Bulletin of the American Physical Society
71st Annual Meeting of the APS Division of Fluid Dynamics
Volume 63, Number 13
Sunday–Tuesday, November 18–20, 2018; Atlanta, Georgia
Session D02: Detonations & Supersonic Combustion |
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Chair: Mark Short, Los Alamos National Lab Room: Georgia World Congress Center B203 |
Sunday, November 18, 2018 2:30PM - 2:43PM |
D02.00001: Thrust and flow field characterization of Rotating Detonation Engines using detailed numerical simulations Prashant Tarey, Praveen K Ramaprabhu, Jacob A McFarland, Douglas Schwer Rotating Detonation Engines (RDE) operate on continuous detonation-based thermodynamic cycles to achieve increased efficiency over the traditional Brayton cycle. A typical RDE design involves an annular cylinder, into which a fuel-air mixture is injected axially and consumed by a rotating detonation wave, while the burnt mixture is expelled to produce thrust. In this work, we report on detailed numerical simulations of an unrolled 2D RDE, operating on a stoichiometric H2-air mixture. Results from two codes are reported, where the conservation equations are solved using Piecewise Parabolic Method (FLASH1) and discontinuous-Galerkin method (JENRE2). In addition to varying the numerics, effect of reaction chemistry was also examined, by performing simulations with an induction time model, a 1-step reaction mechanism, and a detailed (9-species, 19-step) reaction mechanism3. We also report on several quantities of interest including the detonation wave height, thrust, and specific impulse as the ratio of the injector pressure to the ambient pressure is varied.
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Sunday, November 18, 2018 2:43PM - 2:56PM |
D02.00002: Characterization of the Detonation Wave Structure in a Linearized RDE Combustor Channel Supraj Prakash, Romain Fievet, Venkatramanan Raman, Jason Burr, Kenneth H. Yu Rotating detonation engines (RDEs) have gained traction as a viable method of pressure gain combustion for both propulsion and power generation applications alike. The challenge of practical RDE designs is the stabilization of the detonation wave as it processes a mixture of fuel and air azimuthally through an annulus. There is limited knowledge on the detailed flow structure from experimental imaging data. To this end, high fidelity numerical simulations have been used to examine the flow field. In this work, the fundamental wave structure of the detonation wave within a linearized RDE with a fully premixed fuel and oxidizer injection scheme is analyzed. The direct numerical simulation of the linearized model detonation engine (LMDE) is compared to experimental results, and wave behavior is correlated to wave structure and flow properties within the reaction zone. Thus, wave characteristics which aid detonability in a three-dimensional domain are discussed. This analysis is performed on hydrogen fuel with both air and oxygen oxidizers at equivalence ratios of 0.8, 1.0, and 1.2. |
Sunday, November 18, 2018 2:56PM - 3:09PM |
D02.00003: Effects of different injection schemes on the detonation structure of rotating detonation engines Takuma Sato, Fabian Chacon, James Duvall, Mirko Gamba, Venkatramanan Raman Pressure gain combustor (PGC) has drawn more attention as a next-generation combustor. In particular, rotating detonation engines (RDEs) have emerged as a viable candidate for PGC due to their continuous mode of operation. The practical challenge is to optimize the non-premixed injection in order to maximize pressure gain while ensuring a reliable and safe detonation process. For this purpose, the effect of mixing on detonation structure needs to be understood. |
Sunday, November 18, 2018 3:09PM - 3:22PM |
D02.00004: Effects of Injector/Wave Coupling on the Operation of a Rotating Detonation Engine Fabian Chacon, Mirko Gamba We experimentally investigate how the coupled dynamics of the air and fuel injection systems affect the properties of the detonation wave in a laboratory scale rotating detonation engine (RDE) operated under different fuel injection schemes and operating conditions (mass flux and equivalence ratio). Specifically, we evaluate how the dynamic response of the inlet/injector, i.e. its propensity to transmit pressure waves from the channel to the plenums, affects the stability of the wave. Wave stability is quantified in terms of the cycle-to-cycle variation of speed and pressure profiles extracted from simultaneous measurements of dynamic pressure in the air/ fuel plenums and detonation channel, and high speed chemiluminescence imaging marking the location of the detonation wave. We compare two configurations: (1) an axial air inlet with rear facing angled fuel injection; and (2) a radial air inlet with transverse fuel injection. Under operation they exhibit different dynamics that result in the formation of counter-propagating secondary acoustic waves that influence the strength and stability of the primary detonation wave, ultimately affecting the overall properties and performance of the device. |
Sunday, November 18, 2018 3:22PM - 3:35PM |
D02.00005: Evaluation of Techniques for Calculating RDEs Somnic Jacobs, Foluso Ladeinde There seems to be no consensus currently as to the best numerical, turbulence, and combustion models to use for the numerical simulation of the Rotating Detonation Engine (RDE). For example, Oran’s group has proposed very simplified ways of handling combustion, whereas a few others have advocated the use of more complicated kinetic mechanisms in order to capture essential aspects of RDE combustion. The present study compares the performance of different kinetic mechanisms. Furthermore, whereas most studies have limited their models to the laminar case, there has been a recent suggestion that the presence of turbulence might explain the observed reduction in detonation speeds from simulations, relative to the CJ values. Romick et al.* have demonstrated the significance of using Navier-Stokes (NS) models, as opposed to the more prevalent Euler models, in an attempt to capture some physically-important phenomenon in RDE. However, these authors also require that the physical viscosity in Navier-Stokes be significantly greater than the numerical viscosity. The use of turbulence modeling and the required amount of numerical viscosity in the sense of Romick and his co-workers are investigated in this work.
