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Abstract
Numerical simulations are performed to investigate the propagation characteristics of ethylene/air rotating detonation waves in a two-dimensional computational domain, by solving the Navier–Stokes equations with an in-house code. Five injection area ratios (100%, 80%, 60%, 50%, and 40%) are adopted to analyze the differences in the structures of the flow field between full-area and discrete injection, as well as the effects of injection area ratios on the stability of rotating detonation waves and the parameters of detonation waves. The results show that under a full-area injection condition, the reverse waves cause the injection blockage and fuel leakage may occur when the height of the accumulated reactants increases rapidly. Under a discrete injection condition, the nonuniformity distribution of the reactants ahead of the wave affects the stability of detonation waves. The detonative front is distorted and wrinkled, accompanied by local extinction and re-ignition, when the injection area ratio is relatively small. As the injection area ratio reduces, the quantity of reactants consumed by deflagrative combustion increases and the pressurization capacity becomes weaker. The inlet mass flow rate decreases, whereas the inlet blocking ratio stays almost constant. In addition, the wave velocity is influenced by the propagation features of the detonation waves.
Highlights
1 Introduction As a new type of engine based on detonative combustion, rotating detonation engines (RDEs) have a number of advantages, such as self-pressurization, low entropy increase, and high thermal efficiency, compared with traditional engines based on deflagrative combustion [1–4]
The research progress in recent years is summarized in several reviews, for instance, by Kailasanath [25], Anand [2], Ma [26], and Raman [27] et al It is indispensable that sufficient detonable reactants accumulate ahead of the detonative front [28], which maintains the self-sustaining and stable propagation of rotating detonation waves (RDWs)
It should be noted in particular that the presented results in Cases 1 – 4 are extracted from the instants when the RDWs are stable after a sufficiently long propagation period, whereas the results used for analysis in Case 5 correspond to the instants when the RDW can sustain propagating, for the RDW quenches eventually if the injection area ratio (AR) is 40%
Summary
As a new type of engine based on detonative combustion, rotating detonation engines (RDEs) have a number of advantages, such as self-pressurization, low entropy increase, and high thermal efficiency, compared with traditional engines based on deflagrative combustion [1–4]. The RDE is usually composed of the annular or hollow combustion chamber [5], ignition device, propellant injectors, and the nozzle Fuels such as hydrogen [6–8], ethylene [9, 10], methane [11, 12], and kerosene [13] can. The inhomogeneity of the mixture ahead of the wave front has an impact on the propagation features of RDWs, which results from the mixing between reactants and combusted gas with premixed injection [40, 41] and the mixing between fuel, oxidizer and burned products with non-premixed injection [8].
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