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Deflagration-to-detonation transition and detonation propagation in supersonic flows with hydrogen injection and downstream ignition

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Physics of Fluids
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Xiaodong Cai at National University of Defense Technology
Xiaodong Cai
Xinxin Wang at National University of Defense Technology
Xinxin Wang
Haorui Liu
Haorui Liu
Haorui Liu
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Rong Hong at National University of Defense Technology
Rong Hong
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Abstract and Figures

This study investigates the mechanisms of flame acceleration and deflagration-to-detonation transition (DDT) in supersonic flows using transverse hydrogen injection and downstream ignition. Utilizing the graphics processing unit accelerated adaptive mesh refinement approach, we examine the influence of downstream ignition jet pressure on DDT through high-resolution computational simulations. Our results indicate that the transverse injection of hydrogen into the supersonic mainstream generates strong turbulence and numerous vortices due to Kelvin–Helmholtz instability, enhancing fuel mixing efficiency along the flow but deviating from the ideal premixed state. Following the injection of the downstream ignition jet into the supersonic main flow, initial flame acceleration is less effective than in the premixed state due to the non-uniformity of the incoming flow. However, within the boundary layer, the flame remains stable, and the intense turbulence fosters shock–flame interactions. The convergence of multiple compression waves into a shock wave facilitates energy deposition, coupling with the flame to trigger local detonation via the reactive gradient mechanism. The detonation wave exhibits complex wavefront structures, including vertical and oblique fronts induced by boundary layer interactions. Ignition jet pressure significantly impacts the DDT process and detonation wave characteristics, reducing ignition time and affecting the detonation temperature, pressure, and propagation speed. This study provides valuable insights into the dynamics of flame acceleration and DDT in supersonic flows with non-uniform fuel distribution and downstream jet ignition. The findings highlight the critical role of ignition jet pressure in optimizing ignition and detonation processes, offering new perspectives for achieving low-energy, rapid detonation initiation within the tube.
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Deflagration-to-detonation transition
and detonation propagation in supersonic flows
with hydrogen injection and downstream ignition
Cite as: Phys. Fluids 36, 106119 (2024); doi: 10.1063/5.0228960
Submitted: 16 July 2024 .Accepted: 22 September 2024 .
Published Online: 7 October 2024
Xiaodong Cai (蔡晓东),
1
Xinxin Wang (王鑫鑫),
1,a)
Haorui Liu (刘淏睿),
1
Rong Hong (洪荣),
1,2
and Han He (何翰)
1
AFFILIATIONS
1
College of Aerospace Science and Engineering, National University of Defense Technology, Changsha 410073, China
2
China Aerodynamics Research and Development Center, Mianyang, 621000, China
a)
Authors to whom correspondence should be addressed: caichonger@hotmail.com and wazedxwxx@gmail.com
ABSTRACT
This study investigates the mechanisms of flame acceleration and deflagration-to-detonation transition (DDT) in supersonic flows using
transverse hydrogen injection and downstream ignition. Utilizing the graphics processing unit accelerated adaptive mesh refinement
approach, we examine the influence of downstream ignition jet pressure on DDT through high-resolution computational simulations. Our
results indicate that the transverse injection of hydrogen into the supersonic mainstream generates strong turbulence and numerous vortices
due to Kelvin–Helmholtz instability, enhancing fuel mixing efficiency along the flow but deviating from the ideal premixed state. Following
the injection of the downstream ignition jet into the supersonic main flow, initial flame acceleration is less effective than in the premixed state
due to the non-uniformity of the incoming flow. However, within the boundary layer, the flame remains stable, and the intense turbulence
fosters shock–flame interactions. The convergence of multiple compression waves into a shock wave facilitates energy deposition, coupling
with the flame to trigger local detonation via the reactive gradient mechanism. The detonation wave exhibits complex wavefront structures,
including vertical and oblique fronts induced by boundary layer interactions. Ignition jet pressure significantly impacts the DDT process and
detonation wave characteristics, reducing ignition time and affecting the detonation temperature, pressure, and propagation speed. This study
provides valuable insights into the dynamics of flame acceleration and DDT in supersonic flows with non-uniform fuel distribution and
downstream jet ignition. The findings highlight the critical role of ignition jet pressure in optimizing ignition and detonation processes, offer-
ing new perspectives for achieving low-energy, rapid detonation initiation within the tube.
Published under an exclusive license by AIP Publishing. https://doi.org/10.1063/5.0228960
I. INTRODUCTION
Detonation waves can be instigated in two primary ways: direct
initiation and deflagration-to-detonation transition (DDT).
1
In con-
trast to DDT, direct initiation bypasses the flame acceleration phase of
the pre-detonation stage and directly ignites detonation waves.
2
However, achieving this process requires substantial ignition energy,
often reaching up to the kilojoule level, which imposes considerable
demands on the ignition device and renders it unsuitable for practical
engineering use. Consequently, low-energy ignition is commonly used
to initiate detonation combustion via deflagration. This process utilizes
turbulence and flame acceleration mechanisms to achieve localized
detonations under favorable conditions, which then transit into a fully
developed detonation wave.
3
Recent research has focused on understanding the behavior of
detonation waves in non-uniform mixtures. Thomas et al. reported the
formation of secondary shock waves when incident blast waves propa-
gate through concentration gradients in weaker mixtures compared to
uniform mixtures.
4
Kuznetsov et al. emphasized that detonation
behavior in concentration gradients largely depends on the gradient
sharpness; detonation tends to decay in sharp gradients when propa-
gating through non-uniform flows but can potentially restart down-
stream if the driving length is sufficient.
5
These findings highlight the
complexity and sensitivity of detonation processes to mixture gra-
dients. Furthermore, Azadboni et al. revealed through numerical simu-
lations that stronger shock waves and higher flame speeds are
generated in non-uniform hydrogen/air mixtures compared to uni-
form ones.
6
However, at a 30% hydrogen concentration, uniform mix-
tures demonstrated slightly faster flame acceleration and shorter
ignition times. This emphasizes the complex relationship between fuel
concentration and detonation characteristics.
Phys. Fluids 36, 106119 (2024); doi: 10.1063/5.0228960 36, 106119-1
Published under an exclusive license by AIP Publishing
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