Abstract
Transpiration cooling system in hypersonic vehicles still remains a challenge due to the limitations of observing permeability and microstructure evolution of porous medium filled with coolant. To tackle this problem, a novel compression-permeation device is designed with high-resolution X-ray tomography system, and then an investigation on permeability evolution mechanism of a C/SiC porous ceramic under pressure is performed using in-situ X-ray imaging and the compression-permeation device. The experimental results indicate that the pore-space fluid flow is displayed in terms of three-dimensional streamlines, making the permeability mechanism clear. Meanwhile the porosity along the thickness of ceramic under pressure has been obtained by synchrotron tomography testing, and it is also verified that the porosity of C/SiC ceramic fabricated in our research group is basically uniform (>95.4%) along the thickness. Furthermore, we have found the evolution rule for permeability of porous ceramic with water, which depends on the variation of its microstructure under different loads.
Highlights
Transpiration cooling is regarded as the most potential thermal protection system in future hypersonic cruise vehicles for its superior properties such as reusability and maintaining the aerodynamic shape of the advanced vehicles [1, 2]
In order to quantitatively elucidate the permeability evolution behaviors of a C/SiC porous ceramic, an in situ compression-permeation testing rig was designed with high-resolution synchrotron radiation X-ray imaging beam line BL13W1 at the SSRF
The following conclusions can be drawn: 1. The visualization for permeability mechanism of porous ceramic can be displayed by threedimensional streamlines, which can indirectly reflect the porosity and the size distribution of open pores of the porous ceramic
Summary
Transpiration cooling is regarded as the most potential thermal protection system in future hypersonic cruise vehicles (see Fig. 1) for its superior properties such as reusability and maintaining the aerodynamic shape of the advanced vehicles [1, 2]. During the flight process at super high speed, the porous medium is necessarily subjected to complex loads including the external aerodynamic load, seepage pressure of coolant, heat stress caused by aerodynamic heating, and structural load of the vehicles [8,9,10,11,12]. It is a significant issue whether the flow of coolant can be precisely calibrated and the uniformity of coolant in the porous medium can still remain unchanged or not while the porous medium undergoes heavy loads [13,14,15]. None of works have been conducted due to technological cause
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