The deleterious environmental impacts of crude oil, notably significant pollution and escalated greenhouse gas emissions, necessitate alternative fuels. In this context, biodiesel, particularly when blended with diesel, emerges as a viable substitute. This study investigates the emissions and performance characteristics of diesel-biodiesel blends, utilizing microalgae oil-based biodiesel. Variations in the catalyst (potassium hydroxide, KOH), reaction duration (30-110 minutes), and temperature (30-70^oC) were explored to determine their influence on biodiesel yield. The biodiesel produced was characterized using Fourier-transform infrared spectroscopy (FTIR), revealing distinct absorption bands indicative of various functional groups present. Furthermore, emission testing was conducted on a TecQuipment TD202 diesel engine, a naturally aspirated, single-cylinder, four-stroke, direct-injection, air-cooled model. Optimization studies revealed that the optimal biodiesel yield was achieved using 2g of KOH, at a temperature of 60^oC, and within a reaction time of 90 minutes. Emission testing demonstrated a decrease in exhaust gas temperature (EGT) with reduced biodiesel blend ratios and an increase with engine speed across all blends. Carbon monoxide (CO) emissions diminished with lower biodiesel concentrations, whereas carbon dioxide (CO₂) and nitrogen oxides (NO_x) emissions escalated. Total hydrocarbons (THCs) emissions increased with reduced biodiesel content, and smoke opacity escalated with lower biodiesel blend ratios. This investigation methodically examines the emissions from various biodiesel blends, underscoring their potential as a cleaner, more sustainable option for the transportation sector.

This study presents a detailed Computational fluid dynamics (CFD) analysis, focusing on optimizing laminar flow within non-circular ducts, specifically those with square, rectangular, and triangular configurations. The study centers on the effective use of mesh quality and size in these ducts, a factor which is previously underrepresented in those CFD studies that predominantly emphasized turbulent rather than laminar flows. With the help of finite element approach, this study compares the performance of these non-circular ducts, employing Reynolds numbers ranging from 1600 to 2000 and mesh sizes of 6, 12, and 18 mm. A ribbed duct style, arranged in a hybrid manner, is adopted to further this study. Analysis in this paper applied the Single predictive optimization (SPO) technique to the identification of the K-$\varepsilon$-Standard as the preferred viscosity model and a hybrid rib distribution as optimal within the triangular duct configuration. Parameters of a Reynolds number of 1600 and a mesh size of 18 mm emerged as the most effective values for this duct style. Then, the attained results of the Analysis of variance (ANOVA) indicated the F-Criterion's insignificance for Reynolds laminar levels, rendering the laminar viscosity model less relevant within the test section. Additionally, the implementation of the Six sigma procedure (SSP) markedly enhanced both the performance factor (PF) and turbulence intensity, which were observed at 4.90% and 146.77%, respectively. This improvement was most notable in the triangular duct, characterized by rib heights of 66 mm (semi-circle), 66 mm (rectangular), and 38.126 mm (triangular).

In this investigation, the enhancement of heat transfer in pipes facilitated by Fe₃O₄-distilled water nanofluid under the influence of magnetic fields is comprehensively studied. The research primarily focuses on examining the alterations in the thermal boundary layer and fluid flow patterns caused by the application of magnetic fields. It is observed that magnetic fields induce the formation of vortexes, thereby actively influencing the flow patterns within the fluid. These vortexes play a pivotal role in promoting thermal diffusion, resulting in an improved heat transfer rate. The core aim of this study is to quantitatively assess the impact of magnetic nanofluids on the coefficient of heat transfer. A model tube, possessing an inner diameter of 25.4 mm and a length of 210 mm, serves as the basis for the simulations. The investigation encompasses a range of inlet velocities (0.05, 0.1, and 0.5 m/s) and exit pressures to analyze the magnetic field's effect on heat transfer and fluid dynamics. Magnetic flux intensities of one, two, and three Tesla are employed. Notably, the highest temperature of 349 K is recorded in the presence of three magnets, indicating an escalation in temperature with an increase in magnetic strength. However, a diminishing temperature rise is noted over a specified distance with additional magnets. For instance, at a distance of 100 mm, the temperature peaks at 340 K with one magnet, whereas with two magnets, this temperature is attained at a mere 50 mm, suggesting enhanced magnetizer efficiency. Furthermore, the introduction of a magnetic field at the tube's center reveals that high flow velocities tend to counteract the magnetic influence due to their superior force, which impedes the incorporation of metal particles into the fluid. As the magnetic flux value escalates, the nanofluid's magnetic particles either congregate or disperse, thereby obstructing flow and intensifying channel vortices. This phenomenon results in heightened turbulence, instigated by the magnets, which in turn precipitates a rapid increase in fluid flow velocity, thereby impeding the fluid's capacity to adequately absorb heat for efficient heating.

The quest for superior wear-resistant coatings has led to significant advancements in laser cladding technology, yet the escalating requirements for durability under operational conditions challenge the efficacy of existing solutions. This investigation delves into the enhancement of wear resistance in coatings through the integration of particle reinforcement phases, identified as a cost-effective strategy for augmenting coating performance. Emphasis is placed on the systematic classification of particle reinforcements and the methodologies employed for their incorporation. The focus is particularly cast on the incorporation of hard and self-lubricating particles into laser-clad wear-resistant coatings, highlighting innovations in particle addition techniques. An examination of the mechanisms through which hard particles—comprising oxides, carbides, nitrides, borides, and their multifaceted compounds—reinforce coatings is presented, delineating the influence of particle content, size, and morphology on wear resistance. Additionally, the paper explores the state of research on the self-lubricating properties imparted by sulfides, fluorides, graphite, and MAX phase particles under varied thermal conditions. A critical analysis of the benefits and limitations associated with the use of hard and self-lubricating particles in the enhancement of coating durability is conducted. This comprehensive review serves not only to elucidate the current landscape of particle-reinforced, laser-clad coatings but also to inform future research directions aimed at developing coatings capable of withstanding high temperatures and exhibiting exceptional hardness. The commitment to leveraging in situ synthesis for the development of these advanced materials underscores the potential for significant breakthroughs in the field of wear-resistant coatings.