Yes, there are plenty of electric vehicles – and EV truck fleets – ready to take the road in 2022, but there are still segments of the market that use traditional powertrains and traditional liquid fuels.
For these older models, there aren’t many options, says co-founder of the Geneva, IL-based enginemaker ClearFlame.
“Right now, we don’t a have a great solution to those powertrains besides using diesel or a little bit of natural gas,” said B. J. Johnson, CEO of the company, during a live Tech Briefs presentation in late 2021.
By being a kind of “diesel engine without the diesel fuel,” says Johnson, ClearFlame offers a fuel-agnostic engine that employs a high-temperature combustion process. High temperatures enable ignition of lower-reactivity fuel – say, ethanol – and achieve diesel engine operation.
But do higher temperatures lead to extra tailpipe emissions of the pollutant nitrogen oxide, or NOx?
A Tech Briefs reader asked the following question to Johnson during the webcast.
What type of tailpipe emissions are you getting from ethanol? Do you still need a diesel particulate filter (DPS) or a selective catalytic reduction (SCR) after-treatment system to meet emission targets?
Read Johnson’s edited response below.
Johnson: First off, anytime you mention “high-temperature combustion,” a combustion engineer’s brain will go to “excess NOx.” This is more typical if you’re working with petroleum diesel fuel. That’s because, when you’re producing soot during your combustion process, it becomes a lot more challenging to be able to manage the NOx emissions.
By using fuels that are fundamentally soot-free — fuels like ethanol or methanol — you don’t need a diesel particulate filter. And, because you don’t have a soot/NOx tradeoff in the engine, you can also drive down levels of engine-out NOx in this system.
Would you still need a selective catalytic reduction system?
Yes, you probably will still need one, but it’s going to be doing a lot less work. It’s going to be at higher temperatures. You won’t need to worry about catalyst light-off [the minimum temperature necessary to initiate the catalytic reaction].
You’ll have reduced consumption of urea [a component of diesel exhaust fluid]. Although you still probably will need the selective catalytic reduction, long-term, we’re looking at pathways to drive NOx so low that we can eliminate it. Near-term we intend to keep it on there, but still manage NOx within a relatively narrow region by not having to compensate for soot as well.
What do you think? Share your questions and comments below.
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