Low-temperature combustion (LTC) remains an area of high interest with extensive research, even though many challenges must still be overcome before LTC sees commercial acceptance. Though panelists at the SAE WCX 2017 were pessimistic about the prospects for production engines, they remain bullish about the technology’s potential for reducing emissions.
There’s plenty of research going on. The International Energy Assoc., which represents 29 member countries, has dedicated a task force to the technology. Arne Andersson of Volvo Global Truck described an ongoing study into seven fuels used on low temperature engines. Biodiesel, methane and ethanol are preferred, he said.
Delphi Automotive Systems’ Mark Sellnau noted that LTC improves efficiency and reduces emissions, although he said spark ignited engines may only see gains under 10%. He suggested that researchers focus on fuels that are readily available, since there are many other challenges that must be overcome.
“LTC translates to low temperature exhaust, which makes aftertreatment an issue,” Sellnau said. “Also, there’s not much energy to drive a turbo. Compression [ignition] engines are stronger candidates.”
Finding the right fuel remains a central issue for researchers. Magnus Sjöberg of Sandia National Laboratories noted that many fuels don’t have enough energy to “make things happen” at low temperatures. Panelists said that R&D could proceed more quickly if development tools were better.
“One thing we could really use is computational fluid dynamic and chemical models that are actually predictive so we could test virtually instead of only in physical tests,” said Per Tunestal of Sweden’s Lund University. “Tools are not predictive enough, not fast enough and not accurate enough.”
While panelists expressed excitement about ongoing research, they were also honest about predictions for commercial applications. A member of the standing room only audience asked panelists to predict the percentage of engines sold in 10 years that would employ LTC technology, given fairly stable fuel prices.
“Zero,” was the response from Stephen Ciatti of Argonne National Laboratory. Two other panelists concurred with that prediction. Ciatti said diversity is a big challenge for LTC.
“There’s no one best solution. It depends on the level of longevity you want, the type of fuel that’s available, the lowest cost," Ciatti said. "The answers are different for Volvo trucks in Sweden and passenger cars in the U.S."