Emissions reduction is a worldwide priority because of increasing concern over local air quality, climate change, and the health effects of emissions. The transportation sector accounted for about 27 percent of total U.S. greenhouse gas emissions in 2003, with aircraft contributing 9 percent of the transportation sector total, or about 2 percent of total greenhouse gas emissions. Aviation is projected to contribute an increasingly larger share of carbon dioxide (CO2) emissions as air traffic continues to grow. Technology improvements have substantially reduced the amount of emissions generated from aircraft over the past 50 years, and advancements must continue in order to mitigate the effect of a projected doubling of aircraft operations over the next 20 to 25 years (see the graph).
Some aviation growth scenarios predict a doubling of flights as early as 2025.
Long description of figure 1.
At the NASA Glenn Research Center, numerous technologies are under development to adaptively modify aircraft turbine engine performance. These adaptive technologies could lead to improved engine component efficiency and/or reduced weight, reducing overall fuel burn and CO2 emissions. The primary classes of these adaptive technologies are flow control (see the following figure and table), structural control, combustion control, and the enabling technologies that are applicable to each. Some specific technology examples include inlet, fan, and compressor flow control; compressor stall control; blade clearance control; combustion control; active bearings; and enabling technologies, such as active materials and wireless sensors.
| Engine component | Focus of technology |
|---|---|
| Inlets | Maintain performance, engine stability, and durability with shorter inlets (lower weight) Reduce bleed drag and bleed systems weight |
| Fan | Improve operability with shorter inlets |
| Compressors and turbines | Improve flow quality and operability to improve loading conditions, enabling reduced weight |
Adaptive flow-control technologies are just a few of the technologies under investigation at NASA. As a class, these technologies manipulate the flow in turbine engine components to enable improved efficiency, better flow qualities, and lower weight—resulting in better aircraft fuel economy and lower emissions. NASA flow-control technologies focus on the inlets, fan, and compressors and turbines.
Over the past several years, system analyses have been performed to quantify the emissions-reduction potential of a number of adaptive engine technologies. These assessments, concluded in 2006, show that adaptive technologies have the potential to significantly reduce aircraft CO2 emissions. Possible emissions-reduction values range from a fraction of one percent for enabling technologies to as much as 13 percent for flow control in S-shaped inlets on a blended-wing-body transport aircraft. As a group, flow-control technologies show potential for the largest CO2 reduction. From the structural-control technologies, a significant benefit is possible through the development of a shape-memory-alloy-actuated, variable-area fan nozzle when coupled with a low-fan-pressure-ratio/high-bypass-ratio engine. These assessment results can guide the development of a robust adaptive engine technology portfolio.
Mercer, Carolyn R.; Haller, William J.; and Tong, Michael T.: Adaptive Engine Technologies for Aviation CO2 Emissions Reduction. AIAA-2006-5105 (NASA/TM--2006-214392), 2006. http://gltrs.grc.nasa.gov/Citations.aspx?id=155
Glenn contacts: Dr. Carolyn R. Mercer, 216-433-3411, Carolyn.R.Mercer@nasa.gov, William J. Haller, 216-977-7004, William.J.Haller@nasa.gov, Michael T. Tong, 216-433-6739, Michael.T.Tong@nasa.govLast updated: December 14, 2007
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