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J. Graf, C. Martin, P. Grabner, R. Luef:
"Development of testing methods to characterise knock and pre-ignition behaviour of alternative fuels and determination of oil influence on pre-ignition";
Talk: FVV Frühjahrstagung, Magdeburg (invited); 2014-03-27; in: "Heft R566 Informationstagung Motoren, Frühjahr 2014", FVV (ed.); Heft R566, Magdeburg (2014), 33 - 68.

The investigation of knocking, pre-ignition and/or self-ignition behavior of the fuel and lubricating oil is a vital step for optimizing downsizing gasoline engines. To this end new, adjusted test methods need to be developed and - if possible - the irregular behavior is to be characterized in a reproducible and realistic manner based on parameters derived from the investigation.
The knocking and pre-ignition behavior of selected alternative fuels were investigated at the Institute for Powertrains and Automotive Technology of Vienna University of Technology, while the research focus of the Institute of Internal Combustion Engines and Thermodynamics of Graz University of Technology was on the influence of lubricating oil on pre-ignition.
The findings of this research led to modified test methods based on the globally used CFR test engine and produced significant parameters of pre-ignition tendency and knocking behavior of future fuels in modern gasoline engines. The CFR engine was transformed to direct injection instead of carburetor for the further development of the new test methods. To assure the test procedures a fuelmatrix consisting of several splash blends has been considered. Pre-Ignition
phenomenon triggered by a critical condition in the gas phase and caused by a hot spot were investigated seperately. The measurements were impressively confirmed by validation on a single-cylinder research engine with state-of-the-art combustion and on a four-cylinder Serial engine.
An experimental procedure was developed by means of a single-cylinder research engine that allows quantification and evaluation of pre-ignition caused by various lubricating oils and additives to engine oils as well as conclusions about the triggering mechanisms. Predictions about the parameters of influence on the propensity for pre-ignition could be taken by a systematic study of model oils - chemical composition was varied - and engine oil additives.
Tests on the full engine with fully formulated engine oils were carried out to evaluate the transferability of the procedure to real engine behavior and to validate the results. Based on this experimental study the real influence on the behaviour on pre-ignition caused by lubricating oil was confirmed on a gasoline DI-engine and the mechanisms behind were also considered in detail.