The Experts below are selected from a list of 27864 Experts worldwide ranked by ideXlab platform
Jianping Wang - One of the best experts on this subject based on the ideXlab platform.
-
experimental research on ignition quenching reinitiation and the stabilization process in rotating Detonation engine
International Journal of Hydrogen Energy, 2018Co-Authors: Shujie Zhang, Mingyi Luan, Jianping WangAbstract:Abstract This paper presents an experimental research on ignition, quenching, reinitiation and the stabilization process in hydrogen-air rotating Detonation engine with an array of injection holes. The stabilization process can be divided into six sections, including deflagration, deflagration to Detonation transition (DDT) process, coexistence of Detonation with deflagration, coexistence of strong & weak Detonations, unstable to stable Detonation transition and stable Detonation. The phenomenon of single-double-single wave transition is found and analyzed for the first time in the experiment. During the transition, the initial strong Detonation wave weakens until it disappears, and the weak Detonation wave becomes stronger until it propagates steadily. The reinitiation phenomenon is related to the injection pressures of the propellant. Increasing the injection pressure helps to reinitiate, thus avoiding the occurrence of the quenching phenomenon.
-
reinitiation phenomenon in hydrogen air rotating Detonation engine
International Journal of Hydrogen Energy, 2017Co-Authors: Shujie Zhang, Mingyi Luan, Jianping WangAbstract:Abstract This article presents a numerical study on the rotating Detonation engine (RDE). The simulation explores the phenomenon of the reinitiation of Detonations in the RDE with a cylindrical combustion chamber. The process is modelled by the three-dimensional reactive Euler equations with an Arrhenius form of the reaction rate for the premixed stoichiometric hydrogen-air mixture. The Detonation flow goes through three stages: initiation, quenching, and spontaneous reinitiation. The Detonation fronts collide with each other and also have frequent collisions with the outer wall after initiation. While there is a possibility of generating new Detonation fronts from the explosion, it is also likely that the explosion will burn out the surrounding reactive mixtures and snuff out the Detonation waves. The simulation shows that a strong collision between two Detonation wave fronts extinguishes the Detonation flow and consequently renders the engine inoperative for an extended period until a spontaneous reinitiation occurs in the flow. The reinitiation is found to be triggered by a rapid and sharp increase of pressure near the chamber wall.
-
numerical investigation of flow particle paths and thermodynamic performance of continuously rotating Detonation engines
Combustion and Flame, 2012Co-Authors: Rui Zhou, Jianping WangAbstract:Based on the two-dimensional numerical simulation of continuously rotating Detonations in an annular chamber, the paths of flow particles burned by three different processes are tracked and analyzed in detail. The Detonation wave, the deflagration wave, the oblique shock wave, and the contact surface have a small influence on the paths of flow particles. The fluctuation of paths in the azimuthal direction is less than 12% of the circumference of the combustion chamber. The path will deflect when the flow particle encounters the Detonation wave or the oblique shock wave, and it will not deflect when encounters the deflagration wave or the contact surface. About 23.6% fuel is burned by deflagration, and the left is burned by rotating Detonation wave. The thermodynamic performance of continuously rotating Detonations is then discussed. The p–v and T–s diagrams obtained by numerical simulation are qualitatively consistent with the ideal ZND model. The average thermal efficiency of the Detonation combustion in 2D RDE is 31%, and its average net mechanical work is 1.3 MJ/kg. The thermal efficiency of the entire RDE is 26.4%, and its net mechanical work is 30% of the ideal ZND model. The superior performance of continuously rotating Detonations is determined.
Matei I Radulescu - One of the best experts on this subject based on the ideXlab platform.
