The combustion behavior of blended petroleum–biofuel mixtures has increasingly been investigated as interest grows in low-toxicity, biodegradable, and energy-dense biomass-derived fuels. Among higher alkanols, n-butanol is recognized for its favorable physicochemical properties and its compatibility with gasoline-range hydrocarbons (HC) such as iso-octane. In this context, a systematic evaluation of laminar flame propagation and instability characteristics is essential for understanding the combustion performance and operational safety of blended fuels. In the present study, the laminar burning velocity (LBV) and cellular instability of premixed iso-octane/n-butanol/air flames were quantified for a wide range of equivalence ratios (0.7–1.5) at an initial temperature of 423 K and ambient pressure. It was observed that the LBV increased consistently with the addition of n-butanol, whereas the Markstein length (L_b) decreased. Analysis of cellular structures revealed that diffusive-thermal instability strengthened monotonically as the equivalence ratio increased, resulting in more unstable flame propagation under fuel-rich conditions. In contrast, the hydrodynamic instability exhibited a non-monotonic trend, first intensifying and subsequently diminishing with increasing equivalence ratio. The critical Peclet number decreased continuously across the equivalence-ratio range, while the critical flame radius varied non-monotonically. The incorporation of n-butanol was found to enhance both diffusive-thermal and hydrodynamic instabilities and to reduce the critical Peclet number and critical flame radius. These findings underscore the need for careful control of combustion stability in practical applications involving iso-octane/n-butanol mixtures and provide fundamental insight into the flame-structure evolution associated with next-generation alternative fuels.

Solid oxide fuel cell/gas turbine (SOFC/GT) hybrid systems have been recognized as a promising solution in the pursuit of high-efficiency and low-emission power generation, offering electrical efficiencies exceeding 60% and notable fuel flexibility. However, the substantial amount of high-temperature exhaust gas (typically in the range of 700–800 K) released during operation has presented ongoing challenges in effective thermal energy recovery, thereby constraining further improvements in overall system efficiency. In recent years, various waste heat recovery technologies have been explored for their applicability to SOFC/GT systems. Among the most studied are the supercritical carbon dioxide (SCO₂) cycle, the transcritical carbon dioxide cycle (TRCC), the organic Rankine cycle (ORC), the Kalina cycle (KC), and the steam cycle (ST). In this review, the thermodynamic principles, performance metrics, and thermal integration compatibility associated with each technology were critically examined. In addition, a novel waste heat recovery configuration optimized for SOFC–GT hybrid systems was proposed and discussed. This approach was conceptually validated to enhance total system efficiency and to facilitate the development of advanced combined heat and power (CHP) systems. The results contribute to the broader efforts in clean energy system design and offer technical insights into the next generation of high-performance, low-emission power technologies.

Phase change materials (PCMs), an innovative class of functional materials, exhibit the ability to store or release thermal energy through reversible transformations at specific phase transition temperatures, which have been extensively employed in aerospace, military, construction, and refrigeration industries. As oil and gas exploration and development word-widely advance into deeper formations, extremely high-temperature and high-pressure conditions in these environments impose significant challenges on drilling fluids and down-hole instruments, limiting the progress of deep hydrocarbon exploration. To address the technical challenges related to the high-temperature resistant stability of drilling fluids in deep formations, this study investigates the integration of PCMs into drilling fluids. Through theoretical analysis and experimental simulations, the feasibility of utilizing the "phase change heat storage principle" of PCMs to reduce circulating drilling fluid temperatures in boreholes was demonstrated. The results indicate that three selected PCMs exhibit phase transition temperatures in the range of 120–145℃ and phase change latent heat of 90.3–280.6 J/g, showcasing excellent phase change heat storage properties. The materials were found to be compatible with drilling fluids. At a PCM concentration of 12%, the rheological and filtration properties of the drilling fluids still met operational requirements. Incorporating PCMs into drilling fluids effectively reduced the circulating temperature in boreholes, with a more pronounced cooling effect observed at higher PCM concentrations. At a concentration of 12%, the circulating temperature of drilling fluids was reduced by up to 20℃. Additionally, the PCMs demonstrated good reusability, consistently undergoing the "heat storage and release" phase change process, thereby satisfying the circulating cooling demands of drilling fluids. The findings provide a robust reference for PCM integration in high-temperature drilling fluids, particularly in ultra-deep wells with extreme thermal conditions.

A novel approach for analyzing fluid flow dynamics and static pressure distributions within a convergent-divergent nozzle was presented, integrating soft computing techniques with computational fluid dynamics (CFD) simulations performed using Ansys Fluent. The study differs from traditional CFD approaches by leveraging soft computing methods to optimize simulation parameters and enhance the accuracy of predictions. Four distinct fluids—air, hydrogen, nitrogen, and helium—were analyzed across a range of inlet velocities (1 m/s to 5 m/s). The study systematically evaluates the influence of boundary conditions and flow models, including both viscous and inviscid conditions, on the flow patterns and static pressure distributions. The results highlight the substantial impact of fluid density and viscosity on the flow dynamics, particularly for lighter gases such as hydrogen and helium. These gases exhibit higher velocities and less pronounced pressure gradients due to their lower density and viscosity compared to denser fluids like air and nitrogen. Soft computing techniques improve the reliability of these findings by enhancing the predictive capability of the CFD model, allowing for more precise insights into complex fluid behaviors. The implications of these findings are significant across multiple engineering domains, such as aerospace propulsion, chemical processing, and energy systems, where optimizing fluid flow characteristics is critical. The integration of soft computing with CFD provides a robust framework for more accurate modelling of low-density, high-velocity flows and offers valuable insights for the design of more efficient systems. This study underscores the potential of advanced computational techniques in advancing both fluid dynamics research and engineering applications.