Emissions reduction is a worldwide priority, due to increasing concern over local air quality, climate change and health effects of emissions. The transportation sector accounted for about 27% of total US greenhouse gas emissions in 2003, with aircraft contributing 9% of the transportation sector total, or about 2% of total greenhouse gas emissions. Aviation is projected to contribute an increasingly larger share of CO₂ emissions as air traffic continues to grow. Technology improvements have substantially reduced the amount of emissions generated from aircraft over the past fifty years, and advancements must continue so as to mitigate the effect of a projected doubling of aircraft operations over the next 20 to 25 years.

At NASA Glenn Research Center, numerous technologies are under development to adaptively modify aircraft turbine engine performance. These adaptive technologies can lead to improved engine component efficiency and/or reduced weight, both resulting in overall fuel burn and CO2 reductions. The primary classes of these adaptive technologies are flow control, structural control, combustion control, and also 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.

A number of system analyses have been performed over the past several years to quantify the emission reduction potential of a number of adaptive engine technologies. The results from these assessments 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% for flow control in S-shaped inlets on a blended-wing body transport aircraft. As a group, the flow-control technologies show the largest opportunity for 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 be used to provide guidance for the development of a robust adaptive engine technology portfolio.

Glenn Authors and Contacts:
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.gov

Programs/Projects:
Intelligent Propulsion System Foundation Technology Project
Ultra Efficient Engine Technology Project
Revolutionary Concepts in Propulsion Project

Reference:
Mercer, Carolyn R.; Haller, William J.; Tong, Michael T.: Adaptive Engine Technologies for Aviation CO₂ Emissions. AIAA 2006-5105. 42nd AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, Sacramento, California, July 2006.