Abstract
This numerical study was conducted to investigate the flow properties in a model scramjet configuration of the experiment in the T4 shock tunnel. In most numerical simulations of flows in shock tunnels, the inflow conditions in the test section are determined by assuming the thermal equilibrium of the gas. To define the inflow conditions in the test section, the numerical simulation of the nozzle flow with the given nozzle reservoir conditions from the experiment is conducted by a thermochemical nonequilibrium computational fluid dynamics (CFD) solver. Both two-dimensional (2D) and three-dimensional (3D) numerical simulations of the flow in a model scramjet were conducted without fuel injection. Simulations were performed for two types of inflow conditions: one for thermochemical nonequilibrium states obtained from the present nozzle simulation and the other for the data available using the thermal equilibrium and chemical nonequilibrium assumptions. The four results demonstrate the significance of the modelling approach for choosing between 2D or 3D, and thermal equilibrium or nonequilibrium.
Highlights
A supersonic combustion ramjet engine is an air-breathing jet engine, which can be used for hypersonic flight vehicles
With the thermochemical nonequilibrium inflow conditions, the numerical simulations for the model scramjet were conducted using the different inflowthe conditions summarized in Table
The ground tests using model scramjet engines are typically conducted in hypervelocity facilities where the nozzle flow entering the test section is in the thermochemical nonequilibrium state
Summary
A supersonic combustion ramjet (scramjet) engine is an air-breathing jet engine, which can be used for hypersonic flight vehicles. For the development of a scramjet engine, in aerodynamics and combustion tests [1], ground-based test facilities, such as shock tunnels operating under high enthalpy conditions, are mainly used. In most numerical simulations of flow in shock tunnels, the inflow conditions in the test section are determined by assuming the thermal equilibrium of the operating gas. In the case of high enthalpy shock tunnels, such as T4, the flow at the exit of the nozzles entering the test section is known to be in thermochemical nonequilibrium [3,4]. The molecules in the air, which is the typical operating gas for the tests, are partially dissociated and vibrationally excited in the high-temperature reservoir of the nozzle and have little chance of intermolecular collisions in the expansion section of the nozzle, resulting in the so-called vibration freezing. The dissociated molecules do not fully recombine at the lower temperature in the downstream section of the nozzle due to the Energies 2020, 13, 606; doi:10.3390/en13030606 www.mdpi.com/journal/energies
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