Publication Date


Document Type


Committee Members

Rory Roberts (Committee Chair), George Huang (Committee Member), Mitch Wolff (Committee Member)

Degree Name

Master of Science in Mechanical Engineering (MSME)


Usually power take off (PTO) with a two-spool turbofan engine has been accomplished via the high pressure (HP) shaft and bleed air from the high-pressure compressor (HPC). The PTO is used to run various aircraft components such as generators and hydraulic pumps, which also produce waste heat. To better understand the coupled transient nature of balancing engine thrust, power take off and thermal management, a transient variable cycle three stream turbofan engine model has been developed to investigate the integrated behavior. The model incorporates many dynamic features including a third-stream heat exchanger as a heat sink for thermal management and HP/LP shaft PTO. This paper describes a method of controlling HPC surge margin and maintaining the desired thrust while extracting power using both the HP and LP spools. The transient interactions as both PTO and 3rd stream heat rejection are simultaneously applied to the transient variable cycle engine model utilizing different control effectors were investigated. The rate of transient heat rejection was found to impact surge margin. Rapidly applied heat loads caused larger surge margin transients than heat loads applied more gradually despite the same maximum heat rejection. Optimal PTO profiles between the LP and HP shaft to minimize the amount of fuel used for a given PTO amount and flight envelope were also investigated. Finally, a notional mission was simulated with varying flight parameters and dynamic PTO based on optimal PTO profiles along with heat generation and afterburner. The controls were found to be sufficient to successfully run the mission however such simplified controls could induce numerical instabilities in certain mission profiles. This shows that while these simple controls are sufficient for these notional test runs more sophisticated controls will be necessary for a proper generic engine model.

Page Count


Department or Program

Department of Mechanical and Materials Engineering

Year Degree Awarded


Creative Commons License

Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License.