Design, Analysis, and Tests of Differential Planetary Gear System for Open Rotor Power Gearbox (Final Report)

Abstract

The requirements for general aero-engines are becoming increasingly severe to achieve higher efficiency and lower emission. The Open Rotor Engine is one of the next-generation aero-engine concepts expected to satisfy these requirements. The Open Rotor Engine has a set of counter-rotating unducted fans to increase the propulsion efficiency. A 20,000 hp class differential planetary gear system is suitable for driving these counter-rotating fans. To realize a 20,000 hp class differential planetary gear system, there are some design challenges to be accomplished 1) large power (20,000 hp class), 2) sufficiently small and light to fit an engine (envelope), 3) high transmission efficiency over 99.5%, 4) precise misalignment control for gears and bearings, 5) high reliability (50,000 hour MTBF). At Kawasaki Heavy Industries, Ltd., development of the Open Rotor Power Gearbox started in 2007. The purpose of this development is to establish a design practice for the 20,000 hp class gear system and to demonstrate that its readiness level (TRL) is appropriate for whole-engine development. In this development, various state-of-the-art simulation technologies such as lube oil flow CFD, FEA, and tooth contact analysis were fully utilized to optimize the design. Details of the design, fabrication, and validation tests of a full-scale prototype up to 2012 were presented at the IDTC/CIE in 2013. This paper presents a summary of the previous activity and subsequent works and achievements as a final report.

Preliminary Design Framework for the Power Gearbox in a Contra-Rotating Open Rotor

“…the preliminary design of the transmission system independently of the overall CROR modelling ( [24]- [30]), without assessing its impact on the general arrangement.…”

“…Kawasaki Heavy Industries (KHI) investigated a geared CROR engine and the design of its transmission system with a prototype of a DPGB developed to demonstrate a technology readiness level (TRL) appropriate for whole engine development [28]- [30].…”

“…There is a clear need for an alternative approach to estimating the size of the DPGB in an open rotor application, which does not involve convoluted mechanical assessments. The mechanical design of the gearbox has previously either been treated in isolation ([28]- [30]) or not used to inform the engine model ( [4], [26], [27]).…”