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
Xin Li, Yu Pan, Chaoyang Liu, Xiao Liu
Summary: To avoid the thermal choking problem in scramjet, a wall-expansion scheme is usually adopted, but it poses challenges to flame holding. This paper uses large eddy simulation to study the effect of expansion angle change on the flameout limit in the strut-based supersonic combustor. The numerical results show the establishment of the recirculation zone and the role of reflected shock waves in enhancing combustion.
AEROSPACE SCIENCE AND TECHNOLOGY
(2023)
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
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
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)
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
Hongchao Qiu, Libo Lin, Shiqi Zhang, Junlong Zhang, Wen Bao
Summary: The ignition process and flame characteristics in a supersonic combustor with liquid kerosene fuel were investigated. Numerous experiments were conducted under specific conditions, and the combustion establishment process and flame characteristics were observed using a high-speed camera. The results showed that the flame was first established near the igniter flame in the lower half of the combustor, and then spread to the main flow. The ignition process was influenced by equivalence ratios, and two modes of flame establishment were identified, each with different propagation speeds.
JOURNAL OF AEROSPACE ENGINEERING
(2023)
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, 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
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
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
Mechanics
Hongchao Qiu, Libo Lin, Guangjun Feng, Junlong Zhang, Wen Bao
Summary: The annular scram combustor, compatible with both turbines and rockets, has a challenge of establishing and stabilizing flames at supersonic speeds due to its large width. Experimental studies were conducted on a fan-shaped supersonic combustor fueled with liquid kerosene using single-strut and multi-strut injection methods. The multi-strut injection method improved the ignition performance by increasing fuel diffusion range and reducing airflow speed, and the central-flame state had a significant effect on the flame-crossing process.
Article
Engineering, Aerospace
Ji Li, Jingfeng Tang, Haoran Zhang, Lu Wang, Tianyuan Ji, Daren Yu, Ximing Zhu
Summary: This paper investigates the difficulty of combustion organization in round combustors and proposes a method that combines cone-strut configuration and plasma/oxygen addition. The method successfully reduces congestion ratio and achieves combustion organization through optimizing fuel injection and plasma arrangement. This research has important implications for the development of cone-strut configuration in round combustors.
Review
Engineering, Aerospace
Gubran A. Q. Abdulrahman, Naef A. A. Qasem, Binash Imteyaz, Ayman M. Abdallah, Mohamed A. Habib
Summary: This review comprehensively discusses the combustion processes of ignition, flame propagation, and stability under subsonic and supersonic burning conditions. Subsonic combustion research is less common due to maturity and commercialization reasons. Subsonic combustors typically use annular, can, or can-annular flame holders, while supersonic combustors have simpler designs but face challenges in ignition, flame propagation, and stability. Various flame holder designs, such as cavity, strut, and combined cavity-strut holders, are proposed to achieve successful flame propagation and stability.
AEROSPACE SCIENCE AND TECHNOLOGY
(2023)
Article
Thermodynamics
Chengming He, Yicheng Chi, Peng Zhang
Summary: A new method is proposed in this study to address the anharmonicity of torsional modes in complex molecules, reconstructing approximate potential by using information of local minima and Voronoi cells. By introducing two periodicity parameters and multiplicatively weighted Voronoi tessellation, the method has shown promising improved accuracy in higher-dimensional cases.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2021)
Article
Chemistry, Multidisciplinary
Lei Yang, Zhonghong Li, Tao Yang, Yicheng Chi, Peng Zhang
Summary: The study experimentally investigated droplet impact on a smooth solid surface at atmospheric pressure, with a focus on the effects of liquid viscosity on the transition between droplet deposition and disintegration. The critical Weber number separating deposition from disintegration was found to vary with the Ohnesorge number, and a semiempirical correlation of droplet deposition/disintegration thresholds was proposed.
Article
Thermodynamics
Meng Yang, Caiyue Liao, Chenglong Tang, Peng Zhang, Jianling Li, Zuohua Huang
Summary: An experimental investigation was conducted to study auto-ignition behaviors and safety assessments of double-base propellant containing different 1,1-diamino-2,2-dinitroethene (FOX-7) particle sizes under high initial temperature condition. Results showed that the mixture with larger FOX-7 particle size had higher reactivity, while the mixture with smaller particle size was less sensitive to stimulus.
COMBUSTION AND FLAME
(2021)
Article
Chemistry, Multidisciplinary
Mengxiao Qin, Tao Yang, Yuxin Song, Chenglong Tang, Peng Zhang
Summary: In high-temperature conditions, the subpatterns of the thin-sheet splash can be unified in a three-dimensional phase diagram, where the Leidenfrost effect becomes prominent and both deposition and thin-sheet splash transition to Leidenfrost breakup. Additionally, a scaling correlation of the transition surface temperature from thin-sheet splash to deposition was derived based on the analysis of temperature-dependent destabilizing force on the levitated lamella.
Article
Physics, Fluids & Plasmas
Chengming He, Lianjie Yue, Peng Zhang
Summary: This paper presents a computational study on the spin-affected droplet separation during off-center collisions. It is found that increasing the droplet spinning speed tends to suppress the reflexive separation and promote the stretching separation. The roles of orbital angular momentum and spin angular momentum in affecting the droplet separation are further substantiated.
