Energetika最新文献

{"title":"The use of numerical method in an electric grid coupled to a wind farm to compare different kinds of flexible AC transmission systems","authors":"Mimi Belatel","doi":"10.6001/energetika.v68i1.4863","DOIUrl":"https://doi.org/10.6001/energetika.v68i1.4863","url":null,"abstract":"The PSAT software was used in this study to analyse and compare the performance of hybrid compensators such as SSSC-STATCOM (controllers), TCSC-SVC (compensators), and UPFC in an electric grid coupled to a wind farm. The flexible AC transmission system (FACTS) technology is used to provide a continual power flow and to provide new ways to control the electric system network. In the FACTS devices, the UPFC (Unified Power Flow Controller) is one of the most adaptable, flexible, and complicated power electric devices. The active and reactive power flows and the local voltage on the bus can be regulated by UPFC; it can also resolve the problem of harmonics. The TCSC (Thyristor-Controlled Series Capacitor) consists as a series-compensating capacitor shunted by a thyristor-controlled reactor. The SVC (Static Var Compensator) is the first shunt generation FACTS controller. We can observe that the UPFC controller has an effective power flow control, shorter setting time and a shorter overshoot. The UPFC obtained a well-known reputation for high controllability in power systems. The multilevel Unified Power Flow Controller can be operated in Static Synchronous Compensator (STATCOM), in Static Synchronous Series Compensator SSSC and exactly in the UPFC compensator. The results of this research compare the hybrid controllers and investigate the effects of TCSC-SVC, SSSC-STATCOM, and UPFC on voltage, phase angle stability, and the active and reactive power in the tested system. The purpose of this comparison is to improve dynamic voltage regulation, especially when the utilisation of nonlinear loads and the presence of fault and breaker rise. These hybrid controllers have been shown to outperform series or shunt compensators; however, when compared to hybrid compensators SSSC-STATCOM, TCSC-SVC, and UPFC, the results employing the numerical method in the UPFC are more significant. The UPFC is the best hybrid controller in this study, and the compensators SSSC-STATCOM outperform the controllers TCSC-SVC.","PeriodicalId":35639,"journal":{"name":"Energetika","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43572684","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Vibration analysis for the detection of combined mechanical defects of a wind turbine","authors":"Issam Harida, A. Bouras, Rabah Boudiaf","doi":"10.6001/energetika.v68i1.4860","DOIUrl":"https://doi.org/10.6001/energetika.v68i1.4860","url":null,"abstract":"Wind energy is a source of renewable energy derived from the kinetic force of the wind. It has experienced the greatest expansion due, above all, to its low impact on the environment and the gradual reduction of costs, which produce clean, competitive and economically viable energy. In order to ensure the stability of the energy produced, many studies are working to develop a reliable maintenance process based on new online diagnostic techniques, fast and accurate, optimised for wind turbine systems. For this, an experimental study was carried out on a wind system based on electric generators with the aim of contributing to the diagnosis and predictive detection of combined mechanical faults, where the configuration is complex because one fault can hide another. For this, it is imperative to associate each symptom with the appropriate method or methods in order to highlight it unambiguously to detect each defect at the appropriate time. Hence the interest in using more elaborate techniques in order to improve the procedures for detecting and analysing combined faults.","PeriodicalId":35639,"journal":{"name":"Energetika","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48877297","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Prediction of effective heat transfer coefficients for vapour condensation inside horizontal tubes in stratified phase flow","authors":"V. Sereda, V. Rifert, V. Gorin, P. Barabash","doi":"10.6001/energetika.v68i1.4861","DOIUrl":"https://doi.org/10.6001/energetika.v68i1.4861","url":null,"abstract":"In modern condensers of air conditioning systems, heat pumps, evaporators of seawater desalination systems, and heaters of power plants, the process of vapour condensation is carried out mainly inside the horizontal tubes and channels. Heat transfer processes occurring in condensers have a significant effect on the overall energy efficiency of the mentioned systems. In this paper, the experimental investigation of heat transfer during condensation of freons R22, R406a, and R407c in the plain smooth tube with d = 17 mm were