Tractors push biodiesel limits

DULUTH, Ga. – Owners of AGCO tractors are fueling up on B5 biodiesel (containing 5 percent plant- or animal-based methyl esters, not simply pressed oils), but AGCO is looking beyond B5.
Higher blends. The Sisu Diesel and Cummins engine powered tractors are fully approved for B5 blends, but AGCO is determined B5 is just the start. The company is actively reviewing the use of higher blends such as B10, B15 or B20.
Trials designed to push the limits of current Tier III engine technology are even running B50 and B100 biodiesel fuels. Most older engines are approved for levels as high as B100.
Sisu Diesel Tier II engines with Bosch P Type in-line injection pumps and older Sisu Diesel and Valmet engines are approved for B100 biodiesel.
Tests. Other engines and their entire fueling systems are undergoing testing and review for use with biodiesel at levels above B5.
For example, as biodiesel levels near B100, the increased fuel viscosity causes increased injection pressure.
“Resulting stress on the injection pumps could be a concern with heavily loaded engines,” noted Todd Stucke, general marketing manager, AGCO tractors.
AGCO researchers are exploring the effects of B10, B15 and higher biodiesel formulations on engines, fuel injection systems and fuel lines.
Trials at AGCO facilities in South America are evaluating Sisu Diesel engines running at a B50 blend, while in Europe, a trial is running on B100 fuels.
Longevity, productivity. Meanwhile, AGCO engineers are also evaluating a number of engine system longevity and productivity issues at levels of B10, B15 and B20, explained Stucke.
Issues being reviewed include, viscosity, lubrication and density, as well as effects of biodiesel not only on cylinder sleeves and pistons, but also on the fuel delivery system, from fuel lines to injectors.
Lubrication of engine parts during combustion has been shown to be higher than with straight petroleum diesel fuels.
Stucke said the company realizes its tractors represent significant investment to customers, so the company needs to make sure higher percents of biodiesel deliver the power the machines are capable of producing without harming the equipment.
Comparison. Mauno Ylivakeri, director of research and development at Sisu Diesel, compares the evaluation to what took place when sulfur was ordered removed from diesel fuel.
Engine power output is mainly a function of fuel density, viscosity and net heat of combustion. Biodiesel fuels normally have a higher density and viscosity, but a lower heat of combustion than fossil fuels. Increasing the fuel input compensates for the lower heat of combustion.
Engines are being evaluated under load to find the correct combination to promote maximum power output.
“We had a research benchmark for how engines functioned with sulfur,” said Ylivakeri. “We had to do the research to find new benchmarks when it was replaced with alternative lubricity additives. Now, with biodiesel, we are working to establish a new set of benchmarks that ensure engine life and productivity.”