Article
Mechanics
Lin Zhang, Yitao Cao, Jianhan Liang, Yi Wang, Mingbo Sun
Summary: The mixing flow of a sonic transverse jet injection in a supersonic cavity combustor is numerically investigated at two typical inflow velocities. The simulation results show that at low Mach inflow, the separation shock gradually merges with the bow shock, smaller large-scale coherent structures and slower large-scale vortex transport are observed, and narrower range of jet species mass fraction distributions and more upstream large-scale vortices breakdown and dissipation can be observed. The low Mach inflow generates weaker pair of counter-rotating vortices and some trailing counter-rotating vortices, which primarily leads to the weaker jet/cavity interaction.
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
Lei Shi, Xue Yang, Yiyan Yang, Xiang Tang, Fei Qin, Guoqiang He
Summary: Stable operation of the RBCC engine in the scramjet mode is crucial for achieving wide airspace and high-speed flight envelope. The study explores the mechanism of how an embedded rocket enhances ignition and flame stabilization of secondary fuel. Experimental results show that the embedded rocket operating at a low mass flow rate and fuel-rich state can efficiently guide the flame source, enhance fuel-air mixing, and improve combustion.
AEROSPACE SCIENCE AND TECHNOLOGY
(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)
Article
Thermodynamics
Renlin Fang, Dong Di, Cunxiang Ma, Yuanhao Deng, Yunpeng Liu, Yingwen Yan
Summary: This study investigated the ignition and co-flame process of the dual annular combustor (DAC) using high speed camera and Particle Laser Velocimetry (PIV). The flow field structure obtained by PIV included various zones and jets. The ignition process had four stages and showed different performance in each stage. The time of each stage decreased with increasing Reynolds number, reducing the ignition delay time. The flame path analysis revealed that the transverse propagation mode in the head was crucial for ignition. Two co-flame mechanisms were identified in the cross-flame process of the DAC: flame tongue co-flame mechanism and heat reflux combined small flame co-flame mechanism.
COMBUSTION AND FLAME
(2023)
Article
Engineering, Aerospace
Zhenjie Wu, Qifan Zhang, Fangyou Yu, Weihang Luo, Zhanbiao Gao, Lianjie Yue
Summary: In order to investigate the effect of multicavity on flame stabilization mode transition in a scramjet combustor, experiments were conducted with various fuel injection strategies. The flame stabilization mode of the first cavity transitioned under all working conditions with different changes in equivalence ratio and wall static pressure. The transition types were identified as direct-driven local heat release and indirect-driven downstream backpressure. Direct changes in the local equivalence ratio led to significant combustion variations. The difference in combustion intensity between the flame stabilization modes resulted in path dependence and a difference in equivalence ratio at the moment of flame stabilization mode transition. Lowering the equivalence ratio of the first cavity enabled the indirect use of backpressure generated by downstream combustion to promote a smoother transition.
JOURNAL OF PROPULSION AND POWER
(2023)
Article
Mechanics
Jinglong Ma, Xin Hui, Meng Han, Xiao Han, Xinyao Wang, Jianchen Wang, Zixin Chi
Summary: This paper investigates the effect of swirl rotational direction on pressure fluctuations and flame dynamics in centrally staged combustors. The results show that the counter-swirl scheme exhibits higher amplitude and frequency compared to the co-swirl scheme at different main stage equivalence ratios. Analysis using dynamic mode decomposition and the local Rayleigh index reveals that the heat release regions of the counter-swirl scheme are mainly concentrated in the shear layer, with higher velocity gradients, vorticities, and strain rates. The driving sources of thermoacoustic oscillations are located in the inner and outer shear layers, as well as the region where the flame impinges on the liner sidewall.
Article
Chemistry, Physical
Rocky Simon Pinto, T. Sree Renganathan, S. M. D. Hamid Ansari, T. M. Muruganandam
Summary: Hysteresis in flame stabilization mode transitions in a hydrogen-fueled supersonic combustion test rig was experimentally observed and studied. The effects of equivalence ratio on flame stabilization modes were investigated through measurements of shock system, heat release zones, and flame structure. Three different combustion modes were observed, and the hysteresis phenomena between these modes were analyzed.
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
(2022)
Article
Mechanics
Hongchao Qiu, Guowei Luan, Guangjun Feng, Junlong Zhang, Wen Bao
Summary: This study investigates the effect of fuel injection methods on flame oscillation characteristics in an annular combustor. Experimental results show that the flame exhibits different oscillation modes and frequencies under different injection conditions, which are related to pressure gradients and combustion modes. Increasing the spacing between injection struts can alleviate flashback issues.
Article
Engineering, Environmental
Tao Cai, Aikun Tang, Chong Li
Summary: This study reveals the flame dynamics and stability of ammonia/hydrogen co-firing combustion using experimental and numerical techniques. Experimental results confirm five types of micro-flame structures and delineate a flame stability diagram. The study shows that increasing the blending ratio extends the blowoff limit and enhances flame stability.
CHEMICAL ENGINEERING JOURNAL
(2023)
Article
Chemistry, Physical
Rocky Simon Pinto, T. Sree Renganathan, S. M. D. Hamid Ansari, T. M. Muruganandam
Summary: The experimental study investigates the influence of stagnation temperature on hysteresis in flame stabilization in a hydrogen-fueled supersonic combustor. The results show that the variation in stagnation temperature significantly affects the hysteresis between different flame stabilization modes.
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
(2023)
Article
Engineering, Aerospace
Xipeng Li, Weidong Liu, Yu Pan, Ning Wang
Summary: This study investigates the flame stabilization modes of liquid kerosene in a model scramjet combustor, finding that only the cavity-recirculation-region stabilized combustion can be obtained in the single-cavity scramjet combustor, while the flame stabilization mode in the tandem-cavity scramjet combustor is largely determined by the total equivalence ratio.
PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART G-JOURNAL OF AEROSPACE ENGINEERING
(2023)
Article
Thermodynamics
Siqi Wang, Cheng Tung Chong, Tian Xie, Viktor Jozsa, Jo-Han Ng
Summary: The co-firing of ammonia with hydrocarbon fuel is a promising way to reduce carbon dioxide emissions. However, the conventional way of co-firing results in high NOx pollutant emissions, requiring an innovative mitigation strategy. This study examines the combustion characteristics and emissions performance of a partially-mix ammonia-methane dual flame, which shows reduced NO and CO emissions compared to the fully premixed 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
Engineering, Aerospace
Singeetham Pranaykumar, Dinesh Mengu, Akshay Prakash
Summary: An innovative air-throttling injection mechanism is proposed and investigated in this study, aiming to improve the combustion efficiency and mixing efficiency in scramjets. The mechanism shows promising results in terms of flame stabilization, combustion efficiency, and shorter ignition length even at higher Mach numbers.
AEROSPACE SCIENCE AND TECHNOLOGY
(2023)