carried out with the following parameters: ts = 35–40°C, G = 10–100 kg/(m2s), x = 0.8–0.1, q = 5–50 kW/m2, ΔT = 4–14 K. The unique measurements of circumferential heat fluxes and heat transfer coefficients were carried out with the thick wall method during different condensation modes. It can be inferred that with the increase of the heat flux, at the top part of the tube the thickness of the condensate film increases, which leads to the decrease in heat transfer. At the bottom of the tube, the increase in the heat flux enhances heat transfer coefficient, that is characteristic of the turbulent liquid flow in the tube. The obtained results allowed improving the prediction of effective heat transfer coefficients for vapour condensation, which takes into account the influence of condensate flow in the lower part of the tube on the heat transfer. This method generalises with sufficient accuracy (error ± 30%) the experimental data on condensation of freons R22, R134a, R123, R125, R32, R410a, propane, isobutene, propylene, dimethyl ether, carbon dioxide, and methane under stratified flow conditions. Using this method for designing heat exchangers, which utilise such types of fluids, will increase the efficiency of thermal energy systems.","PeriodicalId":35639,"journal":{"name":"Energetika","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44356692","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Carbon burnout from the char of a single cylindrical pellet","authors":"Mykola M. Zhovmir","doi":"10.6001/energetika.v68i1.4852","DOIUrl":"https://doi.org/10.6001/energetika.v68i1.4852","url":null,"abstract":"In countries with limited wood fuel resources, the use of straw for energy should be increased to comply with environmental commitments. Boiler houses burning whole straw bales have limited application because of unfavourable straw logistics and obstacles to their construction in most densely built-up settlements. Straw pellets are more convenient for transportation and safer for storage. Boilers with pellet burning can be operated in fully automatic mode. However, burning straw pellets instead of wood pellets is complicated with increased ash content and lower ash melting temperature. Approaches for low-temperature burning of straw pellets at temperatures below the initial deformation temperature of their ash are of practical interest. At low temperatures, burning is slowing and incomplete burnout with energy loss is possible. The rate of burnout also depends on the form and dimensions of the particle. It was common to accept the rate of carbon burnout as uniform on the reacting surface of the particle. This work aimed to study the low-temperature carbon burnout from the char of the cylindrical pellets of various lengths and to estimate the energy loss with unburned carbon. The aim was achieved by the mathematical description of pellet char burning, in which the actual cylindrical char was regarded as the infinite cylinder intersecting with the endless plate. The burnout of fixed carbon was accepted as layered, the carbon burning fronts as infinitely thin, and different rates of carbon burning in radial and axial directions were accepted. An experimental study of the low-temperature burning of fixed carbon from the char of wood and straw pellets was conducted at free air access at 700°C in the furnace, i.e., the temperature around a single pellet was certainly lower than the possible initial deformation temperature of the pellet ash. The duration of carbon burnout from the char of single cylindrical pellets depending on their lengths was studied. The research findings are as follows. Equations in a dimensionless form, describing changes in the remaining share of unburned fixed carbon in pellet char in time, were deduced analytically. At the experimental burning of single straw pellets, loose particles of ash with no signs of melting formed, but they contained unburned carbon. The share of unburned fixed carbon in ash was 0.016–0.020. The coefficient of determination of calculated and experimental duration of complete burnout of fixed carbon from wood pellet char was R2 = 0.96, and R2 = 0.87–0.91 at incomplete burnout from straw pellet char. The most significant scientific result is that for long pellets, the fixed carbon burnout is controlled mainly by its slower burnout rate in the radial direction, and for the shortest pellets by more intensive burnout rate in the axial direction. The practical value of the results obtained is that the use of shorter pellets, which are characterised by faster burnout, may become purposeful for intensive combus","PeriodicalId":35639,"journal":{"name":"Energetika","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41371500","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Collector factor in a solar chimney power