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ORNL engine research supports new fuel development

ORNL’s marine engine research team, from left, Mike Kass, Eric Nafziger and Brian Kaul, work with ExxonMobil at the National Transportation Research Center. Image credit: Carlos Jones, ORNL

When ExxonMobil was searching for a research partner to operate a one-of-a-kind experimental engine that would enable the development of next-generation lubricants for the marine industry, one place topped the international oil and gas company’s list: ORNL.

Custom-built to one-tenth scale by Mahle Powertrain and Seacoast, the flexible-fuel, single-cylinder marine diesel engine, called the Enterprise, stands 12 feet tall and weighs more than 16,000 pounds, with a rated speed of 625 rpm to match the linear average piston speed of a full-scale engine.

“ExxonMobil came to ORNL because we know fuels and emissions, and we know engines,” said Mike Kass, senior engineer and principal investigator on the project. “However, we knew land engines and nothing about this particular unconventional two-stroke marine engine, so we had a learning curve."

Since the Enterprise was commissioned in 2016 at the DOE’s National Transportation Research Center at ORNL, Kass and his team have not only navigated that learning curve, they’ve also conducted research to inform ExxonMobil products such as a new suite of low-sulfur fuels. Called EMF.5, the suite adheres to sulfur-compliant marine fuel specifications.

“The research at ORNL allowed ExxonMobil to perform controlled engine-based experiments and filled the gap between bench-scale and full-engine tests,” Kass said. “This engine has been an integral part of ExxonMobil’s whole research strategy to develop next-generation lubricants.”

The marine industry is facing the challenge of transitioning to low-sulfur fuels. The International Maritime Organization's low-sulfur fuel requirement begins in 2020, stipulating that container ships must reduce the sulfur content of vessel fuel from 3.5 percent to 0.5 percent.

Fuels lower in sulfur produce fewer emissions and therefore reduce air pollutants. ORNL’s research exploring the impact of various lubricant formulations on fuel efficiency is expected to lead to new lubricant products that will improve energy efficiency.

marine engine lubricant
ORNL researchers at the National Transportation
Research Center study the impact of lubricants
on the marine engine’s efficiency and durability.
Image credit: Carlos Jones, ORNL

“Marine ships are longer than the Empire State Building is tall and wider than a football field,” Kass said. “Fuel accounts for 50 percent of operation costs, and the sulfur emissions from one ship equates to 50 million cars. When you think about more than 90 percent of all goods across the world being shipped via cargo vessels, the pressure on the marine industry to comply with this sulfur regulation is tremendous.”

At the NTRC, Kass and fellow researchers Eric Nafziger and Brian Kaul continue to collect invaluable data on the Enterprise, running the engine for weeks at a time to determine the impact of lubricants or oils on engine efficiency and durability, including wear and corrosion. The team conducts experiments in controlled environments.

“These controlled-environment experiments allow us to eliminate variables such as weather patterns, cargo loads and temperature that would impact the performance and isolate the effects of lubricants,” Kaul said. “Those things do impact fuel efficiency in the field and make it difficult to get repeatable experimental results. That’s an advantage of laboratory experiments here, because we aren’t subject to some of those uncontrolled fluctuations that make it difficult to resolve the effects we’re looking for.”

Kass added that the team is working to install a fuel system to conduct experiments that evaluate the performance of various ExxonMobil lubricants in protecting the engine from wear, corrosion and deposits with new fuel.

As research continues, Kass and his team will continue processing data from the engine, monitoring its performance as it steadily runs at NTRC.

We’ve met all of our objectives with this project. That’s because ExxonMobil understands that science is necessary to meet the low sulfur regulation. They respect the science and research side of it.
It’s been uncharted territory for both of us, but we’ve worked through all of this together to achieve our goals.

- Mike Kass, ORNL senior engineer and principal investigator