-
dynamics of hydrogen oxygen argon cellular Detonations with a constant mean lateral strain rate
Combustion and Flame, 2020Co-Authors: Qiang Xiao, Matei I RadulescuAbstract:Abstract The present work revisits the problem of modeling the real gaseous Detonation dynamics at the macro-scale by simple steady one-dimensional (1D) models. Experiments of Detonations propagating in channels with exponentially expanding cross-sections were conducted in the H2/O2/Ar reactive system. Steady Detonation waves were obtained at the macro-scale, with cellular structures characterized by reactive transverse waves. For all the mixtures studied, the dependence of the mean Detonation speed was found to be in excellent agreement with first principles predictions of quasi-1D Detonation dynamics with lateral strain rate predicted from detailed chemical kinetic models. This excellent agreement departs from the earlier experiments of Radulescu and Borzou (2018) in more unstable Detonations. The excellent agreement is likely due to the much longer reaction zone lengths of argon diluted hydrogen oxygen Detonations at low pressures, as compared with the characteristic induction zone lengths. While the cellular instability modifies the Detonation induction zone, the Detonation dynamics at the macro-scale are arguably controlled by its hydrodynamic thickness. Near the limit, minor discrepancy is observed, with the experimental Detonations typically continuing to propagate to slightly higher lateral strain rates and higher velocity deficits.
-
experimental and numerical investigation of propagation mechanism of gaseous Detonations in channels with porous walls
Combustion and Flame, 2015Co-Authors: Kiumars Mazaheri, Yasser Mahmoudi, Majid Sabzpooshani, Matei I RadulescuAbstract:Abstract In the present work the propagation of gaseous Detonations in a channel with porous walls is investigated experimentally and numerically. The main goal of the study is to determine the role of diffusive turbulent mixing and transverse waves in controlling the Detonation limits in channels with porous walls. Detonations in propane–oxygen and hydrogen–oxygen–argon mixtures, which are characterized by their irregular and regular cellular structures, are considered in the experimental and numerical investigations. Euler simulations are performed for parameters corresponding to both regular and irregular Detonations. In the smooth wall region Schlieren photographs of hydrogen–oxygen–argon Detonation show laminar reaction zones behind the main front. In addition, as the Detonation propagates over the porous wall, due to the mass divergence into the damping section, the frontal wave curvature increases. The number of transverse waves decreases in the porous section which is caused by the attenuation of the Detonation wave. In comparison to the stable argon diluted Detonations, experiments for unstable propane–oxygen Detonations illustrate lower wave curvature and high turbulence in the reaction zone in the porous section. The numerically obtained results for both regular and irregular Detonations show that close to the porous wall the front curvature increases, a finding that is also observed in experiments. If the curvature extends to the whole channel width the Detonation wave fails to propagate. Nevertheless, the numerical critical limit of W / λ for unstable Detonations is found to be higher than that of stable Detonations, which is in contradiction with the experimental results. This discrepancy can be explained by the effect of turbulent diffusive mixing in controlling the reaction rate in highly unstable Detonations, which is not taken into account in the current numerical simulations.
-
diffusion and hydrodynamic instabilities in gaseous Detonations
Combustion and Flame, 2012Co-Authors: Kiumars Mazaheri, Yasser Mahmoudi, Matei I RadulescuAbstract:Abstract To clarify the role played by diffusion in Detonation structure, two-dimensional numerical simulations are performed by solving the Navier–Stokes equations and considering the single step Arrhenius kinetic as reaction model. The effect of diffusion on the generation of vortices produced by hydrodynamic instabilities (Richtmyer–Meshkov (RM) and Kelvin Helmholtz (KH) instabilities) is investigated. Mixtures with both low and high activation energies, characterized by their regular and irregular Detonation structures, are considered. The computations are performed with resolutions ranging from 25 to 10 3 cells per half reaction length of the ZND structure. Resolution studies of the Navier–Stokes solution for irregular Detonations in moderate activation energy mixtures shows that to capture a proper structure, to be at least in qualitative agreement with experimental observations, resolution more that 300 cells per half reaction length is required. However, in mixtures with low activation energy a resolution of 25 cells per half reaction length gives a reasonable physical structure of the Detonation. Results provided by very high resolution for irregular structure Detonations reveal that the major effect of diffusion occurs at shear layers and unburned pockets boundaries. Diffusion suppresses the small-scale vortices produced by KH instabilities and decreases the turbulent mixing rate of burned and partly burned gases at shear layers. However, behind the shock front, where less concentration of small-scale vortices exist, the diffusion of heat and mass from neighboring hot regions of burned material to the unreacted gases increases the burning rate of the un-reacted pockets. Comparison of the structure obtained by solving the Euler equations with the solution of the Navier–Stokes equations shows that, the strength of the shock front in Navier–Stokes solution is higher than that in Euler solution. Due to the absence of hydrodynamic instabilities behind the main front of regular structure Detonations, the results obtained by solving the Euler equations and Navier–Stokes equations are similar for Detonations with regular structure even in high resolution simulations.
