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ClearFlame Engine Technologies completes on-road demo of Class 8 truck with Cummins X15 running E98 ethanol

ClearFlame Engine Technologies, a a startup developing net-zero engine technology (earlier post), successfully completed an on-road demonstration of its proprietary technology that enables a heavy-duty truck diesel engine to operate on low-carbon and carbon-negative fuels, including 100% renewable plant-based fuels.

The demonstration of ClearFlame’s engine technology was implemented by taking a Class 8 diesel truck running on a Cummins X15 500hp 15L heavy-duty engine—commonly used for long-haul truck and off-highway applications—and converting it to run on renewable E98 ethanol.

While the wide availability, cost-effectiveness, and lower emissions of ethanol make it the fuel of choice today for the engine, ClearFlame’s technology is fuel-agnostic and can run on a range of renewable fuels.

ClearFlame’s solution elevates combustion temperatures in order to enable use of non-traditional fuels—that fail to ignite using conventional diesel-style MCCI (mixing-controlled compression ignition)—without sacrificing performance.

In a high-temperature environment, any fuel will behave like diesel fuel, having short ignition delay and burning as it is injected in a mixing fuel plume. Low-sooting fuels allow for the elimination of diesel particulate filtration (DPF). Use of soot-free “Clear” Exhaust Gas Recirculation (EGR) can allow for lower NOx emissions without the competing soot constraint, meeting next-generation emissions standards without added aftertreatment complexity.

Without soot, compression ignition engines are not limited to lean operation and can instead use the stoichiometric air-fuel ratio. ClearFlame uses soot-free “Clear” Exhaust Gas Recirculation (EGR) to maintain this ratio under varying load conditions.

Stoichiometric operation substantially increases power density and leaves an exhaust composition suitable for three-way catalysis (TWC) instead of Selective Catalytic Reduction (SCR) using urea/ammonia (DEF). Simplifying the engine’s aftertreatment system improves its reliability and reduces its cost by about 75%. It also improves its NOx reduction capability to near-zero levels. Using soot-free fuels eliminates the need for a Diesel Particulate Filter (DPF).

Due to the incredible work and dedication of our engineering team we’ve taken a massive step in showing the world how our technology is a game-changer for decarbonization of the heavy-duty transportation sector. This vehicle is truly one-of-a-kind—the only Class 8 truck to run on 100% ethanol fuel without any additives and without any diesel fuel. Driving this vehicle today is actually less carbon intensive than a comparable electric-powered truck. The ClearFlame-enabled engine meets the performance and efficiency requirements customers expect from their diesel trucks, while significantly reducing greenhouse gas emissions and fuel costs.

—Julie Blumreiter, ClearFlame’s co-founder and chief technology officer

The trucks equipped with ClearFlame’s engine technology will reduce CO₂ emissions significantly, while lowering criteria pollutants: particulate matter (soot) and NOx. ClearFlame has the potential to mitigate carbon in the heavy-duty truck sector faster than any alternative, including hydrogen and battery EV, without compromising engine performance, the company says.

ClearFlame is also a cost-effective solution, eliminating the “green premium” paradigm, and offering a fast, scalable, and low-cost option.

ClearFlame’s technology can be used anywhere diesel engines are used today, and leverages existing infrastructure—fuel production and distribution, engine manufacturing and remanufacturing processes, and the heavy-duty parts & services industry. The company is currently focused on heavy-duty markets that don’t have sufficient alternatives to liquid combustion.

ClearFlame will continue testing its trucks under various operating conditions throughout Q1 2022, with customer beta testing underway by the end of 2022. In addition to long-haul trucking, the technology enables emissions reduction for hard-to-electrify applications in a wide range of industries, including agriculture, power generation, and other off-highway markets.

ClearFlame is also working with John Deere on a pilot demonstration project for an off-highway engine platform, demonstrating the versatility of the company’s technology as a retrofit option or original equipment integration.

The demonstration comes less than four months after the company announced it secured $17 million in Series A financing (earlier post), led by Bill Gates-founded Breakthrough Energy Ventures, with participation from Mercuria, John Deere, and Clean Energy Ventures.



Another Compression Ignition engine working on non-traditional diesel fuels is Achates Power. They have been developing Opposed Piston engines also with Cummins (the US Army should get an Advanced Combat Engine Based on the Achates Power concept, built by Cummins).
Achates Power has a hybrid opposed-piston engine project funded by ARPA-E (references: https://achatespower.com/wp-content/uploads/2019/12/Achates-Power-Hybrid-OP-Engine-ARPAE.pdf and https://saemobilus.sae.org/content/2021-01-1242/).
Just thinking . . . The planned RAM Electric Truck will have a “Range Extender” that will let RAM push past it’s competitors (https://www.thedrive.com/news/44248/ram-electric-pickup-will-have-a-combustion-range-extender-ceo).
A hybrid opposed-piston engine series range extender running on gasoline or E85 used only when traveling long distances and pulling a trailer would definitely make the RAM pickup outstanding.


How about a higher energy dense traction battery instead of a complicated polluting ICE as an extender? As battery tech advances, there will be little need for hybrids and their higher costs.


Yes exactly - why not a range-extended EV drive aka series hybrid with ICE generator powered by 95%-plus ethanol or biodiesel?
PS. Not many people are aware that the initial versions of the GM Volt were found to contain inactive software designed to enable some degree of flex-fuel operation.
Paul G


@ Lad; EVUK_co_uk:
You fellows just don't (want to) understand Neanderthals. They happen to love their "stone-axes" and want to stick with them forever. Please don't deprive them of their sole source of happiness.


Cool, rebuild my diesel engine too!
Why BEV if ICE are more ecological!


@Lad, etc.
The system described is not a “Diesel Hybrid”, it is an Emergency Backup Generator for extreme range/load carrying conditions. It is not a permanent part of the pickup up, it could fit in the pickup bed like the Ford patents (https://www.caranddriver.com/news/a34277725/ford-f-150-range-extender-ev-pickup-patent/)
or even in the trailer. Dethleffs (a division of Thor Industries) has an electric trailer
(https://www.greencarreports.com/news/1133124_towing-with-an-ev-are-electric-trailers-the-future) that uses a battery as a “Range Extender”.
It would be better to conserve biofuels or eFuels for Aviation and Maritime use.

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