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The compressor surge line of automotive turbochargers can limit the low-end torque of an engine. In order to determine how close the compressor operates to its surge limit, the Hurst exponent of th ...

BackgroundAortic disease is a key determinant of outcomes in Turner syndrome (TS). The present study characterized aortic growth rates and outcomes over nearly a decade in adult women with TS.Methods and resultsProspective observational study assessing aortic diameters twice with cardiovascular magnetic resonance imaging in women with TS [N = 91; mean follow-up 8.8 ± 3.3 (range 1.6–12.6) years] and healthy age-matched female controls [N = 37; mean follow-up 6.7 ± 0.5 (range 5.9–8.1) years]. Follow-up also included aortic outcomes and mortality, antihypertensive treatment and ambulatory blood pressure. Aortic growth rates were similar or smaller in TS, but the variation was larger. The proximal aorta in TS grew by 0.20 ± 0.26 (mid-ascending) to 0.32 ± 0.36 (sinuses) mm/year. This compared to 0.26 ± 0.14 (mid-ascending) and 0.32 ± 0.17 (sinuses) mm/year in the controls. During 799 years at risk, 7 suffered an aortic outcome (1 aortic death, 2 aortic dissections, 2 aortic interventions, 2 surgical aortic listings) with further 2 aortic valve replacements. At baseline, two women were excluded. One died during subacute aortic surgery (severe dilatation) and one had a previously undetected type A dissection. The combined aortic outcome rate was 1126 per 100 000 observation years. The aortic and all-cause mortality rates were 1 per 799 years (125 deaths per 100 000 observation years) and 9 per 799 years (1126 deaths per 100 000 observation years). Aortic growth patterns were particularly perturbed in bicuspid aortic valves (BAV) and aortic coarctation (CoA).ConclusionAortic growth rates in TS are not increased. BAVs and CoA are major factors that impact aortic growth. Aortic outcomes remain a concern.

International audience; In this paper, the origin and the properties of the oscillation modes in screeching non-ideally expanded rectangular jets are investigated using compressible implicit LES of rectangular supersonic jets. At the exit of a converging diverging rectangular nozzle of aspect ratio 2 and of design Mach number 1.5, the jets are under- and over-expanded. Seven simulations with four different temperature ratios ranging from 1 to 3 and two different nozzle pressure ratios are performed. The geometry of the nozzle and the exit conditions are chosen such that to match the experimental study conducted at the University of Cincinnati. First, the over-expanded jets are studied. It is shown that the total number of shock cells decreases with increased temperature ratio. However, the temperature does not influence the size of the first shock cell and the linear decrease of the shock cell size in the downstream direction. The spreading of the jet is observed to be higher along the minor axis plane than along the major axis plane. The intensity of the screech noise increases with the temperature ratio in the present study although the opposite is observed in the experiments. Moreover, for jet temperature ratios of 2.5 and 3, the strong flapping motion of the jet along the minor axis plane due to the screech feedback mechanism yields to an antisymmetric organization of the Mach wave radiation. Thereafter, the near- and far-field acoustic are studied. In the near-field, screech tones are captured, whose frequencies are consistent with both experimental data and theoretical models. In the far-field, four acoustic components typical of non-ideally expanded supersonic jets are observed, namely the screech noise, the broadband shock-associated noise, the mixing noise and the Mach wave noise. Their directivities and frequencies are in agreement with experimental results and models. The mechanism of the screech noise generation is studied by using a Fourier decomposition of the pressure field. For the four over-expanded jets, a flapping motion along the diagonal or along the minor axis plane of the jet is noted. Finally, the hypothesis that the acoustic waves completing the feedback loop in these jets are linked to the upstream-propagating acoustic wave modes of the equivalent ideally expanded jets is tested. Using a jet vortex sheet model to describe the dispersion relations of these modes, it is found that this hypothesis allows us to explain the antisymmetric jet oscillation observed at the screech frequencies. Based on frequency-wavenumber decomposition of the pressure fluctuations in the jets, it is shown that at the screech frequencies, acoustic waves propagating in the upstream direction at the ambient speed of sound exist also in the jet flow, additionally to the acoustic waves propagating outside of the jet. These acoustic waves belong to the neutral acoustic wave modes of the equivalent ideally expanded jet. These results support the idea that a vortex sheet model of the corresponding 2-D planar ideally expanded jet is capable of predicting the wave modes of a non-ideally expanded rectangular supersonic jet. They also suggest that these waves are involved in the feedback part of the screech mechanism; explaining why, for the simulated screeching rectangular jets, the associated oscillation mode is antisymmetric.