-
nonlinear dynamics of self sustained supersonic reaction waves fickett s Detonation analogue
Physical Review Letters, 2011Co-Authors: Matei I Radulescu, J TangAbstract:The present study investigates the spatiotemporal variability in the dynamics of self-sustained supersonic reaction waves propagating through an excitable medium. The model is an extension of Fickett's Detonation model with a state-dependent energy addition term. Stable and pulsating supersonic waves are predicted. With increasing sensitivity of the reaction rate, the reaction wave transits from steady propagation to stable limit cycles and eventually to chaos through the classical Feigenbaum route. The physical pulsation mechanism is explained by the coherence between internal wave motion and energy release. The results obtained clarify the physical origin of Detonation wave instability in chemical Detonations previously observed experimentally.
-
the ignition mechanism in irregular structure gaseous Detonations
Proceedings of the Combustion Institute, 2005Co-Authors: Matei I Radulescu, Gary J Sharpe, Charles B. Kiyanda, Andrew J HigginsAbstract:Abstract The present study investigated the gas ignition mechanism in typical irregular structure Detonations. In vivid contrast with the results obtained in previous studies for regular structure Detonations, the real and numerical experiments performed in the present study for typical irregular structure Detonations show that ignition is achieved both by the classical adiabatic shock compression mechanism and by turbulent mixing. The latter mechanism is usually overlooked in theoretical descriptions of the Detonation wave structure and models. In the present experiments, schlieren and self-luminous photographs of methane–oxygen Detonation structures indicated that nearly half of the shocked gases cannot ignite from shock compression alone. This gas ignites following the turbulization of burned/unburned gas interfaces and subsequent interactions with pressure waves. In the corresponding numerical experiments, where these turbulent interactions were not resolved, large unreacted pockets of gas were formed. Due to the absence of the unresolved small-scale instabilities, the Detonation wave could not be self-sustained and failed, indicating the importance of turbulent interactions, which are necessary to ensure gas ignition and wave self-sustenance. Experiments on the interaction of a Detonation wave with a fine grid also indicated that the burning rates were amplified as a result of the grid-generated turbulence.
Frederick Schauer - One of the best experts on this subject based on the ideXlab platform.
-
chemiluminescence imaging of an optically accessible non premixed rotating Detonation engine
Combustion and Flame, 2017Co-Authors: Brent A Rankin, John Hoke, Andrew Naples, Daniel R Richardson, Andrew W Caswell, Frederick SchauerAbstract:The Detonations propagating through the annular channel of an optically accessible rotating Detonation engine (RDE) operating on hydrogen–air are visualized using OH* chemiluminescence imaging. The images are useful for observing the instantaneous size and shape of the Detonation structure, oblique shock wave, and possible presence of deflagration between the fuel-fill zone and expansion region containing Detonation products. The Detonation increases in height as the air flow rate is increased for low flow rates, experiences subtle changes for intermediate flow rates, and transitions from one to two waves for higher flow rates. The two Detonation waves typically propagate in the same azimuthal direction. Counter-rotating waves resulting in Detonation–Detonation interactions are observed for some configurations with a reduced number of fuel injection jets. Time-dependent static pressure measurements show that acoustic interactions between the Detonation channel and air plenum are important for low air flow rates and large air injection areas. The OH* chemiluminescence images, pressure, and wave speed measurements provide benchmark data that are useful for evaluating RDE models and simulations, improving fundamental understanding of the Detonation structure in RDEs, and identifying critical design parameters that influence RDE operation and performance.
