October 27, 2020

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U.S. Army’s future vehicles to receive hybrid-electric engines

The U.S. Army has announced that its future air and ground vehicles will receive multi-fuel capable hybrid-electric engines.

According to a recent service news release, Army awarded the University of Wisconsin-Madison a four year, $11.5 million contract for research that’s expected to lead to new designs of multi-fuel capable hybrid-electric engines to address future Army air and ground vehicle needs. Researchers expect to begin work this fall.

At the U.S. Army’s Combat Capabilities Development Command Army Research Laboratory, researchers said they selected the university to help identify new technologies that could allow the Army to use multiple fuel types. The research is also expected to answer key questions about integrating hybrid-electric engines in future Army propulsion and power generation systems.

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“Right now, the Army’s unmanned aircraft are powered by engines built for ground transportation systems; these engines were developed to work with commercially-available fuels such as gasoline and diesel,” said Dr. Mike Kweon, program manager for the laboratory’s Versatile Tactical Power and Propulsion Essential Research Program. “To comply with the Department of Defense single fuel forward policy, our ground and air vehicles must use F-24, [which is] a kind of jet fuel. Even though this fuel has been upgraded with three military additives for greater performance, the fuel lacks fuel property specifications such as cetane number and viscosity.”

These property specifications, as used with personal vehicles, translate to performance and reliability, Kweon said. Army researchers need to know these properties to make sure that the fuels are acceptable for use however Soldiers just need to know the systems are performing as they should and are reliable.

The University of Wisconsin-Madison’s research will lead to the development of enabling technologies for reliable ignition detection and control. Current ground vehicle engines do not perform well with low quality fuels such as fuels with cetane numbers below 40, Kweon said.

Cetane number 40 is the lowest allowed number regulated for diesel fuels in the U.S. The cetane numbers of typical jet fuels go down as low as 30, and can reach 17 or lower for alternative jet fuels.

Future Army propulsion systems also need to meet increasing payload and onboard power requirements along with the desire for new capabilities, such as reduced noise or thermal signature, and improved durability and reliability, he said.

As an immediate solution, the new research will look at how local in-cylinder energy deposition can assist the compression-ignition process, termed energy-assisted compression ignition. This work is expected to create vehicle components that enable engines to accept multiple fuel types.

For future hybrid-electric propulsion and power systems, research will focus on novel oil-less bearing technology that will realize lightweight compact electric generators using exhaust waste energy. In addition, Kweon said researchers will develop, validate and apply tools that will be integrated into a comprehensive modular Hybrid-Electric Optimization and Integration Tool. This will be used to configure future Army hybrid-electric air and ground vehicles.

“The University of Wisconsin-Madison is well-situated to contribute substantially to the understanding and development of the advanced technologies needed by the Army for multi-fuel capable engines and hybrid-electric propulsion systems,” said Prof. David Rothamer, principal investigator for the project team at the University of Wisconsin-Madison. “The University has unique capabilities and research strengths in these areas as a result of the faculty, staff, and facilities of the Engine Research Center and Wisconsin Electric Machines and Power Electronics Consortium. We look forward to working with the Army Research Laboratory and other project partners to address critical Army needs.”

Dr. Mark Tschopp, regional lead for ARL Central in Illinois, said partnerships between the Army, academia and industry are “crucial to the CCDC Army Research Laboratory’s mission to operationalize science for transformational overmatch.”

“By expanding the team to include experts in academia, small businesses, and industry, together we can take concepts and ideas and transform them into future capabilities for the Army,” he said.

This university-led research project is one of 11 funded this summer by the Army’s corporate laboratory as a part of Center for UAS Propulsion efforts to develop technologies for multi-fuel capable engines. Each university partner is helping the Army address the energy demand required to power future unmanned vehicles. Universities also awarded for similar research are the University of Minnesota; University of Michigan; University of Illinois-Urbana Champaign; University of Illinois at Chicago; Iowa State University; University of Delaware; University of North Texas; Texas A&M University; University of Missouri and University of Tennessee-Knoxville.

The research is part of a larger research portfolio of multi-fuel capabilities technologies led by the laboratory to support the Army modernization priority for Future Vertical Lift. The laboratory recently announced the development of a new, advanced scientific model to allow vehicle maintenance specialists to turn to bio-derived fuels in austere locations, and efforts to convert a home-based generator into a power source for autonomous ground and air vehicles.