scholarly journals Numerical Simulation of Hot Jet Detonation with Different Ignition Positions

2019 ◽  
Vol 9 (21) ◽  
pp. 4607 ◽  
Author(s):  
Zheng ◽  
Liu ◽  
Zhao ◽  
Chen ◽  
Jia ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Detonation Wave ◽  
Energy Release ◽  
Detonation Initiation ◽  
Navier Stokes ◽  
Jet Formation ◽  
Jet Flame ◽  
Numerical Studies ◽  
Detonation Transition ◽  
Accelerating Energy Release

Ignition position is an important factor affecting flame propagation and deflagration-to-detonation transition (DDT). In this study, 2D reactive Navier–Stokes numerical studies have been performed to investigate the effects of ignition position on hot jet detonation initiation. Through the stages of hot jet formation, vortex-flame interaction and detonation wave formation, the mechanism of the hot jet detonation initiation is analyzed in detail. The results indicate that the vortexes formed by hot jet entrain flame to increase the flame area rapidly, thus accelerating energy release and the formation of the detonation wave. With changing the ignition position from top to wall inside the hot jet tube, the faster velocity of hot jet will promote the vortex to entrain jet flame earlier, and the DDT time and distance will decrease. In addition, the effect of different wall ignition positions (from 0 mm to 150 mm away from top of hot jet tube) on DDT is also studied. When the ignition source is 30 mm away from the top of hot jet tube, the distance to initiate detonation wave is the shortest due to the highest jet intensity, the DDT time and distance are about 41.45% and 30.77% less than the top ignition.

Numerical Research on the Toroidal Shock Wave Focusing Detonation Initiation

2019 ◽  
Author(s):  
Xiang Chen ◽  
Ningbo Zhao ◽  
Hongtao Zheng ◽  
Xiongbin Jia ◽  
Shizheng Liu ◽  
...  
Keyword(s):  
Shock Wave ◽  
Detonation Wave ◽  
Detonation Initiation ◽  
Operating Conditions ◽  
Initiation Mechanism ◽  
Wave Focusing ◽  
Jet Flame ◽  
Rotating Detonation Engine ◽  
Detonation Engine ◽  
Shock Wave Focusing

Abstract Pressure gain combustion (PGC) is considered to be a potential technology to increase the cycle efficiency of gas turbine. As one viable candidate for PGC, rotating detonation engine (RDE) draws more attention due to its significant advances in continuous mode of operation. In practical, one of the basic challenges for RDE application is to reliably initiate detonation wave. For this purpose, both detonation initiation mechanism and enhancement approach are urgently needed to be understood. In this work, a toroidal shock wave focusing detonation initiator is presented. On this basis, the two-dimensional numerical simulations are carried out to investigate the detonation initiation characteristics by using the toroidal shock wave focusing. All of the flame acceleration, shock wave focusing, detonation wave forming and propagation are analyzed in detail. The numerical results show that the toroidal shock wave focusing initiator developed in this study can rapidly realize the detonation initiation over a short distance and performs significantly better than the traditional smooth or obstructed tube based imitators under different operating conditions. Under the same operating condition, the novel developed initiator decreases time of 59.2% and distance of 84.7% for the smooth tube based initiator, and time of 52% and distance of 78.9% for the obstructed one. Besides, the multi-fields analysis indicates that both the local explosion induced by shock wave focusing in concave cavity and the entrainment vortex generated by shock wave and jet flame in front of diaphragm are important mechanisms to initiate detonation wave. The present study is expected to enhance the understanding of the physical mechanism of shock wave focusing detonation initiation and contribute to the development of detonation propulsion technology.

Numerical Research on the Toroidal Shock Wave Focusing Detonation Initiation

2019 ◽  
Vol 141 (11) ◽  
Author(s):  
Xiang Chen ◽  
Ningbo Zhao ◽  
Hongtao Zheng ◽  
Xiongbin Jia ◽  
Shizheng Liu ◽  
...  
Keyword(s):  
Shock Wave ◽  
Detonation Wave ◽  
Detonation Initiation ◽  
Operating Conditions ◽  
Initiation Mechanism ◽  
Wave Focusing ◽  
Jet Flame ◽  
Rotating Detonation Engine ◽  
Detonation Engine ◽  
Shock Wave Focusing

