<p>      Rotating detonation combustion has been investigated since the 1960s and has gained much attention in the past decade due to its promise of pressure gain. In theory, the pressure gain can provide higher power output at inlet total temperatures similar to those of Brayton cycle engines, leading to increased efficiency and decreased engine size. However, complexities presented by detonative combustion have prevented it from becoming widely adopted, especially for turbomachinery applications. A rotating detonation combustor with a transonic or supersonic exhaust imposes rapid fluctuations in pressure, temperature, and flow angle at the inlet of the turbine. To account for these fluctuations, ad hoc turbine designs have been proposed over the last few years, including supersonic bladed and bladeless variants. Computational fluid dynamics simulations have shown that it is possible to extract a meaningful amount of work from these turbines, but dedicated experimental test rigs are needed to validate these designs at relevant conditions in long-duration tests.</p> <p>     Toward this goal, this thesis focuses on three research elements. The first element is the design of a cooled rotating detonation combustor with a downstream turbine that can operate for long durations. The cooled combustor is accomplished in a two-part procedure: (1) repurposing Purdue University’s Turbine-integrated High-pressure Optical Rotating detonation engine (THOR) and (2) designing a lightweight, gaseous film-cooled combustor shroud with ample configurations for pressure, temperature, and optical measurements.</p> <p>     The second element is the design of three supersonic turbines for use in RDEs: an axial-flow bladed turbine, an axial-flow bladeless turbine, and an axial-inflow/radial-outflow bladed turbine. Each turbine is designed for cold flow testing, and provisions for mounting the axial-flow bladed turbine downstream of the cooled combustor are proposed. Supplemental turbine hardware is also designed to provide precise and repeatable conditions for the turbine tests.</p> <p>     The third element is the construction of an energy absorption dynamometer to measure the power output of the different supersonic turbines. Four types of dynamometers are explored, including hydraulic brakes, electromagnetic brakes, electric generator brakes, and airbrakes. Although the literature declares the electromagnetic brake to be more accurate, the most cost-effective solution is to utilize the compressor side of a donated turbocharger. Combining all research elements yields a new test rig for this new class of supersonic turbines.</p>

<p>In rotating detonation engines the turbine inlet conditions may be transonic with unprecedented unsteady fluctuations, very different from those in conventional high-pressure turbines. To ensure an acceptable engine performance, the turbine passages must be unchoked at subsonic and started at supersonic conditions. Additionally, to maximize the aerodynamic performance potential, ad-hoc designs are required, suited for the oscillations in Mach number and flow angle. This manuscript focuses on designing and characterizing diffusive turbine vanes that can operate downstream of a transonic rotating detonation combustor.  </p> <p><br></p> <p>First, the phenomenon of unstarting is presented, concentrating on the effect of pressure loss on the accurate prediction of the starting limit. Afterward, a multi-objective optimization with steady Reynolds Averaged Navier Stokes simulations, including the endwall and 3D vane design, is performed. The results are discussed, highlighting the impact of the throat-to-inlet area ratio on the pressure loss and the geometric features of the top-performing designs. Compared to previous  research on stator passages with contoured endwalls, considerable reductions in pressure loss and stator-induced rotor forcing are obtained, with an extended operating range and preserving high turning.  </p> <p><br></p> <p>Subsequently, the influence of the inlet boundary layer thickness on the vane performance is evaluated, inducing remarkable increases in pressure loss and downstream pressure distortion. Employing an optimization with a thicker inlet boundary layer, specific endwall design recommendations are found, providing a notable improvement in both objective functions. The impact of the geometry variations on flow detachment is assessed as well.</p> <p><br></p> <p>Finally, the impact of the inlet flow angle on the vane design is studied through a multi-point, multi-objective optimization with different inlet angles. The effect of incidence on the flow field and vane performance is evaluated first. Then, by comparing the optimized geometries with those optimized for axial inflows, several design guidelines are identified </p>

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<p dir="ltr">Burst-mode lasers and burst-mode optical parametric oscillators (OPOs) are applied and developed for planar laser induced fluorescence (PLIF) measurements of key species for high-speed combustion measurements. OH-PLIF in the rotating detonation engine was performed for the first time at wave structure visualization in two different planes and was 10 times faster than any other burst mode OH-PLIF measurements at the time. The same system was used to perform another OH-PLIF experiment at 1 MHz for ~200 pulses to compare key features of the detonation wave structure with computational fluid dynamic simulations and a fundamental detonation tube experiment. The system was also used for seedless velocity measurements in the exhaust by tracking a pocket of OH with a technique called FLASH. A similar OPO was built, aligned, and tuned to perform 1 MHz NO PLIF in a Mach 10 hypersonic tunnel to visualize second mode instabilities and calculate the frequency in the boundary layer transition of a 7-degree cone. A high-efficiency OPO was developed and characterized utilizing the KTP crystal to provide narrow bandwidth pulses for the fluorescence of multiple species. The OPO was pumped at repetition rates up to 1 MHz and was calculated to have a 1.9% UV efficiency from the fundamental 1064 nm output. This is 3 – 5 times increase in efficiency from previous custom and commercial built OPOs. The OPO was applied to the RDC for OH PLIF in the combustor channel and NO PLIF for injector dynamics and response studies. Lastly, a burst-mode laser was used to perform LII on the post detonation blast flow field to measure explosively generated soot. The data was taken at 1 MHz and compared and corrected with a separate set of experiments and computational simulations.</p>