SIMULASI PERFORMA AERODINAMIKA NACA 1408 PADA APLIKASI TURBIN ANGIN DENGAN VARIASI PANJANG GURNEY FLAP

Airfoil merupakan bagian dari turbin angin yang memiliki fungsi untuk mengubah energi angin menjadi gaya. Performa aerodinamika airfoil akan mempengaruhi efisiensi turbin angin secara keseluruhan. Salah satu cara untuk meningkatkan performa aerodinamika airfoil adalah dengan menambahkan gurney flap (GF). Pada penelitian ini dilakukan simulasi airfoil NACA 1408 dengan penambahan GF yang panjangnya divariasikan antara 0,12-0,21%c pada sudut serang 0o. Hasil simulasi dengan software Simflow menunjukkan bahwa nilai Cl/Cd tertinggi dihasilkan pada panjang GF 0,18%c yaitu sebesar 20,185. Selain nilai Cd, Cl, dan Cl/Cd, juga dihasilkan visualisasi distribusi kecepatan dan tekanan udara yang melewati airfoil. Dari hasil visualisasi tersebut terlihat bahwa hasil simulasi sesuai dengan Hukum Bernoulli, yaitu kecepatan bagian bawah airfoil lebih rendah dari bagian atasnya, yang mengakibatkan tekanan bagian bawah lebih tinggi dari bagian atasnya, sehingga menghasilkan gaya angkat (lift force). Kata kunci: Turbin angin, airfoil, NACA 1408, simulasi, Cl/C

Protection of Future Electricity Systems

The electrical energy industry is undergoing dramatic changes: massive deployment of renewables, increasing share of DC networks at transmission and distribution levels, and at the same time, a continuing reduction in conventional synchronous generation, all contribute to a situation where a variety of technical and economic challenges emerge. As the society’s reliance on electrical power continues to increase as a result of international decarbonisation commitments, the need for secure and uninterrupted delivery of electrical energy to all customers has never been greater. Power system protection plays an important enabling role in future decarbonized energy systems. This book includes ten papers covering a wide range of topics related to protection system problems and solutions, such as adaptive protection, protection of HVDC and LVDC systems, unconventional or enhanced protection methods, protection of superconducting transmission cables, and high voltage lightning protection. This volume has been edited by Adam Dyśko, Senior Lecturer at the University of Strathclyde, UK, and Dimitrios Tzelepis, Research Fellow at the University of Strathclyde

