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In this paper, we propose modeling for a single repairable system with a hierarchical structure under the assumption that the failures follow a nonhomogeneous Poisson process (which corresponds to minimal repair action) with a power-law intensity function. The properties of the new model are discussed in detail. The parameter estimators are obtained using the maximum likelihood method. A corrective approach is used to remove bias with order O(n −1), and the respective exact confidence intervals are proposed. A simulation study is conducted to show that our estimators are bias-free. The proposed modeling is illustrated via a toy example on a butterfly valve system, an example of an early-stage real project related to the traction system of an in-pipe robot, and also a real example on a blowout preventer system.

In order to reduce the harmful effect on the environment, using the oxygenated fuels such as biofuel blends as fuel has been on the spotlights for the internal combustion engines. For this rationale; the diesel engine operated with blends of sunflower biodiesel and diesel fuel (blending of 0%, 10%, 20%, and 100% biodiesel fuel with conventional diesel fuel). In this study, an experimental and numerical model for Heat release rate (HRR) and the characteristic performance of diesel engine such as cylinder pressure and emission characteristics (NOx, CO, and HC) in internal combustion engines is presented. To ensure the integrity of modeling, the results were compared with the experimental results. This comparison indicated a good agreement between the two. A Gaussian and Fourier series of second order was used to define a function relating the pressure and emission characteristics. Presented numerical model, implemented in proprietary software AVL FIRE, is able to capture chemical phenomena and to predict pollutant emission concentration trends. © 2017 American Institute of Chemical Engineers Environ Prog, 37: 1540–1550, 2018

Sub-grid closures for filtered two-fluid models (fTFM) useful in large scale simulations of riser flows can be derived from highly resolved simulations (HRS) with microscopic two-fluid modeling (mTFM). Accurate sub-grid closures require accurate mTFM formulations as well as accurate correlation of relevant filtered parameters to suitable independent variables. This article deals with both of those issues. The accuracy of mTFM is touched by assessing the impact of gas sub-grid turbulence over HRS filtered predictions. A gas turbulence alike effect is artificially inserted by means of a stochastic forcing procedure implemented in the physical space over the momentum conservation equation of the gas phase. The correlation issue is touched by introducing a three-filtered variable correlation analysis (three-marker analysis) performed under a variety of different macro-scale conditions typical or risers. While the more elaborated correlation procedure clearly improved accuracy, accounting for gas subgrid turbulence had no significant impact over predictions.

This article presents a comprehensive experimental work for the application of permanent magnets with the intensity of 9,000 G to a four‐stroke four cylinders gasoline engine on fuel lines at a location near to the combustion chamber. By using the permanent magnet, the liquid fuel disintegrates into small diameter, and de‐clustering of the fuel molecules of hydrocarbon has been proved to provide better atomization of the fuel, which makes sure that the fuel strenuously combines with oxygen and results in complete and more efficient burning process inside the combustion chamber. The experimental analysis revealed that magnetic treatment has improved performance and emission characteristics. Analysis over the engine test results with magnetic fuel conditioning showed that the reduction of 4–12% in fuel consumption and reduction in 11, 10, 18, and 10% for CO, CO2, HC, and NOx emissions, respectively, compared to gasoline fuel without magnetic condition. Further, we experimentally investigated the performance of petrol engine parameters such as in‐cylinder temperature and pressure, cylinder, and head cylinder temperature, the temperature of different parts of the piston. As a whole, magnetic fuel treatment has improved combustion and reduced the harmful pollutants of the compression ignition engine.

In low operating temperatures, provided water of Proton-Exchange Membrane Fuel Cells (PEMFCs) is discharged in the state of tiny/large droplets, slugs, and semi-slugs, which strongly depends on the flow channels' characteristics. In this study, the discharge capabilities of channels with different height-to-width aspect ratios are inspected using a transient two-phase numerical simulation. The numerical model includes a segment of the gas channel on the cathode side, and the operating conditions are those related to an actual fuel cell application. Results showed that channels with minimum height could lift the initial slug to the upper part 2.16 times faster and immediately form film flow at the corners. For a fixed width, decreasing channel height from 1.5 mm to 0.5 mm, results in 38.3% faster discharge time and a 62.3% increment in the clearance rate of the gas-diffusion layer. For higher channels, the combined effect of shear stress, gravity, and the adhesive forces of hydrophilic walls cannot lift the initial slug continuously and causes it to rupture, distort, and partially spread over the Gas-diffusion layer (GDL) surface, which leads to mass transport limitation for the cell. Furthermore, when the channel width decreases from 1.5 mm to 0.5 mm for a fixed height, the initial slug leaves the computational domain 51.1% faster. Overall, it was found that the smaller dimensions for height and width show superior cell performance regarding faster water removal, clearer GDL surface, and more uniform flow distribution over the entire electrochemical active area. A channel with a cross-section dimension of 0.5 mm × 0.5 mm is suggested as the best channel design among the analyzed cases for maximum efficiency for the cathode-side flow fields of a PEMFC.

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