The Supercritical Carbon Dioxide Brayton Cycle (sCO₂-BC) is a highly efficient and eco-friendly alternative for marine propulsion. The adoption of sCO₂-BC aligns with the industry’s focus on sustainability and can help meet emission regulations. In this context, the current study introduces a cascade system that harnesses the exhaust gases from a marine Gas Turbine Propulsion System to serve as a heat source for a bottoming Supercritical Carbon Dioxide Brayton Cycle (sCO₂-BC), which facilitates an onboard heat recovery system. The investigation primarily focuses on the recompression cycle layouts of the sCO₂-BC. To assess the performance of the bottoming cycle layouts and the overall cascade system, various parameters of the recompression sCO₂-BC are analyzed. These parameters include the mass flow rate of CO₂ in the bottoming cycle and the effectiveness of both the low-temperature recuperator (LTR) and the high-temperature recuperator (HTR). For conducting the cycle simulations, two codes are built and integrated; this first code models the thermodynamic cycle, while the second code models the recuperators. The research shows that incorporating the sCO₂ Brayton Cycle as a bottoming cycle has the potential to greatly improve the efficiency of the entire system, increasing it from 54% to 59%. Therefore, it provides a useful framework for advancing energy-efficient gas turbine systems and future research.

In modern steam boilers, flue gas recirculation (FGR) is generally adopted as a temperature control method for reheated steam. Some research suggests that FGR does not affect the thermal performance of steam boilers, while other studies report enhanced thermal performance. This investigation aims to enhance energy efficiency by using an iterative calculation approach to provide a thorough energy evaluation of a steam boiler with an integrated FGR system. The research applies thermodynamic and heat transfer principles to model combustion characteristics, radiative heat transfer in the furnace waterwall, and convective and inter-tube radiative heat transfer in the economizer, superheaters, and reheater. The model is validated using specifications from an existing power plant boiler and a parametric analysis to examine the effects of varying FGR rates on heat distribution and thermal performance at full and partial loads. The results show that radiative heat accounts for an average of 45% of the total heat supplied, with up to 10% in the heat recovery section. As the FGR rate increases, radiative heat in the heat recovery section decreases by 50%, while the convective heat transfer increases then drops. The model shows that the ideal FGR is bounded between 0.3 at 50% boiler load and 0.4 at full load. An analysis of the impact of FGR on the various parts of the boiler reveals that the economizer experiences the most significant net change in heat gain, followed by the reheater. The effect of gas recirculation on the economizer can be nearly twice as great as on the reheater, indicating that FGR has substantial influence on components beyond the reheater. The findings indicate that reducing excessive heat in the economizer and reheater can be accomplished under different load conditions by regulating the fuel consumption rate according to the analysis of the effects of FGR on radiative and convective heat transfer across various components.

This research investigates how slitted beams fitted with piezoelectric transducers (PZTs) behave when generating energy from environmental vibrations. By changing slit widths, slit lengths, and tip masses, we investigated the frequency response of these beams using analytical methods and finite element analysis (FEA). The obtained results demonstrate that resonance peaks are brought closer together, and coupling between vibrational modes is enhanced by larger slit spacing, whether or not anti-resonance dips are present, though the magnitudes of these peaks are affected by the width of the slits. The possibility of energy harvesting can be enhanced when resonance peaks are shifted and amplified by heavier tip masses. The FEA results support the analytical model, showing other characteristics such as sharp dips or anti-resonance troughs. This work provides valuable information for future design improvements by highlighting the significance of optimizing slit parameters and tip masses to enhance the efficiency of piezoelectric energy harvesters. This study demonstrates the benefits of using slitted beams with piezoelectric energy harvesting and provides recommendations for their efficient design.

Over the past decade, various researchers have shown the practicality of extracting electrical energy from vibrating structures. The primary objective of this research was to optimize the parameters of a basic cantilever harvester to maximize the energy production of electricity from surrounding mechanical energy. A distributed parameter model and its modal solution were utilized to determine the design variables via a parametric investigation. It is important to ensure sufficient power generation when there is a wide range of frequencies being excited, without any specific frequency being emphasized. The cost function for the optimization problem was defined as the average power within a specific frequency range, considering geometric and physical restrictions. It was discovered that different parameters’ values can be utilized to generate varying maximum power levels for different frequency ranges. Furthermore, a comparative analysis was performed between the finite element method (FEM) using ANSYS and the current harvesting model. The comparison demonstrated a high level of concordance, enabling the utilization of the finite element method (FEM) for subsequent investigation.

The flow characteristics and thermal performance of circular cylinders with V-shape slots are investigated numerically. The simulation is a two-dimensional incompressible flow that employs the semi-implicit finite volume multi-material algorithm MPM-ICE, which is a module of the Uintah framework. The normalized slot width s₂/D ranges from 0.1 to 0.2, and the corresponding increases in total surface area are from ~99% to ~70%, respectively. Compared to the solid cylinder, the slotted cylinder has the largest total drag reduction of ~67% at s₂/D of 0.2. Meanwhile, although the heat transfer is proportional with the surface area, the thermal performance of the V-shape slot first improves with the slot width, and then declines. The heat transfer improvement has an optimum value of ~192% at s₂/D of 0.15. The overall slot performance, defined by the ratio of the heat transfer to the drag force, is best at 0.175.