Aeristech launches new 48V electric supercharger
31 July 2015
UK-based Aeristech has introduced a new 48V electric supercharger capable of continuous operation at high boost levels. Independently validated by Ricardo and MAHLE Powertrain UK, the technology provides greater efficiency and easier packaging than a mechanical supercharger or a two-stage turbocharger.
Aeristech said it overcame the thermal management issues that can restrict other electric boosting devices currently available on the market to only transient operation by using permanent magnet motor technology in place of the more usual switched reluctance type. This has been made cost-effective by developing a patented control and switching technology that enables the use of many cost-competitive components.
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| Results from the MAHLE test. Source: Aeristech. Click to enlarge. |
Aeristech’s 48v eSupercharger has already been demonstrated by MAHLE Powertrain UK in a D-segment appraisal vehicle using its downsized turbocharged 1.2 liter, 3-cylinder gasoline engine. The engine achieved 32.9 bar BMEP at 2000 rpm (+10% over base), delivering 313 N·m (231 lb-ft) and a maximum power output of 193 kW (259 hp)—an increase of 61% over the base engine.
At low speed (1250 rpm), the eSupercharger achieved 28.6 bar BMEP—an increase of 43% over the baseline 20 bar BMEP in the Mahle engine.
Analysis of the power curve showed that the turbocharger run up line was complete by 3000 rpm, resulting in poor low-speed driveability. The addition of the eSupercharger re-instated the low-speed torque. In other words, combining the eSUpercharger and the turbo resulted in a continuous torque curve through the complete engine operating range.
Our system can deliver over 2.5 bar of boost pressure continuously, setting it apart from other systems which only offer short duration boost assist for improving the engine transient response. By using a 48V architecture, we have provided a solution that is easily implemented and competitive in cost for the growing numbers of hybrid and mild-hybrid vehicles that will be launched in the next few years.
By replacing the smaller turbo in a two-stage turbocharging arrangement with our eSupercharger, MAHLE Powertrain UK was able to increase the size of the main turbo without concerns over driveability and transient response. The eSupercharger can not only help increase specific output but is also much easier to accommodate within the engine compartment than a second stage turbocharger because it has greater layout flexibility.
—Aeristech CEO Bryn Richards
In a separate program using WAVE simulation, Ricardo carried out detailed modeling of a 221 kW (296 hp) 2.0-liter gasoline engine with a single-stage turbocharger. Adding a 48V Aeristech eSupercharger enabled the turbine to be increased in size by 80%, improving BSFC (Brake Specific Fuel Consumption), torque and transient response throughout the engine speed range. Ricardo concluded that without the eSupercharger only a larger engine could have met the requirements, if relying on a conventional single-stage turbocharger.
Using an eSupercharger also has advantages for emissions control. Because it is applied to the inlet side of the engine, it reduces the thermal mass in the exhaust stream which helps to maintain catalyst temperature, especially at lower speeds and loads.
Aeristech’s motor control strategy separates commutation and power control. This approach dramatically reduces the cost of many key switching components while ensuring exceptionally accurate high-transient speed control.
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| Aeristech’s controller features very low electrical switching frequency, delivering higher efficiency and torque density. This allows exceptionally accurate high-transient motor control. Source: Aeristech. Click to enlarge. |
The IGBT/MOSFET switches controlling power use a different time constant to the switches handling commutation. The switching frequency is no higher than the running speed, this allows for very accurate transient control of the motor.
This patented control architecture delivers a controller efficiency in excess of 95% with low internal switching frequency and low-cost internal components. Aeristech’s motors are designed for higher speeds and lower internal impedance than would be possible with conventional controllers. Aeristech’s motors are capable of running continuously with high power output.
By achieving high operating speeds, Aeristech’s compressors offer wide and efficient compressor maps and high boost pressures. The motor has class-leading power density and low inertia. The eSupercharger operates at up to 150,000 rpm with a transient response of idle-to-target speed in under 0.4 seconds.
Aeristech is a British clean technology innovation business founded around an innovative permanent magnetic switching architecture that has enabled it to produce what it says is the most power dense electric motor of its type currently available. This core technology forms the basis of the company’s range of products, which include an electric supercharger, full electric turbocharger, fuel cell air compressor and turbine generator.
