With approximately 300 million internal combustion engine (ICE) vehicles in the US transportation sector, approximately 14 million are expected to be purchased by consumers in 2022. Despite the rapid increase in electric vehicle (EV) sales, the market will continue to be dominated by internal combustion engines for decades to come.
The Fuels Institute, which bills itself as a non-advocacy research organization that assesses market issues related to vehicles and the fuels that power them, has released a new report titled “Future Capabilities of Combustion Engines and Liquid Fuels.” The report provides a summary of research and development projects focused on improving ICE efficiency and emissions and reducing the carbon intensity of liquid fuels.
“Although some have reported that work on ICE technology has stopped and no further improvements are possible, this study found thousands of recent citations of research that could lead to significant improvements in the performance and environmental footprint of these vehicles,” says John Eichberger, executive director of the Fuels Institute.
Battery Electric Vehicles (BEVs) and Hydrogen Fuel Cell Vehicles (H2FCVs) are widely recognized as the most effective way to reduce CO2 emissions in the transport sector. But even with aggressive strategies to electrify the transportation system, the market will continue to rely on ICE vehicles, including the deployment of hybrid electric vehicles (HEV) and plug-in hybrid electric vehicles (PHEV).
Gasoline engines for light commercial vehicles
Several fuel efficiency improvements have been made in the design of internal combustion engines for passenger cars over four decades, including variable valve timing and gasoline direct injection (GDI), gasoline engine turbocharging, and engine downsizing (number of cylinders).
GDI engines have been installed in over 50% of gasoline vehicles as of MY 2019 and are expected to continue to increase, according to the Environmental Protection Agency (EPA). The EPA also says vehicle engine downsizing is expected to continue, with over 50% of 2019-year gasoline vehicles equipped with four cylinders or fewer.
Additional ICE design improvements continue to be the subject of research efforts, which include advances with reported improvements in fuel economy or thermal efficiency.
Diesel CI engines for heavy commercial vehicles
Heavy-duty vehicles (Classes 7–8) hauling large volumes of cargo in the United States have generally relied on compression-ignition (CI) diesel engines for a variety of reasons. Diesel engines operate at a higher efficiency than comparable spark ignition (SI) engines.
In addition, diesel fuel has a higher energy density than gasoline. Overall, diesel CI engines were less expensive, resulting in lower running costs. Technology options exist to improve the fuel efficiency of high performance CI engines and implementation of these technology improvements is expected to result in fuel savings in excess of 20%.
HEV powertrain systems
The application of HEV technology to passenger cars has resulted in a real-world average fuel economy improvement of about 30%. Hybrid vehicle technology could potentially be applied to other future light-duty vehicles, depending on commercial feasibility, as HEV production accounts for only 6% to 7% of 2020 light-duty vehicles.
Research into converting the gasoline ICE portion of an HEV from SI to CI has found that gasoline compression ignition (GCI) hybrids reduce well-to-wheels (WTW) greenhouse gas (GHG) emissions by 7% to 43% compared to non-hybridized Reduce GCI and 26% to 55% over traditional SI.
ICE configured for dual fuels and blends
Traditional dual-fuel engines run on a primary fuel such as natural gas while using a small amount of diesel as a pilot ignition fuel. Commercial stationary dual-fuel engines are an established technology, but dual-fuel engines in transportation are currently being researched and developed while testing different fuel combinations and engine designs.
Future developments such as dual-fuel injectors and optimized nozzle designs should ensure higher overall efficiency. Fuel blend research has focused on the primary fuel and the search for alternatives with lower carbon levels than natural gas, such as hydrogen and renewable natural gas (RNG).
Alternative ICE fuels
More than 175,000 natural gas vehicles are already in operation in the USA. Advantages of natural gas as an alternative fuel include domestic availability, an established distribution network and reduced greenhouse gas emissions over traditional gasoline and diesel fuels, particularly when using RNG, according to the Alternative Fuels data center.
Biofuels have been used successfully in the transportation sector for more than 20 years by blending them with traditional petroleum fuels. According to a report by the International Renewable Energy Agency, “Liquid biofuels require little change in fuel distribution infrastructure or the transport fleet and can therefore be deployed quickly, leading to a much-needed reduction in greenhouse gas emissions.”
ICE Zero Emission Pathways
Most research has yet to identify ways to achieve carbon neutrality from a WTW-GHG perspective in relation to internal combustion engines using either liquid or gaseous fuels. A European consortium along with McKinsey & Company are proposing possible carbon neutral or near carbon neutral combinations, but these combinations are not yet commercially available.
Hydrogen internal combustion engines using hydrogen from renewable sources can potentially achieve zero WTW GHG emissions. Hydrogen fuel cells have received a lot of attention, but H2-ICE could also be a viable alternative with engine modifications required. Toyota has invested resources in the development of hydrogen vehicles and has successfully converted a Toyota Corolla into an H2 ICE.
In a 2021 report, the National Academy of Sciences (NAS) summarizes the continued dominance of ICE vehicles for the foreseeable future: “Combustion engines will continue to play a significant role in the new vehicle fleet in MY 2025-2035 for ICE-only vehicles as well Hybrid electric vehicles range from mild hybrids to plug-in hybrids, but will decrease in number as battery electric vehicles and fuel cell electric vehicles become more widespread.
The NAS report also says, “During this time, manufacturers will continue to develop and deploy technologies to further improve the efficiency of conventional pure combustion engine powertrains and how they are implemented in HEVs. Major automakers are taking different paths, with some focusing their R&D and deployment of advanced technologies more directly on BEVs, and others focusing more on advanced HEVs to maximize ICE efficiency.”
Originally posted on Automotive Fleet