ENP Engineering Science Journal

A review of Stall Delay Models and their Application on Hybrid Methods

2022-04-23T13:51:02+00:00

This paper is a review on the stall delay phenomenon that Horizontal Axis Wind Turbines (HAWT) encounter under typical flow conditions and its numerical modelling. Aerodynamic performance predictions of HAWT have been often carried out through Computational Fluid Dynamics method with the combination of the concept of actuator disk i.e. hybrid method. For this purpose, the hybrid method is presented in details together with the numerical modelling of such stall delay phenomenon. Despite modern wind turbines are equipped with sophisticated control systems for avoiding stall, nevertheless, stall is still inevitable in the near root region of the rotor blade. This paper focuses on recent research development materials which have been undertaken on the stall delay phenomenon where the engineering models (stall delay models) of the literature being presented and criticized based on the predictions obtained from the NREL Phase VI wind turbine experiments.

Speed estimation of a Doubly Fed Induction Machine controlled by a Field Oriented Control Strategy

2022-11-21T15:17:17+00:00

This paper studies the estimation problem of speed in a Doubly Fed Induction Machine (DFIM) controlled by a Field Oriented Control (FOC) Strategy. The DFIM is the most responsive in variable speed. The chosen configuration uses two voltage inverters connected to the stator and rotor windings, to adopt the power distribution between them through the pulses distribution of the stator and the rotor in motor operating mode. It is necessary to model the DFIM in three-phase equations and then in two-phase equations faithfully representing the characteristics of the machine. From this model, we can design and simulate the control. The control by oriented rotor flux can be realized by using the speed provided by sensors or estimators. In this paper, we have used the Extended Kalman Filter (EKF) in order to avoid problems caused by the motor speed sensor and improve the robustness of the control and its performance without using any speed sensor.

Production of hydrogen and carbon nanofilaments using a novel reactor configuration: hydrodynamic study and experimental results

2022-11-27T08:14:38+00:00

A novel reactor configuration combining two beds, a central fluidized bed and an annular mobile bed, was designed for the production of hydrogen and carbon nanofilaments via dry reforming of gases produced from the pyrolysis of plastic waste. This combination allows for easy recovery of these nanomaterials and, since the mixture of catalyst and carbon formed is continuously fluidized, it also prevents blockage. Understanding the hydrodynamics is crucial for choosing the optimal operating conditions. Thus, a cold mock-up unit of the same size has been built and used. Since the gases produced by plastic pyrolysis are mainly composed of unsaturated hydrocarbons, the prototype reactor setup has been operated using ethylene as a surrogate molecule. The preliminary experimental results of the reactor operation with ethylene obtained so far are very promising and confirm the operability of the process. Next step is to operate continuously for longer time and reach a production of 1kg/h of carbon nanofilaments.

Microstructural, Mechanical and Electrochemical Characterization of a Flame Sprayed NiFeCrBSi/WC Cermet Coating

2022-12-02T08:32:54+00:00

To increase the lifetime of drilling bits, these components are usually covered with hard metal matrix composites. Nowadays, nickel based metal matrix composites arise as substitutes to cobalt-based ones. The challenge now is to provide an efficient coating with low cost. The aim of this paper is to exploit the characteristics of a newly designed flame sprayed NiFeCrBSi-WC composite coatings. The experimental activities were carried out using the scanning electron microscopy, for the microstructural analysis of coating. Additionally, micro-hardness and nano-indentation tests were carried out to evaluate the resistance of the coatings against penetration. Moreover, the electrochemical behavior was assessed in NaCl and Na₂SO₄ aqueous solutions. The ionic concentrations were varied between 1 g/l to 35 g/l. The results show that the microstructure is dendritic and characterized by the presence of hard chromium carbides and nickel grains in the inter-dendritic space. The coating was subject to a slight decarburization. The presence of carbides and the decarburization make the microhardness of the matrix fluctuates between 300 HV to 900 HV. For the electrochemical response, the increase in ion concentration induces a decrease in the corrosion resistance. In Na₂SO₄ aqueous solutions, the charge transfer is roughly constant for the concentrations above 1 g/l.

Mesophilic anaerobic co-digestion of cheese whey with cow manure in batch reactor

2022-11-21T15:26:14+00:00

Anaerobic digestion is a biological process that takes place under very strict operating conditions, including a pH close to neutrality. This experimental work aims to study the effect of pH control on CH₄ production in mesophilic anaerobic co-digestion of cheese whey with cow manure. Two experiments were conducted in batch reactor, the first without pH adjustment and the second with pH adjustment. The results of the first co-digestion revealed an inhibition of the methanization process by acidification of the medium and accumulation of volatile fatty acids; whereas during the second co-digestion with pH adjustment by sodium bicarbonates (1M), the process was improved with methane levels (> 50%) in the biogas. The accumulated biogas volume was two times higher for the same operating time in the digester.