*Romick et al., Journal of Fluid Mechanics. (2012), vol. 699, pp. 453-464.
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Sunday, November 18, 2018 3:35PM - 3:48PM |
D02.00006: High-Speed Oxy-Combustion Detonation withMulti-Step Finite Rate Chemical Kinetics usingSpace-Time Method Shashank Karra, Sourabh Apte Pulse detonation system using oxy-fuel combustion can be used for direct power extraction especially when combined with magnetohydrodynamics (MHD). In the present work, we investigate the use of a space-time conservation element-solution element (CE/SE) method for simulation of high-speed oxy-fuel pulse detonation shock waves. A CE/SE method results in a consistent multi-dimensional formulation for unstructured tetrahedral meshes by providing flux conservation in space and time and eliminating the need for complex Reimann solvers to capture shocks. |
Sunday, November 18, 2018 3:48PM - 4:01PM |
D02.00007: Assessment of Different Kinetic Mechanisms for DNS of Supersonic Combustion HyeJin Oh, Foluso Ladeinde That simulation results for reactive flows are as important as the kinetic mechanisms used has been reported for mass fraction PDF in reacting compressible mixing layers using DNS [1]. However, more accurate reduced mechanisms have since been developed that are well-suited to supersonic combustion simulations [2]. In this study, various such mechanisms for hydrogen-air combustion in canonical models of the scramjet engine combustor are investigated. The non-premixed combustion type is focused on, and, even though the ultimate interest is supersonic combustion under turbulent conditions, various mechanisms for the opposed-jet flames are initially evaluated to provide some foundations for understanding the dynamics in the eventual turbulent system. A primary objective is the determination of the most computationally efficient kinetic mechanism that is able to accurately model the problem of interest. Mechanisms from a few reaction steps and species to those with scores of these parameters are being investigated and will be reported for DNS of supersonic combustion. [1] Ladeinde, F. et al., 1999, In "Turbulence and Shear Flow - I'', Begell House, Inc., Edit. S. Banerjee & J. Eaton, pp. 321-326. [2] Burke et al., 2012, Int. J. of Chemical Kinetics, doi 10.1002/kin.20603 |
Sunday, November 18, 2018 4:01PM - 4:14PM |
D02.00008: The Role of Fuel Flammability on Shock Dynamics in Supersonic Combustion Foluso Ladeinde, Wenhai Li Better understanding of unstart in scramjets is sought in this study, with motivations coming from several engine failures attributable to this phenomenon. Many studies have reported on the dynamics and control of the associated shock train. However, these studies are based on artificially blocking the flow downstream of the combustor to induce mechanical backpressure as a surrogate for the dynamics in the real, reactive system. Addressing the real system is needed, which is the objective of the present work, especially as it relates to the flammability of different fuels. Reactive calculations using hydrogen, ethylene, and methane [1, 2] are carried out for the purpose of determining the roles played by fuel flammability on shock dynamics in supersonic combustion, and the implication for the performance of the dual-mode scramjet engine. Keeping the injection conditions of the fuels similar, it has been observed in this study that only hydrogen exhibits the shock dynamics phenomenon for the parameters used. Moreover, under pure mixing conditions in the same scramjet model, hydrogen does not exhibit this behavior.
[1] Ladeinde, F. AIAA Paper 2009-127, doi: 10.2514/6.2009-127. [2] Ladeinde, F. & Lou, Z. Journal of Propulsion and Power, 34(3), 2018, pp. 750-762. |
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