QCSEE — Design and Test Contributions to the Rise Open Fan Program

Abstract

Abstract After the successful introduction of commercial turbofan engines with medium bypass ratios, NASA’s Lewis Research Center spearheaded an aircraft propulsion development program in the early 1970’s called “Quiet Clean Short-Haul Experimental Engine” commonly referred to as QCSEE. In addition to the goal of doubling the bypass ratio relative to early production turbofan engines, QCSEE led in pioneering (a) reversible-pitch composite fan blades, (b) a high bypass ratio geared fan/turbine, (c) extensive use of composites, (d) noise reduction technologies, and (e) digital electronic controls. This paper reports on the design, fabrication and testing of two propulsion systems for QCSEE by GE Aviation under contract from NASA in the mid-1970’s. The first design was an Under-the-Wing (UTW) engine, which incorporated a reduction gearbox to drive the low-speed fan with variable pitch to further improve fan efficiency along with elimination of the thrust reverser. The variable pitch fan was used for modulating forward as well as reverse thrust. This design utilized a low-pressure ratio fan (lower tip speed) at take-off and a bypass ratio of 12. The other design entitled as the Over-the-Wing (OTW) engine also used a reduction gearbox to drive a low-speed fixed pitch fan. The OTW engine configuration had a slightly higher fan pressure ratio (higher tip speed) at take-off and a bypass ratio of 10. The design and testing of these fans for the QCSEE program are presented. Key design features of the composite fan blade and the variable pitch mechanism are presented. The QCSEE design was based on a lightweight, high-speed, power turbine driving a slower speed, quiet fan that required a compatible, compact, lightweight, high-power-capability, main reduction gear. Performance results of two reduction gears designed, fabricated, and rig-tested are summarized. A summary of the development of the composite frame and nacelle is presented. Limited highlights of the digital engine control are shown. Finally, overall engine aerodynamic, acoustic, and mechanical test performance are reported in this article. The impact of each of these key QCSEE technologies to existing GE/CFM products, and their contribution to CFM’s current RISE Open Fan technology program will be discussed.