Article
Engineering, Aerospace
Yu Meng, Wenming Sun, Hongbin Gu, Fang Chen, Ruixu Zhou
Summary: This study investigates the combustion mode and instability characteristics of scramjets using the POD method. Experimental observations of flow and combustion behavior were made on a scramjet model with a cavity stabilizer. The results provide insights into the oscillation characteristics of three typical stabilized combustion modes.
Article
Engineering, Aerospace
A. A. Dhankarghare, T. Jayachandran, T. M. Muruganandam
Summary: This study combines a strut and a cavity into a strut cavity and compares it with a wall cavity using numerical simulations at different Mach numbers and aspect ratios. The results show that the wall cavity is more prone to oscillations compared to the strut cavity. The generation process of waves inside the cavity is revisited, where both the unstable shear layer and vortex shedding contribute to the wave generation in supersonic flows.
AEROSPACE SCIENCE AND TECHNOLOGY
(2022)
Article
Mechanics
A. A. Dhankarghare, T. Jayachandran, T. M. Muruganandam
Summary: A study was conducted on flow dynamics in strut cavity and wall cavity at different freestream Mach numbers using numerical simulations. The results showed that oscillations occurred in both cavities for low supersonic Mach numbers and decreased for high values, with the strut cavity responding better to the change in Mach number. The study explored wave propagation and interactions inside the cavities, discussed secondary recirculation, revisited the process of wave generation, provided insights into vortex propagation along the cavity length, and described and compared mass exchange between the cavities and freestream.
Article
Chemistry, Physical
Sai Sreekar Yarasai, Dineshkumar Ravi, Sharan Yoganand, Thundil Karuppa Raj Rajagopal
Summary: A numerical investigation was conducted to analyze the performance and combustion characteristics of a scramjet combustor with and without a cavity. Different geometrical shapes of injectors were considered, including circle, square, and rectangle. The results showed that the circular injector with a cavity exhibited better mixing and combustion characteristics compared to the other injector models.
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
(2023)
Article
Mechanics
Shengzu Guo, Xu Zhang, Qili Liu, Lianjie Yue
Summary: The periodic flame flashback phenomenon was numerically studied in an ethylene-fueled scramjet combustor using a 3D unsteady Navier-Stokes solver. The study revealed that the combustion oscillations and flame flashbacks were maintained in the separated scramjet mode, not connected to the ramjet/scramjet mode transitions. A mechanism with four evolution stages was proposed to explain the flow-flame interaction.
Article
Engineering, Aerospace
Lei Shi, Zhaoyang Tian, Chaowu Dai, Wei Zhang, Zheng Wei, Guojun Zhao, Rui Ran
Summary: The study investigates the effect of high mass flow rate rocket jet on flame stability and combustion characteristics in a cavity-based scramjet combustor through ground direct-connect test. The experimental results show that rocket augmentation can effectively improve combustion pressure and thrust, enhance mixing efficiency and combustion stability, and significantly enhance scramjet performance.
AEROSPACE SCIENCE AND TECHNOLOGY
(2023)
Article
Thermodynamics
Stephen D. Hammack, Timothy M. Ombrello
Summary: This study experimentally investigated the ignition processes in a scramjet flame holder and found that the location of energy deposition plays a crucial role in successful ignition, affecting flame propagation rates and fuel concentration variations.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2021)
Article
Engineering, Aerospace
Jianheng Ji, Zun Cai, Taiyu Wang, Zhenguo Wang, Mingbo Sun
Summary: This study investigates flame behaviors in a cavity-based scramjet combustor under supersonic inflow. The results show that increasing the equivalence ratio leads to a transition in combustion mode, and increasing the cavity aft wall height improves the combustor's self-ignition capability. Moreover, the application of spark plasma effectively suppresses low-frequency combustion oscillations.
Article
Mechanics
Prasanth P. Nair, Abhilash Suryan, Vinod Narayanan
Summary: Combustion at supersonic speeds is crucial for improving performance. The research discovers that the divergence angle of the passive strut has an impact on the mixing efficiency and acoustic behavior. Unstable combustion occurs when the divergence angle is too high, while pressure loss decreases with a smaller divergence angle.
Article
Mechanics
Vignesh Ram Petha Sethuraman, Yosheph Yang, Jae Gang Kim
Summary: This study numerically investigates the interaction between the self-excited shock train flow and the cavity shear layer in a scramjet isolator using detached-eddy simulations. The effects of changing the shock train position and the cavity front wall angle are analyzed, and the propagation mechanism of the pressure disturbance is examined. The results show that the low-frequency shock train oscillation dominates the self-sustained cavity oscillation, and the spatiotemporal cross-correlation analysis reveals the propagation of local disturbances originating from the separated boundary layer and the recirculation zone in the cavity corners. The dynamic mode decomposition analysis demonstrates the shear layer at the leading edge of the cavity and the downstream propagation of large eddies from the cavity, as well as the pairing of coherent structures between the shock train and the cavity's recirculation zone.
Article
Engineering, Aerospace
Hongbo Wang, Xiliang Song, Liang Li, Yuhui Huang, Mingbo Sun
Summary: Experiments were conducted to investigate the near blowoff characteristics of cavity-stabilized flames in an ethylene-fueled scramjet combustor. It was found that there exists an optimal cavity size for ignition and flame stabilization near lean blowoff conditions, determined by the competition between flow residence time and local equivalence ratio.
AEROSPACE SCIENCE AND TECHNOLOGY
(2021)
Article
Mechanics
Jian Fang, Xi Deng, Zhi X. Chen
Summary: A Mach 1.5 non-reactive flow in a cavity-stabilized combustor of a model scramjet was studied via direct-numerical simulation, with focus on the interaction among boundary layer, free shear-layer above the cavity and shock wave. Impingement of the free shear-layer on the aft wall of the cavity leads to strong turbulence, high pressure, and compression waves. The analysis reveals that shear production amplifies turbulence in the core of the shear-layer, while deceleration production has a significant impact above the aft wall of the cavity and around the shock interaction points.
Article
Thermodynamics
Donggang Cao, Haim Elya Brod, Neta Yokev, Dan Michaels
Summary: This study investigates the impact of fuel distribution on flame stabilization and local combustion modes in a cavity-based scramjet through numerical simulations. Different injection schemes lead to distinct flame stabilization locations and combustion modes, shedding light on the relationship between fuel injection strategies and combustion performance.
COMBUSTION AND FLAME
(2021)
Article
Engineering, Aerospace
Xu Zhang, Qifan Zhang, Zhenjie Wu, Lianjie Yue, Zhanbiao Gao, Weihang Luo, Hao Chen
Summary: Hysteresis and catastrophes were observed in a cavity-based scramjet combustor, breaking traditional knowledge about their relationship with ramjet/scramjet mode transitions. The first hysteresis and catastrophes were attributed to flame stabilization mode transitions, while the second were linked to flame/shock interaction mode transitions.
CHINESE JOURNAL OF AERONAUTICS
(2022)
Article
Engineering, Aerospace
Pengfei Xiong, Dong Zheng, Yu Tan, Ye Tian, Jialing Le
Summary: This study experimentally investigates the ignition and flame transient development in an ethylene fueled cavity-based supersonic combustor under low conditions. It is found that ethylene can achieve successful ignition and stable combustion at low inflow Mach numbers, with the combustion mode dependent on the global equivalence ratio (ER). Furthermore, the combustion and shockwaves are observed to strengthen each other until a balance is reached, ensuring stable flow structures and combustion.
AEROSPACE SCIENCE AND TECHNOLOGY
(2021)