Modelling of the thermal chemical damage caused to carbon fibre composites

Previous investigations relating to lightning strike damage of Carbon Fibre Composites (CFC), have assumed that the energy input from a lightning strike is caused by the resistive (Joule) heating due to the current injection and the thermal heat ux from the plasma channel. Inherent within this statement, is the assumption that CFCs can be regarded as a perfect resistor. The validity of such an assumption has been experimentally investigated within this thesis. This experimental study has concluded that a typical quasi-isotropic CFC panel can be treated as a perfect resistor up to a frequency of at least 10kHz. By considering the frequency components within a lightning strike current impulse, it is evident that the current impulse leads predominately to Joule heating. This thesis has experimentally investigated the damage caused to samples of CFC, due to the different current impulse components, which make up a lightning strike. The results from this experiment have shown that the observed damage on the surface is different for each of the different types of current impulse. Furthermore, the damage caused to each sample indicates that, despite masking only the area of interest, the wandering arc on the surface stills plays an important role in distributing the energy input into the CFC and hence the observed damage. Regardless of the different surface damage caused by the different current impulses, the resultant damage from each component current impulse shows polymer degradation with fracturing and lifting up of the carbon fibres.This thesis has then attempted to numerically investigate the physical processes which lead to this lightning strike damage. Within the current state of the art knowledge there is no proposed method to numerically represent the lightning strike arc attachment and the subsequent arc wandering. Therefore, as arc wandering plays an important role in causing the observed damage, it is not possible to numerically model the lightning strike damage. An analogous damage mechanism is therefore needed so the lighting strike damage processes can be numerically investigated. This thesis has demonstrated that damage caused by laser ablation, represents a similar set of physical processes, to those which cause the lightning strike current impulse damage, albeit without any additional electrical processes.Within the numerical model, the CFC is numerically represented through a homogenisation approach and so the relevance and accuracy of a series of analytical methods for predicting the bulk thermal and electrical conductivity for use with CFCs have been investigated. This study has shown that the electrical conductivity is dominated by the percolation effects due to the fibre to fibre contacts. Due to the more comparable thermal conductivity between the polymer and the fibres, the bulk thermal conductivity is accurately predicted by an extension of the Eshelby Method. This extension allows the bulk conductivity of a composite system with more than two composite components to be calculated. Having developed a bespoke thermo-chemical degradation model, a series of validation studies have been conducted. First, the homogenisation approach is validated by numerically investigating the electrical conduction through a two layer panel of CFC. These numerical predictions showed initially unexpected current flow patterns. These predictions have been validated through an experimental study, which in turn validates the application of the homogenisation approach.The novelty within the proposed model is the inclusion of the transport of produced gasses through the decomposing material. The thermo-chemical degradation model predicts that the internal gas pressure inside the decomposing material can reach 3 orders of magnitude greater than that of atmospheric pressure. This explains the de-laminations and fibre cracking observed within the laser ablated damage samples. The numerical predictions show that the inclusion of thermal gas transport has minimal impact on the predicted thermal chemical damage. The numerical predictions have further been validated against the previously obtained laser ablation results. The predicted polymer degradation shows reasonable agreement with the experimentally observed ablation damage. This along with the previous discussions has validated the physical processes implemented within the thermo-chemical degradation model to investigate the thermal chemical lightning strike damage

Investigation of lightning attachment characteristics of wind turbine blades with different receptors

Wind power generation system is one of the most important components of new energy power system. However, lightning disasters seriously threaten the safe and stable operation of wind turbine blades. In order to protect wind turbine blades from lightning, different types of lightning receptors are developed. In this paper, lightning discharge experiments of wind turbine blades are carried out to study the lightning protection effects of tip, side, and metal mesh receptors. The lightning discharge processes of wind turbine blades with different receptors are observed and the lightning protection failure rates are recorded. Electric field simulations have been done to analyze the lightning discharge mechanism and discuss the lightning protection optimization methods of wind turbine blades, which can give references for the lightning protection design of wind power generation system

Numerical and Experimental Study of Lightning Stroke to BIPV Modules

Building Integrated Photovoltaic (BIPV) modules are a new type of photovoltaic (PV) modules that are widely used in distributed PV stations on the roof of buildings for power generation. Due to the high installation location, BIPV modules suffer from lightning hazard greatly. In order to evaluate the risk of lightning stroke and consequent damage to BIPV modules, the studies on the lightning attachment characteristics and the lightning energy withstand capability are conducted, respectively, based on numerical and experimental methods in this paper. In the study of lightning attachment characteristics, the numerical simulation results show that it is easier for the charges to concentrate on the upper edge of the BIPV metal frame. Therefore, the electric field strength at the upper edge is enhanced to emit upward leaders and attract the lightning downward leaders. The conclusion is verified through the long-gap discharge experiment in a high voltage lab. From the experimental study of multi-discharge in the lab, it is found that the lightning interception efficiency of the BIPV module is improved by 114% compared with the traditional PV modules. In the study of lightning energy withstand capability, a thermoelectric coupling model is established. With this model, the potential, current and temperature can be calculated in the multi-physical field numerical simulation. The results show that the maximum temperature of the metal frame increases by 16.07 °C when 100 kA lightning current flows through it and does not bring any damage to the PV modules. The numerical results have a good consistency with the experimental study results obtained from the 100 kA impulse current experiment in the lab