Spark Ignition Aircraft Engine Endurance Test of Aviation ... - FAA

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EXECUTIVE SUMMARY In 2004, the Federal Aviation Administration (FAA) funded the South Dakota State University in a multiyear effort to research the use of aviation-grade ethanol 85 (AGE-85), a blend of at least 85% ethanol denatured with 2% automotive gasoline, less than 1% biodiesel, and pentane isomerate. In a parallel effort, researchers in the Airport and Aircraft Safety Research and Development Division Propulsion and Fuel Systems Branch at the FAA William J. Hughes Technical Center evaluated AGE-85 in an overhauled Lycoming IO360-C, four-cylinder, spark ignition, piston aircraft engine. The engine is type-certificated to operate on either 100 or 100 low-lead (100LL) American Society for Testing and Materials D 910-grade aviation gasoline. The engine fuel control servo was modified with an oversized main metering jet and the fuel distribution nozzles were enlarged to allow increased fuel mass flow. The engine ignition timing was retarded by 5° to 15° before top dead center (BTDC). The test procedures were similar to those of Title 14 Code of Federal Regulations Parts 33-49. The test evaluated engine endurance performance at severe and controlled conditions addressing such issues as wear, performance, materials compatibility, range, efficiency, oil dilution, and deposit formation. The majority of the testing was performed at full-rated power and engine speed under maximum engine and oil temperatures, at best power fuel mixture setting. The fuel was tested from sealed drums containing less than 0.2% water on a volume basis. Under the conditions of this test, the results indicated that there was no excessive wear on any of the high-contact, high-stress parts of the engine except for the hammered effect on the exhaust valve faces and seats. This may have been a consequence of operating the engine at the 5° retarded timing. There were minimal piston face and valve deposits and moderate intake valve deposits. There were minimal fuel system deposits and engine varnish and sludge buildup. Prior to the start of the endurance test and at the completion of the endurance test, a series of power baselines were run using both AGE-85 at the 15° BTDC ignition timing and isooctane (ISO) at the standard ignition timing of 20° BTDC. The engine produced an average of 4.3 (2.8%) more peak horsepower when operating on the AGE-85 than it did when operating on ISO. However, peak power required 39.7 lb/hr (56.5%) more fuel mass flow with the AGE-85 than with ISO. This equates to an average increase of 5.6 gal/hr (35%) fuel volume flow. This reduced the efficiency from an average peak power brake-specific fuel consumption (BSFC) of 0.470 lb/break horsepower (bhp) hr for ISO to 0.716 lb/bhp hr for AGE-85. The AGE-85 produced 1.8% more power at best economy fuel mixture than 100LL but required 55.8% more fuel mass flow. This reduced the average best economy BSFC from 0.415 lb/bhp hr for ISO to 0.640 lb/bhp hr for AGE-85. Average exhaust gas temperatures were 20°F higher with AGE-85 than with ISO at the best power mixture. Using AGE-85 would increase fuel weight by 9% above 100LL values due to its 6.4 lb/gal mass density versus 5.87 lb/gal for 100LL and would reduce engine range by 35%. This testing showed that without significant modifications to existing engine design beyond retarding the ignition timing, such as increasing cylinder compression ratios, changing valve timing, and derating engine power, adjustments to the fuel schedule for a 100- or 100LLcertificated engine would be required to provide upwards of 57% more fuel mass flow or 35% ix
more fuel volume flow. Future tests will compare the detonation performance of AGE-85 at standard engine ignition timing to 100LL in a 100/100LL-certificated IO360-A engine. x
Page 1 and 2: DOT/FAA/AR-06/43 Office of Aviation
Page 3 and 4: 1. Report No. DOT/FAA/AR-06/43 4. T
Page 5 and 6: LIST OF FIGURES Figure Page 1 Oil F
Page 7 and 8: 46 Posttest Connecting Rod Bearing
Page 9: LIST OF ACRONYMS 100 low-lead 100LL
Page 13 and 14: At the completion of the test, the
Page 15 and 16: The engine was installed in a test
Page 17 and 18: Table 4. Parameter Settings for End
Page 19 and 20: Figure 1. Oil Filter Inspection Fig
Page 21 and 22: Figure 4. Corrected Power at 2700 r
Page 23 and 24: Figure 8. Corrected Power at 2300 r
Page 25 and 26: Figure 10. Corrected BSFC vs Fuel M
Page 27 and 28: Figure 12. Corrected Power and Aver
Page 31 and 32: Table 8 provides a summary of the e
Page 37 and 38: output from all six cylinders. Pist
Page 39 and 40: The oil filter was cut open and the
Page 41 and 42: Figure 29. Top of Piston Face of Cy
Page 43 and 44: Figure 33. Bottom of Piston Face an
Page 45 and 46: Figure 39. Posttest Crankshaft Conn
Page 47 and 48: The camshaft lobes, shown in figure
Page 49 and 50: Figure 59 shows a combustion chambe
Page 51 and 52: Figure 63. Posttest Rocker Arm Show
Page 53 and 54: Visual observation of the intake tu
Page 55 and 56: Future testing should address effec
Page 57 and 58: Table A-2. Middle and Rear Main Cra
Page 59 and 60: Table A-4. Valve Tappet Outer Diame
Page 61 and 62:
Table A-10. Top Piston Ring Side Cl
Page 63:
Table A-14. Intake Valve Seat Width
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Spark Ignition Aircraft Engine Endurance Test of Aviation ... - FAA

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