Engineering Review

Progress of auxetic and semi-auxetic materials

2023-02-27T09:52:37+00:00

Auxetic materials with negative Poisson's ratios, display the unique behavior owing to their micro-structure or geometrical build. Auxetic materials resist deformities when subjected to uniaxial, biaxial, and shearing stresses. Cellular based materials are known for their excellent impact and shock energy absorption. When foams are incorporated with auxetic geometry, their impact energy absorption in-creases. Combination of auxetic materials with conventional materials yield semi-auxetic materials. Ideally, layered structures where facing materials are metallic sheets sandwiching polymeric foam cores are popular. The auxetic materials can be combined with conventional materials to obtain P-N-P and N-P-N semi-auxetic sandwiched structures with diverse potential in several applications like automotive, aerospace, sports equipment, and protective armors.

Electrical, thermal and electro-magnetic analyses of a 100 kHz interleaved power electronic transformer

2023-04-11T10:42:32+00:00

In this paper, the finite element electrical, thermal and electro-magnetic analysis of an interleaved power electronic transformer structure operable at 100 kHz is presented. The analysed power electronic transformer structure is modelled with an EE-shaped core and interleaved primary and secondary windings. Electromagnetic analysis was done on the structure to study its properties like magnetic flux density, magnetic field, current density and relative permeability. Electrical and thermal analysis was done on the transformer to study its operating efficiencies and losses in isolation, buck and boost working modes. The analyses were done for different frequencies to ascertain that 100 kHz is the better choice of frequency for the designed power electronic transformer. The results are compared to a non-interleaved power electronic transformer structure to study the improvement obtained in the interleaved model. It was seen that transformer efficiencies of about 99 % could be obtained on using interleaved winding technique rather than non-interleaved method. Finite element modelling software-Altair FLUX was used to simulate the transformer and analytic equations were used to verify the obtained results.

Potential use of recycled cork as aggregates for lightweight self-compacting concrete production

2023-06-28T14:04:50+00:00

This work questions the possibility of using expanded black cork aggregates (EBCA), for the production of lightweight self-compacting concrete. Five concrete mixtures were tested: concrete made entirely with natural aggregate as a control concrete and four concrete mixtures made with cork recycled aggregate (5, 25, 50 and 75% replacement in volume of natural aggregate). The estimation of the success of the formulations was judged by studying the properties of concrete in the fresh state by the slump flow, T₅₀₀, L-box and the sieve stability tests. In the hardened state, the properties of the concrete produced have been determined by compressive and flexural strengths and bulk density tests. The experimental results showed that as the replacement level of natural aggregates by EBCA increased, the flowability of the concrete decreased. However a good flowability was obtained for concrete mixtures containing EBCA until 50%, satisfying the recommendations of self-compacting concrete given by EFNARC 2002. The obtained results indicate the possible use of EBCA for the production of lightweight self-compacting concrete, the replacement of 50% of natural aggregates by EBCA allows obtaining a formulation which corresponds to a lightweight self-compacting concrete with a density of 1750kg/m³ and a compressive strength of 8MPa. The experimental results showed that as the replacement level of natural aggregates by EBCA increased, the flowability of the concrete slightly decreased. However a good flowability was obtained for all mixtures, satisfying the recommendations of self-compacting concrete given by EFNARC 2002. The results obtained suggest a possible use of expanded black cork aggregates for the production of lightweight self-compacting concrete. The replacement of 50% of natural aggregates by cork aggregates allows obtaining a formulation which corresponds to a lightweight self-compacting concrete with a density of 1750kg/m³ and a compressive strength of 8MPa.

Comparison of the nanoindentation results of two generation of powder metalurgy produced materials for plastic industry

2023-04-05T12:19:13+00:00

In this article properties and nanoindentation characteristics of stainless PM steels M390 Microclean® and M398 Microcelan® are investigated. As a first part the literature sources about PM steels, stainless steels and thermo chemical treatment were studied to collect information about the problems which can be found out during the thermal or thermo chemical treatment of M390 and M398 for improvement of their mechanical and anticorrosion properties. The optical microscopy of both materials is presented to show the structure and get more complex picture about them. Main reason of this article – nanoindentation was performed on Hysitron Triboindenter TI 950. For both samples 7 indentation points were chosen on the SPM scan – 4 for carbides and 3 for basic matrix. Based on results the nanohardnes H and reduced modulus of elasticity Er, the reduced modulus of elasticity of phases ES was counted. Nanohardnes H of matrix matches with Ferrite what confirmed the information from material producer. Nanohardnes of carbides is equal to results from other tested material from CEDITEK.

Total loss torque waveform estimation for a turbocharged diesel engine

2023-04-24T11:55:52+00:00

The indicated (gas) torque is a key parameter for reciprocating engine. It reports on various aspects of the engine, such as the quality of the combustion process, the fuel combustion rate and the average effective pressure. This is a good indicator of the stability of the engine at work. The form of the instantaneous indicated torque is precious information for the control and diagnosis of the engine. The study of the simulation of crankshaft dynamics illustrates the need to know the total loss torque (i.e. the addition of friction torque, auxiliary torque and load torque) to achieve the indicated torque. To date, it has proven difficult to obtain an accurate predictive expression of the instantaneous total loss torque. This expression includes adequate simulation of friction of all moving parts of the engine (piston ring and skirt, crankshaft bearings, valve gear...), auxiliaries and load. Based on experimental results conducted on a four cylinders turbocharged diesel engine, this work offers a simple and practical solution for estimating the total torque loss. The proposed method makes it possible to successfully estimate total torque losses under a wide range of engine operating conditions. The result prediction has been confronted to experimental data.

