Engineers who analyze combustion processes do not need more variables. However, biofuels, which have burning and performance characteristics that differ sharply from petrodiesel, will alter the way engines perform.
Blended fuels are making solid headway as producers and equipment owners attempt to offset high oil costs. The renewable fuel’s real growth will come in an era of new low-emissions, electronically controlled engines.
“Injection pressures continue to rise; now they’re around 2000 bar, and we’ll see higher levels in 2010-2012. Biodiesel will see a high-tech environment,” said Marcus Parche, Senior Engineering Vice President for Commercial Fuel Injection, Robert Bosch.
Using biodiesel involves a number of issues. Parameters such as operating temperatures change, and different blends provide varying power levels. As operators move to higher percentage blends, performance will change noticeably.
“Engine performance is basically stable up to 30% biodiesel, with only 1 or 2% power reduction. When you go to 100%, it goes down 4 to 10%,” said John Cottrell, CNH Integration Manager at Fiat Powertrain Technologies.
Engine makers must also determine the long-term impact of blended fuels. Until that is determined, it will be difficult to establish warranty periods.
“The majority of problems stem from the quality of the fuel. Today there are no warranties for using fuel blends greater than 5%,” said Cottrell.
Those quality concerns come from many issues. One is that production techniques for biodiesel are still new. A National Renewable Energy Laboratory survey in 2006 found that nearly half the samples of biodiesel failed tests because they had impurities.
Another issue is that biodiesel can loosen deposits in fuel tanks. “Biodiesel has high solvency. It removes deposits in the tank, which may cause clogging,” said Cottrell.
However, preventing these deposits from causing problems is fairly straightforward. Equipment operators have already found simple solutions for that problem. “Immediately when you first load in bio-diesel, the fuel filter should be changed, and you should expect to change the filters more often,” said Mike Weinert, Director, John Deere Power Systems. He added that Deere has seen few problems when operators use quality fuel.
Proponents of biofuels also note that biodiesel is not well suited for harsh winter climates. “There’s some cold flow degradation. If winter conditions are severe, you should go with petrodiesel,” said Weinert.
The fuel is also less than optimal in environments where it will not be used over long periods. “In field fleet tests, B20 can be used successfully if fuel storage time is less than six months and you use adaptive filtration,” said Parche.
Engineers developing engines will have to consider many parameters that change with the use of biodiesel. One bright spot is that they will not have to learn to use new tools while they are learning about biodiesel characteristics.
“The introduction of biofuels is unlikely to significantly change the tools applied to combustion analysis. However, we are developing the ways these tools are used. Some future engines will require capability to detect and adapt to a wider range of fuel properties,” said Graham B. Weller, Heavy Duty Diesel Group Director at Ricardo.