In some cases, a multinozzle combustor may exhibit flowfields in which individual nozzles hold two distinct flow or flame shapes in an alternating pattern. This study presents flowfield measurements for nonreacting and reacting flows in a rectangular combustor with two adjacent swirl-stabilizing nozzles at varying internozzle spacing. During tests of the wider nozzle spacings, with a reacting flow fueled by propane, there are differences between the flows of the two nozzles. Planar laser-induced fluorescence of the OH molecule (OH PLIF) shows that the flame remains anchored in the shear layer. Thus, the flame from one nozzle penetrates into the combustor, whereas the other flame is anchored close to, and almost parallel with, the dome wall. When the fuel is changed to methane, the asymmetry between the two nozzles is removed; therefore, the combustion properties, in addition to nozzle design, have an effect on the presence of this alternating flow pattern. A hypothesis based on turbulent opposed jets is p...

A jet exhausting over a plate at different distances away from the nozzle was investigated to simulate jets exhausting over airframe surfaces and the jet-ground interaction during take-off and landing operations. A supersonic rectangular nozzle of 2:1 aspect ratio and 1.5 design Mach number was tested with and without the plate. Far-field acoustics from the cold and heated jets at over-expanded, design, and under-expanded conditions were measured at the reflected, sideline, and shielded azimuthal directions. When the plate starts at the nozzle exit, the "scrubbing" and "scattering" noise from the surface-jet interaction was observed at the low-end frequencies of the reflected and shielded measurements and increased as the plate approached the jet. In the sideline, the plate attached to the nozzle exit diminished the broadband shock-associated noise while the shadowgraph results showed a connection to weakening of the shock-cell structures. In the cold jet, screech was mitigated with the plate attached at the nozzle exit. When the plate was moved away from the nozzle, screech tones were intensified at the under-expanded condition. Crackle levels were significantly intensified in the sideline within a range of plate positions. Noise levels in the shielded region were considerably lower due to the shielding effect.

Four detailed chemical kinetic mechanisms are used in conjunction with an empirical detonation cell width model to numerically assess strategies to increase the detonation sensitivity of ethylene–oxidizer mixtures. Using this method, reasonable agreement is achieved with computed cell width and the available experimental data. Elevated initial pressures significantly reduce cell width for a wide range of equivalence ratios, yielding 80% reduction at stoichiometric conditions for a tenfold increase in pressure. Elevated initial temperatures have almost no effect on the cell width at stoichiometric conditions, but yield 80% reduction at lean conditions when the initial temperature is doubled. Reduced nitrogen dilution within the oxidizer dramatically reduces the cell width for the entire computed range of equivalence ratios. Introducing hydrogen as a fuel additive yields mild improvement to detonation sensitivity at stoichiometric conditions, but requires relatively high H2 concentrations and is ineffective when coupled with elevated initial pressures. Introduction of supplemental oxygen and increasing the initial reactant pressure appears to be the most effective approach to enhance detonability for ethylene–oxidizer mixtures.

Slurries conveyed in conduits generate erosion caused by particle impacts on the walls. Those impacts result from the average velocity and the turbulence of the carrying liquid. We investigate the erosion and relevant flow features, when the dilute slurry passes from the inner to the outer annulus through four equally spaced rectangular apertures on the periphery of the tube dividing these two conduits. The flow of dilute slurry was solved numerically. A consideration was given to the effects of particle size on erosion rate and statistical distribution of impact velocity, angle, and total erodent mass inducing wear. In addition, the numerical solution of the continuous phase velocity was validated with measurements. A confined trailing vortex forms at the longitudinal edge of the aperture, amplifying the erosive wear on the outer wall of the annulus. A large amount of particles passes near the aperture׳s horizontal downstream edge and intensifies the erosion rate above it. The effect of these flow features becomes more pronounced for larger particles. The statistical analysis of impact velocity, angle, and mass showed that the mean velocity in the channel dominates erosion caused by impacts of large particles. On the other hand, the near-wall turbulence mainly affects the erosion resulting from impacts by small particles.

