alterado para: “Contribution to the Physical Understanding of Supercritical Fluid Flows: a Computational Perspective”. Computational methods for jet/spray characterization: transcritical and supercritical conditions

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Supercritical Injection Modeling by an Incompressible but Variable Density Approach

Publication . Magalhães, Leandro; Silva, A. R. R.; Barata, Jorge M. M.

Supercritical nitrogen jet behavior is modeled using an incompressible but variable density approach developed for variable density jets. Following mechanical and thermal breakup concepts, several injection conditions relevant to liquid rocket propulsion are analyzed, considering heat transfer in the injector. Regarding axial density distributions, different levels of agreement with experimental data are encountered for potential core, subsided core, and plateau formations. Further comparisons with compressible formulations from the literature are a good indicator of the proposed methodology’s suitability for the simulation of supercritical injection behavior.

2023-01-25Journal article

Open access

Computational study on coaxial nitrogen-hydrogen injection at supercritical conditions

Publication . Magalhães, Leandro; Silva, André; Barata, Jorge M M

In the present work, we perform a computational study on the mixing of nitrogen and hydrogen at supercritical conditions. A coaxial injection configuration is considered where nitrogen is injected through the central post with a hydrogen co-flow. The flow in both injectors as well as in the combustion chamber is considered in the computations. This preliminary version presents the radial density profiles maximum of both species and radial density profiles at selected locations.

2021-12-29Journal article

Embargoed access

Numerical Modeling Of Freezing Water Droplets

Publication . Magalhães, Leandro; Meireles, Rúben D. S. O.; Silva, A. R. R.; Barata, Jorge M M

This work enhances the understanding of droplet dynamics under cryogenics conditions through an in-house developed analytical tool used to predict the supercooling of water droplets. The physical process is based on a full-scale four-stage supercooling process in which the recalescence stage is assumed instantaneous and the crystallization kinematics of the droplet neglected. The transition temperature of each stage is obtained, resorting to a theoretical balance for the droplets internal energy against the heat loss to the environment. In this way, the representation for the droplets temperature curves alongside the time. The droplets are considered spherical, and the internal motion is so vigorous that complete mixing occurs. The droplets convective effects are accounted for using the Ranz-Marshall classical formulation.

2022-05-15Conference object

Embargoed access

Description of an incompressible variable density approach for the description of supercritical fluids flows

Publication . Magalhães, Leandro; Cleto, João M. N.; Silva, A. R. R.; Barata, Jorge M M

The simplification of the incompressible but variable density jet is based on the visualization of data similarity. Given the initial encouraging results obtained in the past, we extend, in the present paper, this hypothesis to a broader range of conditions to ascertain its applicability and its role as an alternative to the more commonly fully-compressible formulations encountered in the literature. Transcritical and supercritical injection conditions are considered for nitrogen, which works as a surrogate for the oxygen-hydrogen mixture combination, characteristic of liquid rocket propulsion. A close agreement is found between experiments and numerical results in terms of axial profiles and jet spreading rates.

2022-05-09Conference object

Open access

On The Stratification Of Density At Supercritical Liquid-Like Conditions

Publication . Magalhães, Leandro; Silva, A. R. R.; Barata, Jorge M M

Efficiency optimization of power systems such as diesel and liquid propelled rocket engines leads to mixture behavior to enter transcritical and supercritical regimes, where distinct coupling mechanisms from those at subcritical conditions govern the thermophysical processes. In the present manuscript, we numerically evaluate the effect of pseudo-boiling at supercritical liquid- and gas-like conditions (reminiscent to liquid and gas phases) and compare the results against experimental nitrogen injection data, which serves as a surrogate for the oxygen-hydrogen propellant combination encountered in most liquid rocket engines. Thus, we can evaluate supercritical fluid behavior using nitrogen without including combustion and finite-rate kinetics into the computational model. We can show the occurrence of density stratification at both liquid- and gas-like conditions, directly connected to the event of the pseudo-phase change inside the injector, meaning that in certain situations, we can have the same fluid behavior for both pseudo-phases. However, density stratification at liquid-like conditions has not been demonstrated in the literature. Therefore, it is an argument in favor of the importance of injector heat transfer in the computational modeling of such flows.

2022-05-15Conference object

Embargoed access