-
overview of performance application and analysis of rotating Detonation engine technologies
Journal of Propulsion and Power, 2017Co-Authors: Brent A Rankin, John Hoke, Andrew Naples, Matthew L Fotia, Christopher A Stevens, Thomas A Kaemming, Scott W Theuerkauf, Frederick SchauerAbstract:Recent accomplishments related to the performance, application, and analysis of rotating Detonation engine technologies are discussed. The pioneering development of optically accessible rotating Detonation engines coupled with the application of established diagnostic techniques is enabling a new research direction. In particular, OH* chemiluminescence images of Detonations propagating through the annular channel of a rotating Detonation engine are reported and appear remarkably similar to computational fluid dynamic results of rotating Detonation engines published in the literature. Specific impulse measurements of rotating Detonation engines and pulsed Detonation engines are shown to be quantitatively similar for engines operating on hydrogen/air and ethylene/air mixtures. The encouraging results indicate that rotating Detonation engines are capable of producing thrust with fuel efficiencies that are similar to those associated with pulsed Detonation engines while operating on gaseous hydrocarbon fuels....
-
imaging of oh chemiluminescence in an optically accessible nonpremixed rotating Detonation engine
53rd AIAA Aerospace Sciences Meeting, 2015Co-Authors: Brent A Rankin, John Hoke, Andrew Naples, Daniel R Richardson, Andrew W Caswell, Frederick SchauerAbstract:The Detonation propagating through the annular channel of an optically accessible nonpremixed rotating Detonation engine (RDE) is visualized in this work using OH* chemiluminescence imaging. The fuel and air are injected from separate streams and partially premix in the channel in front of the Detonation wave. The OH* chemiluminescence images allow observation of the size and shape of the Detonation structure, trailing edge oblique shock wave, and possible presence of deflagration between the fuel fill region and expansion region containing detonated products. The OH* chemiluminescence images are useful for evaluating the effects of the air mass flow rate, equivalence ratio, air injection area, and fuel injection scheme on the Detonation structure and its corresponding impact on RDE operation and performance. The Detonation increases in height as the air mass flow rate is increased for low flow rates, experiences subtle changes in size and shape for intermediate flow rates, and transitions from one-wave to two-waves as the flow rate is further increased. For fuel lean conditions, the high OH* emissions from the Detonation are distributed more broadly in space. For stoichiometric and fuel rich conditions, the high OH* emissions typically are confined to a more narrow region near the Detonation wave front. The wave front is more concave with respect to the fuel fill region in front of the Detonation as the air injection slot is increased from low to intermediate values. The angle between the wave front and fuel injection surface in front of the Detonation becomes more acute as the air injection slot is further increased. Reducing the number of fuel injection holes has significant effects on the Detonation structure including transition from one-wave to two-waves. The waves typically co-rotate with the Detonations propagating in the same azimuthal direction for most conditions in which two-waves are established in the channel. Counter-rotating waves with the Detonations propagating in the opposite azimuthal direction are observed for some conditions. The observation of two counter-rotating Detonation waves demonstrates one occasional effect of non-ideal mixing between the fuel and air in a nonpremixed RDE. The OH* chemiluminescence images are useful for evaluating RDE models and simulations, improving fundamental understanding of the Detonation structure in nonpremixed RDEs, and identifying critical design parameters that influence RDE operation and performance.
-
rotating Detonation engine operation
50th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition, 2012Co-Authors: James A Suchocki, John Hoke, Andrew Naples, Frederick Schauer, Rachel RussoAbstract:A Rotating Detonation Engine engineered and manufactured by Pratt and Whitney Seattle Aerosciences Center was loaned to the Air Force Research Laboratory at WrightPatterson Air Force Base for further testing and development. The engine was originally designed for ethylene and oxygen, but was altered in order to use hydrogen and air. The engine was tested at a wide range of flow rates and equivalence ratios with hydrogen-air in order to obtain a matrix of the operating space. Although a considerable portion of the test matrix contained successful Detonations, all of the Detonations that occurred for the tested configuration were in the fuel rich operating regime. In the pursuit of greater thrust output and a wider range of operability, the air was slightly enriched with additional oxygen. The addition of extra oxygen not only increased the range of thrust output and operability, it also allowed the engine to detonate at high enough air mass flows that two Detonation waves were established in the engine. The Detonation wave activity during the approach and through the transition from one Detonation wave to two Detonation waves was analyzed in order to gain a deeper understanding of the transition phenomenon.
