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![CJ speed, velocity deficit and curvature values (D CJ [m/s], D/D CJ , κ [m −1 ]) at UCP and LCP for stoichiometric H 2 -air and DME-O 2 (-CO 2 ) mixtures with 0%, 0.1% and 1% O 3 .](profile/Zifeng-Weng/publication/364830346/figure/tbl1/AS:11431281092909043@1667033254166/CJ-speed-velocity-deficit-and-curvature-values-D-CJ-m-s-D-D-CJ-k-m-1-at-UCP.png)
CJ speed, velocity deficit and curvature values (D CJ [m/s], D/D CJ , κ [m −1 ]) at UCP and LCP for stoichiometric H 2 -air and DME-O 2 (-CO 2 ) mixtures with 0%, 0.1% and 1% O 3 .
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![CJ speed, velocity deficit and curvature values (D CJ [m/s], D/D CJ , κ...](profile/Zifeng-Weng/publication/364830346/figure/tbl1/AS:11431281092909043@1667033254166/CJ-speed-velocity-deficit-and-curvature-values-D-CJ-m-s-D-D-CJ-k-m-1-at-UCP_Q320.jpg)
The influence of ozone on quasi-steady curved detonations was numerically studied in stoichiometric H 2-air and DME-O 2 (-CO 2) mixtures with 0%, 0.1% and 1% O 3 addition. Detonation speed-curvature (D-κ) relations were determined for both fuels. The H 2-air mixture has one critical point related to high-temperature chemistry whereas the DME-O 2 (-...
Citations
... On the other hand, when the second stage of heat release was decreased to zero to mimic various losses at the wall, a LVD with a single dominant cell width was obtained. Thus, LVD regimes could be studied using curved detonation models, e.g., [8,9], because the curvature of the leading shock results from the lateral expansion of the flow. Indeed, the front of the expansion wave -the "sonic locus" -penetrates deeper into the reaction zone, i.e., closer to the leading shock, as the expansion rate increases relative to that of the heat release. ...
Detonation waves in rich H2-NO2/N2O4 mixtures exhibit a complex double cellular structure, attributed to a two-stage heat release process with significantly different amplitudes and time scales. Understanding the propagation characteristics of such detonations is crucial due to their potential applications in propulsion systems, explosion safety, and reactive flow modeling. While previous experimental studies have characterized this double structure over a range of equivalence ratios and initial pressures, the influence of boundary layer losses and flow divergence on detonation structure remains an open question. This study addresses this gap by using numerical simulations to examine the role of boundary layers in detonation propagation and velocity deficits. A weakly-curved detonation model incorporating boundary layer losses was first used to predict the detonation dynamics. This model successfully reproduces the high-velocity detonation (HVD) regime, where the Chapman-Jouguet (CJ) velocity is maintained, and a double cellular structure is observed. However, it fails to capture the low-velocity detonation (LVD) regime. To overcome this limitation, two-dimensional (2D) unsteady numerical simulations were conducted using a reduced reaction mechanism. These simulations incorporated a novel boundary layer modeling approach, following Mirels' theory, to better approximate frictional losses in a confined tube. The simulations were performed at several pressures to analyze their impact on detonation wave dynamics. At the highest pressure simulated, 100 kPa, the results confirmed a near-ideal CJ velocity with a well-defined double cellular structure consisting of large primary detonation cells overlaid with finer substructures. Then at critically low pressures, for example at 30 kPa, a significant velocity deficit was observed, accompanied by the emergence of a highly irregular single-cell detonation structure, indicating a transition from a quasi-steady state to a weaker, unstable detonation regime. The numerical findings support the role that boundary layer losses may play in modifying detonation characteristics, thus providing a plausible interpretation for prior experimental observations of velocity deficits in low-pressure detonations. This study suggests that flow divergence and boundary layer-induced momentum losses should be considered when modeling detonations in confined geometries. Future work will focus on increasing numerical resolution to better resolve the two-stage heat release process and further explore the transition between double and single cellular detonation structures. These results contribute to a deeper understanding of detonation physics, with potential applications to aerospace propulsion and explosion safety modeling.
