Advances in Turbofan Engines: AUSPerspective

Abstract

Turbofan engines have been the mainstay of large aircraft propulsion systems since the first turbofan‐powered commercial airliner was introduced in the late 1960s, replacing the less efficient and noisier turbojets. Engine manufacturers have continually improved the overall engine efficiency by both increasing the propulsive efficiency of the fan system and increasing the thermal efficiency of the core. Combustor technologies have also advanced, resulting in significantly lower emissions even as the overall pressure ratio of the cores has increased. Low operating costs improve aircraft economic competitiveness and motivate the efforts for fuel efficiency/noise reduction, while emissions reduction tends to be regulation driven. The historical improvements in turbofan efficiency, noise, and emissions are reviewed. Current‐generation turbofan systems can still achieve both propulsive and thermal efficiency gains. However, the engine cycle and configuration changes that benefit efficiency can potentially have negative consequences for emissions and noise. Complementary efforts in combustion technology and noise reduction are needed for a balanced approach to engine development. The current development efforts within the United States for next‐generation engines with lower fuel burn, noise, and emissions are summarized. Additionally, research efforts are discussed for generation‐after‐next systems that are typically more electric and/or hybrid.