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16 pages, 16359 KiB

Open AccessArticle

Numerical Simulation on Primary Breakup Characteristics of Liquid Jet in Oscillation Crossflow

by Tao Zhang, Xinyu Song, Xingping Kai, Yeguang He and Rundong Li

Aerospace 2023, 10(12), 991; https://doi.org/10.3390/aerospace10120991 - 25 Nov 2023

Viewed by 1391

In order to understand the breakup characteristics of a transverse liquid jet flow in an actual combustion chamber, a numerical study was conducted using the Volume of Fluid (VOF) method combined with grid adaptation technology. The study focused on the primary breakup characteristics [...] Read more.

In order to understand the breakup characteristics of a transverse liquid jet flow in an actual combustion chamber, a numerical study was conducted using the Volume of Fluid (VOF) method combined with grid adaptation technology. The study focused on the primary breakup characteristics of liquid jets under the conditions of a steady and oscillating air crossflow. The simulated mediums were set to water and air. The research findings revealed that fluctuations in the incoming gas velocity can influence the development speed of surface waves and the mode of jet breakup during the initial stage of jet development as compared to the steady condition. In both conditions, the surface waves were initially observed to appear within 1/4 T–2/4 T. The surface wave of the jet develops faster under steady conditions because the average velocity of the steady flow is higher than that of the oscillation flow during this stage. As a result, the fragmentation of the jet is primarily influenced by the surface wave. Under an oscillating flow, the rear of the jet begins to break up earlier due to the slower development of surface waves. The velocity of the oscillating air inflow increases over time, and the speed of surface wave development also increases, gradually leading to the dominance of surface-wave-induced jet breakup. In the second stage of air inflow oscillation, an “up and down slapping” phenomenon occurs at the tail of the jet. Additionally, increasing the air inflow velocity leads to a longer jet breakup length and a higher number of droplets near the jet column. Surface waves are observed on both the windward and leeward sides of the jet. The penetration depth of the jet fluctuates with changes in the crossflow velocity, and the response of the jet penetration depth to the velocity fluctuations in the transverse air is delayed by half a period. Full article

(This article belongs to the Special Issue Fundamental Detonation Mechanism and Advanced Detonation Propulsion Technology)

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15 pages, 56056 KiB

Open AccessArticle

Effects of Injector Configuration on the Detonation Characteristics and Propulsion Performance of Rotating Detonation Engine (RDE)

by In-Hoi Koo, Keon-Hyeong Lee, Min-Su Kim, Hyung-Seok Han, Holak Kim and Jeong-Yeol Choi

Aerospace 2023, 10(11), 949; https://doi.org/10.3390/aerospace10110949 - 8 Nov 2023

Cited by 2 | Viewed by 2564

Abstract

Fuel injection and mixing affect the characteristics of detonation initiation and propagation, as well as the propulsion performance of rotating detonation engine (RDE). A study on the injector is carried out in the present investigation. A rectangular-shaped hole-type fuel injector (RHFI) and slit-type [...] Read more.

Fuel injection and mixing affect the characteristics of detonation initiation and propagation, as well as the propulsion performance of rotating detonation engine (RDE). A study on the injector is carried out in the present investigation. A rectangular-shaped hole-type fuel injector (RHFI) and slit-type fuel injector (SFI) were designed and compared experimentally at equivalent conditions. The investigation of the detonation propagation modes and the analysis of propulsion performance were carried out using fast Fourier transform (FFT), short-time Fourier transform (STFT), and unwrapped image post-processing. Under 50, 75, and 100 g/s flow rate conditions at an equivalence ratio of 1.0 ± 0.05, the RHFI has relatively stable detonation propagation characteristics, higher thrust, and specific impulse performance. Additionally, the results of the experiment indicate that the number of detonation waves affects performance. Full article

(This article belongs to the Special Issue Fundamental Detonation Mechanism and Advanced Detonation Propulsion Technology)

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22 pages, 7581 KiB

Open AccessArticle

Numerical Study of the Effects of Injection Conditions on Rotating Detonation Engine Propulsive Performance

by Lisong Shi, E Fan, Hua Shen, Chih-Yung Wen, Shuai Shang and Hongbo Hu

Aerospace 2023, 10(10), 879; https://doi.org/10.3390/aerospace10100879 - 12 Oct 2023

Cited by 7 | Viewed by 1943

Abstract

A three-dimensional upwind conservation element and solution element method (CESE) in cylindrical coordinates is first developed to effectively solve the unsteady reactive Euler equations governing a hydrogen–air rotating detonation engine (RDE) with coaxial structures. The effects of the annular width on the structure [...] Read more.

