Author ORCID Identifier

https://orcid.org/0009-0001-1531-6302

Semester

Fall

Date of Graduation

2025

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Mechanical and Aerospace Engineering

Committee Chair

Andrew Nix

Committee Co-Chair

Donald Ferguson

Committee Member

Hailin Li

Abstract

Rotating detonation engine (RDE) combustion systems have been a topic of interest in the pressure gain combustion community for their benefits over traditional gas turbine engine combustors. However, cooling requirements for these engines are significantly higher and less predictable than those of non-detonating engines. To understand and quantify the high-speed heat transfer dynamics within an RDE, a novel high-frequency heat flux sensor is presented. This study aims to design a robust, single-sided sensor that can withstand the high temperature and harsh environment of an RDE for extended durations. Screen printing is used to deposit a layered, platinum-yttria-stabilized zirconia (YSZ) film onto a ceramic substrate that is bonded through high temperature sintering. Different layering schemes are used to improve sensor durability by ensuring a gradual transition in thermal expansion coefficient from the substrate to the platinum elements. After fabrication, the sensors are calibrated by characterizing their resistance with respect to temperature in an instrumented furnace. The heat flux magnitude of the sensor is validated using a hot plate as a heat source, and the results are compared to a finite-element analysis (FEA) model. The sensor response and durability is then tested inside a water-cooled RDE. The time averaged and phase-averaged wall heat flux is compared with calorimetry data and CFD simulations, respectively. The simulations were conducted independently from this study. The Time-averaged heat flux followed a trend similar to that of the calorimetry data, although the sensor was quicker to respond. Phase-averaged heat flux shows a period of cooling followed by significant heat release periods before and after the detonation wave usually associated with secondary combustion. These pe riods of secondary combustion and cooling are not present in the CFD simulations. Heat flux measurements are taken with two injector geometries, one with deflagra tion and the other with two-wave detonation. The novel sensor showed extended survivability to other thin film sensors, with a lifetime of about 3.80 seconds in deflagration and 2.75 seconds in two-wave detonation as opposed to below 0.5- 1.0 seconds of exposure time for similar studies. An additional 2.0 seconds of data would record an additional 14,000 wave passing events for a peak detonation frequency of 7 kHz, a significant increase in the collected detonation data for a given test. At a peak detonation frequency of 7 kHz, approximately 21,000 detonation waves are recorded by the heat flux sensor. Detonation wave speeds calculated from high speed data are within 80-95% CJ speed. Average heat flux reached approximately 1.78 MW/m2 in deflagration and 3.10 MW/m2 in detonation, comparable with the heat flux magnitude from water calorimetry. Unsteady high-speed heat flux is compared with gas ionization data to correlate their peaks and observe detonation wave passage, although high-speed data appear highly stochastic. Some brief periods of consistent phase shifting are observed between gas ionization and heat flux peaks, coupled with weaker or non-existent peaks from the heat flux signal. A phase averaged waveform is constructed for both signals with a peak phase-averaged heat flux between 60-68 MW/m2. The phase-averaged heat flux is compared to CFD to identify regions of secondary combustion. These regions can be used to estimate the percentage of detonation of the total heat release from the engine cycle. Using the phase-averaged heat flux, the percent detonation is estimated to be 77.2%. This percentage compares well with estimates using OH* chemiluminescence in a previous study on the same test rig.

Download

Share

COinS