The Trend of Bypass Ratio in Aero Engines: An Overview

Abstract

The demand for turbofan engines for civil aviation is increasing continuously as the air transportation system is changing exponentially. Large and long-haul flight have raised the demand on high thrust engines. But at the same time, focus on fuel efficiency of the engines and control on exhaust gas emissions and noise are increasing keeping in mind the economy and environmental considerations. International Civil Aviation Organization has promulgated the emission and noise levels for civil turbofan engines and making it more and more stringent day by day. This has made an increasing trend of engine bypass ratio to address the fuel efficiency and the noise level of the engine. On the other hand, combat aircraft need to have high ‘g’ manoeuvrability, a faster response to throttle adjustment and high thrust-weight ratio thus preferring a low-bypass ratio world-wide. This paper covers the history of turbofan engines staring from its inception and presents the trend of bypass ratio in aero engines for both transport and combat aircraft. The paper also highlights the current developments and upcoming ultra-high bypass turbofan engine programs along with aircraft noise standards.