Spatial distribution and characterization of consumers of E-grocery services in sicily: Insights for sustainable urban logistics

2023-08-28T12:09:32+00:00

The present research aims to provide new insights into e-commerce patterns. The study investigates the correlations between variables related to demographics, residence and online food and beverage purchasing habits. Data was acquired through the administration of an online questionnaire during 2022. The results helped identify the location of the city most
affected by the analysed phenomenon. The novelty of the research focused on the analysed area of island type characterised by the strong food and wine traditions and the need to want to analyse what possible effects the growth in demand for e-grocery may have on certain parts of the city.
The results obtained make it possible to lay the foundations for deeper studies on the demand for E-grocery relative to an island context and make it possible to investigate in subsequent steps different types of correlations between socio-demographic and spatial variables connected to the dislocation of homes and the main poles of attraction for the purchase of physical and virtual food and drink markets.

Prediction models for manganese, iron and ammonium in raw water for a drinking water treatment plant Butoniga (Croatia)

2023-07-21T12:21:24+00:00

Drinking water treatment plant Butoniga is one of the main water supply facilities for potable water in Istria (Croatia). Water for treatment process is captured from the Butoniga reservoir which is a small and relatively shallow reservoir. As such, reservoir is very sensitive to eutrophication and degradation processes caused by climate change and human activities in surrounding watershed. In summer months during tourist season, when water production is the highest and the reservoir water level is the lowest, the water temperature is the most critical parameter during treatment process. Because of this, to capture colder water, raw water for treatment is captured from the lowest water intake which captures water from the lowest water layer in the Butoniga reservoir. This layer have another problem, which are increased concentrations of manganese, iron and ammonium under lower pH values. Regarding this, prediction models seven days in advance were made for manganese, iron and ammonium, which are some of the most critical parameters during summer months and have significant influence on treatment process of raw water. For modelling purposes, machine learning software Weka was used to build models in form of model trees. Obtained prediction models for manganese, iron and ammonium have high accuracy compared to the measured data with a good prediction of the peak values. Therefore, obtained models can help in optimization of treatment processes on treatment plant which are depending on the quality of raw water in Butoniga reservoir.

Performance of PLL based DSGCPS and fll controlled ssgcps under normal condition and different grid faults: a comparative study

2023-06-30T08:31:03+00:00

This paper presents two separate studies to address the increasing need for renewable energy sources in the grid to cope with the rising energy consumption. Firstly, a Double Stage Grid Connected Photovoltaic System (DSGCPS) based on Phase Locked Loops (PLL) is developed using Matlab-Simulink. Secondly, a model of a single-stage grid-connected photovoltaic system (SSGCPS) controlled by a frequency locked loop (FLL) is created with comparable environmental parameters and a loading pattern. The research compares the active and reactive power flow dynamics and DC link voltage fluctuations of both systems. Results indicate that the SSGCPS is the preferred option due to its lower hardware requirements. However, it has a lower performance in cases of grid faults compared to DSGCPS. Moreover, the study analyzes the Total Harmonic Distortion (THD) of both models, a crucial factor for performance analysis. The comparative study shows that DSGCPS performs better than SSGCPS during fault in terms of THD. In conclusion, it can be inferred that both models have unique advantages and disadvantages, which are contingent on specific operating conditions.

Adaptive shoot-through duty ratio control methodology of stand-alone quasi Z-source inverter

2023-06-30T08:36:18+00:00

This paper presents an adaptive shoot-through duty ratio control methodology for a stand-alone three-phase quasi-Z-source inverter (qZSI). In practice, variable active and reactive load powers must be met by a qZSI-based stand-alone system. In this context, existing shoot-through control schemes for qZSI adjust the capacitor voltage or DC-link voltage at a fixed reference value. This causes extra voltage stresses on switches, high distortions, and an operating range reduction of the power inverter under variable load demands. On the contrary, the proposed shoot-through control scheme adjusts the shoot-through duty ratio adaptively based on load voltage feedback to improve performances. In this logic, the controllable shoot-through duty ratio facilitates various improved features in comparison to conventional schemes under load power variations. These features include reduced voltage stress across the switches, reduced distortions, and an extended operating range. The suggested proportional-integral (PI)-based scheme has a single control loop with a single measured quantity, i.e., sensing of load voltage only. The proposed concept has been verified via both simulation and experimental studies.

Optimal design of wind energy generation in electricity distribution network based on technical-economic parameters

2023-06-30T09:02:36+00:00

To satisfy the electricity customers and avoid some environmental constraints and issues, the transition towards renewable energy sources became more crucial, given its merits and advantages, such as mitigating pollution and enhancing the reliability of the targeted distribution system. This paper uses different recent metaheuristic optimization algorithms to address the optimal setting and sizing of Wind Turbine Generator (WTG) units when connecting to Electricity Distribution Network (EDN). The chosen algorithms have been implemented to optimize and minimize a Multiple-Objective Function (MOF), which is considered the sum of the techno-economic parameters of the Total Active Power Loss (TAPL), the Total Voltage Deviation (TVD), and the Investment Cost of WTG (IC_WTG), when taking into consideration the daily uncertainties and variations of the load-sources powers. The effectiveness of the selected algorithms was validated on the two standard test systems of IEEE 33-bus and 69-bus. The simulation results in this paper revealed the superiority of the Gorilla Troops Optimizer (GTO) algorithm compared with other new metaheuristic optimization algorithms in terms of providing the best-optimized results. Accordingly, the GTO algorithm showed excellent effectiveness and robustness in identifying the optimal setting and sizing of the WTG units into EDN. Hence, mitigating the daily active power losses until 1.415 MWh for the first test system and 1.072 MWh for the second one, also improving the bus voltage profiles while providing a favourable investment cost of the installed WTG units, all simultaneously with daily uncertainties for load demand and WTG power variation.