Diesel Isn’t Dead

Cofounder of Convergent Science defends the internal-combustion engine, fully expecting already - sophisticated designs to run even cleaner and more efficiently in the future.

June 1, 2018

Ryan Gehm, based on keynote by Convergent Science’s Dr. Kelly Senecal

Spray and combustion predictions in a heavy-duty diesel engine using CONVERGE CFD software. New combustion strategies are being explored to further increase engine efficiency and reduce emissions. (Image: CONVERGENT SCIENCE)

Comparing the perception of the internal combustion engine’s imminent demise to the plot of an Edgar Allan Poe short story is an effective attention-getter. Dr. Kelly Senecal, owner and Vice President of Convergent Science, began his presentation on “The premature burial of internal combustion” by drawing a parallel to the horror experienced in the 1800s when many people had a real fear of being buried alive due to hundreds of cases in which doctors mistakenly pronounced someone dead. Point taken: despite many recent media reports to the contrary, gasoline and diesel engines still have a long, productive life ahead of them.

“The IC engine is an enormously complex system — there’s no way we’ve found the optimum yet,” he said. “I know a lot of people think that we’ve hit our limits on efficiency; I think this is still a huge opportunity and there’s a lot of room for improvement.”

Speaking in the Kohler booth at the Intermat exhibition in Paris, Senecal admitted he’s not an “engine guy,” explaining the reason he became fascinated with engines is they’re one of the most difficult problems to solve using computer methods: “They have turbulent flow, reacting flow, they have moving boundaries, phase changes. They’re really complicated problems and we can use CFD to help us capture what’s happening in the designs.”

Senecal is one of the original developers of the CONVERGE computational fluid dynamics (CFD) software package. He still works closely with engineers on problems related to combustion modeling and other fluid-flow phenomena.

“We need to think about the whole emissions [life cycle] when we compare technologies — for example, with electrification, how the electricity is being generated and so forth,” he said. “And we should explore all technologies — I’m against picking winners and losers instead of setting targets and seeing which technologies get us there.”

Nothing against electric

The Intermat presentation echoes a TEDx talk Senecal gave in late 2016, not long before the calendar flipped to 2017 — or “the year combustion died,” as he refers to it — because of the aforementioned proliferation of news articles reporting companies’ and countries’ plans to go IC engine-free by dates largely ranging from 2020 to 2040.

“I’m not against electric, hybrid or even fuel cells — all of these technologies have their place and should continue to be explored and improved,” Senecal said. “What I am against is the demonization of the IC engine.” He noted that this is particularly an issue in the automotive industry, to a lesser extent — as of now — in the off-highway sector.

The “dawn of the demonization” began with the Volkswagen “diesel-gate” scandal, he claims.

The pros and cons of each technology need to be fully considered. Citing a letter U.K. professors wrote in response to one particular article about diesel’s death, Senecal noted that many studies show 90% of ground transportation energy will continue to come from hydrocarbon-based fuels in 2040. Also, battery production is not emissions-free; in fact, it produces quite a lot of greenhouse gases, he said.

“Worldwide, about 70% of electricity is generated from fossil fuels still,” he said. “This idea that battery-electric vehicles are zero-emissions is just incorrect.”

Prediction of fuel sprays in the cylinder of a diesel engine using CONVERGE. Optimizing combustion chamber shape together with spray targeting is critical for achieving the best air utilization. (Image: CONVERGENT SCIENCE)

An often-overlooked factor, he said, is non-exhaust particulate emissions from tires, brakes and road surfaces. “I’m not sure yet exactly how this applies to the construction-equipment industry, but it must,” he said. “Because the PM emissions are so low coming from engines now, what’s produced from the tires and the brakes is comparable. And the heavier the vehicle, the more non-exhaust particulate matter you’ll get.”

Electric vehicles show promise, particularly in certain applications such as small excavators and loaders used in cityscapes, but they’re far from a sure bet in many applications. For that reason, investment in the IC engine must continue, said Senecal. “If electric vehicles in the future don’t meet expectations, there’s danger that we’ll lose an opportunity to improve this technology.”

Improving an ‘ancient’ technology

It may be 100-plus year-old technology, but the IC engine has aged well, becoming more efficient and emitting far fewer pollutants in recent decades, driven by a combination of government mandates and innovation.

“Computer modeling has been a major factor in improving efficiency and emissions for heavy-duty diesel engines and will have an even bigger impact in the future as computers get faster and models get more predictive,” he said. “CFD allows a designer to truly understand why certain designs perform better than others as information is available at every point in space and at every time-step.”

Many technologies and strategies can be further explored, through modeling and/or experimentation, to continue this positive trajectory for heavy-duty diesel engines, according to Senecal. These include heat-loss reduction (e.g., insulated combustion-chamber surfaces), higher flow injectors for faster injection rates, optimized combustion chamber shape and matching with fuel spray targeting for best air utilization, higher compression ratios, and mild hybridization.

Heavy-duty diesel fuel injector flow predictions in CONVERGE. A cut-plane through two of the nozzle holes shows the velocity field in the needle and sac regions. High-flow injectors are being explored to help increase engine efficiency. (Image: CONVERGENT SCIENCE)

“Vehicles used in agriculture and construction and for long-distance travel will continue to be powered by the IC engine,” he said. “It’s clear that at this point in time the IC engine best meets the needs of the market.

“Diesel engines have a high energy content in their fuel. They have high compression ratios, which means high efficiency. They have high torque. And fueling vs. charging — I have an electric leaf blower at home and every time that battery runs out I have to wait a couple hours for it to charge. I can’t imagine working on the jobsite [in heavy equipment] and having to worry, ‘Do I have to charge my battery after a few hours?’”

No worries: because diesel is not on its deathbed just yet.