... Subsequent to ignition, a right-traveling planar shock is introduced according to the Rankin-Hugoniot relations. To model the chemical kinetics of DME, we adopt the 39-species/175-step detailed DME mechanism [48,49], which is extensively used in studies of cool flame dynamics [35,50,51] and supersonic combustion [52][53][54]. ...
... The numerical root-finding algorithm developed by Veiga-López et al. [27] for detonations with friction was adapted to handle weakly curved detonations. The model has been used successfully in previous work that investigated the influence of low temperature chemistry on steady detonations with curvature losses [28,29]. ...
... The numerical root-finding algorithm developed by Veiga-López et al. [27] for detonations with friction was adapted to handle weakly curved detonations. The model has been used successfully in previous work that investigated the influence of low temperature chemistry on steady detonations with curvature losses [28,29]. ...
... For instance, Akbar et al. [3] showed that ammonia acts as a detonation inhibitor. Weng et al. [4] provided a sensitivity comparison with other commonly studied fuels and showed that ammonia is rather insensitive to detonation, even more so that methane. However, many of the detonation characteristic of ammonia-based mixtures are to date unknown. ...
... Neglecting diffusion, heat transfer, viscosity, body force, and the cellular structure, a one-dimensional (1D) steady or quasi-steady detonation wave in an ideal gas can be described by the set of governing equations described in [4]. ...
... Further details on the algorithm implemented to automate the aforementioned solution procedure and on the existence of solutions without a sonic point are included in the work of Mejía-Botero et al. [27]. Our solver has been used in the past to study detonations with curvature [31][32][33] and friction [27] losses. The ability of the model and the solver to estimate detonability limits was assessed by Mejía-Botero et al. [34], showing that it is in reasonable agreement with experimental data. ...
The effect of heat and momentum losses on the steady solutions admitted by the reactive Euler equations with sink/source terms is examined for stoichiometric hydrogen–oxygen mixtures. Varying degrees of nitrogen and argon dilution are considered in order to access a wide range of effective activation energies, E a,eff / R u T 0 , when using detailed thermochemistry. The main results of the study are discussed via detonation velocity-friction coefficient ( D – c f ) curves. The influence of the mixture composition is assessed, and classical scaling for the prediction of the velocity deficits, D ( c f,crit ) / D CJ , as a function of the effective activation energy, E a,eff / R u T 0 , is revisited. Notably, a map outlining the regions where set-valued solutions exist in the E a,eff / R u T 0 -- α space is provided, with α denoting the momentum–heat loss similarity factor, a free parameter in the current study.
... As discussed in [24,25,26], the quasi-steady approach is applicable if (1) the characteristic chemical length-scale is much smaller than the detonation wave radius, and (2) the characteristic chemical time-scale is much shorter than the characteristic time-scale describing the variation of the detonation front velocity. Setting α to zero, the classical Zeldovich-von Neumann, Doering (ZND) model for steady planar detonation is recovered, which is also applied for part of the analysis. ...
... Fig. 15-left provides the D − κ curves which relate for a given detonation deficit the curvature at which a steady solution is obtained. A good estimation of the maximum curvature (κ max - Fig. 15-botom-right) that a detonation wave can withstand is known as the critical point, i.e., the upper turnover point [25,26]. It is observed that the amount of ammonia in the blend has a dramatic effect on this parameter, reducing κ max from 13 m −1 to 0.07 m −1 between pure-hydrogen and pure-ammonia cases, that is, four orders of magnitude. ...
