Southwest Research Institute is investigating clean automotive technologies to enable traditional internal combustion (IC) engines to efficiently run on hydrogen fuel.
Government and industry researchers have in recent years sought methods to transition transportation energy usage away from fuels that emit carbon dioxide (CO2) — a greenhouse gas (GHG) that contributes to climate change — to hydrogen and other alternative fuels that emit less CO2 on a well-to-wheel basis. According to the U.S. Environmental Protection Agency, transportation alone produced 29% of total U.S. GHG emissions in 2019, the largest share.
Researchers have long aimed to use hydrogen in place of gasoline, diesel, and natural gas in IC engines. While hydrogen burns well inside IC engines thanks to a high flame speed, its unique properties, such as its low ignition energy, pose engineering challenges to be overcome. These properties promote pre-ignition, a process during which a mixture of air and fuel ignites in the unburned fuel, leading to uncontrolled combustion and subsequently damaging the engine.
SwRI’s Powertrain Engineering Division is researching potential solutions to these challenges, including higher-efficiency approaches to preexisting hydrogen IC engine concepts. The hope is that automakers can use the improved hydrogen-fueled engines to transition from current CO2-emitting engines to the zero-emission future.
“If we can adapt an existing IC engine design to burn hydrogen efficiently, then we have another option to reach zero CO2 emissions,” said Dr. Thomas E. Briggs Jr., SwRI staff engineer. “An efficient hydrogen IC engine can give us that necessary zero-CO2 emission characteristic while also providing an economically-attractive solution to the transportation industry.”
Briggs, Dr. Graham Conway, SwRI principal engineer, and Dr. Terry Alger, director of SwRI’s Automotive Propulsion Systems Department, recently ran simulations of four novel approaches for using spark-ignited combustion of hydrogen to fuel an IC engine.
“In the late 2000s, hydrogen IC engine development was being heavily funded by the U.S. Department of Energy and internally by a number of automakers,” said Briggs. “Our research builds upon some of the ideas that came about from that research period.”
According to Briggs, the research of that time demonstrated a hydrogen-fueled SI engine that could achieve 45% brake thermal efficiency (BTE) in the laboratory, which was competitive with diesel engines at the time. Today’s gasoline engines typically have BTEs of 30–43% and modern diesel engines have BTE’s from 42-50%. By comparison, each of SwRI’s simulated approaches show a development path to achieve at least 50% BTE.
“Higher brake thermal efficiency translates to lower fuel consumption,” Briggs said. “None of the simulations we completed represent fully optimized calibrations for a combustion system, but they all show thermal efficiencies comparable to a baseline diesel engine, with nitrogen oxides (NOx) emissions consistent with diesel combustion but no carbon monoxide, hydrocarbon, soot or CO2 emissions. It is very promising.”
Briggs, Conway and Alger recently received a patent for technology that improves hydrogen fuel injection management, optimizing air-fuel mixtures and minimizing the risk of pre-ignition. The team is working with engine suppliers to acquire a suitable fuel injector to move into the second phase of their research.
“SwRI is in a strong position to pick up the threads from previous hydrogen engine developments and improve on them,” said Briggs. “With a strong background in automotive engineering, emissions testing and hydrogen energy research, we are well-positioned to lead a shift to cleaner hydrogen-fueled vehicles.”
SwRI has a multidisciplinary team dedicated to hydrogen energy research initiatives to deploy decarbonization technologies across a broad spectrum of industries.