Summary When the supercritical CO2 power cycle is employed in confined spaces, such as nuclear‐powered ships and spacecraft, its size should be given priority. To estimate the component size, the one‐dimensional heat exchanger model developed in this study is used in a recompression supercritical CO2 cycle integrated on a small‐scale lead‐cooled fast reactor. A parameter analysis was performed to study the influence of several key parameters on the levelized cost of electricity, thermal efficiency, and system size. Moreover, four types of multi‐objective optimizations were conducted to provide optimization schemes for different scenarios. Results indicated that the increased turbine inlet temperature improved the thermoeconomic but augmented the system volume. The size of the low‐temperature recuperator was observably enlarged near the optimal flow split ratio, thereby increasing the system volume. Pareto optimal solution of bi‐objective optimization based on the levelized cost of electricity and system size reached the lowest system volume of 3.71 m3. Additionally, the best trade‐off result of three‐objective optimization was a thermal efficiency of 42.14%, a levelized cost of electricity of 56.30 $∙MWh−1, and a system volume of 4.43 m3. Meanwhile, maximal and minimal pressure drops of CO2 appeared in the cooler and intermediate heat exchanger, respectively.

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In this article, in order to obtain better vibration characteristics of circular composite sandwich cylindrical shells (CCSCS), the free vibration and damping property of CCSCS has been performed with parameter analysis. First, the equations of motion of CCSCS are deduced by adopting a displacement continuous piece-wise model based on Hamilton's principle and first order shear theory, in which shear strain and rotary inertias of all layers are considered. Second, the exact Navier method is adopted to obtain the solutions of these vibration equations and is authenticated by comparison with the results of open literatures. Finally, the change rule of free vibration and damping property versus thickness, shear parameter, and some structure parameters ratios are presented graphically, then a series of valuable conclusion are proposed to make CCSCS obtain higher rigidity and damping property.

To maximize the performance of the intermediate turbine duct (ITD) under off-design conditions, the loss generation in a one-half stage turbine was quantified using entropy generation and the global entropy generation rate. The numerical results solved by the unsteady Reynolds-averaged Navier–Strokes equations were first verified. Then, the aerodynamic losses within the high-pressure turbine stage were evaluated by efficiency loss under nine operating conditions composed of three rotor speeds and three rotor tip gaps. Finally, the disturbance modes caused by the upstream wake were captured by the dynamic mode decomposition method. Different from the influence of tip gaps, losses of the high-pressure turbine and the ITD are due to the swirl angle display an opposite trend. Under the influence of the interaction between the tip leakage flow and the shroud flow of the ITD, the viscous dissipation and turbulent dissipation increase with a larger tip gap owing to the dominant counter-rotating vortices and secondary flow occurring near the upstream of the ITD shroud. In addition, a large gap seems to enlarge the swirl component of the inflow angle, especially over 80% passage height, leading to greater dissipation losses in these areas. At the ITD inlet, two pairs of counter-rotating vortices at the shroud and the hub are, respectively, captured by the axial velocity mode. Large tip gaps enhance endwall vortices near the shroud and make the up vortex pairs merge into one pair.

To provide deep dives about aerodynamic loss mechanisms in Wells turbines for wave energy conversion, a loss audit analysis was performed by numerical experiments in a monoplane Wells turbine with guide vanes. The interactions between the tip-leakage and leading-edge vortices during the stall process were captured by an improved vortex identification method, which revealed the relationship between vortex interactions and stall mechanisms by identifying coherent structures and tracking the vortex core trajectory. Finally, the influence of vortex interactions on exergy transfer was quantified. The results indicate that the lost kinetic energy and mixing losses dominate the loss generation in the Wells turbine stage under stall conditions. Under the beneficial effect of tip leakage flow, leading-edge separation first begins at the equilibrium region between the tip-leakage and leading-edge vortices. As the leading-edge vortices expand toward the blade tip, the intensified leading-edge vortex interacts with the casing suction-side corner vortex and accelerates the dissipation of the tip-leakage vortices. Consequently, the contributions of viscous irreversibilities outweigh those of shaft work, being the dominant factor in the decrease in flow exergy, leading to a decrease in exergy utilization by 38.46% from the pre-stall condition to the stall condition.