plant: CFD analysis for the pilot plant in Manzanares","authors":"E. Cuce, Harun Sen, Pinar Mert Cuce","doi":"10.6001/energetika.v68i1.4856","DOIUrl":"https://doi.org/10.6001/energetika.v68i1.4856","url":null,"abstract":"Solar chimneys are popular systems for their simple structures and clean energy generation. Thanks to its semi-permeable structure, the collector, one of the system’s basic elements, transfers solar radiation to the system. As a result of the heating of the system air under the collector by the solar radiation passing through the collector, it is directed to the high chimney in the collector centre. During the upward movement of the system air, it converts its energy into electricity via a turbine. Due to its large structure, estimating the amount of energy entering the collector system creates a great cost. The ideal size for the collector is therefore important. This study offers a recommendation for the ideal collector size for the pilot plant in Manzanares in terms of collector size and power output. While 59 kW power output is obtained with the system with a collector radius of 122 m in the reference case, it is observed that the power output increases by 78% when the collector radius is increased to 170 m and the collector area is doubled. The ratio of the ideal collector radius to the reference size for the pilot plant should be in the range of 1–1.5.","PeriodicalId":35639,"journal":{"name":"Energetika","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41648245","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Swirler geometry effects (dh/do ratio) on synthetic gas flames: Part 1: Combustion and emission characteristics","authors":"Harun Yilmaz, Omer Cam, I. Yilmaz","doi":"10.6001/energetika.v67i1.4535","DOIUrl":"https://doi.org/10.6001/energetika.v67i1.4535","url":null,"abstract":"Swirling flows increase combustion performance via favouring flame stability, pollutant emissions, and combustion intensity. The strength of a swirling flow is characterized by a parameter known as swirl number, which is highly related to the dh/do ratio. In this study, effects of the swirler dh/do ratio on combustion and emission characteristics of the synthetic gas flames of premixed 20%CNG/30%H2/30%CO/20%CO2 mixture were experimentally investigated in a laboratory-scale swirl stabilized combustor. For this purpose, twelve different swirl generators were designed and manufactured. dh/do ratios of these swirlers were set as 0.30 and 0.50, and the geometric swirl number was varied between the values of 0.4 and 1.4 (at 0.2 intervals). All experiments were conducted at a fuel-lean equivalence ratio (ϕ = 0.6), room temperature, and local atmospheric conditions of the city of Kayseri, Turkey. A data logger was utilized to plot axial and radial temperatures and NOx, CO, and CO2 profiles, which were exploited to assess combustion and emission performance. Results showed that the dh/do ratio had a non-monotonic effect on the behaviour of combustion and emission of the tested synthetic gas mixture. Depending on the swirl number, increments and decrements were observed in temperature and emission values.","PeriodicalId":35639,"journal":{"name":"Energetika","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45505717","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Lietuvos vandens telkinių antropogeninių pokyčių žalos vertinimas","authors":"Brunonas Gailiušis, Aldona Tomkevičienė, Aldona Jurgelėnaitė","doi":"10.6001/energetika.v67i1.4538","DOIUrl":"https://doi.org/10.6001/energetika.v67i1.4538","url":null,"abstract":"Straipsnyje nagrinėjamos ūkinės veiklos neteisėtų veiksmų sukeltos žalos hidroelektrinių vandens telkiniams, kaip kraštovaizdžio objektams, nustatymo problemos. Siūloma žalą upei, ežerui ar tvenkiniui skaičiuoti priklausomai nuo vandens telkinio vertės, kurią lemia teritorijos gamtosaugos tikslai, vandens telkinio dydis ir būklė bei pažaidos lygis. Paliekant galioti dabartinius žalos kraštovaizdžio kompleksams ir objektams nustatymo pagrindinius principus Lietuvoje, siūlome pasitelkti patikimus hidrografijos šaltinius, objektyvius, nuotoliniu būdu stebimus, hidrologijos rodiklius ir hidroenergetikos duomenis. Svarbiausias upės, ežero ar tvenkinio morfometrinis rodiklis yra vandens paviršiaus plotas, kuris nustatant žalą patikimai ir objektyviai paimamas iš upių, ežerų ir tvenkinių kadastro. Ežero (tvenkinio) vandens lygio ar upės debito pokyčiai dėl neteisėtos ūkinės veiklos stebimi nuotoliniu būdu ir registruojami. Skaičiuojant žalą, vietoje absoliučios vandens lygio pokyčių reikšmės siūlome vertinti pažeidimą santykiniu lygio arba debito pokyčiu, apskaičiuotu kaip neteisėto lygio ar debito pokyčio santykis su maksimaliu ežero (tvenkinio) gyliu arba atitinkamai reglamentuotu upės debitu. Toks santykinio pokyčio vertinimas atspindi