The peculiar phenomenon of longitudinal pulsed detonation (LPD) in a rotating detonation combustor (RDC) is studied using hydrogen–air mixtures, by utilizing: (i) two air injection schemes having different inlet areas, and (ii) a convergent nozzle assembly with different spacers that affixes to the RDC exit. By varying the air injection pressure ratio and the backpressure, the regime of occurrence and the mechanism of this pulsed detonation instability are investigated. Immense evidence to suggest that LPD is caused by a peculiar detonation initiation mechanism enabled by a reflected shock wave from the RDC exit is discovered through an ensemble axial pressure profile analysis. Distance–time plots show that a single cycle of the pulsed detonation has two components: a fast-moving axial forward decaying detonation wave (with 75% of the ideal detonation speed) and a slower reflected detached shock wave (with 30% of the ideal speed). When the weak reflected wave comes in contact with the fresh reactants at the RDC headwall, another strong axial detonation is produced, thereby continuing the cycle without external ignition. LPD is also found to have three diverse facets, namely, inception, sustenance and operating frequency. For similar backpressures, the two air injection schemes have completely different operating regimes, leading to the inference that while backpressure is necessary for the onset of the pulsed detonation instability, by virtue of enabling reflected shock waves from the exit, lower air injection pressure ratio dictates the sustenance of the instability. A narrow band of injection pressure ratios, between 1.4 and 1.85, under back-pressurized RDC operation has high proclivity to produce sustained periodic longitudinal pulsed detonations in the combustor. Above this range, stable rotating detonation is preferred, and below this range, the operation is distinguished by the mixed presence of both rotating and pulsed detonations for a given test point, finally breaking down into chaotic instability for lower pressure ratios. The frequency of the pulsed detonation operation is found to depend on the initial combustor pressure and equivalence ratio, with higher frequency observed with an increase in backpressure and equivalence ratio.

Periodic behavior in the reaction zone of a multiple-nozzle combustor undergoing self-sustaining combustion oscillations is examined. Understanding of the thermoacoustic interactions among heterogeneous arrays of swirl cups is important to enable the implementation of this low NOx approach. This combustor has three stages: a high-swirl pilot stage, a low-swirl intermediate stage, and a low-swirl outer stage. Liquid jet A fuel is supplied to all three fuel stages, which is characteristic of the high-power operation mode. Four test conditions are examined in which thermoacoustic coupling is observed at a well-defined frequency. Phase-averaged images of the OH* chemiluminescence emission show dramatic changes in the OH* emission, which is dominated by recurrent weakening and reignition downstream of the low-stability intermediate and outer fuel stages. The pilot stage reaction zone also displays periodic variation in intensity that is 90 deg out of phase and precedes the intermediate and outer fuel stages. O...

The hysteretic behavior of flashback (FB) and flash forward (FF) in methane and natural gas flames, stabilized by a low swirl fuel injector, is investigated using high speed OH* chemiluminescence and particle image velocimetry. Due to the lack of vortex breakdown, the two mechanisms discussed are boundary layer and turbulence induced FB. Two hysteresis cycles were identified, one when FB is induced by increasing the equivalence ratio starting from lean conditions, and the other by decreasing the equivalence ratio starting from rich conditions. Impact of relevant parameters including Reynolds number (Re), equivalence ratio, fuel type, combustion chamber geometry, preheating, and mixing tube protrusions are investigated. As Re is increased, the equivalence ratio at which both rich and lean flashbacks occur approaches stoichiometric conditions. However, the range of the hysteresis cycle between FB and FF is independent on Re. The transition processes during FB and FF are quite variable and their duration is independent on Re. The mean duration of FB transition initiated from lean conditions is nearly twice longer than the rich branch and also longer than both the lean and rich FF. The geometry of the combustion chamber affected neither FB nor FF. However, preheating increased the equivalence ratio at which FB occurred but did not affect FF. Also, FB had significant effect on the mean flow field.

Nitrous-oxide emissions and the equivalence ratio resulting in lean extinction of two adjacent gas turbine fuel/air nozzles are measured as the spacing between the two nozzles is varied. Two swirl-stabilized nozzle types are tested: a high-stability pilot design, and a low-emission design with a much lower swirl number. Jet A is used as the fuel. The lean blowout point is tested for both nozzle types at each spacing. Increased spacing results in blowout at a lower equivalence ratio, which is likely due to increased air velocity between the nozzles that occurs at closer spacings. The spacing has a dramatic effect on the nitrous-oxide emissions index (grams of nitrous-oxide produced per kilogram of fuel burned) for the three possible nozzle combinations. The nitrous-oxide index emissions are greatest when two nozzles are placed close, and they decrease as the internozzle distance grows. The excited hydroxyl radical (OH)* chemiluminescence imaging shows how the OH* intensity is greater on the side of the noz...

