surfaces of the turbocharger by coating the appropriate turbocharger surfaces using a thermal barrier coating (TBC). A TBC is a thermally insulating coating that can sustain an...