Ammonia is a promising compound for chemical storage of renewable energy produced from non-continuous sources. However, the low reactivity of ammonia requires to use ammonia-hydrogen blends as a fuel for combustion applications. The present study corresponds to a first numerical assessment of the potential of ammonia-hydrogen-air mixtures as reactive mixtures for detonation engine applications. Both ideal and curved detonation models were employed to calculate the detonation properties, entropy production, and NOx production for mixtures with varying amounts of ammonia and hydrogen under a wide range of initial thermodynamics conditions. Interestingly, our calculations show that the entropy production and the amount of nitrogen oxides produced at the Chapman-Jouguet state respectively decreases and increases with the proportion of hydrogen in the ammonia-hydrogen blend. These aspects could have a great impact on engine efficiency and air pollution and should be considered with care. Our results also demonstrate that only mixtures with relatively low amounts of ammonia, i.e., XNH3 lower than 0.25 of the fuel blend, can be employed for detonation engine applications.
... For a curved quasi-steady detonation, there is a restricted number of shock velocities, for which a singularity does not appear when solving for the detonation structure. The quasi-steady model is widely used to explain the behavior of detonation propagation in narrow [75,76] and in expanding [77,78] channels. We have recently studied the effect of lowtemperature chemistry and ozone addition on the dynamics of quasi-steady detonations and provided detailed discussions in [79,75]. ...
... The quasi-steady model is widely used to explain the behavior of detonation propagation in narrow [75,76] and in expanding [77,78] channels. We have recently studied the effect of lowtemperature chemistry and ozone addition on the dynamics of quasi-steady detonations and provided detailed discussions in [79,75]. The competition between chemical heat release (CHR) and unsteadiness along Lagrangian paths and their effect on the substantial derivative of pressure and velocity are examined next. ...
Modified Lotka-Volterra chemical schemes were developed with the goal of performing numerical simulation of detonation driven by single- and multi-stage heat release profiles. An initiation reaction was added to the original Lotka-Volterra model to create an induction zone, which is an important characteristics of combustion process. The kinetics parameters of the reaction rates were adjusted, so that up to eight peaks of heat release could be generated in the steady detonation reaction zone. The structure of steady detonations driven by modified Lotka-Volterra models were examined in detail. Interestingly, the stability criteria typically employed to characterize detonations, i.e., the reduced activation energy and the χ parameter, do not seem to be applicable for LV schemes exhibiting multi-stage heat release profiles. The applicability of these multi-step chemical models to unsteady detonation simulation was verified through preliminary results obtained for one- and two-dimensional numerical simulations. Under super-critical detonation initiation by a point-energy source, some LV schemes led to an unusual behavior with large velocity oscillations at large over-drive but a rather steady propagation at near Chapman-Jouguet velocity. Two-dimensional cellular detonation driven by LV scheme with two stages of heat release and a high activation energy of the initiation step demonstrates some features which are characteristics of a double cellular structure. The present work constitutes a first step toward the understanding of the features and dynamics of detonation driven by LV schemes as further work is needed to fully grasp the complex responses induced by multiple stages of heat release on detonation dynamics.
Hydrogen is a key pillar in the global Net Zero strategy. Rapid scaling up of hydrogen production, transport, distribution and utilization is expected. This entails that hydrogen, which is traditionally an industrial gas, will come into proximity of populated urban areas and in some situations handled by the untrained public. To realize all their benefits, hydrogen and its technologies must be safely developed and deployed. The specific properties of hydrogen involving wide flammability range, low ignition energy and fast flame speed implies that any accidental release of hydrogen can be easily ignited. Comparing with conventional fuels, combustion systems fueled by hydrogen are also more prone to flame instability and abnormal combustion. This paper aims to provide a comprehensive review about combustion research related to hydrogen safety. It starts with a brief introduction which includes some overview about risk analysis, codes and standards. The core content covers ignition, fire, explosions and deflagration to detonation transition (DDT). Considering that DDT leads to detonation, and that detonation may also be induced directly under special circumstances, the subject of detonation is also included for completeness. The review covers laboratory, medium and large-scale experiments, as well as theoretical analysis and numerical simulation results. While highlights are provided at the end of each section, the paper closes with some concluding remarks highlighting the achievements and key knowledge gaps.
