When you light up a Tiki torch, the last thing you are likely thinking about is combustion engine efficiency. But that’s exactly the connection that engineers at the University of Notre Dame made in a recently published study.
The engineers are using the torches as part of an apparatus that mimics a diesel engine’s soot oxidation process—when soot in the engine exhaust collects on a particulate filter and has to be burned off—in order to develop a more efficient way to trigger that process.
“We have discovered and developed low-cost catalysts for soot oxidation that are based on silica glass,” said Paul McGinn, the study’s co-lead author and professor of chemical and biomolecular engineering at Notre Dame. McGinn and co-principal investigator Changsheng Su at Cummins Inc. developed a way to coat diesel particulate filters with the silica glass, which slowly releases potassium ions that act as catalysts to reduce the temperatures needed to trigger soot oxidation.
A standard diesel particulate filter is a ceramic cylinder with a porous honeycomb-like structure. As exhaust enters the filter, the interior walls trap soot particles, “cleaning” the exhaust of those particulates. To burn off the soot buildup, exhaust temperatures need to reach 600°C—which is difficult to attain in urban environments where the engine keeps starting and stopping.
“We’ve developed an inexpensive glass coating that’s one to two microns thick and apply it to the diesel particulate filters,” said McGinn. “The glass delivers a potassium catalyst slowly over 150,000 miles of driving and allows for what’s called passive regeneration. So, when you’re out on the highway at high speed, the exhaust temperature gets high enough to burn off soot buildup continuously.”
To test their improved filter, the team constructed a sophisticated reactor equipped with a soot generator and sensors. The flow of oxygen, air-to-fuel ratios, and rate of soot production can all be controlled within the reactor. The Tiki torches provide the soot buildup needed for testing.
This research will likely be of particular interest to diesel vehicle producers. Diesel engines emit soot particles and nitrogen oxides (NOx), both of which contribute to global warming and can cause people to experience breathing problems. The challenge for automakers and engineers is to reduce emissions without sacrificing vehicle performance. It’s no easy task: when the engine is adjusted to emit low levels of NOx, soot levels increase—and vice versa.
The team’s next step is to look at how it can further adjust the silica glass composition to also reduce NOx emissions—increasing the viability of this method to reduce greenhouse gas pollution created by diesel engines.
Read more about the quest to make more efficient combustion engines at Fiat Chrysler Creates New Aluminum Alloy for Engines.