A three-dimensional upwind conservation element and solution element method (CESE) in cylindrical coordinates is first developed to effectively solve the unsteady reactive Euler equations governing a hydrogen–air rotating detonation engine (RDE) with coaxial structures. The effects of the annular width on the structure of the detonation front and the relationship between the thrust and mass flow rate are then investigated. Additionally, RDEs with various injection conditions are systematically analyzed regarding flow patterns and propulsion performance. The results reveal a positive correlation between the specific impulse and the area ratio of the injection slot to the head-end wall. Nevertheless, the specific impulse shows minimal dependence on the injector slot’s location when the area ratio is constant. Ultimately, it is concluded that the area ratio between the injector and the head-end wall is critical in determining the loss of specific impulse. Full article

(This article belongs to the Special Issue Fundamental Detonation Mechanism and Advanced Detonation Propulsion Technology)

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27 pages, 3290 KiB

Open AccessArticle

Numerical Simulation of Chemical Propulsion Systems: Survey and Fundamental Mathematical Modeling Approach

by Jihyoung Cha

Aerospace 2023, 10(10), 839; https://doi.org/10.3390/aerospace10100839 - 26 Sep 2023

Cited by 4 | Viewed by 2724

Abstract

This study deals with the mathematical modeling and numerical simulation of chemical propulsion systems (CPSs). For this, we investigate and summarize a comprehensive collection of the simulation modeling developments of CPSs in academic works, applications, and industrial fields. Then, we organize and analyze [...] Read more.

This study deals with the mathematical modeling and numerical simulation of chemical propulsion systems (CPSs). For this, we investigate and summarize a comprehensive collection of the simulation modeling developments of CPSs in academic works, applications, and industrial fields. Then, we organize and analyze the simulation modeling approaches in several ways. After that, we organize differential-algebraic Equations (DAEs) for fundamental mathematical modeling consisting of the governing Equations (ordinary differential equations, ODEs) for the components and other equations derived from several physical rules or characteristics (algebraic equations or phenomenological equations, AEs) and then synthesize and summarize the fundamental structures of analytic mathematical modeling by types (liquid-propellant rocket engines, solid-propellant rocket motors, and hybrid-propellant rocket motors) of CPSs. Full article

(This article belongs to the Special Issue Fundamental Detonation Mechanism and Advanced Detonation Propulsion Technology)

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14 pages, 3149 KiB

Open AccessArticle

Experimental Study on the Propagation Characteristics of Rotating Detonation Wave with Liquid Hydrocarbon/High-Enthalpy Air Mixture

by Bingyue Jia, Yining Zhang, Hao Meng, Fanxiao Meng, Hu Pan and Yanji Hong

Aerospace 2023, 10(8), 682; https://doi.org/10.3390/aerospace10080682 - 31 Jul 2023

Cited by 2 | Viewed by 1940

Abstract

Rotating detonation engines (RDEs) are a promising propulsion technology featuring high thermal efficiency and a simple structure. To adapt the practical engineering applications of ramjet RDEs, rotating detonation combustion using a liquid hydrocarbon and pure air mixture will be required. This paper presents [...] Read more.

Rotating detonation engines (RDEs) are a promising propulsion technology featuring high thermal efficiency and a simple structure. To adapt the practical engineering applications of ramjet RDEs, rotating detonation combustion using a liquid hydrocarbon and pure air mixture will be required. This paper presents an experimental study on the propagation characteristics of rotating detonation waves with a liquid hydrocarbon and high-enthalpy air mixture in a hollow cylindrical chamber. The parameters, such as the equivalence ratio and inlet mass flux, are considered in this experiment. The frequency and the propagation velocity of rotating detonation combustion are analyzed under typical operations. The experimental results show that the peak pressure and propagation velocity of the rotating detonation wave are close to the C-J theoretical values under the inlet mass flux of 400 kg/(m²s). Both the propagation velocity and peak pressure of the rotating detonation wave decrease as the mass flux and equivalence ratio are reduced while the number of detonation wavefronts increases. Detonation wave instability tends to occur when the inlet mass flux decreases. There is a transition progress from thermo-acoustic combustion to rotating detonation combustion in the experiment under the condition of mass flux 350 kg/(m²s) and the equivalent ratio 0.8. The static pressure in the chamber is higher during detonation combustion than during thermo-acoustic combustion. These experimental results provide evidence that rotating detonation waves have the potential to significantly improve propulsion performance. The findings can serve as a valuable reference for the practical engineering application of rotating detonation engines. Full article