As a one-stop-shop for electrically driven pressure charging solutions, Aeristech designs, tests and develops every aspect of the system, from the bearings to the compressor wheel, to suit the customers’ individual application. The company is working with vehicle manufacturers and suppliers to licence innovative proprietary technologies to reduce tailpipe emissions, increase fuel efficiency and heighten driving characteristics of the next generation of ‘right-sized’ diesel and gasoline engines.
People normally think of superchargers as something to add power to an engine (at a greater fuel usage) but they can also be used to increase efficiency at less than ideal loads.
An example with my Prius. "pulse and glide" works because during the "pulse" part of the cycle, the engine is at its ideal efficiency. Pulsing the ICE artificially raises it's load to more closely match the current driving conditions. With an electric supercharger, even a mild one, you can get the same efficiency without having to pulse and glide (and annoying people behind you).
This could be used to keep the engine at its peak BSFC, increasing efficiency for the same load compared to engines without inlet augmentation.
With hybrids and PHEVs this may allow a smaller engine to be used, further increasing efficiency. Plus you get the benefit of a wider power envelope for emergencies.
Posted by: Gransee | 31 July 2015 at 02:35 PM
It is a pity they can't "program in" micro pulse and glide where you keep a very narrow velocity band (say 59-61 or 58-62 mph) and let the engine management system handle it.
(It would have to be a specific driving mode.)
Perhaps, it would refuse to engage if it found a car following.
It strikes me that PnG should be an integral part of the system rather than an annoying trick that hypermilers do.
If this supercharger helps, great.
I am sure it could be less annoying if the system was designed to do it. (You could keep a low artificial engine noise running in the car so people inside noticed it less [optionally].)
Posted by: mahonj | 01 August 2015 at 12:28 AM
Agreed, on long drives I have wished that the cruise control had more hybrid friendly modes. Like changing its attack on hills. Allowing safer drafting ;) etc.
Excited about what this company is doing with electric superchargers. I can see them become standard on hybrids and range extenders. They need higher voltage models though. Like at least a 200v model. This would allow lighter construction and lower disc loading (greater air efficiency) for a given package.
And the effect would be better than pulse and glide because typical hybrid engines are optimized for a particular speed on a level grade. At speeds less than that, the cylinder loading drops and you have to pulse at a higher rpm to maintain at least some of the BSFC efficiency lost. But inlet augmentation raises the cylinder load allowing a lower RPM which is even more efficient than the normal BSFC peak for that engine.
For an engine optimized for say 55mph on a level grade, you could improve efficiency for speeds less than that by artificially increasing cylinder load while keeping RPMs low. This might allow the engine to instead be naturally balanced for say 75mph and operate even more efficiently at 55 than the other engine because RPMs are lower than the previous engine. I am not sure though, simulations would have to be run to verify this.
And of course, another advantage is a wider envelope. Atkinson engines like that used on the Prius are anemic at low RPMs. At high acceleration from low speed the super charger could overload the cylinder like a conventional super charger is normally used and I suspect this would still be more efficient than using the battery at high current. It also allows a smaller engine to be used since engine bulk is mostly about acceleration (only a fraction is used at cruise). A smaller engine would reduce the mass you need to accelerate in the first place.
Maybe the auto industry would use these mostly in non-hybrids to cut weight and increase efficiency while keeping/adding a little bit of pep.
Posted by: Gransee | 01 August 2015 at 07:18 AM
This looks like a great way to bypass the driveability issues of a turbo-Miller cycle while keeping the efficiency gains. It could wind up all over.
Posted by: Engineer-Poet | 01 August 2015 at 12:48 PM
Sounds promising! What is the value proposition - cost trade offs between this w/single scroll and double scroll turbos? I like the idea of an even smaller ICE in PHEVs!
I have also been wondering when the 48v systems will start up in the mainstream auto world. I think of the mass of 12v parts in the system and the reluctance to include another whole set of parts for headlights and bulbs and motors and bats etc. Any one doing 48v systems in mainstream yet, or soon?
Posted by: william g irwin | 02 August 2015 at 05:14 AM