Computer aided design and optimization of bi-layered tube hydroforming process

Tube hydroforming is one of the unconventional metal forming processes in which high fluid pressure and axial feed are used to deform a tube blank in the desired shape. However, production of bi-layered tubular components using this process has not been investigated in detail in spite of the large number of research studies conducted in this area. Bi-layered tubing can be useful in complex working environments as it offers dual properties that a single layer structure doesn’t have. Consequently, for wider implementation of this technology, a detailed investigation on bi-layered tube hydroforming is required. In this research, both single and bi-layered tube hydroforming processes were numerically modelled using the finite element method (ANSYS LS-DYNA). Experiments were conducted to check the numerical models validation. In addition, Response Surface Methodology (RSM) using the Design-Expert statistical software has been employed along with the finite element modelling to attain a detailed investigation of bi-layered tube hydroforming in the X-type and T-type dies. The process outputs were modelled as functions of both the geometrical factors (tube length, tube diameter, die corner radius, and thicknesses of both layers.) and the process parameters (internal pressure coordinates, axial feed, and coefficient of friction.). Furthermore, the desirability approach was used in conjunction with the RSM models to identify the optimal combinations of each the geometrical factors and process parameters that achieve different objectives simultaneously. In addition, a different optimization approach that applies the iterative optimization algorithm in the ANSYS software was implemented in the process optimization. The finite element models of single and bi-layered tube hydroforming processes were experimentally validated. A comparison of both processes was carried out under different loading paths. Also, response surface modelling of the bi-layered tube hydroforming process outputs was successfully achieved, and the main effects and interaction effects of the input parameters on the responses were discussed. Based on the RSM models, the process was optimized by finding the inputs levels at which the desired objectives are satisfied. Finally, a comparison of the RSM based optimization approach and the iterative optimization algorithm was performed based on the optimum results of each technique

Performance analysis of a vertical axis wind turbine using computational fluid dynamics

Vertical axis wind turbines (VAWTs) have gained popularity in the last few decades due to their numerous advantages when deployed in urban areas. Despite this, Vertical axis wind turbines have complex aerodynamics, dynamic stall, hence lower performance. Low/zero starting torque, noise, visual impact, as well as blade safeness are further hurdles when they are fitted into the physical environment. Due to these pertinent issues that comes to play in a vertical axis wind turbine, the current investigation explores an augmented vertical axis wind turbine (AVAWT) having a rotor and a stator. The outcome of the study highlighted the effect of mesh density and the type of turbulence model selected in the determination of the forces being exerted on the blade using computational fluid dynamics. Investigation into the effect of time steps showed lesser effect of this parameter on the performance of the blade computationally. The newly developed augmented turbine blades improved the output power by 1.35 times in comparison to an open rotor. The shape for the conical surface and the stator blade impacted the performance as well. Furthermore, it was deduced that there was higher dynamic stall for scenarios where the tip speed ratios were lower. The study showed the importance of the stator in a vertical axis wind turbine in ensuring that the incoming wind attains some acceleration as well as creating a lower pressure outlet but overall aids in the improvement of the power and torque coefficients by more than 36%

Mechanical pretreatment of waste paper for biogas production

In the anaerobic digestion of lignocellulosic materials such as waste paper, the accessibility of microorganisms to the fermentable sugars is restricted by their complex structure. A mechanical pretreatment with a Hollander beater was assessed in order to reduce the biomass particle size and to increase the feedstock’ specific surface area available to the microorganisms, and therefore improve the biogas yield. Pretreatment of paper waste for 60 min improves the methane yield by 21%, from a value of 210 ml/gVS corresponding to untreated paper waste to 254 ml/gVS. 30 min pretreatment have no significant effect on the methane yield. A response surface methodology was used to evaluate the effect of the beating time and feedstock/inoculum ratio on the methane yield. An optimum methane yield of 253 ml/gVS was achieved at 55 min of beating pretreatment and a F/I ratio of 0.3

Two dimensional Cu based nanocomposite materials for direct urea fuel cell

In this work, Cu2O nanoparticles were successfully prepared onto the surface of two-dimensional graphitic carbon nitride (g-C3N4) by using a simple solution chemistry approach. An environment-friendly reducing agent, glucose, was used for the synthesis of Cu2O NPs onto the surface of g-C3N4 without using any surfactant or additives. The surface composition, crystalline structure, morphology, as well as other properties have been investigated using XPS, XRD, SEM, FTIR, FESEM, EDS, etc. The electrochemical measurements of the prepared materials demonstrated that Cu2O exhibited a weak oxidation activity towards urea, while g-C3N4 has no activity towards urea oxidation. The Cu2O supported on the surface of g-C3N4 (Cu2O-g-C3N4) demonstrated a significant activity towards urea oxidation that reached two times that of the unsupported one. The significant increase in the performance was related to the synergetic effect between the Cu2O and g-C3N4 support. The prepared composite materials demonstrated high stability towards urea oxidation as confirmed from the stable current discharge for around 3 h without any noticeable degradation performance

Nanocrystalline Mg2Ni for hydrogen storage

This is an accepted manuscript of an article published byElsevier in Reference Module in Materials Science and Materials Engineering on 14/12/2020, available online: https://doi.org/10.1016/B978-0-12-815732-9.00061-9 The accepted version of the publication may differ from the final published versionHydrogen continues to receive increased attention as the most promising energy carrier enabling sustainable and eco-friendly energy systems. Despite the various advantages of hydrogen fuel, storing hydrogen in a light-weight and compact form is the barrier towards the commercialization of the hydrogen technologies. Thus, the availability of a reliable, inexpensive, safe and efficient hydrogen storage technology is crucial to support and foster the transition to a hydrogen-powered world. Among the possible hydrogen storage solutions, storing hydrogen in the solid-state, such as metal hydrides, is the safest and most attractive method for on-board hydrogen storage. The metal hydrides can release highly pure hydrogen, via a low-pressure endothermic process, suitable to be used directly in the hydrogen fuel cell devices. This article presents an overview of using Mg and Mg2Ni-based alloys for solid-state hydrogen storage. A review of the hydrogen storage technologies is presented first and then the most recent developments on Mg and Mg2Ni-based hydrogen storage materials are highlighted.Published versio

Mathematical model of a proton-exchange membrane (PEM) fuel cell

This work presents a mathematical modelling of a proton-exchange membrane fuel cell (PEMFC) system integrated with a resistive variable load. The model was implemented using MATLAB Simulink software, and it was used to calculate the fuel cell electric current and voltage at various steady-state conditions. The electric current was determined by the intersection of its polarisation curve and applied as an input value for the simulation of the PEM fuel cell performance. The model was validated using a Horizon H-500xp model fuel cell stack system, with the following main components: a 500 W PEM fuel cell, a 12 V at 12 A battery for the start-up, a super-capacitor bank to supply peak loads and a 48 V DC-DC boost converter. The generated power was dissipated by a variable resistive load. The results from the model shows a qualitative agreement with test bench results, with similar trends for stack current and voltage in response to load and hydrogen flow rate variation. The discrepancies ranged from 2% to 6%, depending on the load resistance applied. A controlled current source was utilised to simulate the variation of fan power consumption with stack temperature, ranging from 36.5 W at 23°C to 52 W at 65°C. Both model and experiments showed an overall PEMFC system maximum efficiency of about 48%