William A Hargus - One of the best experts on this subject based on the ideXlab platform.
-
Descending Modal Transition Dynamics in a Large Eddy Simulation of a Rotating Detonation Rocket Engine
'MDPI AG', 2021Co-Authors: Armani Batista, Mathias C. Ross, Christopher Lietz, William A HargusAbstract:Rotating Detonation rocket engines (RDREs) exhibit various unsteady phenomena, including modal transitions, that significantly affect their operation, performance and stability. The dynamics of the Detonation waves are studied during a descending modal transition (DMT) where four co-rotating Detonations waves decrease to three in a gaseous methane-oxygen RDRE. Detonation wave tracking is applied to capture, visualize and analyze unsteady, 3D Detonation wave dynamics data within the combustion chamber of the RDRE. The mechanism of a descending modal transition is the failure of a Detonation wave in the RDRE, and in this study, the failing wave is identified along with its failure time. The regions upstream of each relative Detonation show the mixture and flow-field parameters that drive Detonation failure. Additionally, it is shown that descending modal transitions encompass multiple phases of Detonation decay and recovery with respect to RDREs. The results show high upstream pressure, heat release and temperature, coupled with insufficient propellants, lead to Detonation wave failure and non-recovery of the trailing Detonation wave during a descending modal transition. Finally, the Wolanski wave stability criterion regarding Detonation critical reactant mixing height provides insight into Detonation failure or sustainment
-
experimental evidence of h2 o2 propellants powered rotating Detonation waves
Combustion and Flame, 2020Co-Authors: Jonathan Sosa, Robert F Burke, Kareem Ahmed, Daniel J Micka, John W Bennewitz, Stephen A Danczyk, Eric J Paulson, William A HargusAbstract:Abstract The paper presents experimental evidence of continuous Detonation in a rotating Detonation rocket engine (RDRE) powered by H2/O2 propellants. High-speed chemiluminescence imaging is used to characterize the Detonation wave dynamics by introducing a tracer in the hydrogen fuel flow. The results show continuous five-wave co-rotating Detonations at various equivalence ratios and flow rates demonstrating the potential for H2/O2 propellant based RDREs for upper-stage rocket engines.
Andrew J Higgins - One of the best experts on this subject based on the ideXlab platform.
-
Propagation of gaseous Detonation waves in a spatially inhomogeneous reactive medium
Physical Review Fluids, 2017Co-Authors: Xiaocheng Mi, Charles B. Kiyanda, Hoi Dick Ng, Andrew J Higgins, Nikolaos NikiforakisAbstract:Detonation propagation in a compressible medium wherein the energy release has been made spatially inhomogeneous is examined via numerical simulation. The inhomogeneity is introduced via step functions in the reaction progress variable, with the local value of energy release correspondingly increased so as to maintain the same average energy density in the medium, and thus a constant Chapman Jouguet (CJ) Detonation velocity. A one-step Arrhenius rate governs the rate of energy release in the reactive zones. The resulting dynamics of a Detonation propagating in such systems with one-dimensional layers and two-dimensional squares are simulated using a Godunov-type finite-volume scheme. The resulting wave dynamics are analyzed by computing the average wave velocity and one-dimensional averaged wave structure. In the case of sufficiently inhomogeneous media wherein the spacing between reactive zones is greater than the inherent reaction zone length, average wave speeds significantly greater than the corresponding CJ speed of the homogenized medium are obtained. If the shock transit time between reactive zones is less than the reaction time scale, then the classical CJ Detonation velocity is recovered. The spatio-temporal averaged structure of the waves in these systems is analyzed via a Favre averaging technique, with terms associated with the thermal and mechanical fluctuations being explicitly computed. The analysis of the averaged wave structure identifies the super-CJ Detonations as weak Detonations owing to the existence of mechanical non-equilibrium at the effective sonic point embedded within the wave structure. The correspondence of the super-CJ behavior identified in this study with real Detonation phenomena that may be observed in experiments is discussed
-
propagation of gaseous Detonation waves in a spatially inhomogeneous reactive medium
Physical Review Fluids, 2017Co-Authors: Andrew J Higgins, Charles B. Kiyanda, Nikolaos NikiforakisAbstract:Concentrating the energy release of a medium in spatially discrete pockets affects Detonation waves. In a numerical study, Detonations are observed to propagate at average speed as much as 10% greater than the corresponding Chapman-Jouguet speed of the homogenized medium due to nonequilibrium at the effective sonic plane.
