Depletion of fossil fuel and massive emissions of hazardous greenhouse gases are prompting many researchers to focus on greener renewable fuel such as biodiesel, which has the potential to replace petrodiesel partially. This review covers various aspects related to biodiesel feedstock and its effects on biodiesel characteristics, biodiesel production methods, blending techniques, biodiesel properties, combustion, engine performance, and emission analysis, the effects of different additives on biodiesel characteristics, and some challenges associated with biodiesel. Moreover, different relevant empirical correlations of biodiesel properties and combustion parameters are presented. Despite alkali catalysis being the most adopted transesterification process, lipase catalysis and heterogeneous catalysis are potential processes for future biodiesel production from low‐cost feedstock. Biodiesel has higher viscosity, density, flash point, cetane number, and pour point while having low heating value in comparison with petrodiesel. Most studies conducted on diesel engine led to a reduction in brake power, brake thermal efficiency, carbon monoxide, sulfur dioxide, particulate matter, and unburned hydrocarbons, and increased brake specific fuel consumption and oxides of nitrogen are associated with biodiesel compared to petrodiesel. In brief, biodiesel is comparable to petrodiesel. However, before there is a large‐scale application of biodiesel in the automotive sector it has to overcome some challenges such as its compatibility with engine components, its instability, its effect on engine wear, deposit formation, and clogging of fuel filters and injectors. Increased focus should also be given to second‐generation biodiesel over first‐generation biodiesel because second‐generation biodiesel can offset production costs, reduce deforestation, and solve the food versus fuel problem. © 2022 Society of Chemical Industry and John Wiley & Sons, Ltd.

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Biodiesel has emerged as a promising renewable fuel, which can help reduce dependency on fossil fuel and has potentiality to replace petrodiesel partially. Usage of biodiesel results in decreased carbon monoxide, hydrocarbon, and particulate matter emission. However, it has some drawbacks such as increased nitrogen oxides (NOx) emission, lower calorific value, and poor engine performance, which restrict wide usage of biodiesel as a potential substitute in compression ignition engine. There is a scope to overcome these problems by applying metal based nanoparticles (NPs) as fuel additive. This article reviews the preparation and stability of nanofluid and the effect of metal based NPs on fuel properties, combustion, performance, and emission characteristics. It has been concluded that inclusion of nanoadditives increases cetane number and calorific value of blended fuel. According to the most authors, metal based NP doped biodiesel blend enhances ignition characteristics, improves engine performance, and reduces emissions including NOx compared to biodiesel blend without additive. However, some concerns and challenges identified in this article need to be addressed to make this technology feasible for commercial application in near future.

This paper presents an evaluation of five different turbulence models by comparing the numerical data derived from these models using ANSYS Fluent with experimental data at a Reynolds number and a Mach number of 0.05 × 106 and 0.015 respectively based on the centerline chord of the airfoil for the flow over NACA 0012 and NACA 2412 airfoils. Moreover, the aim of the present study is to demonstrate the difference in aerodynamic characteristics of the airfoils in order to find aerodynamically more advantageous airfoil. It is concluded that Spalart-Allmaras model and k-ω SST model are capable of providing the most accurate prediction for lift coefficient at a low angle of attack for both airfoils. Standard k - ε model gives a slightly low value of lift coefficient at low angle of attack and slightly high value of lift coefficient at high angle of attack for both airfoils. k-ω SST model, Spalart-Allmaras model, Transition k-kL - ω model, and γ-Rⅇθ Transition SST model can predict drag coefficient reasonably at low angle of attack. At a high angle of attack, however, no turbulence model is able to give a satisfactory prediction for lift coefficient as well as drag coefficient, which implies that these models are unable to predict post-stall characteristics. NACA 2412 airfoil produces more lift coefficient than that of the NACA 0012 airfoil at all angles of attack. Moreover, the drag coefficient of NACA 2412 airfoil is less than that of the NACA 0012 airfoil, which implies that NACA 2412 airfoil exhibits better aerodynamic performance. The lift to drag coefficient ratio of NACA 2412 airfoil is also higher than that of the NACA 0012 airfoil indicating NACA 2412 airfoil to be more fuel economic.

Cavitation and cavitation-induced noise are harmful to both marine propellers and marine wildlife. Thus, it is required to reduce cavitation in marine propellers by developing the best design marine propellers. Moreover, proper material should be selected during the construction of marine propellers to withstand high-pressure loads. This paper presents an evaluation of the hydrodynamic characteristics such as cavitation and cavitation-induced noise of AU-outline GAWN series and B-series marine propellers at 0˚, 5˚, 10˚, and 15˚ rake angles using Computational Fluid Dynamics (CFD) analysis. Moreover, the study aims to find out the optimized propeller material among Nickel-Aluminum-Bronze (NAB), S2 glass, Aluminum 6061, and carbon fiber reinforced plastic (CFRP) materials. It is concluded that the lowest cavitation noises are 153.3 dB and 153.1 dB at a 10° rake angle for AU-outline GAWN series and B-Series marine propellers respectively. S2 glass is observed to be the optimum material at low rake angles, while CFRP is the optimum material at high rake angles compared to all other potential materials for both AU-outline GAWN series and B-series propellers.