A fundamental investigation into the relationship between lubricant composition and fuel ignition quality. (15th November 2015)

• Record Type: Journal Article
• Authors: Kuti, Olawole Abiola; Yang, Seung Yeon; Hourani, Nadim; Naser, Nimal; Roberts, William L.; Chung, Suk Ho; Sarathy, S. Mani
• Is Part Of: Fuel. Volume 160(2015)
• Page Start: 605
• Page End: 613
• Publication Date: 2015-11-15
• Subjects: Low speed pre-ignition (LSPI) -- Direct injection spark ignition (DISI) -- Ignition quality tester (IQT) -- Lubricant base oils -- iso-octane -- Total ignition delay; Fuel -- Periodicals; Coal -- Periodicals; Coal; Fuel; Periodicals; 662.6
• DOI: 10.1016/j.fuel.2015.08.026
• Languages: English
• ISSNs: 0016-2361

Abstract

Abstract: A fundamental experiment involving the use of an ignition quality tester (IQT) was carried out to elucidate the effects of lubricant oil composition which could lead to low speed pre-ignition (LSPI) processes in direct injection spark ignition (DISI) engines. Prior to the IQT tests, lubricant base oils were analyzed using ultra-high resolution mass spectrometry to reveal their molecular composition. High molecular-weight hydrocarbons such as n C16 H34, n C17 H36, and n C18 H38 were selected as surrogates of lubricant base oil constituents, and then mixed with iso -octane ( i C8 H18 -gasoline surrogate) in proportions of 1 vol.% ( i C8 H18 = 99 vol.%) and 10 vol.% ( i C8 H18 = 90 vol.%) for the IQT experiments. In addition, lubricant base oils such as SN100 (Group I) and HC4 and HC6 (Group III) and a fully formulated lubricant (SAE 20W50) were mixed with iso -octane in the same proportions. The IQT results were conducted at an ambient pressure of 15 bar and a temperature range of 680–873 K. In the temperature range of 710–850 K, the addition of 10 vol.% base oils surrogates, base oils, and lubricating oil to the 90 vol.% i C8 H18 reduces the average total ignition delay time by up to 54% for all mixtures, while the addition of 1 vol.% to 99 vol.% i C8 H18 yielded a 7% reduction within the same temperature range. The shorter total ignition delay was attributed to the higher reactivity of the lubricant base oil constituents in the fuel mixtures. A correlation between reactivity of base oils and their molecular composition was tentatively established. These results suggest that the lubricants have the propensity of initiating LSPI in DISI engines. Furthermore, similar results for n -alkanes, lubricant base oils, and fully formulated commercial lubricants suggest that it is the hydrocarbon fraction that contributes primarily to enhanced reactivity, and not the inorganic or organometallic additives.