PHYSICAL REVIEW FLUIDS
(2022)
Article
Thermodynamics
Tao Yang, Yicheng Chi, Peng Zhang
Summary: This study computationally investigated the triple flickering buoyant diffusion flames of methane gas arranged in an equilateral triangle. The four distinct dynamical modes observed in candle-flame experiments were computationally reproduced for the first time. The modes were interpreted from the perspective of vortex interaction and particularly vorticity reconnection and vortex-induced flow. This study establishes a bridge between vortex dynamics and the nonlinear dynamics of the triple-flame system, contributing to the understanding of larger dynamical systems of multiple flickering flames.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2023)
Article
Chemistry, Physical
Yicheng Chi, Qinghui Meng, Chengming He, Peng Zhang
Summary: The present work proposes a systematic method to assess and explain the performance of various variants of the multi-structural approximation with torsional anharmonicity (MS-T) method. The validity of the simplest variant, MS-T(2NN), is systematically validated for large alkanes and their transition states. A metric-based method is proposed to explain the good performance of MS-T(2NN), which includes the torsional conformers with dominant contributions to the partition function calculations. The same observation and explanation apply to the other variants, MS-2DT and MS-3DT. This method provides a mathematically rigorous and computationally effective diagnosis tool for torsional anharmonicity in the partition function calculation of large molecules.
JOURNAL OF PHYSICAL CHEMISTRY A
(2022)
Article
Mechanics
Chuansheng Liu, Jun Yu, Chenglong Tang, Peng Zhang, Zuohua Huang
Summary: In this study, the liquid film behaviors created by an inclined jet impinging on a vertical glass wall were investigated using a brightness-based laser-induced fluorescence method. The liquid film consists of different zones and exhibits expansion without changing its elliptical shape with higher impingement velocity. A normalized linear correlation was proposed to estimate the liquid film thickness, and the Reynolds number distribution was deduced based on the film thickness distribution using the continuity equation and empirical convection model.
Article
Thermodynamics
Yifan Yang, Haodong Zhang, Xi Xia, Peng Zhang, Fei Qi
Summary: This paper investigates the formation conditions and onset mechanism of the blue whirl. Experimental studies are conducted using a forced-ventilation fire whirl apparatus. The results show that a stable blue whirl can be formed when the circulation exceeds a threshold value of about 0.07 m2/s. The study also proposes a new swirl number, S P , which accurately predicts the emergence of the recirculation zone and supports the proposed vortex breakdown mechanism for the blue whirl onset.
PROCEEDINGS OF THE COMBUSTION INSTITUTE
(2023)
Article
Thermodynamics
Yicheng Chi, Tao Yang, Peng Zhang
Summary: This study experimentally investigates a nonlinear dynamic system of triple flickering buoyant diffusion flames in an isosceles triangle arrangement. The study focuses on establishing a controlled gas-fuel diffusion flame experiment and developing a Wasserstein-space-based methodology for dynamical mode recognition. Seven distinct stable dynamical modes are identified using this experiment and methodology.
COMBUSTION AND FLAME
(2023)
Article
Mechanics
Saroj Ray, Yicheng Chi, Peng Zhang, Song Cheng
Summary: The impacts of liquid droplets with stationary droplets on a surface have significant importance in various applications. In this study, we experimentally and theoretically investigated head-on collisions of unequal-size droplets of the same liquid on wetting surfaces, analyzing collision outcomes and characterizing the bouncing process. An analytical model based on energy balance was developed to calculate key parameters, showing good agreement with experimental data. The results indicate that the maximum spread diameter of falling droplets weakly depends on the impact Weber number and is smaller for higher size ratios.
Article
Energy & Fuels
Saroj Ray, Peng Zhang, Song Cheng
Summary: This paper presents a theoretical model for microexplosion and puffing in a single isolated emulsion droplet at high ambient temperature and one atmospheric pressure. The model considered transient heating of the droplet, bubble growth dynamics, bubble motion, and bubble interactions (e.g., bubble coalescence). The simulated microexplosion delay times are compared with the experimental data from the literature, with good qualitative and quantitative agreements obtained. The simplified model bears practical potential in enabling spray combustion modeling of water-emulsified fuels with considerably reduced computational costs.
Article
Mechanics
Chengming He, Weihang Luo, Peng Zhang, Zhixia He, Lianjie Yue
Summary: The present study experimentally verifies and computationally explains an improved design concept for the spray combustion of a gas-liquid pintle injector with variable swirl intensities. The results show that swirl enhances the combustion performance by increasing total pressure and specific impulse. Numerical simulations further demonstrate that swirl promotes the breakup of liquid jet or film, resulting in smaller droplet sizes and a more uniform spatial distribution. This study provides a viable approach to quickly screen pintle injector designs.
Article
Engineering, Multidisciplinary
Chengming He, Lianjie Yue, Peng Zhang
Summary: This study proposed a computational model to investigate the spinning effects on the post-collision velocities of bouncing droplets. The model discovered the significant interaction between orbital angular momentum and spin angular momentum, affecting the post-collision velocities. These findings have been analyzed for their physical meaning and incorporated into the proposed model.
ATOMIZATION AND SPRAYS
(2021)
Article
Chemistry, Physical
Meng Yang, Caiyue Liao, Chenglong Tang, Peng Zhang, Zuohua Huang, Jianling Li
Summary: The potential energy surfaces of three nitrotoluene isomers were theoretically constructed, revealing differences in the isomerization pathways and high energy barriers for the reactions. Reactions involving -NO2 isomerizing to ONO and C-NO2 bond dissociation were found to play important roles among the initial channels for p-nitrotoluene and m-nitrotoluene, while H atom migration and C-NO2 bond dissociation were dominant for o-nitrotoluene. Rate constant calculations showed that O transfer isomerization reactions are prominent at low to intermediate temperatures, with direct C-NO2 bond dissociation prevailing at high temperatures for p-nitrotoluene and m-nitrotoluene, and H atom migration being predominant for o-nitrotoluene.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2021)