An experimental investigation into the effect of chevron spacing and distribution on supersonic jets was performed. Cross-stream and streamwise particle imaging velocimetry measurements were used to relate flow field modification to sound field changes measured by far-field microphones in the overexpanded, ideally expanded, and underexpanded regimes. Drastic modification of the jet cross-section was achieved by the investigated configurations, with both elliptic and triangular shapes attained downstream. Consequently, screech was nearly eliminated with reductions in the range of 10–25 dB depending on the operating condition. Analysis of the streamwise velocity indicated that both the mean shock spacing and strength were reduced resulting in an increase in the broadband shock associated noise spectral peak frequency and a reduction in the amplitude, respectively. Maximum broadband shock associated noise amplitude reductions were in the 5–7 dB range. Chevron proximity was found to be the primary driver of peak vorticity production, though persistence followed the opposite trend. The integrated streamwise vorticity modulus was found to be correlated with peak large scale turbulent mixing noise reduction, though optimal overall sound pressure level reductions did not necessarily follow due to the shock/fine scale mixing noise sources. Optimal large scale mixing noise reductions were in the 5–6 dB range.

Current treatment options are successful in 40% to 60% of children with persistent obstructive sleep apnea after adenotonsillectomy. Residual obstruction assessments are largely subjective and do not clearly define multilevel obstruction. We endeavor to use computational fluid dynamics to perform virtual surgery and assess airflow changes in patients with Down syndrome and persistent obstructive sleep apnea. Three-dimensional airway models were reconstructed from respiratory-gated computed tomography and magnetic resonance imaging. Virtual surgeries were performed on 10 patients, mirroring actual surgeries. They demonstrated how surgical changes affect airflow resistance. Airflow and upper airway resistance was calculated from computational fluid dynamics. Virtual and actual surgery outcomes were compared with obstructive apnea-hypopnea index values. Actual surgery successfully treated 6 of 10 patients (postoperative obstructive apnea-hypopnea index

The performance of a tangentially-injecting initiator tube of a rotating detonation combustor (RDC) is assessed for a range of initiator conditions. Two initiator fuels are evaluated for a range of RDC channel pressures, and channel widths to determine the effect on the blast wave generated by the initiator tube. Blast wave trajectories exhibit asymmetric bias in the initiator injection (forward) direction. The energy content is estimated by fitting the blast wave trajectory to a theoretical model for blast propagation. Maximum energy deposition is achieved for a rich H 2 –O 2 initiator mixture ( ϕ > 2), which provides twice the energy deposition of the highest performing C 2 H 4 –O 2 mixture. The highest recorded initiator energy deposition is an order of magnitude smaller than the critical value to directly initiate detonation in a stoichiometric H 2 –air mixture, precluding direct initiation for this configuration. RDC initiation behavior is assessed for a near-stoichiometric H 2 –air mixture using the highest-performing initiator tube setting, and verifies the absence of direct initiation. A complex, transitory period follows the subcritical initiation event and culminates in stable detonation rotation within several milliseconds.

Objectives/Hypothesis Voice disorders, such as unilateral vocal fold paralysis or paresis, and vocal fold scarring feature structural asymmetries of the vocal folds. Studies on how structural asymmetries affect voice has mostly been limited to computational simulations and experiments on mechanical models. The purpose of the current study is to examine the effects of asymmetries in left–right position, height, and length of the vocal folds on the intraglottal flow characteristics, as well as acoustics in the canine larynx model. Study Design Basic science. Methods Measurements of intraglottal flow velocity fields were taken in excised canine larynges using particle image velocimetry. Asymmetries of the vocal folds are induced by translating the vocal processes in space using a prong apparatus connected to a micrometer. Results Asymmetries in length height and abduction produced a reduction in the intraglottal vortices strength and subsequently the glottal efficiency. Conclusion Current findings can affect future recommendations for surgical interventions that are used to treat unilateral vocal fold paralysis. Level of Evidence N/A. Laryngoscope, 2016

An airbreathing pulse detonation engine-crossover system is developed to characterize the feasibility of shock-initiated combustion within an airbreathing pulse detonation engine. A shock wave is transferred through a crossover tube that connects a spark-ignited driver pulse detonation engine to the airbreathing, driven pulse detonation engine. Detonations in the driven pulse detonation engine develop from shock-initiated combustion caused by shock wave reflection. The pulse detonation engine-crossover system increases system efficiency through decreased deflagration-to-detonation transition distance while employing a single spark source to initiate a system consisting of multiple detonation tubes. The initiation effectiveness of shock-initiated combustion is compared to spark discharge initiation and detonation injection through a predetonator. Increasing the Reynolds number enhances combustion wave acceleration. However, for all initiation methods, the system requires a device to transition the combusti...