(This article belongs to the Special Issue Fundamental Detonation Mechanism and Advanced Detonation Propulsion Technology)

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16 pages, 13927 KiB

Open AccessArticle

Numerical Investigation of the Oblique Detonation Waves and Stability in a Super-Detonative Ram Accelerator

by Zhanlin Feng, Kuanliang Wang and Honghui Teng

Aerospace 2023, 10(6), 549; https://doi.org/10.3390/aerospace10060549 - 8 Jun 2023

Cited by 1 | Viewed by 1606

Abstract

This study numerically investigates the effects of diluent gas proportion, the overdrive factor, and throat width on the wave structure and thrust performance of a ram accelerator operating in super-detonative mode. For premixed gas of a high energy density, a typical unstart oblique [...] Read more.

This study numerically investigates the effects of diluent gas proportion, the overdrive factor, and throat width on the wave structure and thrust performance of a ram accelerator operating in super-detonative mode. For premixed gas of a high energy density, a typical unstart oblique detonation wave system is observed due to the ignition on the front wedge of the projectile, and the detonation waves move downstream to the shoulder as the energy density decreases. In the start range of the overdrive factor, the wave position also shows a tendency to move downstream as the projectile velocity increases, accompanied by oscillations of the wave surface and thrust. As the throat width increases, the wave standing position changes non-monotonously, with an interval of upstream movement and Mach reflection. The typical wave structure of a ram accelerator in super-detonative mode is identified, as well as the unstart stable wave features and the unstable process for choking, which can provide theoretical guidance for avoiding unstart issues in ram accelerators and optimizing their performance. Full article

(This article belongs to the Special Issue Fundamental Detonation Mechanism and Advanced Detonation Propulsion Technology)

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15 pages, 3626 KiB

Open AccessArticle

Criticality for Oblique Detonation Waves Induced by a Finite Wedge in a Hydrogen–Air Mixture

by Jianxiu Qin and Dehua Zhu

Aerospace 2023, 10(6), 508; https://doi.org/10.3390/aerospace10060508 - 27 May 2023

Viewed by 1569

Abstract

Two-dimensional oblique detonation waves (ODWs) induced by finite wedges in a stoichiometric hydrogen–air mixture have been investigated numerically based on reactive Euler equations with a detailed chemical reaction model. The main zone affected by the expansion wave emanating from the turning point of [...] Read more.

Two-dimensional oblique detonation waves (ODWs) induced by finite wedges in a stoichiometric hydrogen–air mixture have been investigated numerically based on reactive Euler equations with a detailed chemical reaction model. The main zone affected by the expansion wave emanating from the turning point of a wedge is the flowfield downstream of the intersection point of the oblique shock wave (OSW) and the expansion wave. The ODW would be reduced to Chapman–Jouguet (CJ) detonation or decoupled combustion downstream. Three combustion regimes, detonation, decoupled combustion, and no ignition, were observed successively, as the wedge length decreases. It is found that the location of the intersection point is a key parameter for the detonation initiation. When the intersection point is located upstream of the ODW transition point, the expansion wave may quench ODW. Then, the critical wedge length is obtained by theoretical analysis of wave structures and the initiation criterion of ODWs for finite wedges is proposed. When the wedge length is greater than the critical wedge length, ODWs can be initiated. On the contrary, the initiation of ODWs do not occur. For wedge lengths small enough, no ignition occurs. Previously proposed criteria that use the induction length are also examined and compared with the present critical wedge length criterion in this study, and the latter is proven to achieve better results. Full article

(This article belongs to the Special Issue Fundamental Detonation Mechanism and Advanced Detonation Propulsion Technology)

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13 pages, 3945 KiB

Open AccessArticle

Effects of Ozone Addition on Multi-Wave Modes of Hydrogen–Air Rotating Detonations

by Yang Wang, Cheng Tian and Pengfei Yang

Aerospace 2023, 10(5), 443; https://doi.org/10.3390/aerospace10050443 - 11 May 2023

Cited by 3 | Viewed by 1836

Abstract

Ozone addition presents a promising approach for optimizing and regulating both combustion and ignition mechanisms. In Rotating Detonation Engines (RDEs), investigating the impact of ozone addition is particularly important due to the fact of their unique operating conditions and potential for improved efficiency. [...] Read more.

