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"Detonation waves."
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Effect of oxygen rich environment on detonation characteristics of pulse detonation engine
The detonation tests of propane/air pulse detonation engine at normal temperature were carried out in this paper. The effects of chemical ratios on the detonation performance of propane/air pulse detonation engine in oxygen-rich environment were studied. The propagation modes and characteristics of detonation waves and the detonation characteristics of the engine under different conditions were analyzed. Detonation tests were conducted on propane/air mixtures with oxygen mass fraction of 20%, 25%, 30% and 35% respectively. The results showed that: In the detonation experiment of the propane/air mixture with oxygen content of 20%, 25% and 30%, the flame wave propagation velocity in the detonation tube is low, which fails to form a stable detonation wave. The detonation effect of the fuel mixture with oxygen content of 20% is the worst, and the propagation velocity of flame wave is 384.00 m/s. In the experiment of propane/air mixture with oxygen content of 35%, the detonation velocity and pressure obtained by pressure signal analysis are both greater than the theoretical CJ detonation velocity, and the detonation state is successfully reached.
Journal Article
Propagation characteristics of rotating detonation with high-temperature hydrogen gas
The rotating detonation characteristics of high-temperature hydrogen-rich gas were studied. Hydrogen-rich gas was generated by the pre-combustion of hydrogen, and a rotating detonation experiment of hydrogen-rich gas and air was subsequently performed. The auto-initiation of high-temperature hydrogen-rich gas was observed in the experiment, and the influence of pre-detonation tube ignition on the steady propagation of the detonation wave was analyzed. The results show that high-temperature hydrogen-rich gas and air have the ability to spontaneously form rotating detonation waves. The operation of the pre-detonation tube has a significant influence on the propagation mode and propagation velocity of the continuous rotating detonation wave after auto-initiation. The rotational detonation wave formed by the auto-initiation of hydrogen-rich gas and air has a short instability in the propagation process. The propagation velocity of the detonation wave before and after the unstable state is 1345.4 m/s and 1425.3 m/s, respectively, the unstable state is 1345.4 m/s and 1425.3 m/s, respectively.
Journal Article
Perturbed Initial Value Problem for Chaplygin System with Combustion
In the present paper, the authors consider the perturbed initial value problem of the Chapman-Jouguet model for the Chaplygin gas. We obtain the unique solution by analyzing the elementary waves under the global entropy conditions. We observe that the combustion wave solution may be extinguished after perturbation which tells the instability of the unburnt gas. And we also capture the transitions between the deflagration wave and the detonation wave.
Journal Article
Thermochemical study of the detonation properties of boron- and aluminum-containing compounds in air and water
Contrary to the conventional chemical propulsion systems based on the controlled relatively slow (subsonic) combustion of fuel in a combustor, the operation process in pulsed detonation engines (PDEs) and rotating detonation engines (RDEs) is based on the controlled fast (supersonic) combustion of fuel in pulsed and continuous detonation waves, respectively. One of the most important issues for such propulsion systems is the choice of fuel with proper reactivity and exothermicity required for a sustained and energy-efficient operation process. Presented in the paper are the results of thermodynamic calculations of the detonation parameters of boron- and aluminum-containing compounds (B, B
2
H
6
, B
5
H
9
, B
10
H
14
, Al, AlH
3
, Al(C
2
H
5
)
3
, and Al(CH
3
)
3
)
in air and water. The results demonstrate the potential feasibility of using the considered compounds as fuels for both air- and water-breathing transportation vehicles powered with PDEs and RDEs. As a verification of the reliability of the calculated results, the detonation parameters of diborane, aluminum, and isopropyl nitrate in air were compared with experimental data available in the literature.
