Next-gen “tailored” turbo systems will enable extreme engine downsizing

  • 26-Apr-2010 01:24 EDT

The quest to boost efficiency and reduce NVH within turbocharger and other vehicle systems is driving use of more powerful computer analysis of subcomponents, as shown by this finite-element rendering of a pump impeller by Concepts NREC.

What do miniature pumps for treating water in a nuclear reactor, “fish-safe” hydroelectric turbine impellers, and axial fans designed to replace helicopter tail rotors have in common with the humble automotive turbocharger?

Much more than meets the eye, because design and engineering knowledge gained from developing advanced turbomachines of all types and sizes is being applied to creating the next generation of turbo systems for gas and diesel ICEs, said Fred Becker, Engineering Sales Director at Concepts NREC.

The 50-year-old Vermont company specializes in turbomachinery design, engineering, and development for a broad range of commercial, consumer, military, and agricultural applications. It has long been involved in automotive turbo systems R&D, prototyping, and testing.

“We’ve seen a steady increase in our engagement with the automotive OEMs regarding the trend to downsized and boosted engines to improve fuel efficiency,” Becker told AEI during the recent SAE World Congress. “They’re trying to expand the operating range and effectiveness of the single turbocharger, and two-stage systems, while also trying to understand what the next generation of turbocharger design and operating characteristics will look like.”

“It’s a paradigm shift, as engine swept volume continues to be reduced,” he said.

Becker noted that the next-gen turbos will be “tailored” to meet the duty cycles of the downsized four-, three, and even twin-cylinder gasoline engines, which powertrain engineers say will feature sophisticated boosting systems which integrate the turbo unit with cooled exhaust gas recirculation (EGR) and even particulate filters.

According to Becker, much of the turbo systems development work being done in the auto industry is “evolutionary—a half-point gain here and there,” he asserted. “But in order to achieve the significant gains needed by the powertrain guys, we’ve got to really push the aerodynamics inside the turbo system.”

Automotive OEMs which have engaged Concepts NREC for next-generation turbo systems development stressed that their upcoming smaller engines must deliver driveability and performance characteristics similar to the larger naturally aspirated engines they are replacing, Becker said. But engineers don’t want the parasitic losses and, in some cases, package disadvantages that come with positive-displacement superchargers.

Likewise, the trend toward fewer cylinders with ever-smaller displacements—the list of OEMs with sub-1.4-L gas engine programs is growing—puts a premium on R&D and validation expertise in analytics, fluid mechanics, thermal management, turbomachine structure, component optimization, materials, and system controls, to name a few of the key disciplines in which Becker’s company specializes.

“It’s a difficult challenge, but we’re already way up on the learning curve,” he observed. He said OEMs are changing their view of turbochargers as discrete components to that of integrated multifunctional systems.

The new approach means R&D specialist Concepts NREC, along with turbocharger suppliers such as BorgWarner and Honeywell Turbo Systems (and newcomers including Continental and the BoschMahle joint venture), increasingly are viewing the next generation of technologies as “energy recovery” systems rather than boosting devices. Becker’s company interfaces with the OEM powertrain development teams as well as turbo-system Tier 1s.

Becker said NVH attenuation is one of the hottest areas of development for which Concepts NREC is being asked to provide CAE, CFD, and 3-D analysis support to the OEMs. And quelling turbocharger noise is but one of many targets in this critical area.

“Coolant pumps and compressors are being redesigned for quieter operation and expanded operating range. Cooling fans can be made quieter and more efficient at various speeds. We’re right in the thick of all these areas, in addition to the advanced turbocharger work,” Becker reported.

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