Continuously Rotating Detonation Wave: Its Propagation Mechanism, Operating Characteristics And Propulsive Application

Rotating detonation model engines and a thrust measurement system were designed, and investigation on propagation mechanism and working characterization of continuously rotating detonation waves fed with H₂/air, H₂/O₂ and CH₄/O₂, and their propulsive application were experimentally and numerically carried out in this thesis.Firstly, study on near-limit detonation behavior, detonation onset and adjust after perturbation was performed in a confined detonation tube for further analysis of the structures and propagation characteristics of continuously rotating detonation waves. It is reported that the accuracy of detonation limit is affected by the tube length, thus the limit study should be carried out in a long tube with an ample length exceeding the affected length of the initial conditions. Velocity deficit and maximum velocity fluctuation were elecated dramatically when approaching the detonability limit. It means instability is the increasingly dominant mechanism during this process. A staggered perforated plate was used to extinguish or interfere with a fully developed detonation wave. With initial pressure higher than the critical value, re-initiation in a “stable” mixture occurs only in the downstream range within several-tube-diameter length that can be affected by the perforated plate, while re-initiation in an “unstable” mixture occurs not only in the downstream near-field of the perforated plate, but also in the downstream far-field with dozens of times tube diameter by DDT from local explosions. If the blockage ratio remains the same but increase the pore size to a certain extent, the perturbation shows perturbation effect. This triggers the unstable propagation mode. Originally it requires longer propagation distance to exhibit its instability. Therefore, herein the perforated plate provides a rapid way to eliminate the unstable propagation mode.In order to provide more insight into propagation mechanism of continuously rotating detonation waves, propagation mode of rotating detonation is divided into synthetic propagation mode, dual-wave collision mode, low-speed detonation mode and unstable detonation propagation mode for the first time, and the cause of formation for its mode is analyzed as well. The ratio of combustion chamber pressure to backpressure is found to be a critical factor which influences the stability. In the model engine（with basic configuration）, if the equivalence ratio is constant, as the flow mass increases, the propagation mode in the combustion chamber successively follows: never initiation--low-speed detonation mode-- unstable detonation mode-- synthetic propagation mode. Herein the synthetic propagation mode includes stable single-wave mode, single/dual-wave hybrid mode and dual-wave（multi-wave） mode. Generation of the low-speed detonation mode and the unstable detonation mode is due to oblique shock waves. The oblique shock waves are resulted from low ratio of combustion chamber pressure to backpressure at the exit behind rotating oblique wave. These waves are pushed into the combustion chamber to perturb the injection spread and cause instability. For the synthetic propagation mode, since the combustion chamber exhausts supersonic flow, the backpressure does not affect internal flowfield. Moreover, in some special configurations（e.g., 0.2 mm wide air injection throat） or cases of N2 injection, the combustion chamber may also exhibit dual-wave collision mode. In this scenario, mixed layer establishment is critical to maintain collision.Effect of confined configurations（e.g., combustion chamber channel length, channel thickness, channel curvature and axially shrinking channel at the outlet） on the propagation process and the thrust performance of H₂/air continuously rotating detonation were intensively analyzed. Results show that the above confined configurations affect the flowfield structure of detonation（i.e., detonation height, pressure before detonation front and stability）, flowfield parameters, flow mass, thrust and specific impulse. Moreover, the results indicate that the channel length exists an optimal value and the channel curvature exists a limit for continuously rotating detonation propagation under specified supplying condition.Empty barrel as a special confined configuration was studied with continuously rotating detonation fed with CH₄/O₂ and H₂/air. The propagation process and detonation structure of CH₄/O₂ rotating detonation was observed. For the H₂/air flow, propagation velocity and pressure peak increases as the mass rate increases. Detonation propagation in the chamber successively follows dual-wave collision mode-- dual-wave mode--single-wave mode. For the first two modes, propagation is affected by upward oblique shock waves produced by the product expansion in relative high backpressure. Studies have shown that the annular channel is not a necessary condition to maintain rotating detonation. However injecting sufficient combustible mixture is critical to maintain stable rotating detonation. Under current flow mass, the thrust performance generated by rotating detonation in the empty barrel is not good.Propulsive application of continuously rotating detonaton combustion was realized, and thrust yielded by the detonation model engine was measured and analyzed in typical propagation modes. Results show that: the continuously rotating detonation wave can work stably for long duration to produce stable and reliable thrust in the model engine. More detonation heads increase the thrust stability. Also, oscillation frequency of thrust couples with high-frequency of detonation wave. The detonation wave propagation mode and the stability varys with increasing flow rate, and the corresponding thrust rises, with specific impulse grows and tends to be constant. Equivalence ratio affects the detonation propagation mode, propagation velocity and the thrust performance. The flow rate, combustion chamber pressure and thrust grow rapidly with the increase of injection pressure. With the increase of the injection area, larger flow rate and injection pressure is needed to establish condition for stable single-wave rotation.Based on strong adaptability of rotating detonation, the vector control technology of continuously rotation detonation engine was adequately studied, with its feasibility was demonstrated as well. There exist two types of vector control modes: Mode I is twice thrust deflection in a rotating cycle: rotating detonation engine undergoes vector controltwice the propagation frequency. Mode II is rotating detonation engine remains deflection to the low pressure injection direction. In order for the rocket-base rotating detonation engine application, the working characteristics of detonation wave and its thrust characteristicsin more sensitive H₂/O₂ and CH₄/O₂ mixtures were also implemented. Limited by many reasons, there is a noticeable disparity of the specific impulse index between the H₂/O₂ experimental detonation and theperformance theory; Rotation of CH₄/O₂ detonation is very stable, but the proportion of N2 dilution affectsthe rotation characteristics significantly. With the increase of mass flow, the total specific impulse performance has been improved.