Journal Article
Detonation behaviors in a curved tube with and without an obstacle
Experiments were conducted to investigate detonation propagation in a curved tube filled with stoichiometric 2H
2
+
O
2
+
7Ar and CH
4
+
2O
2
. The test section of the experimental setup was a semicircular channel with an internal radius of 500 mm. Detonation velocities were calculated based on the arrival time of the wave front, monitored by pressure transducers. The detonation cellular evolution was recorded using smoked foils. The results revealed that after crossing the obstacle, the detonation wave failed and promptly re-initiated. It then decayed from an overdriven detonation to a steady-state detonation. The detonation development processes were divided into five regimes. The formation of the boundary behind the obstacle and the generation mechanism of the overdriven detonation were thoroughly analyzed. The formation of the boundary behind the obstacle is associated with the curved shock front and the non-uniform cellular structure. The re-initiation distance for an unstable mixture in a curved tube was significantly shorter than that in a straight channel. In the absence of the obstacle, the cell width decreased radially outward, a linear relationship was determined. The speed of the detonation wave initially decreased and then gradually increased.
Journal Article
Deflagration-to-Detonation Characteristics and Detonation Wave Structure of the Flake Aluminum Powder–Air Mixture
The explosion process of the flake aluminum powder–air two-phase flow is experimentally studied in a large-scale long straight horizontal tube with a length of 32.4 m and an inner diameter of 0.199 m. The deflagration-to-detonation transition (DDT) of the aluminum powder–air mixture is analyzed after being ignited by a 40-J electric spark, and the DDT of the mixture at different mass concentrations is compared. The results show that self-sustained detonation can be achieved in the range of 286–532 g/m
3
of the flake aluminum powder concentration, and the DDT process of the aluminum powder–air mixture at the concentration of aluminum particles 409 g/m
3
(optimal concentration) is analyzed in detail. The detonation velocity and detonation pressure at the optimal concentration are 1690 m/s and 58 bar, respectively. During the self-sustained detonation stage, the detonation overpressure of the multiphase fuel–air mixture exhibits a typical constant oscillation characteristic, while the detonation velocity remains stable. In addition, a double-headed mode helical detonation phenomenon is observed in the detonation wave front of the aluminum powder–air mixture. The structure of the detonation wave, the flow field parameters, and the interaction between the shock wave and the three-wave point trajectory are analyzed. The detonation cell size at the optimal concentration is approximately 486 mm.
Journal Article
Operation characteristics of a disk-type rotating detonation engine
In the present work, operation characteristics of a disk-type rotating detonation engine (DRDE) with a constant chamber area were experimentally studied for various total mass flow rates and a wide variety of equivalence ratios of hydrogen–air mixtures. From the direct visualizations, the rotating detonation wave was found to propagate near the outer wall of the combustion chamber, regardless of the wave mode. For the present test conditions, single- and double-wave modes are observed, depending on the equivalence ratio of the mixture. The pressure gain was evaluated based on a one-dimensional flow model together with the chamber static pressure measured with the capillary tube average pressure technique. Although the present DRDE configuration provided a negative pressure gain for all the test conditions, it was found that the single-wave mode was superior to the double-wave mode in terms of the pressure gain.
Journal Article
Influence of the Dynamic Stiffness of Shells on the Critical Detonation Thickness of a Low-Sensitivity Explosive
The relationship between the critical detonation thickness in transverse wedges made of plastic-bonded TATB and the acoustic stiffness of the adjacent material and the speed of sound in it was determined by streak photography. Wedge-shaped charges were initiated over the entire lateral surface by a steady detonation wave.
Journal Article
Review on Recent Advances in Pulse Detonation Engines
Pulse detonation engines (PDEs) are new exciting propulsion technologies for future propulsion applications. The operating cycles of PDE consist of fuel-air mixture, combustion, blowdown, and purging. The combustion process in pulse detonation engine is the most important phenomenon as it produces reliable and repeatable detonation waves. The detonation wave initiation in detonation tube in practical system is a combination of multistage combustion phenomena. Detonation combustion causes rapid burning of fuel-air mixture, which is a thousand times faster than deflagration mode of combustion process. PDE utilizes repetitive detonation wave to produce propulsion thrust. In the present paper, detailed review of various experimental studies and computational analysis addressing the detonation mode of combustion in pulse detonation engines are discussed. The effect of different parameters on the improvement of propulsion performance of pulse detonation engine has been presented in detail in this research paper. It is observed that the design of detonation wave flow path in detonation tube, ejectors at exit section of detonation tube, and operating parameters such as Mach numbers are mainly responsible for improving the propulsion performance of PDE. In the present review work, further scope of research in this area has also been suggested.
Journal Article