Turbos Tackle New Propulsion Applications

May 1, 2018

Honeywell’s Geoff Duff: From Formula SAE to boosting future mobility. (Image: Honeywell)

Turbo machines continue to drive engine “right-sizing” trends while adding complementary technologies such as electric motors. They’re also finding new applications for vehicle propulsion. Pairing an advanced turbo system with its latest hydrogen fuel cell stack helped Honda create the recently introduced Clarity Fuel Cell. The 5-passenger sedan offers an anticipated U.S. EPA driving range exceeding 300 miles (483 km), a refueling time of under five minutes and zero tailpipe emissions except water.

Honeywell Transportation Systems engineers worked closely with Honda counterparts to deliver an industry-first 2-stage turbo compressor for the Clarity application. The Honeywell machine operates at a maximum 4 bar (58 psi) and the fuel-cell “stack” has a 20-kW continuous rating—claimed to be more than double the power density of comparable stacks and delivering 60% more power density compared with Honda’s previous-generation FCX Clarity. It also marks the first automotive use of Honeywell Aerospace air-foil bearings. Cooled by the machine’s own compressed air, the bearings eliminate the potential for “poisoning” the stack with oil mist.

Such applications expand Honeywell’s turbocharger horizons, noted Geoff Duff, Director of Applications Engineering, North America. A 15-year veteran at Honeywell Transportation Systems, Duff was an ardent Formula SAE competitor during his undergrad years at Purdue University. He spoke recently with Automotive Engineering Editor Lindsay Brooke.

The century-old ICE proves that it’s ‘not dead yet’ with new boosting solutions that help extend its life. What new engine trends do you see emerging?

Well, fuel cells are part of our electrified strategy. We see engines moving to power densities of well over 100-kW/L. Gasoline engines will continue to push toward higher compression ratios and BTEs well past 40%. Coupling boosting with hybrid systems really starts to open a bright future for IC engines as they get more efficient. New ways to optimize the ICE create bigger demand for air and new challenges from a boosting perspective. This trend will continue as we push gasoline engines to behave a bit more like diesels.

The SpCCI from Mazda and VR variable compression ratio engines from Nissan are potential next steps. We’ll have to see how they play out. There are also heavy Miller-cycle applications. The common theme across all of these is they require boost. This is where we’re seeing some of the technology we’ve developed start to be applied. Variable geometry (VNT) turbos and new gas and diesel turbos focused on transient response and high efficiency in the critical areas of the operating map.

Turbochargers have become multi-role devices.

Yes. For example, running Miller-cycle creates a reduction in power, which creates a challenge for the turbocharger. That’s where the benefits of variable geometry (VNT) technology can make up some of the losses. It can provide boost where a traditional wastegate turbo doesn’t have the compressor power to drive the kind of boost needed at low speeds and low loads. A tremendous amount of our work with customers is around ensuring bypass flow and enhancing catalyst light-off to help reduce emissions. A solution: we’re doing a lot of work with electric actuation.

Where is electrically-assisted turbo technology going?

Honeywell is taking a complete-systems approach. We’re developing very high-speed electric motor controls and diagnostic software. We’ve been able to overcome thermal challenges through the design of the motor itself, how we cool it and how we cool its controls. We’ll soon have the manufacturing technology to build electric turbos to enter production in the 2021-2022 timeframe.