Numerical study on the integration of supersonic turbine guide vanes and three-dimensional hydrogen/air rotating detonation combustor

In experimental studies, single-wave mode and two counter-rotating wave mode are often observed in rotating detonation combustors. To investigate the mechanism behind different propagation modes, high-resolution numerical simulations of two-dimensional detonation in hydrogen/air mixtures are conducted by solving the reactive Navier–Stokes equations with a detailed chemical mechanism. The numerical results show that the occurrence of the dual-wave detonation propagation mode is positively influenced by an increase in both the channel width and the initial pressure. The dual-wave modes are observed when increasing the channel width, and it is found that the dual-wave modes are caused by increasing the residual premixed gas height near the inner wall. When increasing the initial pressure, the initial peak detonation heat release increases, which leads to the increase in the hot spot intensity formed, and it is found that the dual-wave modes are mainly caused by the interactions between the initial detonation wave and the inner wall. However, the initial equivalent ratio appears to have a relatively minor impact on the detonation propagation mode due to a relatively narrow range variation of physical properties. The peak heat release rate exerts a greater influence on the change of the propagation mode than the induction time does through a wider range test on rotating detonation engines' working condition. Moreover, the velocities and the cell sizes of detonation waves propagating in different directions with different channel widths are also analyzed, revealing that the characteristics of the detonation waves propagating in different directions are nearly the same.

Numerical investigation of detonation initiation in a modeled rotating detonation engine

Han,

Bian,

Shi

et al. 2024

Influence of oncoming flow parameters on rotating detonation combustor with supersonic turbine guide vanes

Wen,

Su,

Wang

et al. 2024

Rotating detonation combustion can greatly improve the performance of air-breathing turbojet engines due to its self-pressurization and high combustion efficiency. Detonation wave propagation is closely related to oncoming flow parameters. The supersonic turbine guide vane plays a role in weakening the uneven oscillation caused by the propagation of the detonation wave. Therefore, the study of the influence of oncoming flow parameters on the coupling between the rotating detonation combustor and the supersonic turbine plays a key role in the design of the rotating detonation supersonic turbine engine. In this paper, we study the influence of oncoming flow parameters (Aw/At∼25–15, P0∼ 0.5–1.5 MPa, T0∼ 250–350 K, pb∼ 0.5–1.5 atm, and Φ∼ 0.6–1.4) and propagation direction (D ∼ R-L) on the performance and flow mechanism of the coupling of a rotating detonation combustor with supersonic turbine guide vanes; a total of 27 cases are calculated and analyzed. According to the study, the injection parameters mainly determine the premixed fuel injection flow rate and its physical and chemical characteristics, thereby affecting the secondary detonation of the detonation wave. The detonation wave will exhibit four propagation modes: single wave mode, multi-wave mode, multi-wave co-propagation mode, and multi-wave reverse-propagation mode. The formation of multi-wave modes is the result of multi-wave collision, annihilation and secondary detonation of detonation waves. Under different parameter conditions, the intensity of the secondary detonation is different. The single wave mode is due to the low stoichiometric ratio and low total temperature inhibiting the secondary detonation. As for the reverse propagation mode and multi-wave collision, multi-wave co-propagation is caused by the interaction between the new detonation wave caused by the secondary detonation and the detonation wave. The interaction between rotating detonation and supersonic turbine guide vanes is mainly reflected in the interaction between oblique shock waves and supersonic turbine guide vanes, which will generate basic wave structures such as channel shock waves, reflected shock waves, and dovetail waves. The interaction area between the slip lines and the oblique shock waves and the guide vanes of the supersonic turbine will form local high temperature zones, resulting in a large local thermal load. These laws provide reference for the coupling design of rotating detonation and supersonic turbine.

Thermal radiation hazards of the external flow field for vented hydrogen–air explosion: Effect of nitrogen fraction

Li,

Song,

Zhang

et al. 2024

An experimental investigation is conducted to examine the impact of nitrogen fraction on vented explosions of hydrogen–air–nitrogen mixtures in a 1-m-long cylindrical duct at 1 bar and 281 K. The study employs high-speed shadowgraph imaging, a pressure testing system, and infrared thermal imaging to record the venting process. The results showed that as the nitrogen fraction increases, the rupture time of the vent cover gradually increases. However, the internal peak overpressure exhibits an opposite trend, with P2 (caused by the ignition of unburned gas outside the tube by the escaping flame) near the vent consistently dominating. The frequency of Helmholtz oscillations initially decreases and then increases with increasing nitrogen fraction. Higher nitrogen fractions are associated with a greater likelihood of lower external peak overpressure but a decreasing trend in maximum external impulse. The maximum temperature shows an initial decrease followed by an increase with the addition of nitrogen fraction. This trend is also observed for flame length, flame width, high-temperature duration (>500 °C), and heat energy. Furthermore, the study determined safety zones that are free from thermal radiation damage.