A University of Cincinnati experimental study is conducted on a Pulse Detonation Engine (PDE)-Crossover System to investigate the feasibility of repeated, shock-initiated combustion as a means to generate detonation within an annular array of detonation tubes. An optimization study of the system finds that reducing driver PDE length increases auto-ignition failures in the driver PDE due to undesirable feedback of hot products from the driven PDE. Initiation performance in the driven PDE is strongly dependent on initial driven PDE skin temperature in the shock wave reflection region. The optimum initiation performance is achieved within the driven PDE by filling the driver PDE with reactants past the crossover tube entrance. Increasing operating frequency negates the detrimental effect of increased nitrogen dilution. An array of detonation tubes connected with crossover tubes is developed using optimized parameters. Successful operation utilizing shock-initiated combustion through shock wave reflection is achieved and sustained. Results from this array show that if initially driven PDE tubes are operating successfully, all subsequently driven PDE tubes also operate successfully.

This study characterizes the mixing performance and non-reacting injection flow field within a rotating detonation engine. Initial reactant mixing is accomplished through a counter-rotating vortex pair developing from a jet-in-a-crossflow situation. Radially injected air wraps around the fuel jet, shearing the hydrogen into the vortex structure. The three-dimensional baseline geometry produces poor hydrogen/air mixing in the injection zone due to low fuel penetration into the wide, cross-flowing air stream and low air entrainment into the vortex structure. Injection parameters, including reactant flow rate, injection area, and fuel injection distribution, are varied to assess the impact on mixing. Decreasing air injection area and fuel injection area improve fuel penetration into the air stream and the vortex mixing mechanism, enhancing the level of mixedness within the annulus. For a given air injection area, an optimized number of fuel injection holes exists that provides the greatest level of mixedness. Variations from the optimized geometry reduce the effectiveness of the vortex mixing mechanism. Staggering fuel injection holes produces a decrease in mixedness when compared to collinear fuel injection.

A numerical procedure for load and response prediction in the context of acoustic fatigue is investigated on a model problem. Contrary to design guidelines, where the load needs to be specified (for example, based on experiments), the procedure used herein consists of simulating the load with computational fluid dynamics and then using the simulated load as a load input to a finite element simulation of the exposed structure. The model problem studied is a ramped backward-facing step with a thin aluminum panel fitted downstream of the step, parallel to the flow. The vortices generated in the wake of the step impose a time-varying load on the aluminum panel. The numerical results on the load and response are compared to experimental results. The load is simulated with large-eddy simulations with a wall function. The mean reattachment length, load intensity, and spectrum compare well with the measurements, with the exception of a somewhat overpredicted cutoff frequency. The panel response prediction compare...

This paper presents a comprehensive study of the unsteady flow field in a new concept lean direct injection gas turbine burner, which aims at a clean and efficient combustion with application to sustainable aviation and pollution abatement. Large Eddy Simulation (LES) and planar particle image velocimetry are employed to capture the characteristics of the swirling flow issued from the multiple-jet swirler under both the confined and unconfined conditions. The results are compared, and good agreement shows the capability of LES in capturing the large-scale flow structures. The iso-contour of axial and swirl velocities shows that the swirling flow is featured by multiple jets. These jets interact with the central recirculation zone (CRZ) and reform it into a “starfish” shape. Under the effect of the confinement, the flow displays a larger spreading angle of the jets and an outer recirculation zone (ORZ). A distinctive connection between the CRZ and the ORZ is evidenced to occur through the channels between the multiple jets. The outward flow in the channels is identified to oscillate at a Strouhal number of 0.1. To characterize the evolution, the unsteady large-scale structures, proper orthogonal decomposition (POD), and spectra POD (SPOD) analyses are performed. It is found that a single helix and a double helix are manifestations of two independent global modes in the SPOD analysis. The former shares the same frequency with the outward flow, and the latter is solely affected by the confinement.

