The thickness of the hot component in a turbine engine is usually small. Therefore, the traditional prediction model of anisotropic thermal conductivity (ATC) based on the periodic hypothesis may be improper for use in the thermal analysis of ceramic matrix composite (CMC) components with a thin-wall structure. Thus, the prediction model for the ATC of a 2.5-D braided CMC was investigated, taking into account the actual thickness of the CMC thin-wall structure. An RVE (Representative Volume Element) model with a periodic boundary and a full-size model with the actual thickness were built to study the temperature field, the heat flux field, and the effective thermal conductivity of the CMC. A validation experiment was carried out to verify the accuracy of the two prediction models. The effect of the composite’s thickness on the ATC and the critical thickness suitable for the RVE model were also studied. The results showed that in the thermal analysis of the thin-wall structure, the RVE model had a large deviation in the estimation of the effective thermal conductivity in the thickness direction. The relative error between the numerical data based on the RVE model and the experimental data reached 10.93%, while the relative error was only 3.53% for the full-size model. Additionally, with increasing thickness, the effective thermal conductivities, based on the RVE model and the full-size model, were close to each other. For the critical thickness for the RVE model, which would be suitable for the prediction of the ATC, if the material’s thermal properties such as the absolute value ratio and the level of anisotropy changed, the corresponding critical thickness was also different. For the ATC of the SiC/SiC composites used in this study, the critical thickness was found to be 18.4 mm, nearly 31 times larger than the RVE model’s thickness.

Developing high-efficiency and low-carbon propulsion systems is a pressing concern within the aviation field. This paper studies a hybrid power system that combines a solid oxide fuel cell and a gas turbine (SOFC-GT) with propane as fuel, which is easy to store and has a high energy density. The analysis focuses on key parameters such as compressor pressure ratio, fuel utilization rate, and fuel distribution. And a balance between system efficiency and the power-to-weight ratio has been achieved through multi-objective optimization. The conclusions indicate that system efficiency and system weight in the hybrid power system are optimized in opposite directions. Within the design parameters, the hybrid power system’s efficiency achieves 0.621, the specific fuel consumption is 115.2 g/kWh, and the power-to-weight ratio is 0.569 kW/kg. Further discussion on the application of this hybrid system in long-endurance unmanned aerial vehicles shows an efficiency of 0.651 during the cruise phase, indicating a promising application prospect of a propane-fueled SOFC-GT hybrid system in the aviation field.

The heat transfer performance of a solar external receiver tube with guide vanes was numerically studied under non-uniform heat flux conditions. Models of the smooth tube and the tube with guide vanes were built. The distributions of the temperature, velocity, turbulence intensity, and Nu predicted by these two models were compared to investigate the heat transfer enhancement and the mixing effect of the guide vanes. The effect of the Re and the α on the heat transfer enhancement was also studied. The results show that the guide vanes form spiraling flows, reduce the maximum tube and molten salt temperatures, and improve the heat transfer. In addition, a more uniform temperature distribution is achieved compared to the smooth tube, allowing the molten salt to work safely under higher heat flux conditions in the receiver tube with guide vanes. It was observed that a larger Re enhances the heat transfer on the tube wall and achieves a longer effective distance of enhanced heat transfer in the downstream region, while the spiraling flow, the heat transfer enhancement, and the mixing are stronger for a larger α.