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Hypersonic air-breathing propulsion (>Mach 5) based on scramjet offers new solutions to both the military strike platform and the civil transportation. However, the hypersonic flight seriously challenges the engine thermal protection. One of the key problems is the tricky flow and thermal behaviors of hydrocarbon fuel in regenerative cooling channels under the complex thermal boundaries and channel geometry, which may cause heat transfer deterioration and structure over-temperature. To improve the cooling design, the double-layer regenerative cooling channels are focused and compared with the traditional single-layer channels. The flow and thermal behaviors of hydrocarbon fuel under different cooling configurations are numerically studied. Cooling performance of double-layer channels is superior than single-layer channels. Tw,max falls by 295.2 K/17.7%. Gravity direction and magnitude show negligible influence on the heat transfer. Regarding channel height ratio, H1/H2 = 1.1/1 achieves optimal cooling performance in present conditions. Double-layer-channel scheme presents high practicability in scramjet cooling. [ABSTRACT FROM AUTHOR]

The present work deals with the thermal degradation, the physical characterization, and kinetic mechanisms of green epoxy resin‐based biocomposites (BC) reinforced by banana leaf fiber (BLF). The two main samples have been manufactured using the vacuum bag resin transfer molding method. The first, BLF‐based BC, is used as a control sample, while the second sample is coated with 6% wt. of intumescent fire retardant (IFR), which contains APP and boric acid. The effect of IFR coating has been investigated using thermogravimetric analysis (TGA) under inert and oxidative atmospheres and kinetic studies of model‐free and model‐based approaches have been applied for predicting the kinetic parameters of thermal degradation reactions. The TGA results show that the IFR coating delays the thermal degradation around 13–20 K of BLF‐based BC materials, which leads to an increase of 8% in the char residue under inert atmosphere. In addition, the sample has been characterized by SEM, EDS, and FTIR analysis (before and after the TGA test). The effectiveness of the IFR protective role is displayed on the SEM micrographs by showing the hole of the char enclosed and built the foam layer. The kinetic parameters from model‐free and model‐based curve fitting of BLF‐based BC and BLF‐based BC‐coated IFR are obtained, while the effect of IFR on the kinetic parameter increased the activation energy (model‐free and model‐based) under inert atmosphere. The fitting methods and optimization procedure gave excellent results for kinetic parameters, showing a particularly good correspondence with the TGA experimental data. [ABSTRACT FROM AUTHOR]

In this work, a thermal behaviour comparison of a new bamboo-based and banana-based Green Bio-Composites (GBC) is conducted using thermogravimetric analysis (TGA) and cone-calorimeter experiments. An Intumescent Fire-Retardant (IFR) coating (a mixture of Exolit IFR36 and boric acid) has been applied on the investigated GBC materials in order to explore the flammability resistance of such GBCs. Vacuum Bag Resin Transfer Moulding (VBRTM) technique has been used to manufacture the samples. TGA test have been conducted under oxidative atmosphere with three different heating rates while cone calorimeter tests have been performed with a horizontally exposure on the top surface of the sample. The outcomes of TGA revealed that Bamboo-based (BM-GBC) and Banana-based (Bn-GBC) materials exhibited similar thermal degradation patterns. However, BM-GBC outperformed Bn-based in the cone calorimetry analysis, this is proven by the fire reaction parameters as well as the higher char residue. In addition, IFR coating improved the flame retardancy of both GBCs, reduced the Peak Heat Release Rate (PHRR) by approximately 40–50% and smoke production (SEA) by 26%. SEM and EDS analysis of char residue were performed to deeply investigate the effectiveness of the IFR as a protecting layer. [ABSTRACT FROM AUTHOR]