ANALYTICAL INVESTIGATION OF THE PERICYCLIC VARIABLE-SPEED TRANSMISSION SYSTEM FOR HELICOPTER MAIN-GEARBOX
Open Access
- Author:
- Saribay, Zihni Burcay
- Graduate Program:
- Aerospace Engineering
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- November 11, 2009
- Committee Members:
- Edward C Smith, Dissertation Advisor/Co-Advisor
Edward Smith, Committee Chair/Co-Chair
Surendra B Rao, Committee Chair/Co-Chair
Robert Charles Bill, Committee Member
Kon Well Wang, Committee Member
Joseph Francis Horn, Committee Member
Liming Chang, Committee Member - Keywords:
- Helicopter Transmission
face-gear
pericyclic variable-speed transmission
elastohydrodynamic lubrication - Abstract:
- In the recent years, there has been significant interest in the new developments and improvements of the rotorcraft transmission systems. The main goal of the rotorcraft transmission research is the reduction of overall gear train weight while maintaining the efficiency and reliability. The Pericyclic Variable-Speed Transmission (PVT) System is one of the potential candidates of the future rotorcraft drive trains to achieve these goals. Hence, this thesis explores the feasibility of the Pericyclic Variable Speed Transmission (PVT) for rotorcraft transmissions. The contributions of this research are grouped in two main categories. These two categories are in the component level and in the system level. These contributions are originated from the analysis of the Pericyclic Variable Speed (PVT) System. In the component level, a new concept of face-gear meshing is presented first time in the gear research field. The meshing of a face-gear with another face-gear is presented at high shaft angles as an alternative to bevel gears. The conjugacy of this new face-gear meshing concept is formulated and demonstrated. The geometry, unloaded mesh kinematics and loaded mesh kinematics of the conjugate meshing face-gear pair is analyzed. The physics behind the meshing face-gear teeth contact is revealed using theory of gearing, differentiable geometry and elastohydrodynamic lubrication theory. The existence of the lubricant film formation between the meshing teeth is demonstrated. The behavior of the sliding friction coefficient is analytically simulated through the meshing cycle. In the system level contributions, the Pericyclic Variable Speed (PVT) Transmission is presented as a new unique innovative gear train mechanism. The speed change capability is analyzed for rotorcraft demands. The power flow behavior is explored for its use in variable speed transmission systems. The established component level contributions are evaluated with the PVT at the system level. The efficiency and load carrying capacity of the PVT face-gears are analyzed at the helicopter torque levels. The dynamic motion of the nutating gear mechanisms is studied to capture the load carrying capacity of the PVT support bearings. A design analysis of the PVT system with 24:1 reduction ratio at 764HP power level is conducted to replace 3 reduction stages of the existing K-MAX intermeshing rotor transmission system. The design and analysis tools established in this research are applied in the design study. The achieved design is compared to the existing K-MAX transmission. Approximately 50% weight reduction and 70% volume reduction are accomplished with the PVT system with less than 1% lower efficiency than existing K-MAX drive train gears.