A fundamental investigation into the relationship between lubricant composition and fuel ignition quality
Yang, Seung Yeon
Roberts, William L.
KAUST DepartmentChemical and Biological Engineering Program
Clean Combustion Research Center
Mechanical Engineering Program
Physical Sciences and Engineering (PSE) Division
Permanent link to this recordhttp://hdl.handle.net/10754/594070
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AbstractA 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 nC16H34, nC17H36, and nC18H38 were selected as surrogates of lubricant base oil constituents, and then mixed with iso-octane (iC8H18-gasoline surrogate) in proportions of 1 vol.% (iC8H18 = 99 vol.%) and 10 vol.% (iC8H18 = 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.% iC8H18 reduces the average total ignition delay time by up to 54% for all mixtures, while the addition of 1 vol.% to 99 vol.% iC8H18 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. © 2015 Elsevier Ltd. All rights reserved.
CitationKuti OA, Yang SY, Hourani N, Naser N, Roberts WL, et al. (2015) A fundamental investigation into the relationship between lubricant composition and fuel ignition quality. Fuel 160: 605–613. Available: http://dx.doi.org/10.1016/j.fuel.2015.08.026.
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Ignition delay time sensitivity in ignition quality tester (IQT) and its relation to octane sensitivityNaser, Nimal; Sarathy, Mani; Chung, Suk-Ho (Fuel, Elsevier BV, 2018-06-22) [Article]Cetane number (CN) is a commonly used metric to rate the ignition quality of distillate fuels. In this work, a concept of sensitivity in ignition delay time (IDT) obtained with an ignition quality tester (IQT) is proposed, which is correlated to octane sensitivity (OS), i.e., the difference between research octane number (RON) and motor octane number (MON). The concept is based on the determination of IDT using the ASTM D6890 standard and IDT obtained at a temperature lower than that prescribed by the standard. The IDT measured at this lower temperature is referred to as IDT_l , which is obtained via a calibration procedure similar to the ASTM D6890 standard, but with a higher value of reference IDT for calibration with n-heptane. The IDT_h (measured at the derived cetane number (DCN) ASTM D6890 condition) of a given test fuel and a binary primary reference fuel (PRF) mixture of iso- octane and n-heptane was measured to identify a PRF with matching IDT_h as the test fuel. The ratio of low temperature IDTs of the non-PRF test fuel and PRF, i.e., IDT_l,non-PRF/IDT_l,PRF was defined as IDT sensitivity (IDS), which was correlated with the OS of the test fuel. The RON and MON values of a wide range of fuel classes including surrogate fuels and fully blended practical fuels were estimated, and showed satisfactory agreement with measured RON/MON values. The RON values of many pure components that could not be measured with standard test methods were also estimated. Two certification diesels and Saudi Arabian pump grade diesel were also tested.
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Advisor: Im, Hong G.
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