2D Euler Modeling of Rotating Detonation Combustion in Preparation for Turbomachinery Matching

Paschereit

et al. 2023

Self Cite

A time resolved, two-dimensional reactive Euler solver is employed to simulate Rotating Detonation Combustion (RDC). The influence of combustor diameter, axial length, combustion annulus mass flux, outlet throat area, and air injector area on the flow field geometry and performance is studied. There is a similarity in the unsteady outlet state for cases at equal combustor aspect ratio. It is demonstrated that generalization of Equivalent Available Pressure methodology for the non-constant heat capacity ratio case is not trivial and can introduce significant errors. To bypass this issue, an alternative approach for performance quantification is introduced. Mass flux and outlet throat area are found to have a significantly stronger effect on performance compared to diameter and axial length. Yet, the influence of the latter two is significant. The angle of the oblique shock is quantified and is shown to correlate with the ratio of detonation height and axial combustor length. The results suggest that entropy generation due to shock processing is the driving mechanism behind performance deviation due to changes in combustor diameter and axial length. Approximate predictions about the shock processing can be made using geometric dependencies of the flow field.

“…The RDC model used for this study was described in detail in a previous study [11]. Therefore, only a brief overview is given here.…”

Section: Methodsmentioning

confidence: 99%

Section: A Numerical Validationmentioning

confidence: 99%

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Investigation of Geometric RDC Dependencies Using a Fast Reactive Euler Solver

Garan

Paschereit

et al. 2023

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“…Both Mach-corrected CTAP method and EAP assume the high-enthalpy flow is choked at the exit throat. The actual Mach number varies spatially and temporally around the combustor [14], so the sonic assumption that is functional for steady flow will not be appropriate for the transient RDC system. Fievisohn et al [15] measured the total pressure by EAP and Mach-corrected CTAP method and compared the static pressure at the exit throat based on these two methods.…”

Section: Introductionmentioning

confidence: 99%

Experimental Comparison of Different Pressure Gain Measurement Techniques for RDCs

Kayser

Wei

et al. 2023

Rotating Detonation Combustors (RDC) feature an inherently unsteady internal flow field with characteristic frequencies in the kHz range, which makes accurately quantifying the achieved pressure gain challenging. The present study therefore considers three methods to determine the stagnation pressure of the high-enthalpy outlet flow: Mach-corrected Capillary Tube Averaged Pressure (CTAP) measurements of 𝒑 t,4 , direct Kiel probe measurements of 𝒑 t,8 , and Equivalent Available Pressure (EAP) measurements using a thrust stand. The methods differ significantly in their relative accuracy and the amount of required instrumentation. A parametric study with all three approaches was conducted at TU Berlin over a range of configurations and operating conditions to compare the acquired data. To this end, a 5 kN class thrust stand was used along with a calibration method and base drag measurement setup. Further, a low Mach number correction was implemented for Mach-corrected CTAP and EAP data at conditions where the M 8 = 1 assumption breaks down. The EAP data displays the highest amount of scattering due to the large number of calibration that need to be taken into account. The base drag pressure distribution on the outlet flanges, which can amount to 12.78% and more of EAP, varies significantly with the operating condition. All three methods generally agree well with one another, with EAP being the most conservative. Kiel probe measured stagnation pressure is on average about 5% higher than EAP and 3% higher than the Mach-corrected 𝒑 t,4 . This underlines that methods with reduced instrumentation may be useful for pressure gain estimation. Nevertheless, it also shows that a standardized data reporting method may be required in the community to compare different experiments.

“…These velocity and pressure deficits are often not captured in many computational fluid dynamic (CFD) simulations of RDCs. Klopsch et al applied a two-dimensional, time-resolved reactive Euler solver to model the aforementioned RDC configuration and reported CJ velocities between 89% and 95% [3]. In a complimentary high-fidelity computation by Nassini, the predicted wave speed was 19% higher than the measured one at similar operating conditions [4].…”

Section: Introductionmentioning

confidence: 99%

Low-Order Model for Detonation Velocity Suppression in Rotating Detonation Combustors

Barnouin

Gutmark

et al. 2023

A Rotating Detonation Combustor (RDC) is a novel pressure gain combustion device, in which a detonation wave processes steadily around an annulus. It has been experimentally observed that detonation waves in the RDC propagate slower than the idealized Chapman-Jouguet (CJ) speed (as low as approximately 60%) and with lower than expected peak pressures. This work then attempts to develop a low-order model to identify the impact of non-ideal processes on these key detonation properties. Three mechanisms are incorporated: the buffer region created by non-premixed reactant injection, parasitic combustion of reactants, and suppression of the heat release through the detonation. While these sophisticated processes are only coarsely described by such a low-order model, it is shown that their effect results in a partial heat release that supports the detonation wave and can capture the deficit in detonation properties. One special aspect of this model is that it is designed to utilize relatively easily measured experimental data as inputs. This has the objective of providing rough, first order estimates of these more sophisticated processes than would otherwise be available by typical RDC combustor diagnostics. A parametric analysis is conducted for stable detonation runs on the RDC at TU Berlin. Convergence between predicted and experimental values show that a significant proportion of the heat release is lost in the buffer zone, undergoes parasitic combustion or is unable to contribute to the detonation heat release.