Abstract
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.
Highlights
Detonation combustion has attracted plenty of attention from researchers because of its high thermal efficiency, low entropy generation and self-pressurization characteristic [1,2]
According to the formation process of detonation waves and operating characteristics in the engines, detonation engines can be divided into rotating detonation engine (RDE) [3,4], pulse detonation engine (PDE) [5,6]
The results showed that the expansion of burnt fuel against the closed section of the tube behind flame front increased flame speed and turbulence when the ignition position was a certain distance from the closed section
Summary
Detonation combustion has attracted plenty of attention from researchers because of its high thermal efficiency, low entropy generation and self-pressurization characteristic [1,2]. According to the formation process of detonation waves and operating characteristics in the engines, detonation engines can be divided into rotating detonation engine (RDE) [3,4], pulse detonation engine (PDE) [5,6]. The common detonation initiation techniques are mainly divided into two categories: one is direct detonation, and the other is indirect detonation initiation. Indirect detonation initiation requires less ignition energy, becoming the main direction of the detonation domain. A weak energy ignition source triggers combustion and leads to a transition to detonation through the accumulation of energy, which is a commonly used indirect detonation initiation method [8].
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