FTIR Examines Engine Deposits

Michael K. Robinson

CHESTER, UK -- Collaborators from Queen's University in Kingston, Ontario, Canada, and the Shell Research and Technology Centre Thornton in Chester have combined chemical separation with Fourier transform infrared (FTIR) spectroscopy to examine residues on diesel engine pistons after lubricant tests. Their report, published in Applied Spectroscopy [volume 51, page 827 ], details a method for using spectroscopy to analyze complex substances.
H.F. "Gus" Shurvell at Queen's University said that his group chose FTIR spectroscopy because it was well-suited to examining engine deposits. Earlier efforts by other researchers to use IR spectroscopy to study engine deposits suffered from analyzing the untreated deposits directly. Because engine deposits contain ash (inorganic material), soot (carbon by-products) and organic materials, they can create a confusing absorption spectrum that nullifies much of the detail needed for accurate analysis.

Using FTIR spectroscopy to examine lubricant deposits on diesel engine pistons may eventually improve the performance of the engines, which power a variety of heavy equipment.

Using an array of chemicals, the researchers separated the three types of materials for FTIR analysis. The group used a Bomem MB 120 infrared spectrometer for the tests. The results revealed that the technique was successful in distinguishing between the compounds deposited at different locations on a piston. Deposits closer to the top of the piston showed a higher degree of lubricant degradation than those lower down. Shurvell said this likely was because the area close to the piston's top comes in more direct contact with combustion.
Shurvell said deposits can affect engine performance in different ways. While many deposits can hinder performance, still others may enhance it. FTIR spectroscopy can give researchers and engineers a clearer idea of which lubricants and additives work best.
Much of the diagnosis of engine deposits is the result of many years of mechanical experience rather than hard scientific evidence. "We are trying to introduce some science into the process of examining engine deposits," Shurvell explained.
His collaboration with Shell's laboratory is continuing. He said they currently are using IR spectroscopy to determine how lubricant additives interact at various temperatures. Preliminary results indicate that at room temperature, some additives interact in ways that reduce their effectiveness, but when those additives are at higher engine temperatures, they do not interact perniciously.