With road transport accounting for 10% of the global carbon footprint & the price of crude oil
rising from £39 per barrel in 2009 to a predicted £64 in 2015, the need for greener, more
economical road transport has never been so imperative. The turbocharger, which uses
exhaust gases to increase the engine’s efficiency, allows car manufacturers to downsize their
engines & still meet their customers’ power and performance demands. A turbocharged diesel
engine is up to 40% more fuel efficient & produces 50% less CO2 and NOx emissions than a
standard diesel engine of the same power.
Initially, ball-bearings were used in turbocharger turbines, but due to durability issues they are
not suitable above 100,000rpm. OEMs have thus adopted oil bearings, at the expense of a
much higher friction coefficient (oil bearing friction: 0.003 – 0.04, ball bearing friction: 0.001
– 0.0015), reducing their efficiency, & contributing to ‘turbo lag’ - the time required to change
power output in response to a throttle change i.e. a ‘hesitation’ when accelerating.
To tackle these problems, BHPTL wish to develop novel foil-free static-dynamic hybrid air
bearings & ceramic (silicon nitride) turbines for turbochargers. Air bearings have near zero
frictions, & ceramic turbines have a density 38% that of Inconel, the material currently used
for turbocharger turbines. Silicon nitride can withstand temperatures over 300 higher, is 1.8
times harder & has a flexural strength 1.3 times that of Inconel, so is much more durable.
These properties are expected to at least double the turbine’s acceleration and RPM
considerably reducing turbo-lag, increasing intake air pressure & hence improving
turbocharged cars’ performance & service life. The reduced turbo-lag and increased
performance will reduce the amount of time drivers’ have to accelerate before changing up a
gear, positively impacting fuel reduction