NASA and DLR tests show alternative fuels can cut dangerous soot emissions from jet engines in half
DLR A320 and NASA-operated sampling inlets that measure jet engine exhaust emissions (photo: NASA/Bruce Anderson)
Thu 12 Nov 2015 – Ongoing research by NASA and the German Aerospace Center (DLR) indicates that burning blended alternative fuels in jet engines results in a 50% reduction in soot emissions as opposed to traditional jet fuel alone. Soot has both an adverse impact on human health and, as it absorbs heat, has a climatic warming effect when emitted at high altitudes. In their latest collaboration, NASA has supplied several instruments for DLR’s Emissions and Climate Impacts of Alternative Aviation Fuels (ECLIF) experiments. These involve measuring the exhaust from a parked DLR Airbus A320 as it burns eight different types of standard and alternative fuels that contain varying amounts of aromatic compounds and sulphur impurities. NASA says the ECLIF data will help confirm and supplement its own alternative aviation fuel research that it has been carrying out since 2009.
In the ECLIF work, the NASA instruments are placed around 100 feet (30 metres) behind the A320 jet engine exhaust, and the emissions from a total of around nine hours of ground-based operation will now be sampled, data recorded and analysed.
NASA has conducted two programmes, the Alternative Aviation Fuel Experiment (AAFEX) in 2009 and 2011, and the Alternative Fuel Effects on Contrails and Cruise Emissions (ACCESS) in 2013 and 2014. AAFEX was similar to DLR’s ECLIF activities in that instruments were used to measure exhaust coming from a combination of fuels being burned by a jet engine attached to NASA’s DC-8 test aircraft.
The first ACCESS programme involved instrumented research aircraft trailing behind the DC-8 in flight, which not only measured the exhaust chemical content from various mixtures of alternative fuels, but also studied the emissions’ effects on the formation of contrails. During ACCESS II in 2014, other aircraft, including DLR’s Falcon jet and a CT-133 from the National Research Council of Canada, participated in the airborne data gathering. The same Falcon was used for DLR’s ECLIF project in three weeks of airborne testing that was completed October 9.
“The ground test data is being used to help interpret the flight data,” said Bruce Anderson of NASA’s Langley Research Center in Virginia, which is joined by NASA’s other research facilities in Cleveland and Edwards, California in the alternative fuel studies.
“On the ground, we are able to use a more extensive sensor suite to characterise exhaust composition over a much broader range of thrust settings and for greater lengths of time, which yields much better statistics for delineating differences in emissions between the fuels.”