Article
Chemistry, Physical
A. C. Rajesh, S. Jeyakumar, Kandasamy Jayaraman, Mehmet Karaca
Summary: This study investigates the flow performance of a dual wall-mounted cavities in a strut-injector mounted scramjet combustor under steady-state and transient reacting conditions. The research compares two-dimensional Reynolds Averaged Navier-Stokes approach and Delayed Detached Eddy Simulation for computing the steady and unsteady flow characteristics. The results show that the dual cavities arrangement accelerates complete combustion and modifies the flow structures due to intense shock shear layer interactions.
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
(2023)
Article
Engineering, Aerospace
Subhasis Chakravarthy, Pitambar Randive, Sukumar Pati
Summary: This study numerically investigated the effect of air throttling on the combustion performance of an ethylene-fueled scramjet combustor, showing that the flow rate and location of throttling have a strong interplay with combustion efficiency. The introduction of air throttling enhanced combustion efficiency due to the generation of pre-combustion shock train, with optimum efficiency achieved when throttling is about 20% of the inlet mass flow rate at a specific distance downstream from the cavity.
Article
Thermodynamics
Nozomu Kato, Seong-kyun Im
Summary: This study experimentally investigated flame dynamics under various backpressure conditions, finding that the presence of a cavity can enhance combustion, reduce flame fluctuation, and promote unstart, with different effects on the ramjet mode. Further research using spatially resolved diagnostic techniques is needed to identify flame locations for ramjet mode and unstart.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2021)
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
Thermodynamics
A. C. Rajesh, S. Jeyakumar, Kandasamy Jayaraman, Mehmet Karaca, A. Antony Athithan
Summary: The effect of dual cavity locations with strut injection configuration on supersonic flow under reacting conditions is evaluated numerically. The study investigates the shock wave patterns and their association with shear layer mixing features at different locations of the top wall cavity and bottom wall cavity. The flow pattern, static pressure and temperature distributions, and performance analysis of the dual cavity designs associated with the results of the DLR scramjet are analyzed.
INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER
(2023)
Article
Green & Sustainable Science & Technology
S. K. Kireeti, G. Ravi Kiran Sastry, S. K. Gugulothu, B. Deepanraj, L. Syam Sundar, M. Arthi
Summary: A numerical study compared the fluid flow characteristics of three and four-strut injectors, finding that the enhanced formation of recirculation regions and vortices, as well as increased shock wave interactions, contributed to better combustion performance with four-strut injectors.
SUSTAINABLE ENERGY TECHNOLOGIES AND ASSESSMENTS
(2022)
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
Engineering, Aerospace
Guangjun Feng, Junlong Zhang, Muxin Chen, Hongchao Qiu, Wen Bao
Summary: This paper discusses the diffusion characteristics of liquid kerosene in a supersonic combustor equipped with a thin strut under the effect of evaporation and combustion heat-release. A series of experiments and numerical simulations were conducted, and the results showed that the diffusion of kerosene vapor is affected by both the injection momentum and the evaporation momentum. The combustion heat-release greatly enhances the diffusion ability of kerosene vapor by increasing the evaporation strength of liquid kerosene and pressure in the heat-release zone, and the diffusion and combustion of kerosene are positively coupled with each other.
Article
Thermodynamics
Donggang Cao, Haim Elya Brod, Neta Yokev, Dan Michaels
Summary: A hybrid RANS/LES study of a cavity-based scramjet was conducted, showing good agreement between simulations and experiments. The flame was stabilized by the subsonic cavity shear layer and propagated downstream into the supersonic flow. The vortex dynamics, mixing, and combustion were investigated, revealing significant contributions from the subsonic combustion regions and near the walls.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2023)
Article
Engineering, Aerospace
Amit Thakur, Nishanth Thillai, Amritesh Sinha
Summary: Numerical simulations were conducted to study non-reacting and reacting flow behind a rearward step flameholder in Mach 1.6 supersonic flow with fuel injection at the step base. The findings indicated that injecting air in tandem with hydrogen at the step base showed the most improvement in combustion characteristics compared to other configurations.
PROPULSION AND POWER RESEARCH
(2021)
Article
Engineering, Aerospace
Suneetha Lakka, Pitambar Randive, K. M. Pandey
Summary: The study compares the combustion characteristics of combustors with and without cavities and investigates the impact of cavity parameters on the performance of a strut-based scramjet combustor. The research reveals the formation of a strong recirculation zone in the cavity region, improving mixing and combustion efficiency.
Article
Mechanics
Wen Shi, Ye Tian, Jialing Le, Fuyu Zhong
Summary: The study found that using pilot hydrogen can effectively suppress oscillations in internal flow and improve the stability of ethylene flame in a scramjet. The stability of the pure ethylene flame is poor without pilot hydrogen. Injection of pilot hydrogen ahead of the cavity is crucial for stabilizing the ethylene flame.
