DEVELOPMENT OF A COMBINED THERMAL MANAGEMENT AND POWER GENERATION SYSTEM USING A MULTI-MODE RANKINE CYCLE A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Mechanical Engineering By: NATHANIEL M. PAYNE B.S., Ohio Northern University, 2019 2021 Wright State University Cleared for Public Release by AFRL Public Affairs on June 2, 2021 Case Number: 2021-0296 The views expressed in this article are those of the author and do not reflect the official policy or position of the United States Air Force, Department of Defense, or the U.S. Government. WRIGHT STATE UNIVERSITY GRADUATE SCHOOL April 27, 2021 I HEREBY RECOMMEND THAT THE THESIS PREPARED UNDER MY SUPERVISION BY Nathaniel M. Payne ENTITLED Development of a Combined Thermal Management and Power Generation using a Multi-Mode Rankine Cycle BE ACCEPTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF Master of Science in Mechanical Engineering. __________________________ Dr. Mitch Wolff, Ph.D. Thesis Director __________________________ Dr. Raghu Srinivasan, Ph.D., P.E. Chair, Mechanical & Materials Engineering Committee on Final Examination: ________________________________ Dr. Rory Roberts, Ph.D. ________________________________ Dr. José Camberos, Ph.D. ________________________________ Levi Elston, M.S. ________________________________ Barry Milligan, Ph.D. Vice Provost for Academic Affairs Dean of the Graduate School ABSTRACT Payne, Nathaniel M. M.S.M.E., Department of Mechanical and Materials Engineering, Wright State University, 2021. Development of a Combined Thermal Management and Power Generation System using a Multi-Mode Rankine Cycle. Two sub-systems that present a significant challenge in the development of high- performance air vehicle exceeding speeds of Mach 5 are the power generation and thermal management sub-systems. The air friction experienced at high speeds, particularly around the engine, generates large thermal loads that need to be managed. In addition, traditional jet engines do not operate at speeds greater than Mach 3, therefore eliminating the possibility of a rotating power generator. A multi-mode water-based Rankine cycle is an innovative method to address both of these constraints of generating power and providing cooling. Implementing a Rankine cycle-based system allows for the waste heat from the vehicle to be used to meet the onboard power requirements. This application of a Rankine cycle differs from standard power plant applications because the transient system dynamics become important due to rapid changes in thermal loads and electrical power requirements. Both an experimental and computational investigation is presented. An experimental steady state energy balance was used to determine a 5.1% and 11.5% thermal and Second Law efficiency, respectively. Transient testing showed an increase in power generation of 283% in 30.5 seconds when starting from idle, with a steady state power generation of 230 W. In addition to the power generation, the experimental system removed 10.7 kW from the hot oil loop which emulates a typical aircraft cooling fluid. Experimental results were iv used in the development of dynamic computational models using OpenModelica, an open- source modeling tool. Deviation between model and experimental results was within 5% for component models and 3.5% when analyzing the system energy balance. Testing of the vehicle level model included steady state, transient, and simulated mission, which was used to characterize performance and develop the system controls. During transient testing, the system controls demonstrated the ability to meet both the cooling and power requirements of the system through rapid response times and minimal temperature overshoot (2.72%). The development and testing of this model provides an opportunity for scaling and optimization of a combined power and thermal management system across a wide range of vehicle sizes and operating conditions. v TABLE OF CONTENTS 1. Introduction .................................................................................................................................. 1 1.1 Problem Overview ................................................................................................................. 1 1.2 Approach ................................................................................................................................ 2 1.3 Thesis Organization ............................................................................................................... 2 2. Background .................................................................................................................................. 4 2.1 Motivation and Historical use of Thermal management Systems in Aircraft ........................ 4 2.1.1 Early Use of Aircraft Thermal Management Systems .................................................... 4 2.1.2 Thermal Management Needs .......................................................................................... 5 2.1.3 Materials ......................................................................................................................... 6 2.2 Thermal Management Systems .............................................................................................. 8 2.2.1 Passive Thermal Management Systems .......................................................................... 9 2.2.2 Regenerative Thermal Management Systems ............................................................... 10 2.2.3 Film Cooling ................................................................................................................. 21 2.3 Power generation ................................................................................................................. 24 2.4 Modeling .............................................................................................................................. 26 2.4.1 OpenModelica ............................................................................................................... 26 2.4.2 Evaporator Modeling .................................................................................................... 27 3. Methodology .............................................................................................................................. 30 3.1 Innovative Solution .............................................................................................................. 30 3.1.1 Rankine Cycle Review .................................................................................................. 30 3.1.2 Implementation for Aircraft Thermal Management Applications ................................ 31 3.1.3 Multi-Mode Rankine Cycle .......................................................................................... 33 3.2 Experimental System ........................................................................................................... 34 3.2.1 System Description ....................................................................................................... 34 3.2.2 System Data Acquisition System .................................................................................. 37 vi 3.3 Experimental System Operation Conditions ........................................................................ 38 3.4 Steady State Testing ............................................................................................................. 39 3.5 Transient Testing ................................................................................................................. 40 4. Model Development................................................................................................................... 44 4.1 HPTMS Package Development ........................................................................................... 44 4.2 Heat Exchangers .................................................................................................................. 46 4.2.1 Moving Boundary Method ............................................................................................ 46 4.2.2 Heat Exchanger Configurations .................................................................................... 53 4.2.3 Transient Effects ........................................................................................................... 57 4.3 Turbine ................................................................................................................................. 58 4.4 Fluid Models ........................................................................................................................ 62 4.5 Pump .................................................................................................................................... 63 4.6 Open-Source Models Used .................................................................................................. 64 4.7 Solver Overview .................................................................................................................. 65 4.8 SHEEV Model ..................................................................................................................... 65 4.9 Vehicle Level Model ............................................................................................................ 66 4.10 Vehicle Model Operating Conditions ................................................................................ 70 5. Results .......................................................................................................................................