Ozone addition presents a promising approach for optimizing and regulating both combustion and ignition mechanisms. In Rotating Detonation Engines (RDEs), investigating the impact of ozone addition is particularly important due to the fact of their unique operating conditions and potential for improved efficiency. This study explores the influence of ozone concentration, total temperature, and equivalent ratio on the combustion characteristics of a hydrogen–air mixture infused with ozone. Utilizing the mixture as a propellant, the combustion chamber of a continuous rotating detonation engine is replicated through an array of injection ports, with numerical simulations conducted to analyze the detonation wave combustion mode. Our results show that an increase in total temperature leads to an increase in the number of detonation waves. Incorporating a minor quantity of ozone can facilitate the ignition process for the detonation wave. Increasing the ozone content can result in the conversion from a single-wave to dual-wave or multi-wave mode, providing a more stable combustion interface. A low ozone concentration acts as an auxiliary ignition agent and can significantly shorten the induction time. As the total temperature increases, the detonation propagation velocity and the peak heat release rate both decrease concurrently, which leads to a decline in the exit total pressure and an augmentation in the specific impulse. Employing ozone exerts a minimal impact on the detonation propagation and the overall propulsion performance. The requirement for ozone-assisted initiation differs noticeably between rich and lean combustion. Full article

(This article belongs to the Special Issue Fundamental Detonation Mechanism and Advanced Detonation Propulsion Technology)

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12 pages, 3795 KiB

Open AccessArticle

Unsteady Oblique Detonation Waves in a Tunnel Induced by Inflow Mach Number Variation

by Shuzhen Niu, Pengfei Yang, Kuanliang Wang and Honghui Teng

Aerospace 2023, 10(4), 330; https://doi.org/10.3390/aerospace10040330 - 27 Mar 2023

Cited by 4 | Viewed by 2037

Abstract

Oblique detonation waves (ODWs) have been investigated widely aiming at facilitating their application in hypersonic engines. However, there is a lack of research on unsteady ODWs which are unavoidable in the hypersonic air-breathing scenario. In this study, unsteady ODWs triggered by the variation [...] Read more.

Oblique detonation waves (ODWs) have been investigated widely aiming at facilitating their application in hypersonic engines. However, there is a lack of research on unsteady ODWs which are unavoidable in the hypersonic air-breathing scenario. In this study, unsteady ODWs triggered by the variation of the inflow Mach number (M₀) have been studied and the geometric model is a tunnel with an outward-deflection upper wall to mimic an engine outlet. Numerical results demonstrate that when M₀ deviates from the designed state, two typical wave structures arise, featuring a Mach stem of detonation or a post-corner recirculation zone. A sudden change in M₀ leads to the transition of these two structures, generating unsteady ODWs temporally with a multi-segment-complex wave surface caused by triple points. The wave structures near the corner have been analyzed in detail, revealing how the Mach stem and the recirculation zone evolve into each other. Furthermore, the effects of unsteady ODWs on hypersonic propulsion applications have been discussed, providing possible ways to suppress the Mach stem of detonation. Full article

(This article belongs to the Special Issue Fundamental Detonation Mechanism and Advanced Detonation Propulsion Technology)

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21 pages, 17410 KiB

Open AccessArticle

Numerical Investigation of the Detonation Cell Bifurcation with Decomposition Technique

by Pradeep Kumar Pavalavanni, Jae-Eun Kim, Min-Seon Jo and Jeong-Yeol Choi

Aerospace 2023, 10(3), 318; https://doi.org/10.3390/aerospace10030318 - 22 Mar 2023

Cited by 10 | Viewed by 1784

Abstract

Bifurcation of the characteristic cells into multiple smaller cells and decay of those cells into single large characteristic cell is observed frequently. In the present study the bifurcation phenomenon of the detonation front is investigated for marginally unstable detonations using decomposition technique. Numerical [...] Read more.