Survey and Classification of Hybrid GMPPT Techniques for Photovoltaic System under Partial Shading Conditions

2022-12-05T12:35:26+00:00

A maximum power point tracking process is a very important task to harvest the maximum power available from a photovoltaic generator. For this reason, resorting to the development of new and more effective methods is an absolute necessity. Numerous advanced methods have been successfully employed to extract the real maximum point, such as neural networks and metaheuristic techniques. These techniques deal effectively in such conditions. However, the use of the algorithm alone has some limitations. In order to solve these drawbacks, the combination of two or more different techniques provides more advantages over single MPPT algorithms and improves the performance of the overall system. This paper mainly focus in reviewing the most important and recent hybrid global MPPT techniques proposed in the literature and proposes a classification of these methods with a comparison of their performances. All surveyed hybrid GMPPT methods are divided into four categories according to algorithms types involved in the MPPT method. This review study intends to make it easier for the user to make the convenient selection of which method to adopt especially in the presence of a variety of methods which are continuously developing in the literature. For this reason, resorting to the development of new and more effective methods is an absolute necessity to avoid the aforementioned problems. In the same context, numerous advanced methods have been successfully employed to extract the real maximum point, such as neural networks and metaheuristic techniques. These techniques deal effectively in such conditions. However, the use of the algorithm alone has some limitations. In order to solve these drawbacks, the combination of two or more different techniques provides more advantages over single MPPT algorithms and improves the performance of the overall system. This paper mainly focus in reviewing the recent hybrid global MPPT techniques proposed in the literature and proposes a classification of these methods with a comparison of their performances. All surveyed hybrid GMPPT methods are divided into four categories according to algorithms types involved in the MPPT method. This review study intends to make it easier for the user to make the convenient selection of which method to adopt especially in the presence of a variety of methods which are continuously developing in the literature.

Objective Evaluation of the Pathological Voice Based on Deep Learning Neural Networks in an Algerian hospital environment

2022-11-30T08:49:18+00:00

In this study, we propose a method based on Recurrent Neural Networks, to objectively evaluate the process of rehabilitation of the pathological voice, in an Algerian clinical environment. We choose Unilateral Laryngeal Paralysis as the pathology of the voice. In this paper, we used a Deep Learning system of pathological voice detection by Long Short Term Memory neural model (LSTM). As the dysphony studied in our work concerns essentially the laryngeal vibration, we choose the acoustic parameters based on the instability of the frequency and the amplitude of the laryngeal vibration: Jitter and Shimmer, Noise parameters and Cepstraux MFCC coefficients (Mel Frequency Cepstral Coefficients). A pathological voice detection rate of 88.65% shows important results brought by the rehabilitation technique adopted in Algerian clinical setting. The exclusive and abusive use of hearing to evaluate the effect of speech rehabilitation in the Algerian hospital environment remains insufficient. It is important to correlate perceptual data with objective methods based on detection and classification methods by introducing relevant acoustic parameters, for an effective and objective management of vocal pathology assessment.

Breakout Stocks Identification using Machine Learning Approaches

2022-11-21T15:22:14+00:00

Stock market offers a platform for people to engage in trading. It contributes to the growth of nation. Decision making regarding investments needs to be done very carefully so that an investor does not suffer massive loss. Since the share market is susceptible to experience huge change at any given moment, with the probability of profit comes huge risks of losing a fortune. In our research, we have worked on prediction of breakout stocks. If identified properly, it can help one to invest efficiently. We have used multiple machine learning approaches as ML models can offer more effective predictions compared to other methods due to the ability to learn and adapt from dataset information. In our experiment, the models have yielded very good results.

An Overview on the Recent Advances of the Voltage Source Converter Control Modes in Terms of their Roles in Transmission Grid Ancillary Services

2022-10-14T14:53:52+00:00

Voltage Source Converters (VSC) are expected to be one of the major actors in future AC transmission grids. Their role includes the interconnection of renewable energy, from distributed sources such as residential PV to large Offshore Wind Farms (OWF) using HVDC. With the ongoing decommissioning of traditional power plants with their synchronous generators, VSCs must now bring support functions to the grid. The aim of this paper is to review the different grid services that can be achieved through VSCs and discuss their compatibility with the state-of-the-art VSC controls especially the so-called grid-following and grid-forming controls. After presenting the upcoming issues of future grids and classifying the main VSC controls, this paper deals with the different additional control laws which make it possible to support the AC grid. Some recommendations regarding future grid services classifications and power and energy requirements are given. A comparative table is also proposed to assess the role of the different control modes.

Beneficiation of Oolitic Iron Ore Sourced from Gara Djebilet using Coal-Based Direct Reduction prior to Magnetic Separation

2022-12-20T08:41:06+00:00

A process involving coal-based direct reduction followed by wet low-intensity magnetic separation is presented in this paper with the objective of promoting the Fe content and reducing the P assay of phosphorus-rich oolitic iron ore. A final direct reduced iron powder assaying 92.5 wt% Fe and 0.2wt % P at a recovery rate of 95.9% was obtained when a mixture of ore-coal-CaO was reduced at 1200°C during 60 min in the presence of 7.5% sodium sulfate. In addition, microscopic analyses reported that the oolitic texture was completely destroyed, and most of the iron occurred in the metallic state. These findings suggest the ease utilisation of the ore mined from Gara Djebilet in the steelmaking industry as a substitute to scrap steel in electric arc furnace.