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In the passenger vehicle market especially, approaches including turbocharging, downsizing, electrification and many others are helping reduce the amount of CO2, NOx and particulate matter released into the environment.
But while emissions, and the limits governments have set for the automotive industry, are hugely important, consumers are arguably more focused on fuel economy. Thankfully the drive to reduce emissions is inextricably linked to fuel efficiency, and technologies are converging to offer improvements in both, namely electrification and turbocharging.
Go-to solution
Turbocharging has become one of the go-to technologies in order to downsize combustion engines and reduce emissions but maintain performance. And it’s been hugely successful, with very few companies now offering naturally aspirated engines in their line-ups – everything from a VW Golf to a McLaren Senna use the technology. And it’s now being joined by electrification.
Yes, we’ve been bombarded by adverts for electric, plug-in hybrid and hybrid cars, but electrification also takes more subtle roles too, namely on-board 48V e/e architectures that replace or supplement the traditional 12V system and open the door to a stream of new opportunities to change the performance and efficiency of vehicles.
Higher-voltage, 48V networks have already been integrated on vehicles including the Bentley Bentayga and Audi Q7, but on those they were used to control active suspension and to provide greater levels of outright performance respectively.
But now these two technologies – turbocharging and electrification – are being linked to create systems that can have a huge impact on fuel efficiency.
Electric turbochargers integrated into vehicles with charged engines and a 48V architecture can help overcome some of the challenges found in a conventional set-up. Turbo lag is one of the most obvious, while engines that run at higher speeds in order to provide sufficient performance can also benefit because it can reduce the strain on the system.
Many Tier One suppliers are looking at the technology, including BorgWarner which has developed its eTurbo system.
The technology is comprised of a mechanical turbocharger with an electric motor directly coupled to the shaft which serves as either a motor or a generator. The system delivers the traditional benefits of a standard turbocharger with the added advantage of electrified boost assistance, improving response. But the system can also capture excess turbine energy to generate electrical power and reduce emissions through aftertreatment management and precise air/fuel mix control.
Boost response
The eTurbo’s improvement in transient boost response along with steady-state torque improvement should enable firms to further downsize engines, resulting in better fuel economy and reduced emissions without big losses in performance. BorgWarner’s system is especially suited for Miller cycle engines – a combustion concept that is seeing more interest as the automotive industry looks to improve efficiency and that has been adopted by VW.
Efficiency isn’t the only benefit the electric turbocharger brings; they can harvest excess exhaust energy and convert it into electrical energy to be used in ancillary systems or for charging the battery, meaning less pressure on the combustion engine and a reduction in the amount of fuel needed. The technology can also help drive on-demand exhaust gas recirculation by increasing engine backpressure to reduce emissions.
Tougher targets
The push to make vehicles more efficient isn’t going to end any time soon, and the targets for emissions – and intrinsically linked fuel efficiency – will become far stricter as we look to wean ourselves off fossil-fuel-powered vehicles. Linking turbocharging and electrification will be part of the puzzle in achieving that.
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Content published by Professional Engineering does not necessarily represent the views of the Institution of Mechanical Engineers.