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Accession Number PB2013-101358
Title Lead Deposit Effects on Unleaded Aviation Fuel Antiknock Performance.
Publication Date Aug 2012
Media Count 29p
Personal Author A. Ivanov D. Atwood M. A. Nelson
Abstract To investigate the potential impact of preexistent lead deposits on unleaded fuel antiknock performance of piston aircraft engines, full-scale engines were operated on leaded fuels prior to testing with unleaded fuels. The full-scale engine results showed an increase in unleaded fuel antiknock performance equivalent to 1 to 4 Motor Octane Number (MON) when tested after engine operation with leaded fuel. The MON increase was more pronounced at leaner fuel mixtures, and the effect subsided with continued operation with unleaded fuel. However, it is important to note that this result was based on a short-duration (76-hour) lead exposure test and engine operation with leaded fuel for longer periods may increase the persistence of this effect. Based on these experimental findings, and those cited in this report, it is highly recommended that detonation tests with unleaded fuel be performed with a clean engine that was not previously used for leaded fuel operation. Test engines that must be periodically operated for short durations with leaded fuel should be run for at least 30 to 45 minutes with an unleaded fuel after any Pb fuel operation and prior to detonation tests with unleaded fuels, provided the engine was initially lead-free. These laboratory tests were performed without engine fuel filters, fuel pockets, or plumbing wells that would allow liquid leaded fuel to be trapped in the fuel system. Use of such traps requires increased operating purge times using unleaded fuels after using Pb-based fuels to eliminate Pb effects on the tests.
Keywords Alternative fuels
Aviation fuels
High octane
Lead memory
Pb memory
Performance evaluation
Piston engine
Unleaded fuels

Source Agency Department of Transportation Federal Aviation Administration
NTIS Subject Category 97K - Fuels
51C - Aircraft
81J - Reciprocation & Rotating Combustion Engines
Corporate Author William J. Hughes Technical Center, Atlantic City, NJ.
Document Type Technical report
Title Note Technical note.
NTIS Issue Number 1302
Contract Number N/A

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