Large-eddy simulation of kerosene spray combustion in a model scramjet chamber

Abstract

Large-eddy simulation (LES) of kerosene spray combustion in a model supersonic combustor with cavity flame holder is carried out. Kerosene is injected through the ceiling of the cavity. The subgrid-scale (SGS) turbulence stress tensor is closed via the Smagorinsky's eddyviscosity model, chemical source terms are modelled by a finite rate chemistry (FRC) model, and a four-step reduced kerosene combustion kinetic mechanism is adopted. The chamber wall pressure predicted from the LES is validated by experimental data reported in literature. The test case has a cavity length of 77 mm and a depth of 8 mm. After liquid kerosene is injected through the orifice, most of the droplets are loaded with recirculation fluid momentum inside the cavity. Due to lower velocity of the carrier fluid inside the cavity, sufficient atomization and evaporation take place during the process of droplet transportation, resulting in a rich fuel mixture of kerosene vapour accumulating inside the cavity. These rich fuel mixtures are mixed with fresh air by the approach Q1 mixing layer at the front of the cavity and are thus involved in burning accompanied with the approach boundary layer separation extending towards upstream. The combustion flame in the downstream impinges onto the rear wall of the cavity and is then reflected back to the front of the cavity. During the recirculation of hot flow, heat is compensated for evaporation of droplets. The circulation processes mentioned above provide an efficient flame-holding mechanism to stabilize the flame. Comparisons with results from a shorter length of cavity (cavity length of 45 mm) show that, due to insufficient atomization and evaporation of the droplets in the short distance inside the cavity, parts of the droplets are carried out of the cavity through the boundary layer fluctuation and evaporated in the hot flame layer, thus resulting in incomplete air fuel mixing and worse combustion performance. The flow structures inside the cavity play an important role in the spray distribution, thus determining the combustion performance.

Parametric Study of Fuel Distribution Effects on a Kerosene-Based Scramjet Combustor

“…[22]. The mechanism has been evaluated by lots of experimental and numerical results and has been proved to show reasonable accuracy in a relatively broader range [21,[23][24][25].…”

A review of numerical simulation and modeling of combustion in scramjets

“…The second problem that was simulated for validation purposes was based off the work of Zhang et al 34 Zhang et al conducted LES of kerosene spray combustion in a model scramjet chamber using ANSYS CFX 11.0. Kerosene was injected through the ceiling of a cavity; a finite rate chemistry model using a four-step reduced kerosene combustion kinetic mechanism was used.…”

“…Kerosene was injected through the ceiling of a cavity; a finite rate chemistry model using a four-step reduced kerosene combustion kinetic mechanism was used. 34 The subgrid-scale model implemented was the Smagorinsky's eddyviscosity model. Zhang et al validated their work by comparing the wall static pressure distribution from their LES to experimental values obtained by Yu et al 35 Figure 24 shows the wall static pressure distribution as predicted by ANSYS Fluent compared to the experimental work of Yu et al and the computational work of Zhang et al Figure 24 shows the wall static pressure distribu The validation work that was shown is limited in scope since it only involves comparisons between experimentally and computationally obtained pressure measurements and shock wave images.…”

Modeling Analysis of an Actively Cooled Scramjet Combustor Under Different Kerosene/Air Ratios

“…W ITH the advance of computational resources, high-fidelity full-scale combustor modeling, especially those based on large Eddy simulation (LES), is of great help for the understanding of internal flow characteristics and the performance-based design of scramjet combustors. However, till now, only very few scramjet modelings are fueled by kerosene [1][2][3], whereas most of them are fueled by hydrogen (e.g., those based on HyShot I&II [4] or SCHOLAR cases [5]). Kerosene is a more practical choice for lowcost scramjets cruising at Mach numbers (Ma) between 4 and 8, which is the short-term goal of hypersonic flight in the next few decades.…”

“…Even using surrogate species, the detailed mechanisms still contain thousands of elementary reactions. The mechanisms used in previous kerosene-fueled supersonic combustion modeling [1][2][3] are mostly simple global or semikinetic mechanisms. To date, few reduced or skeletal kerosene mechanisms specially developed for supersonic combustion have been proposed in the literature.…”