Jingzhe Li’s research while affiliated with Ningbo University and other places

We present a numerical simulation of a two-phase rotating detonation fueled by liquid ethanol and pre-heated air in a two-dimensional rotating detonation combustor. The study aims to understand the structure and shock interactions of the two-phase rotating detonation wave (RDW) using a two-way coupled Eulerian–Lagrangian framework. Initially, the flow field is ignited with a gaseous rotating detonation, followed by the injection of liquid ethanol and pre-heated air at near-stoichiometric and fuel-lean conditions. Observations reveal incomplete evaporation of the newly injected liquid droplets, which affects the propagation of the initial gaseous RDW and leads to its decoupling. Subsequently, a two-phase RDW is re-initiated. Different types of shock waves are identified in the unsteady flow field, and their interactions and contribution to the re-initiation of the rotating detonation are discussed. An analysis of the established two-phase rotating detonation elucidates mechanisms underlying droplet evaporation and RDW propagation, highlighting the roles of incident shocks, transverse waves, and Mach stems. Additionally, we investigate the two-phase RDW under the fuel-lean condition, where the excessive presence of air mixing with unburned ethanol vapor can cause pre-ignition, leading to a chaotic rotating detonation field. The existence of reversed shock waves and ongoing collisions with the RDW can gradually reduce its intensity, induce fluctuations in the propagation velocity of the two-phase RDW, and ultimately lead to quenching.

In this short letter, we report an experimental investigation on the integration of film cooling for thermal protection in a 72-mm cylindrical rotating detonation engine (RDE). The cooling scheme involves injection of cooling air through a series of cat-ear-shaped film cooling holes densely distributed along the outer wall of the cylindrical combustor. Our findings reveal the successful initiation of the RDE and sustained propagation of the rotating detonation wave (RDW) when film cooling is activated, and the outflow reaches a supersonic state. Experimental observations corroborate the numerical simulations, indicating a lateral expansion tendency of the cooling jet under the influence of the high-frequency RDW.

The advance of the rotating detonation engine (RDE) toward practical applications demands the integration of effective cooling schemes. In this study, a three-dimensional simulation of the hydrogen-enhanced kerosene-air RDE with inclined cylindrical film cooling holes is conducted to analyze the influence of the cooling flow on the two-phase rotating detonation flow field based an Eulerian–Lagrangian model. The liquid kerosene is injected at the ambient temperature with hydrogen-assisted combustion enhancement. Results suggest that a stable propagation of the kerosene-fueled rotating detonation wave can be maintained after the introduction of cooling air and the three-dimensional structure of the flow field is analyzed. It is found that the periodic sweeping action of the detonation wave leads to temporary blockages of the film cooling holes, causing interruptions in the outflow of cooling air. Additionally, the investigation highlights the intensified heating and evaporation of kerosene droplets near the outer wall of the RDE, whereas the presence of cooling air prevents the accumulation of kerosene vapor near the outer wall. It is revealed that the film cooling efficiency exhibits a lower value in the vicinity of the fuel injection surface, but gradually increases along the length of the combustion chamber.

We conduct an experimental investigation on the integration of film cooling for thermal protection in a 72-mm cylindrical rotating detonation engine (RDE). The cooling scheme employs the injection of cooling air through a series of cat-ear-shaped film cooling holes densely distributed along the outer wall of the cylindrical combustor. Our findings reveal successful initiation of the RDE and sustained propagation of the rotating detonation wave (RDW) when film cooling is activated.

To address the thermal protection challenges associated with the rotating detonation engine (RDE) in engineering applications, this study employs a three-dimensional numerical simulation based on the Eulerian–Lagrangian model to investigate the flow field of the kerosene-fueled rotating detonation with hydrogen addition. We explore the interaction between the rotating detonation flow field and the cooling air induced by multiple columns of uniformly distributed film cooling holes and also analyze the cooling effectiveness of film cooling. In the flow field where the rotating detonation wave passes through the film hole periodically at a high frequency, an increase in the number of film hole columns can decrease the fluctuation amplitude of the cooling air mass flow rate, and the recovery time of the blockage of film cooling holes shortens within a complete rotating detonation cycle. At a low injection pressure of 0.4 MPa, the cooling jet can barely be injected into the combustor. As the injection pressure increases to 0.6 and 0.8 MPa, the mass flow rate of cooling air increases significantly with enhanced cooling efficiency; however, a further rise to 1.0 MPa may result in the detachment of cooling air from the surface, without providing additional improvements in the protection area and cooling efficiency. Along the axial direction of the RDE, film cooling holes demonstrate an enhancement in cooling efficiency, which is found to maximize near the outlet.

In this study, a numerical investigation based on the Eulerian-Lagrangian model is conducted to explore a rotating detonation engine (RDE) fueled by liquid ethanol. The focus is on examining the characteristic phenomena of the two-phase rotating detonation wave (RDW) caused by droplet evaporation and varying inlet conditions. To enhance the evaporation of liquid fuel, pre-heated air is used, and both liquid and pre-vaporized ethanol are simultaneously injected. The distribution of ethanol droplets reveals an initial concentration near the injection surface and accumulation in the fuel-refill zone. Here, liquid droplets gradually evaporate after absorbing latent heat from the surrounding gas. The subsequent interactions between the evaporating droplets and the RDW vary with the droplet size. For droplets with diameters of $d_0$= 5-15 $\mu$m, after being swept by the RDW, a secondary evaporation process occurs, leading to an enlargement of the width of the reaction zone. However, the chemical reactions still predominantly take place in close proximity to the detonation front. As further increases, droplet evaporation persists in the post-detonation expansion zone over a long distance until the remaining droplets are fully evaporated and eventually burned by the hot products. The study also analyzes the extinction of rotating detonations and the emergence of new detonation waves resulting from local explosions and consequent shock collisions. It is demonstrated that variations in the diameter of injected droplets and inlet temperature can lead to different operating modes with varying numbers of RDWs.

A three-dimensional simulation of the rotating detonation engine (RDE) with film cooling is conducted. The aim of this study is to analyze the fluid dynamics and heat transfer of the detonation flow field under the influence of cooling flow from the film holes. Results suggest that when the rotating detonation wave sweeps the film holes, the shape of the wave structure will deform, and the detonation products will invade and block the outflow from the film holes; however, this only occurs temporarily. The structure of the detonation wave will quickly restore to its stable form and, meanwhile, the cooling flow also recovers rapidly and provides adequate protected area on the wall surface and effective thermal protection time in a full propagation cycle of the detonation wave. A parametric analysis indicates that the effective outflow time improves with the increase of the mass flow rate of the cooling flow; on the other hand, the cooling efficiency is more significant downstream from the inlet of the combustor to the outlet. In addition, the thrust and specific impulse of the RDE are also examined under the influence of film cooling.