Because of environmental problems, it becomes necessary to develop alternative fuels that give engine performance at par with diesel. Among the alternative fuels, biodiesel and its blends hold good promises as an eco-friendly and the most promising alternative fuel for Diesel engine. The properties of biodiesel and its blends are found similar to that of diesel. Many researchers have experimentally evaluated the performance characteristics of conventional Diesel engines fueled by biodiesel and its blends. However, experiments require enormous effort, money and time. Hence, via finite-time thermodynamics simulation, an air-standard Diesel cycle model with heat transfer loss and variable specific heats of working fluid is analyzed to predict the performance of Diesel engine. The effect of compression ratio, cut-off ratio and fuel type on output work and thermal efficiency is investigated through the model. The fuels considered for the analysis are conventional diesel, rapeseed oil biodiesel and its blend (20 % biodiesel and 80 % diesel by volume). Numerical simulations showed that the output work and thermal efficiency of the engine decrease with increase of cut-off ratio for all fuels. Also, the model predicts similar performance with diesel and biodiesel blend which means that the biodiesel blend (20 % biodiesel and 80 % diesel by volume) could be a good alternative and eco-friendly fuel for conventional Diesel engines without any need to modify the engine.
Effective mechanical properties of nanocomposites reinforced with multiwalled carbon nanotubes (MWCNTs) have been determined using Finite Element Analysis (FEA). The effects of several parameters on nanocomposite effective mechanical properties are investigated. First, FEA models are created consisting of MWCNTs with different spring constants to investigate the effects of the interlayer van der Waals forces. Next, the reinforcing efficiency of MWCNTs in different matrices is investigated using models consisting of matrices with different moduli of elasticity. In addition, the effects of MWCNT volume fraction are investigated. Finally, models were created to determine effective mechanical properties of nanocomposites reinforced with Single-Walled Carbon Nanotubes (SWCNTs). Comparison of the results suggests that SWCNTs are more efficient in strengthening the matrix than MWCNTs. Also, Young's modulus prediction for multiwalled carbon nanotube in a propylene matrix is compared to experimental data investigated by Andrews et al. (2002), and good agreement is observed.
Carbon nanotubes (CNTs) possess exceptional mechanical properties and are therefore suitable reinforcements for composite materials. Nanotube efficiency in reinforcing the matrix depends on the CNT alignment, volume fraction and configuration, as well as matrix properties. In this investigation, finite element method (FEM) is used to investigate the effects of nanotube waviness ratio, volume fraction, and matrix modulus on properties of CNT based polymer nanocomposites. Nanocomposite mechanical properties are evaluated using a 3D nanoscale representative volume element. Models consisting of CNTs with different waviness ratios are created to investigate the effects of nanotube configuration on nanocomposite mechanical properties. Next, the effect of nanotube volume fraction on nanocomposite moduli of elasticity is investigated. Finally, the effects of matrix modulus are investigated by analysing models consisting of matrices with different moduli. The results of this investigation are compared with those found in the literature and good agreement is observed.
This study is concerned with the performance analysis and comparison of air standard Diesel and Diesel-Atkinson cycles with heat-transfer loss, friction like term loss and variable specific-heat ratio of the working fluid based on finite-time thermodynamics. Also numerical examples are detailed to show the relations between the output power and the compression ratio, between the thermal efficiency and the compression ratio, as well as the optimal relation between the output power and the thermal efficiency of both cycles. Furthermore, the effects of variable specific-heat ratio of the working fluid, heat transfer and the friction-like term loss on the performance of both irreversible cycles are analyzed. Comparison of the performance of cycles shows that the heat efficiency and the output power of an air standard Diesel-Atkinson are higher than the Diesel ones and the points of maximum output power and thermal efficiency of Diesel-Atkinson cycle occur at the lower compression ratio. Reduction of Noxis another advantage of Diesel-Atkinson cycle. The results obtained in this paper provide guidance for the design of Diesel and Diesel-Atkinson engines.
In this investigation, the effective mechanical properties of fullerene nanocomposites considering interface effects were characterised. Load transfer in nanocomposite materials is achieved through the fullerene/matrix interface. Thus, to determine nanocomposite mechanical properties, the interface behaviour must be determined. A single fullerene and the surrounding polymer matrix are modelled. Two cases of perfect bonding and an elastic interface are considered. Two models are suggested for elastic interface. The first elastic interface model consists of a thin layer of an elastic material surrounding the fullerene. In the second elastic interface model, a series of spring elements are used as the fullerene/matrix interface. The results of numerical models indicate the importance of adequate interface bonding for a more effective strengthening of polymer matrix by fullerene. Also, Young's modulus prediction for fullerene in epoxy matrix is compared to experimental data investigated by Rafiee et al. (2011), and good agreement is observed.
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