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
Metallurgy & Metallurgical Engineering
Zhe Zhang, Xing Jin, Wen-xiong Xi
Summary: The study analyzed the combustion characteristics under different injection conditions, revealing that an increase in total pressure of strut fuel injection leads to a decrease in combustion efficiency. However, increasing the total pressure of strut fuel injection within a proper range can expand the combustion area downstream. Increasing the total pressure of cavity fuel injection within the range of 0.5-2.0 MPa expands the combustion range and improves combustion efficiency, but excessive total injection pressure of cavity fuel can result in a sharp drop in efficiency. Increasing the total injection pressure of the plasma jet raises the height of the cavity shear layer and improves the equivalence ratio of the gas mixture in the cavity, with a maximum combustion efficiency of 82.1% achieved at a total pressure of 1.25 MPa. The combustion-assisted effect of different plasma jet media varies significantly, with O2 having the most significant effect on the combustor.
JOURNAL OF CENTRAL SOUTH UNIVERSITY
(2021)
Article
Engineering, Aerospace
Wenbo Yu, Chen Yue, Yuxin Fan, Yu Deng
Summary: A novel strut design was proposed for the trapped vortex cavity flameholder to improve the performance of pilot flame propagation. Experimental investigations were conducted under high subsonic flow conditions to study the effects of the strut on ignition performance and flame propagation performance. It was found that the combination of cavity and strut weakened ignition performance but improved blowout performance and flame stability.
Article
Engineering, Aerospace
Youyin Wang, Wen Shi, Xuan Wang, Junlong Zhang, Jin Gao, Jingfeng Tang, Juntao Chang, Wen Bao
Summary: This study investigates a 20-degree deflection angle wave-elimination variable geometry combustor, demonstrating through numerical simulations and experimental tests its superior performance in a wide range of operating speeds, especially at high Mach numbers. The wave-elimination design improves the total pressure recovery coefficient of the combustor under different conditions, showing significant advantages for improving the performance of variable-geometry combustors in future hypersonic aircrafts.
AEROSPACE SCIENCE AND TECHNOLOGY
(2021)
Article
Engineering, Aerospace
Jingying Zuo, Dingyuan Wei, Silong Zhang, Jiang Qin, Wen Bao, Naigang Cui
Summary: Film cooling is an effective method for achieving thermal protection and reducing skin friction in scramjet combustors. Combustion of the coolant film has double effects on film cooling performance and reduces skin friction. Additionally, shock waves generated after ignition of hydrocarbon fuel significantly influence skin friction distribution.
AEROSPACE SCIENCE AND TECHNOLOGY
(2021)
Article
Mechanics
Nan Li, Juntao Chang, Kejing Xu, Daren Yu, Wen Bao
Summary: The study investigated the unstable behavior of a shock train system in a back pressured duct with incident shocks. It found that as the shock train enters the SWBLI region, divergent vibration emerges, leading to instability. An analysis based on the feedback mechanism identified a criterion for this instability.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Engineering, Aerospace
Hongchao Qiu, Junlong Zhang, Jin Gao, Juntao Chang, Wen Bao
Summary: An experimental study was conducted on a strut/wall combined fuel injection scheme in a flush-wall scramjet combustor fueled with liquid kerosene. Results showed that increasing fuel equivalence ratio enhances core flame and leads to the formation of wall flame, while optimizing the position of wall fuel injectors can improve combustion efficiency.
AEROSPACE SCIENCE AND TECHNOLOGY
(2021)
Article
Thermodynamics
Youyin Wang, Wenxin Hou, Junlong Zhang, Jingfeng Tang, Juntao Chang, Wen Bao
Summary: This paper analyzes the pressure rise mechanism of the dual mode scramjet engine and the characteristic of the isolator maximum pressure rise. The operating range and performance of the scramjet under the pressure rise limit are investigated using a constant cross-sectional area combustor. The study suggests a variable divergent section to balance pressure under different freestream Mach numbers and equivalence ratios.
Article
Engineering, Aerospace
Ji Li, Jingfeng Tang, Junlong Zhang, Ximing Zhu, Haoran Zhang, Wen Bao, Daren Yu
Summary: The paper explores the establishment process of flame with a plasma igniter in an axisymmetric kerosene combustor under certain conditions and investigates several typical flameholding modes and their influencing factors. It reveals that a weak flame can spontaneously transform into a stronger flame during the flame establishment process, and classifies flameholding into four types.