esminį vandens telkinio režimo skirtumą tarp didelių bei gilių ir mažų bei seklių telkinių. Straipsnyje pasiūlyta žalos kraštovaizdžiui dėl neteisėtos ūkinės veiklos vandens telkiniuose vertinimo metodika, paremta objektyviais hidrologiniais ir morfometriniais rodikliais bei stebėjimų duomenimis.","PeriodicalId":35639,"journal":{"name":"Energetika","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44346841","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Swirler geometry effects (dh/do ratio) on synthetic gas flames. Part 2: dynamic flame behaviour at external y altered acoustic conditions","authors":"Harun Yilmaz, Omer Cam, I. Yilmaz","doi":"10.6001/energetika.v67i1.4536","DOIUrl":"https://doi.org/10.6001/energetika.v67i1.4536","url":null,"abstract":"In a combustion device, unsteady heat release causes acoustic energy to increase when acoustic damping (energy loss) is not that effective, and, as a result, thermo-acoustic flame instabilities occur. In this study, effects of the swirler dh/do ratio (at different swirl numbers) on dynamic flame behaviour of the premixed 20%CNG/30%H2/30%CO/20%CO2 mixture under externally altered acoustic boundary conditions and stability limits (flashback and blowout equivalence ratios) of such mixture were investigated in a laboratory-scale variable geometric swirl number combustor. Therefore, swirl generators with different dh/do ratios (0.3 and 0.5) and geometric swirl numbers (0.4, 0.6, 0.8, 1.0 1.2 and 1.4) were designed and manufactured. Acoustic boundary conditions in the combustion chamber were altered using loudspeakers, and flame response to these conditions was perceived using photodiodes and pressure sensors. Dynamic flame behaviour of respective mixture was evaluated using luminous intensity and pressure profiles. Results showed that the dh/do ratio has a minor impact on dynamic flame behaviour.","PeriodicalId":35639,"journal":{"name":"Energetika","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43307095","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"TG pyrolysis of a mixture of dried sludge from urban wastewater and wood pellets and identification of the composition of the resulting gases by infrared spectroscopy","authors":"G. Stravinskas, A. Šlančiauskas","doi":"10.6001/energetika.v67i1.4534","DOIUrl":"https://doi.org/10.6001/energetika.v67i1.4534","url":null,"abstract":"The recent tendency of sewage sludge disposal is targeted towards the gasification for heat generation in small towns far from waste incineration plants. The scope of this article is to present the investigation into the mixture of dried sewage sludge and wood pellets during pyrolysis by thermogravimetry (TG) with evolved gas analysis by TG-coupled Fourier transformation infrared spectroscopy (FTIR) method. The maximum intensity of mass loss of sewage sludge material occurs at 300–310°C temperature and it differs from wood cellulose case of 360°C. The 50:50% mixture of these materials was investigated in more details. Pyrolysis reaction kinetics is described by a variation of three constituent parts from TG data. Prefactor A and activation energy E of the Arrhenius law were found, and reaction order n was determined by the Ozawa method employing Avrami phase change. The maximum of gas evolution is always related to the most intense mass loss, and gas composition correlates with the initial material.","PeriodicalId":35639,"journal":{"name":"Energetika","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42442409","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Piezoelectric ceramic for energy harvesting from ambient vibration","authors":"M. Zarog","doi":"10.6001/energetika.v67i1.4537","DOIUrl":"https://doi.org/10.6001/energetika.v67i1.4537","url":null,"abstract":"Direct piezoelectric conversion is very popular in generating power from mechanical stress. There is continuous progress in power harvesting from mechanical vibration. In this article, experimental tests on a piezoelectric circular plate, to evaluate the electric power produced by the piezoelectric conversion at low acceleration over a wide range of ambient vibration frequency, are presented. The experimental analysis is presented and discussed. The results demonstrate the potentiality of using low-cost piezoelectric diaphragms to harvest energy from ambient vibration. Under low acceleration (5.36 m/s2), the vibration frequency was varied in the range of 10– 200 Hz and the generated power was measured. Under a very small dynamic force (less than 0.06 N), the output power of 1.5 mW was obtained with an 8.5 mm drum harvester across a load resistance of 17.8 kΩ at a frequency of 173 Hz.","PeriodicalId":35639,"journal":{"name":"Energetika","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48332387","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}