Hideyuki Imai

Computational Fluid Dynamics Simulations and Experiments for Reduction of Oil Churning Loss and Windage Loss in Aeroengine Transmission Gears

The demand for power generation capacity has increased considerably due to the electric drive of cabin air conditioners and commercial aircraft engines. It is estimated that power losses may increase in the accessory gearbox due to generators and pumps that augment fuel consumption. To reduce these losses, a computational fluid dynamics simulation technique that analyzes oil churning and windage losses was developed and improvements were made to the shrouds of bevel gears, which have large losses in the gearbox. It was revealed experimentally that shrouding reduced losses up to 36% as compared to unshrouded gears.

CFD Simulation for Reduction of Oil Churning Loss and Windage Loss on Aeroengine Transmission Gears

In recent years, the demand for power generation capacity has increased considerably due to the electric drive of air conditioners and so on in the engines of civil aircraft. Therefore, it is estimated that power losses may increase in the gearbox because of generators and pumps that in turn augment fuel consumption. To understand the phenomena of losses in the gearbox and to reduce these losses, Computational Fluid Dynamics (CFD) simulation that analyzes oil churning loss and windage loss was developed and improvements were made to the shroud of bevel gears. The CFD agreed with experimental results on a bevel gearbox of a 100-seater aircraft. And, it was shown that the suppression of momentum transfer from the rotating gears to oil clusters is of importance. In addition, it was revealed that the loss was reduced up to 36% compared to non-shrouded gears by shrouding in the experiments. This CFD simulation can be applied to many types of gearboxes that have spur gears, bearings and seals.Copyright

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

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.Copyright

Design and Test of Differential Planetary Gear System for Open Rotor Power Gearbox

The open rotor engine is a next generation aero-engine that satisfies the demand for high fuel efficiency and low CO2 emission. A differential planetary gear system is incorporated in the open rotor engine to connect the turbine output shaft and fan rotors in order to counter-rotate the fan rotors as well as allow the turbine and fan rotors to operate at more efficient speeds. The open rotor gear system is required to have not only 20,000 hp high power transmission, but also an increasingly high efficiency, high reliability and light weight. To achieve these requirements, the following design works were conducted; (1) a low misalignment and lightweight carrier, (2) a flexible structure to absorb the displacement caused by the flight load, (3) an optimum gear tooth modification and (4) reduction of oil churning and windage losses. Also, extensive analyses and simulations such as lube oil flow CFD, FEA and tooth contact analysis were conducted. A full scale prototype gear system was manufactured and validation tests were conducted using a newly constructed test rig to validate the design concept. A slow roll test, rated performance test and efficiency test were conducted. And the design concept was found to be valid. This paper describes details of the prototype design and the results of the validation tests.Copyright

Light Weight and Low-Misalignment Planetary Gear System for Open Rotor Power Gearbox

The future aero engines expected to have the best fuel efficiency are those with the open rotor propulsion system. It has two rows of propellers rotating in opposite directions. The rotational speeds of the propellers are reduced by a power gearbox. The power gearbox is designed as a differential planetary gear system with double helical teeth. The gearbox for aero engines needs to be lightweight and highly reliable. Misalignment on the gear pair affects adversely the reliability of the gears. The misalignment analysis of the power gearbox based on finite element analysis was carried out. The inclination of the planet spindles associated with the twisting deformation of the planet carrier was identified as the major cause of the misalignment. We developed an innovative design method to achieve the low misalignment and lightweight at the same time by optimizing the stiffness balance of the planet carrier. The optimization analysis was carried out extensively in the design work. The planet carrier design was named Analysis Configured Engineering planet Carrier (ACE CARRIER). A stress measurement was planned to validate the design concept of the ACE CARRIER. A test gearbox was manufactured.Copyright