• + Honeywell leads the way in TwoStage revolution
  • + Series systems help optimize performance and emissions reduction

Multiplying the Turbo Advantage for Commercial Vehicles

Posted 05.19.2011

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On- and off-highway, sometimes it pays to compound the benefits of turbocharging by having two turbos in a series arrangement – for higher power density, increased durability, improved fuel economy, lower emissions and reduced response time.

Multiplying the Turbo Advantage for Commercial VehiclesAs diesel engine manufacturers develop innovative technologies to achieve their power, torque, fuel efficiency and emissions targets, TwoStage turbos from Honeywell are increasingly being adopted across a wide range of applications – from small downsized 4 cylinder construction vehicles to heavy-duty trucks and massive 24 cylinder mining equipment. The series turbo configuration is proving effective in meeting current and future NOx emissions targets and is emerging as a favored approach for supplying increased pressure ratios with inherent reliability.

In TwoStage series turbocharging, fresh air is drawn into the first stage compressor, where its pressure is raised about 2 to 2.5 times. This pressurized air is then drawn into the second stage compressor, where air pressure is further raised 2 to 2.5 times. The air is then cooled and the resulting charge air at the engine’s intake manifold is typically 4 to 5 times that of atmospheric pressure. By splitting the compression of the charge air between two turbos, both compressors operate at peak efficiency. Also, the lower pressure ratios for each stage mean lower rotating speeds, which results in longer life for the bearing systems, compressor wheels and turbine wheels.

“Series turbocharging offers the biggest benefits to engine manufacturers who apply Miller cycle, or Atkinson cycle strategies, or who require very high EGR rates” says Peter Haug, Director of Product Engineering at Honeywell Turbo Technologies. “The turbo system, particularly when combined with inter-stage cooling, demonstrates a significant improvement in engine thermal efficiency, leading to reduced fuel consumption. Another key benefit is the reduction in formation of particulates and NOx during combustion, the key regulated emissions in diesel engines.”

Honeywell is a pioneer in the TwoStage technology. First developed for high-altitude mining equipment in the early 1990s, the TwoStage turbo system was adopted by Caterpillar for its ACERT on-highway truck engines in 2003. Ever-tighter emissions requirements are also making this technology attractive for smaller displacement medium-duty engines. Currently, Honeywell’s TwoStage turbo technology is widely adopted in on- and off-highway segments in both the US and Europe.

While most TwoStage systems incorporate advanced wastegate and free-floating turbos, some OEMs are also opting for TwoStage systems that include variable geometry architectures to meet low end torque criteria, to backpressure the engine for exhaust aftertreatment regeneration, and to drive high pressure exhaust gas recirculation (EGR).

“We are confident that TwoStage turbo technology will see wider adoption around the world due to its inherent ability to help meet performance and emissions goals while maintaining system robustness,” says Peter Haug. ”We are strengthening our leadership in this technology through advances in low pressure aerodynamics, bearing systems, high temperature compressor wheel materials, sealing systems, and the best is yet to come.”