-
formation of transverse waves in oblique Detonations
Proceedings of the Combustion Institute 2 34 1913-1920, 2013Co-Authors: Jimmy Verreaul, Andrew J Higgins, Robe StoweAbstract:The structure of oblique Detonation waves stabilized on a hypersonic wedge in mixtures characterized by a large activation energy is investigated via steady method of characteristics (MoC) calculations and unsteady computational flowfield simulations. The steady MoC solutions show that, after the transition from shock-induced combustion to an overdriven oblique Detonation, the shock and reaction complex exhibit a spatial oscillation. The degree of overdrive required to suppress this oscillation was found to be nearly equal to the overdrive required to force a one-dimensional piston-driven Detonation to be stable, demonstrating the equivalence of two-dimensional steady oblique Detonations and one-dimensional unsteady Detonations. Full unsteady computational simulations of the flowfield using an adaptive refinement scheme showed that these spatial oscillations are transient in nature, evolving in time into transverse waves on the leading shock front. The formation of left-running transverse waves (facing upstream) precedes the formation of right-running transverse waves (facing downstream). Both sets of waves are convected downstream away from the wedge in the supersonic flow behind the leading oblique front, such that the mechanism of instability must continuously generate new transverse waves from an initially uniform flow. Together, these waves define a cellular structure that is qualitatively similar to a normal propagating Detonation. © 2012 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
-
formation and structure of steady oblique and conical Detonation waves
AIAA Journal, 2012Co-Authors: Jimmy Verreault, Andrew J Higgins, Robert StoweAbstract:The formation and structure of oblique Detonation waves initiated by semi-infinite wedges and cones are presented. For wedge or cone angles less than the deflection angle required for an oblique Chapman–Jouguet (CJ) Detonation, different wave structures have been previously reported. Using the method of characteristics and numerical simulations, it is shown that, for such low wedge or cone angles, a CJ oblique Detonation is eventually initiated following an induction process. It its thus demonstrated that shock-induced combustion with the reaction front remaining uncoupled to the oblique shock in the far field is not a valid solution. Simulations with semi-infinite cones reveal that the effect of the front curvature around the cone axis allows oblique Detonations to be formed at angles lower than that of a planar CJ oblique Detonation.
-
the ignition mechanism in irregular structure gaseous Detonations
Proceedings of the Combustion Institute, 2005Co-Authors: Matei I Radulescu, Gary J Sharpe, Charles B. Kiyanda, Andrew J HigginsAbstract:Abstract The present study investigated the gas ignition mechanism in typical irregular structure Detonations. In vivid contrast with the results obtained in previous studies for regular structure Detonations, the real and numerical experiments performed in the present study for typical irregular structure Detonations show that ignition is achieved both by the classical adiabatic shock compression mechanism and by turbulent mixing. The latter mechanism is usually overlooked in theoretical descriptions of the Detonation wave structure and models. In the present experiments, schlieren and self-luminous photographs of methane–oxygen Detonation structures indicated that nearly half of the shocked gases cannot ignite from shock compression alone. This gas ignites following the turbulization of burned/unburned gas interfaces and subsequent interactions with pressure waves. In the corresponding numerical experiments, where these turbulent interactions were not resolved, large unreacted pockets of gas were formed. Due to the absence of the unresolved small-scale instabilities, the Detonation wave could not be self-sustained and failed, indicating the importance of turbulent interactions, which are necessary to ensure gas ignition and wave self-sustenance. Experiments on the interaction of a Detonation wave with a fine grid also indicated that the burning rates were amplified as a result of the grid-generated turbulence.