Zero Emissions Diesels: How Ducted Fuel Injection can Save the Diesel Engine

Emissions. This has been a massive focus of the US Government and governments all over the world, for that matter, for the last few decades. More specifically, emissions output from vehicles, and especially diesel engines, has been under the watching eye of the EPA.

As we’ve discussed in other articles and videos, the EPA has nearly killed the diesel engine with emissions restrictions that force engine manufacturers to introduce new emissions components that ultimately give us, the end consumers, a more expensive and less reliable engine. And looking forward, future emissions standards appear to be so strict that it’s unlikely the diesel internal combustion engine will continue.

That being said, just because the upcoming emissions standards appear to be nearly impossible to meet, it can be done with the right innovation, which takes us to Sandia National Laboratories, the masterminds behind a new type of diesel injection system which can almost completely eliminate diesel engine emissions output and potentially save the diesel engine from death.

Where it Came From

This new type of diesel injector that we’re looking at today is known as Ducted Fuel Injection, and as I mentioned a moment ago, it’s been developed by Sandia National Laboratories, and more specifically by Charles Mueller at Sandia’s Combustion Research Facility.

And in case you didn’t know, the design of the injector in any given internal combustion diesel engine has a massive impact on power, fuel efficiency, and ultimately emissions output.

Because of that, we’ve already seen massive amounts of innovation in the industry over the years, with diesel engines ranging from indirect injection, direct injection, common rail injection, and most recently, we’ve seen some engine manufacturers switching from the tried and true piezo injector back to solenoid-type injectors as innovation has improved both types of injectors massively.

The Ducted Fuel Injector

With this new ducted fuel injection, however, things are very different. In fact, the entire idea behind this new type of injector actually comes from the Bunsen burner, which you can find in just about any science classroom in the US.

Quote “If you unscrew the tube on a Bunsen burner and you light the gas jet, you get a tall, sooty orange flame,” Mueller said. “Turn off the gas, screw the tube back on, and re-light the burner. Now you get a nice, short blue flame right at the end of the tube. The flame is blue because there isn’t any soot.” – Charles Mueller.

And interestingly enough, according to Mueller, the injectors we see in today’s diesel engines create local igniting mixtures that contain 2 to 10 times more fuel than is needed for complete combustion.

“When you have that much excess fuel at high temperature, you tend to produce a lot of soot. Installing the ducts enables us to achieve diesel combustion that forms little to no soot because the local igniting mixtures contain less excess fuel.” – Charles Mueller.

It works that instead of the fuel injector spraying fuel straight into the open combustion chamber, there are ducts just outside the injector openings the fuel is sprayed through. The ducts are shaped such that as the fuel is sprayed into them, the air is pulled in from the back of the ducts.

You can see this in this diagram that comes from Scientific American, which I’ll leave linked down in the description in case you want to check out some of the nitty-gritty details of this injection system for yourself.

Ultimately, this allows the air and fuel to mix much better and create a better air-to-fuel ratio, which then leads to much improved and cleaner burning. According to Sandia, they claim that soot can be reduced by as much as 50% to 100% with this type of system, depending on the conditions.

Emissions Output

The simplest way to explain how this would reduce emissions output in the real world is that with the injector reducing exhaust soot by 50% to 100%, that means you can massively increase exhaust gas recirculation to then massively decrease NOx emissions output without soot becoming a problem.

This would then also bring with it the added benefit of improving the reliability of exhaust gas recirculation systems, which historically struggle with reliability in the long-term due to soot build-up in the exhaust gas coolers, the valves that control the flow of the system, and more.

With that would also come a reduced cost of operating, as the improved air/fuel ratio and combustion would lead to improved fuel efficiency, and if you follow the effects of that down the line, that means any goods which have to go through the transportation system, which is basically everything, would become cheaper for the end consumer.

A hidden benefit to this type of injector is that it could allow diesel engine manufacturers to revert some of the changes they’ve made in recent years and potentially remove parts such as the diesel particulate filter or the diesel exhaust fluid injection system, or both. The result could still be a reduced output of soot and NOx, but with massive improvements to engine reliability and cost of operating by removing those components.

When Does it Come to Market?

So at this point, you might be wondering when we’ll see this injector used in the real world on diesel engines, and the answer to that isn’t yet clear. What I mean by this is that this injector is still in the research stages. However, it shows enough promise that companies such as Ford and Caterpillar are throwing money at Sandia to help advance the technology.

And really, this injector is showing so much promise that we’re now seeing other companies in the automotive space, such as Toyota, doing their own research and development on this and coming to nearly the same conclusion, which is simply massive reductions in soot.

In theory, this injector should be able to be easily retrofitted into older diesel engines, especially very cumbersome engines like powerplants, ships, and trains. Even something like a semi-truck with a caterpillar, international, or Detroit engine could be targeted for retrofitting with this injector. The point is, that the design of this injector won’t be limited to brand new engines, at least according to Sandia.

And to be fair, the hard part isn’t necessarily getting a new innovation to work in a simulation or even in small-scale real-world testing; rather, the big hurdles can actually come when it’s time to scale it up and bring it to the real world on a big scale.

Things such as reliability, cost, use of materials, and so much more are factors that must be accounted for, so although we have yet to see this injector used at scale or really at all, it’s very promising, and if it ultimately works out, this injector could ultimately save the diesel engine from being killed through EPA restrictions.

The Transportation Industry

But because the transportation industry is very focused on reliability, it could be a while until we see this new injector adopted, as new technologies are very slowly adopted in this industry unless forced through government regulation.

And it makes sense. Why switch injectors if you don’t have to? Why risk a potential decrease in reliability and a massive dip in profits when the engine isn’t working? Until this injector is proven to be as reliable or more reliable than current injection systems, it probably won’t see quick adoption unless there’s a clear and significant upside of reduced cost of ownership and potentially the removal of reliability plaguing emissions systems such as the DPF and SCR systems.

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