Rouzbeh Shafaghat

The growing demand for energy and the environmental impacts associated with fossil fuels have increased interest in renewable alternatives such as ethanol for spark-ignition (SI) engines. Although ethanol–gasoline blends are widely used, a single fixed blend ratio cannot be considered optimal over the entire operating range of an engine. In this study, a numerical framework is developed to determine speed-dependent optimal ethanol–gasoline blend ratios for a single-cylinder SI engine operating under steady-state full-load conditions. A one-dimensional engine model is first developed in GT-Power and validated using experimental data obtained with pure gasoline. The validated model is then coupled with MATLAB/Simulink, where a quasi-steady supervisory control and optimization algorithm is implemented. The optimization procedure, based on the fmincon algorithm, aims to maximize ethanol substitution while limiting power deviation and simultaneously reducing brake specific fuel consumption (BSFC), carbon monoxide (CO) and unburned hydrocarbon (UHC) emissions. Simulations are performed at engine speeds between 2000 and 3000 rpm with ethanol fractions ranging from 0% to 50%. The results indicate that ethanol contents above 50% lead to unstable engine behavior under fixed ignition timing. Moreover, the optimal ethanol fraction increases with engine speed, reaching up to 28% at 3000 rpm, while the associated power loss remains below 3%. Overall, the proposed framework provides a quasi-steady optimization approach for adapting fuel blend ratios to engine operating conditions and may serve as a foundation for future development of real-time fuel blending strategies in SI engines.

In recent years, maritime transportation has expanded significantly, and improving efficiency and increasing thrust in marine propulsion systems have become primary objectives. In this context, given the importance of the tandem canard configuration in enhancing the performance of propeller-driven propulsion systems, the present study investigates the tandem canard configuration for the KP505 propeller installed on the KCS container ship. The experimental evaluation focuses on the effects of varying the diameter ratio and distance ratio between the propellers on the hydrodynamic coefficients. Following calibration and validation, experimental results were obtained for four diameter ratios of 0.85, 0.90, 0.95, and 1.00, and five distance ratios ranging from 0.10 to 0.20. Performance characteristics were analyzed in terms of thrust and torque coefficients, as well as efficiency, across different advance coefficients. The results indicate that the tandem canard configuration can lead to notable improvements in thrust and torque coefficients, as well as overall efficiency. Specifically, the thrust coefficient increased by up to 20%, and the efficiency improved by up to 5%. The most favorable tandem canard configuration was identified at a diameter ratio of 0.95 and a distance ratio of 0.40. Notably, implementing this configuration at an advance coefficient of 0.80 (the design point of the KP505 propeller) led to an increase in the thrust coefficient of up to 6.65% and an efficiency improvement of up to 3.32%.

Water scarcity necessitates efficient desalination technologies compatible with limited energy resources. This study employs CFD to optimize thermoelectric‐based dehumidifier performance in open‐cycle humidification–dehumidification desalination systems. Numerical simulations utilizing the mixture multiphase model and realizable k‐ε turbulence model evaluated four fin configurations: simple fins and fins with circular, triangular, and square protrusions. At 309.15 K inlet temperature, the circular protrusion geometry achieved maximum water production of 126.65 g/h, followed by triangular (119.42 g/h), square (117.43 g/h), and simple fin designs (114.94 g/h). The circular configuration demonstrated a GOR of 0.57, representing a 24% increase in thermal efficiency compared to the baseline simple fin (GOR = 0.46). Despite requiring only 3.9% additional material mass, the circular design achieved the highest normalized water production of 1.327 g/h per gram of fin mass, outperforming triangular (1.262), simple (1.251), and square (1.249) configurations. Performance enhancement resulted from increased heat transfer area, elevated turbulent kinetic energy in protrusion regions, and improved thermal boundary layer disruption. These findings demonstrate that optimized fin geometry, particularly designs incorporating circular protrusions, can substantially enhance water production efficiency in HDH systems, highlighting the critical role of heat sink design optimization in improving overall system performance.

Accurate determination of friction head loss in water distribution networks is crucial and depends on pipe material and roughness coefficients. This study addresses the variability of the roughness coefficient for polyethylene pipes across different velocities and temperatures, utilizing both computational and experimental methods based on the Darcy–Weisbach and Hazen–Williams equations. Conducted at NIT (Babol Noshirvani University of Technology), the research involved 48 case tests. Results indicate that the commonly used Hazen–Williams coefficient (135–145) is only valid for velocities exceeding 0.7 m/s and temperatures between 20 and 30 °C; outside these ranges, corrective factors are necessary. Two regression equations were formulated to optimize the Hazen–Williams coefficient according to flow velocity and temperature. Application of these corrective coefficients in a real water network demonstrated the potential impact on friction head loss of up to 19%. The findings suggest that using these correction factors is as significant as the effect of 4 years of pipe aging. The study highlights the importance of considering minimum winter temperatures in design risk management for water networks to optimize performance and mitigate head loss.

This study investigates the enhancement of thermal performance in Evacuated Tube Solar Collectors (ETCs) by integrating graphene nanoparticles into the heat transfer fluid. Improvement the efficiency of ETCs is crucial for maximizing solar energy utilization, particularly in regions with diverse climatic conditions. To achieve this, we conducted experiments comparing the thermal performance of the ETC under two conditions: with and without graphene nanoparticles, and at varying flow rates of condenser water (5, 10, 15, and 20 L/h) in an open space in Babol, northern Iran, over two periods in August 2022. Measurements included ambient temperature, input and output water temperatures, heat pipe temperature, and water flow rate. Key performance indicators, such as the average Nusselt number, useful heat output, and convection heat transfer, were calculated. The results indicate that the Nusselt number increased by 10.64% and overall thermal performance improved when utilizing the acetone-graphene nanofluid at a flow rate of 20 L/h under vacuum conditions (-0.6 bar) with a volume fraction of 0.08% nanoparticles. This work demonstrates a significant enhancement in thermal energy storage capabilities of ETCs, showcasing the potential of nanofluids in solar thermal applications, thereby contributing novel insights into the engineering optimization of solar collectors.

Bioethanol-gasoline blends are used to reduce fossil-fuel consumption in SI engines (SIE). In this experimental study the effect of different blends of gasoline- bioethanol on the performance and emissions of a carbureted, single-cylinder, and four-stroke SIE is investigated at low load. Tests were performed at various speeds and the constant equivalence ratio. The results showed that ηth,b decreased with the increase of ethanol percentage, and the latent heat of evaporation increased with the increase of ethanol blend percentage. Considering that the constant equivalence ratio, increasing the percentage of ethanol caused a decrease in the intake air mass and volumetric efficiency and simultaneously reducing the volume efficiency and increasing the latent heat caused a decrease of the air-fuel mixture temperature, misfiring, and resulted in the flame being extinguished. Tout and Tbody dropped up to 8.37% and 12.63%, respectively. The emission of NOX also decreased up to 93.73%. Of course, UHC will increase up to 160%. The emission of CO and CO2 increased by 92.5% and decreased by 23.98%, respectively. In conclusion, addition of ethanol to gasoline causes a decrease in ηth,b and a significant decrease in the emission of NOX and CO2 pollutants; however, it will increase UHC and CO emissions.