Bifurcation of the characteristic cells into multiple smaller cells and decay of those cells into single large characteristic cell is observed frequently. In the present study the bifurcation phenomenon of the detonation front is investigated for marginally unstable detonations using decomposition technique. Numerical analysis is carried out with detailed chemical kinetics for detonation propagation in H₂/O₂ mixtures at 10 kPa. The dynamic characteristics of the instability at the detonation front, such as the local oscillation frequency and the coherent spatial structure of the oscillation are also studied with dynamic mode decomposition (DMD) technique. The coherent structures of the primary and secondary detonation cells are analyzed during the cell bifurcation process and the mechanism in which the secondary cells are formed is investigated. It is demonstrated that the modal analysis categorizes the instability phenomena clearly and can be effectively utilized to identify the origin and source of the instability. Full article

(This article belongs to the Special Issue Fundamental Detonation Mechanism and Advanced Detonation Propulsion Technology)

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25 pages, 14449 KiB

Open AccessArticle

Numerical Study of Unstable Shock-Induced Combustion with Different Chemical Kinetics and Investigation of the Instability Using Modal Decomposition Technique

by Pradeep Kumar Pavalavanni, Min-Seon Jo, Jae-Eun Kim and Jeong-Yeol Choi

Aerospace 2023, 10(3), 292; https://doi.org/10.3390/aerospace10030292 - 15 Mar 2023

Cited by 4 | Viewed by 1886

Abstract

An unstable shock-induced combustion (SIC) case around a hemispherical projectile has been numerically studied which experimentally produced a regular oscillation. Comparison of detailed H₂/O₂ reaction mechanisms is made for the numerical simulation of SIC with higher-order numerical schemes intended for [...] Read more.

An unstable shock-induced combustion (SIC) case around a hemispherical projectile has been numerically studied which experimentally produced a regular oscillation. Comparison of detailed H₂/O₂ reaction mechanisms is made for the numerical simulation of SIC with higher-order numerical schemes intended for the use of the code for the hypersonic propulsion and supersonic combustion applications. The simulations show that specific reaction mechanisms are grid-sensitive and produce spurious reactions in the high-temperature region, which trigger artificial instability in the oscillating flow field. The simulations also show that specific reaction mechanisms develop such spurious oscillations only at very fine grid resolutions. The instability mechanism is investigated using the dynamic mode decomposition (DMD) technique and the spatial structure of the decomposed modes are further analyzed. It is found that the instability triggered by the high-temperature reactions strengthens the reflecting compression wave and pushes the shock wave further and disrupts the regularly oscillating mechanism. The spatial coherent structure from the DMD analysis shows the effect of this instability in different regions in the regularly oscillating flow field. Full article

(This article belongs to the Special Issue Fundamental Detonation Mechanism and Advanced Detonation Propulsion Technology)

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15 pages, 7294 KiB

Open AccessArticle

Experimental Proof of Concept of a Noncircular Rotating Detonation Engine (RDE) for Propulsion Applications

by Jae-Hyuk Lee, Jae-Hoon Ryu, Eun-Sung Lee, Hyung-Seok Han and Jeong-Yeol Choi

Aerospace 2023, 10(1), 27; https://doi.org/10.3390/aerospace10010027 - 28 Dec 2022

Cited by 7 | Viewed by 2883

Abstract

A noncircular engine cross-section could provide great flexibility in the integration of propulsion into the airframe. In this work, a tri-arc RDE was constructed and tested as an example of noncircular cross-sectioned RDE. The operational characteristics of detonation wave propagation and thrust performance [...] Read more.

A noncircular engine cross-section could provide great flexibility in the integration of propulsion into the airframe. In this work, a tri-arc RDE was constructed and tested as an example of noncircular cross-sectioned RDE. The operational characteristics of detonation wave propagation and thrust performance were investigated and compared with an equivalent circular RDE under the same operating conditions. High-speed camera images, short-time Fourier transform (STFT), and fast Fourier transform (FFT) were used for the investigation. The tri-arc RDE showed very similar characteristics to the circular RDE but exhibited slightly better stability and propulsion performance than the circular RDE. We consider that repeated curvature changes positively affect the stability of detonation wave propagation. The experimental data show contradicting results from the numerical analysis with a homogeneous mixture assumption in which the detonation pressures at the convex corner were greater than those at the concave corner. It is reasoned that the tri-arc injector design provides a non-uniform mixture composition, resulting in a strong detonation at the convex corner. Overall, the noncircular RDE of a tri-arc shaped cross-section is demonstrated, one which performs slightly better than an ordinary circular-shaped RDE both in detonation stability and performance. Full article

(This article belongs to the Special Issue Fundamental Detonation Mechanism and Advanced Detonation Propulsion Technology)

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