AVL pushes water-cooled electric turbos

Water-cooled electric superchargers, developed as a hybrid system for commercial vehicle applications, and designed to reduce NO_x and CO₂ emissions, are proposed at the 19th Supercharging Conference in Dresden this week.

Delegates to the conference have heard a technical paper on electric supercharging from AVL.

AVL, which has worked closely with Controlled Power Technologies GmbH (CPT) on the application of this up and coming boosting technology, as validated in the 48V LC Super Hybrid programme, primarily funded by the Advanced Lead-Acid Battery Consortium (ALABC), which demonstrates an air-cooled light duty version of the compressor in a large family saloon, powered by lead-carbon batteries.  

GM Powertrain and THY Engineering similarly focused on electric supercharging in their technical papers. 

Electric compressors are decoupled from the engine, allowing pressurised air to be delivered almost instantaneously – spinning up to 70,000 rev/min in a fraction of the response time of a turbocharger – with a mass flow rate of up to 800kg/h.  

The result is said to provide efficient combustion and torque delivered at low engine revs thereby improving the dynamic response of a downsized turbocharged engine.

It is possible to reduce fuel consumption by as much as 10 per cent, according to developers who note that it is an efficient way of using 2 to 9kW of stored electrical power.  Depending on the rate of fuel injection, this can mean an additional 15-70bhp (20-90kW) at the crankshaft for up to 30s.  

“CPT’s family of heavy duty compressors has been developed as original equipment for a wide range of diesel engines in off-highway and commercial vehicles using either 24V or 48V architecture in a low cost hybrid system,” says Nick Pascoe chief executive CPT.  

CPT has build on experience gained by commercialising its VTES electric supercharger for passenger cars. 

“We sold our VTES business to Valeo in late 2011, and now focus on trucks and buses,” claims Pascoe. “An electric compressor facilitates radical downsizing with fewer cylinders and smaller engine displacement. That’s how we gain the extra fuel economy, but without compromising vehicle performance.   It really does mean getting a quart out of a pint pot.”

“We are now applying CPT’s switched reluctance motor-generator technology to electric supercharging of large diesel engines,” says Andy Dickenson senior manager responsible for CPT’s COBRA technology.   “COBRA (Controlled Boosting for Rapid response Applications) can help reduce NO_x and particulates as well as CO₂ emissions, thereby moderating the need for expensive exhaust after-treatment to meet Euro 6 requirements.”

“COBRA can reduce diesel tailpipe emissions of urban buses and trucks with their continuous stop-start operation,” added Dirk Zepp, sales manager CPT GmbH.   “Another major environmental advantage of our switched reluctance technology is the elimination of permanent magnets in our electrical machines, which replace the need for expensive rare earth metals by using integrated electronic switching.”  

“An electric compressor facilitates radical downsizing with fewer cylinders and smaller engine displacement,” says Pascoe.  “That’s how we gain the extra fuel economy, but without compromising vehicle performance.   It really does mean getting a quart out of a pint pot.”

CPT is an independent, clean-tech company, based in Germany, the UK and the USA.  Its core competencies include low voltage power electronics, advanced control software and the application of low voltage electrical machines to gasoline and diesel engines.