Double shock diamonds establish in the exhaust of modular convergent-divergent nozzles. These consist of two shock structures; one originating from the nozzle throat and another from its exit. Analyzing the shock pattern developing for different fluidic injection operating conditions, it is shown that fluidic injection allows the rearrangement of the shock structures relative to each other. Overlapping the two structures caused large pressure oscillations in the exhaust and high amplitudes of shock associated noise, whereas staggering the shock structures mitigated these effects. The screech tone frequency did not change for all injection operating configurations, although the shock diamonds had been shifted drastically with respect to each other. Hence, the screech phenomenon is dominated by the primary shock spacing originating from the nozzle throat.

Rotating detonation combustors (RDC) offer a significant prospective increase in stagnation pressure across it owing to the presence of one or more rotating detonation waves spinning inside the combustor at the kilohertz regime. Naturally, considerable research impetus has been directed towards this technology in recent years to understand the driving mechanics to harness the associated potential of pressure gain combustion (PGC). One such area of focus has been the off-design operating modes of these devices which cause a myriad of instabilities. The current paper is focused towards the discussion of one such instability regime—low frequency instabilities (LFI)—in RDCs. We review three types of LFIs in RDCs based on prior findings, and propose mechanisms for the same.

The operating range and wave speed performance of a Rotating Detonation Combustor (RDC) is characterized for hydrogen-air mixtures for three fuel injection schemes and two air injection schemes. The fuel injection scheme is altered by changing the total number of injection orifices and the individual orifice area, while maintaining the same fuel mass flux across the three schemes. The operability, performance and combustion-induced pressure rise due to the addition of a back-pressurizing convergent nozzle is also characterized. While the operating range is largely unaffected by changes in the length-to-diameter ratio of the fuel injector orifices, higher length-to-diameter ratios correspond to a lower number of transitional RDC operation where there is a sudden abatement of the continuously propagating detonation wave, once established inside the combustor. Increased air injection area diminishes the operability, while producing high stochasticity in the performance of the RDC. The length-to-diameter ratio of the fuel orifices has a significant impact on the number of detonation waves that can exist in the chamber. For the highest length-to-diameter ratio of the fuel orifices, and at the highest air flow rates, the RDC supports multiple detonation waves inside the chamber. Without the convergent nozzle attachment, 80% of Chapman–Jouguet (C–J) detonation speed is achieved for all three fuel injection schemes. C–J detonation wave speed is achieved in the annulus when the RDC is back-pressurized using the nozzle. The ratio of reactant fill-height to the detonation cell-width tapers at the lean and rich operating conditions, while peaking at an equivalence ratio of around 1.2. The detonation-induced static pressure rise produced in the RDC is found to be dependent on the air flow rate and the equivalence ratio of the reactants.

The behavior of the oxidizer inlet and the fuel injection plenums during the operation of a Rotating Detonation Combustor (RDC) is studied using pressure sensors in the air injection gap, the fuel plenum, and in the combustor. Significant pressure feedback from the rotating detonation wave is observed in the air injection gap. Pressure feedback into the fuel plenum is relatively weaker. The average normalized cross-correlation between the pressure–time series in the air injection gap and within the combustor is greater than 0.3. The air injection gap has a considerable base sinusoidal oscillation in the same frequency range as a previously discovered waxing-and-waning instability in the combustor. The fundamental frequency in the air injection gap is the same as the RDC operation frequency for almost all test cases, indicating the high efficacy of the sensors in the air inlet to attain the operating frequency. Frequency analysis reveals notable spatial variation in the fuel plenum dynamics. The low frequency oscillation in the air injection gap is found to be constant at 235 (±2.5) Hz for all the air flow rates and equivalence ratios tested.

This investigation characterizes the mixing processes and injection flow field within a rotating detonation engine. The axisymmetric baseline geometry produces poor fuel/air mixing in the immediate injection region due to reduced fuel penetration into the wide, perpendicularly flowing air stream. Injection parameters including reactant flow rate, injection area, and placement of the fuel injection are varied from the baseline geometry to assess the impact on mixing. Decreasing reactant injection areas improves fuel penetration into the cross-flowing air stream, and turbulent diffusion of the fuel is enhanced within the annulus increasing local equivalence ratio. When fuel is injected into the air slot, local equivalence ratio is enhanced due to the increasing mixing length between the recirculation region and fuel injection. Emulating nozzle integration by increasing annulus back-pressure increases local equivalence ratio in the injection region due to increased convection residence time.