AEROSPACE SCIENCE AND TECHNOLOGY
(2021)
Article
Thermodynamics
Hongchao Qiu, Junlong Zhang, Guangjun Feng, Juntao Chang, Wen Bao
Summary: This study presents the design of an axisymmetric variable geometry scramjet combustor equipped with a strut flame holder. Numerical calculations and experiments were conducted to investigate the performance of the combustor. The results demonstrate that the designed combustor can operate effectively in a wide range of flight Mach numbers, with good performance at high Mach numbers.
COMBUSTION SCIENCE AND TECHNOLOGY
(2023)
Article
Engineering, Aerospace
Lihan Li, Xin Li, Jiang Qin, Silong Zhang, Wen Bao
Summary: This study conducted numerical simulations to investigate the impact of dimple depth-diameter ratio on the cooling channel of a scramjet. The results showed that increasing the ratio can improve heat transfer efficiency but also increase pressure loss. The optimal depth-diameter ratio for hydrocarbon fueled regenerative cooling channels was found to be 0.2.
INTERNATIONAL JOURNAL OF AEROSPACE ENGINEERING
(2021)
Article
Thermodynamics
Jianfei Wei, Silong Zhang, Jingjia Xue, Xingyu Zhou, Jiang Qin, Wen Bao
Summary: Film cooling using gaseous hydrocarbon fuel is an effective method to meet the requirements of thermal protection and friction reduction in hydrocarbon-fueled scramjet engines. The characteristics of the hydrocarbon film cooling and friction reduction are influenced by the wall thermal state through chemical reactions. Numerical investigations show that wall cooling heat flux has a positive effect on film cooling performance but a negative effect on friction reduction performance. The endothermic chemistry in the hydrocarbon film can enhance cooling comparable to regenerative cooling, but the wall shear stress is less sensitive to the wall thermal state.
APPLIED THERMAL ENGINEERING
(2022)
Review
Engineering, Aerospace
Yunfei Li, Juntao Chang, Chen Kong, Wen Bao
Summary: This article provides an overview of the development and applications of machine learning in the field of fluid mechanics. Machine learning offers a wide range of analysis methods for understanding flow mechanisms and for practical applications. Machine learning algorithms can enhance flow information and perform tasks automatically.
CHINESE JOURNAL OF AERONAUTICS
(2022)
Article
Thermodynamics
Xin Pan, Yuefei Xiong, Cong Wang, Jiang Qin, Silong Zhang, Wen Bao
Summary: Precooling is crucial for hydrocarbon-fueled TBCC engines to expand the flight Mach number and improve specific impulse. The low-temperature endothermic fuel precooling scheme shows great potential in enhancing heat sink and overall performance.
Article
Thermodynamics
Xin Pan, Jiang Qin, Silong Zhang, Wen Bao
Summary: Precooling technology with a low-temperature endothermic fuel is a potential solution for the reduction of specific impulse in hydrocarbon-fueled turbojet engines. Methanol cracking reaction can enhance the cooling effect but may decrease the compactness of the precooler with an increase in the longitudinal pitch-to-diameter ratio. Decreasing the transverse pitch-to-diameter ratio can increase the cooling effect but will result in significant pressure loss.
CASE STUDIES IN THERMAL ENGINEERING
(2022)
Review
Engineering, Aerospace
Chengkun Lv, Juntao Chang, Wen Bao, Daren Yu
Summary: The paper provides a summary report on recent research progress in the control of airbreathing aero-engines, covering different control problems and methods, as well as issues related to hypersonic flight and turbine-based combined cycle engines. It serves as a useful reference for researchers working in this field.
PROPULSION AND POWER RESEARCH
(2022)
Article
Engineering, Aerospace
Junlong Zhang, Libo Lin, Zhaohui Yao, Wen Bao
Summary: In this paper, the unstart boundary of the strut-equipped variable geometry combustor was experimentally verified at Mach 2 condition. The study focuses on the requirements of fuel equivalent ratio and combustor expansion ratio for the working boundary of the supersonic combustor. Through simulation analyses and static regulations, the optimization of flow field structure and successful ignition were achieved. Experimental investigations were then conducted to adapt the fuel equivalent ratio and expansion ratio for performance enhancement, leading to qualitative and quantitative conclusions about the starting boundary and performance distribution pattern of the combustor.
Article
Thermodynamics
Kunlin Cheng, Jiang Qin, Duo Zhang, Wen Bao, Wuxing Jing
Summary: The closed-Brayton-cycle (CBC) power generation system is a potential high-power electricity generation scheme for hypersonic vehicles, but it is limited by finite cold source onboard. This study proposes a combined power generation system based on supercritical carbon dioxide closed-Brayton-cycle and multi-stage thermoelectric generator (TEG) to extend the available temperature range of the cold source and increase electric power output.