Abstract Pressure gain combustion (PGC) is considered to be a potential technology to increase the cycle efficiency of gas turbine. As one viable candidate for PGC, rotating detonation engine (RDE) draws more attention due to its significant advances in continuous mode of operation. In practical, one of the basic challenges for RDE application is to reliably initiate detonation wave. For this purpose, both detonation initiation mechanism and enhancement approach are urgently needed to be understood. In this work, a toroidal shock wave focusing detonation initiator is presented. On this basis, the two-dimensional numerical simulations are carried out to investigate the detonation initiation characteristics by using the toroidal shock wave focusing. All of the flame acceleration, shock wave focusing, detonation wave forming, and propagation are analyzed in detail. The numerical results show that the toroidal shock wave focusing initiator developed in this study can rapidly realize the detonation initiation over a short distance and performs significantly better than the traditional smooth or obstructed tube based imitators under different operating conditions. Under the same operating condition, the novel developed initiator decreases time of 59.2% and distance of 84.7% for the smooth tube based initiator, and time of 52% and distance of 78.9% for the obstructed one. Besides, the multifield analysis indicates that both the local explosion induced by shock wave focusing in concave cavity and the entrainment vortex generated by shock wave and jet flame in front of diaphragm are important mechanisms to initiate detonation wave. This study is expected to enhance the understanding of the physical mechanism of shock wave focusing detonation initiation and contribute to the development of detonation propulsion technology.

scholarly journals Numerical Simulation of Deflagration to Detonation Transition in a Straight Duct: Effects of Energy Release and Detonation Stability

2014 ◽  
Vol 6 (06) ◽  
pp. 718-731
Author(s):  
Hua-Shu Dou ◽  
Zongmin Hu ◽  
Boo Cheong Khoo ◽  
Zonglin Jiang
Keyword(s):  
Numerical Simulation ◽  
Energy Release ◽  
Reaction Model ◽  
Initial Energy ◽  
Weno Scheme ◽  
Model Parameters ◽  
Activation Temperature ◽  
Deflagration To Detonation Transition ◽  
Detonation Transition ◽  
Straight Duct

AbstractNumerical simulation based on the Euler equation and one-step reaction model is carried out to investigate the process of deflagration to detonation transition (DDT) occurring in a straight duct. The numerical method used includes a high resolution fifth-order weighted essentially non-oscillatory (WENO) scheme for spatial discretization, coupled with a third order total variation diminishing Runge-Kutta time stepping method. In particular, effect of energy release on the DDT process is studied. The model parameters used are the heat release atq= 50,30,25,20,15,10 and 5, the specific heat ratio at 1.2, and the activation temperature atTi= 15, respectively. For all the cases, the initial energy in the spark is about the same compared to the detonation energy at the Chapman-Jouguet (CJ) state. It is found from the simulation that the DDT occurrence strongly depends on the magnitude of the energy release. The run-up distance of DDT occurrence decreases with the increase of the energy release forq= 50 ~ 20, and increases with the increase of the energy release forq= 20 ~ 5. This phenomenon is found to be in agreement with the analysis of mathematical stability theory. It is suggested that the factors to strengthen the DDT would make the detonation more stable, and vice versa. Finally, it is concluded from the simulations that the interaction of the shock wave and the flame front is the main reason for leading to DDT.

RANKING OF FUEL-AIR MIXTURES IN TERMS OF THEIR PROPENSITYTO DEFLAGRATION-TO-DETONATION TRANSITION

2020 ◽  
Author(s):  
S. M. FROLOV ◽  
◽  
V. I. ZVEGINTSEV ◽  
V. S. AKSENOV ◽  
I. V. BILERA ◽  
...  
Keyword(s):  
Detonation Wave ◽  
The Other ◽  
Practical Application ◽  
Deflagration To Detonation Transition ◽  
Other Hand ◽  
Pressure Gain Combustion ◽  
Reactive Mixture ◽  
Detonation Transition ◽  
The One ◽  
Energy Converting

The term "detonability" with respect to fuel-air mixtures (FAMs) implies the ability of a reactive mixture of a given composition to support the propagation of a stationary detonation wave in various thermodynamic and gasdynamic conditions. The detonability of FAMs, on the one hand, determines their explosion hazards during storage, transportation, and use in various sectors of the economy and, on the other hand, the possibility of their practical application in advanced energy-converting devices operating on detonative pressure gain combustion.

Numerical Simulation of Muzzle Flow Field of Gun Based on CFD

2013 ◽  
Vol 291-294 ◽  
pp. 1981-1984
Author(s):  
Zhang Xia Guo ◽  
Yu Tian Pan ◽  
Yong Cun Wang ◽  
Hai Yan Zhang
Keyword(s):  
Numerical Simulation ◽  
Flow Field ◽  
Stokes Equation ◽  
Wave Structure ◽  
Flow Fields ◽  
Single Equation ◽  
Navier Stokes ◽  
Turbulent Model ◽  
Navier Stokes Equation ◽  
Numerical Simulation Result

Gunpowder was released in an instant when the pill fly out of the shell during the firing, and then formed a complicated flow fields about the muzzle when the gas expanded sharply. Using the 2 d axisymmetric Navier-Stokes equation combined with single equation turbulent model to conduct the numerical simulation of the process of gunpowder gass evacuating out of the shell without muzzle regardless of the pill’s movement. The numerical simulation result was identical with the experimental. Then simulated the evacuating process of gunpowder gass of an artillery with muzzle brake. The result showed complicated wave structure of the flow fields with the muzzle brake and analysed the influence of muzzle brake to the gass flow field distribution.

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