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  • Öğe
    (Gazi Universitesi, 2014) Karamangil, M. Ihsan; Yenice, Seckin; Kaynakli, Omer; Sürmen, Ali
    Oil film on cylinder liner has been suggested as a major source of engine-out hydrocarbon emissions. In this study, a mathematical modeling for the rate of absorption/desorption of the fuel in the oil film has been developed for gasoline, LPG and methane. It was seen that the absorption/desorption mechanism of LPG and methane into the oil film were lower than gasoline. It was determined that the most dominant parameter of this difference was Henry's constant, which was related to solubility. As interaction time of oil film-fuel vapor was longer at low engine speeds, the quantities of HC absorbed/desorbed increased. The quantities of HC absorbed/desorbed increased with increasing inlet pressure and compression ratio.
  • Öğe
    Mathematical modeling of hydrocarbon emissions from oil film for different fuels
    (Elsevier, 2014) Karamangil, M. Ihsan; Sürmen, Ali; Yenice, Seckin
    Oil film on the inner surface of the cylinder liner is one of the major sources of the vehicle-out HC emissions as fuel vapor is absorbed by the oil film under high pressure and then released after late expansion stroke when the pressure is low. This process is extensively affected by type of the fuel and lubricating oil. In this theoretical study, the effect of different engine parameters on oil film HC emissions for various fuels, such as iso-octane, methanol, ethanol, LPG and methane, is investigated. The results show that fewer HCs are released from the oil film when using gaseous fuels, such as LPG and methane, than when using liquid fuels. The fuels can be ranked according to their effect (from greatest to least) on HC emissions as follows: iso-octane, methanol, ethanol, LPG and methane. The most important parameters affecting the HC absorption/release mechanism are found to be Henry's coefficient and the diffusion coefficient. As interaction time of oil film-fuel vapor was longer at low engine speeds, the quantities of HC absorbed/desorbed increased. The quantities of HC absorbed/desorbed increased with increasing inlet pressure and compression ratio.
  • Öğe
    Enhancing the heavy load performance of a gasoline engine converted for LPG use by modifying the ignition timings
    (PERGAMON-ELSEVIER SCIENCE LTD, 2015) Erkus, Baris; Karamangil, M. Ihsan; Sürmen, Ali
    This paper presents the results of the experiments conducted on a spark-ignition (SI) engine fuelled with liquefied petroleum gas (LPG) by varying the ignition timing at the excess air coefficients of 1.0 and 1.3. Experiments were carried out at wide open throttle (WOT) position and at engine speed of 4300 rpm aiming to determine the lean operation performance of an engine when fuelled with LPG at full load. Performance parameters, namely brake power, brake-specific fuel consumption (BSFC), brake thermal efficiency and exhaust emissions such as unburned hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxides (NOx), were studied. It was shown that advancing the ignition timing improved the performance of LPG-fuelled SI engine for excess air coefficients higher than 0.8. The highest brake power and the lowest BSFC were obtained with modified ignition timing at an excess air coefficient of 1.0. The lowest exhaust emissions were obtained with an excess air coefficient of 1.3. In general, advancing the ignition timings caused increase in HC and NO emissions, while the effect of ignition timing on CO emissions was negligible.
  • Öğe
    Development of a variable-profile cam to enhance the volumetric efficiency of IC engines
    (INDERSCIENCE ENTERPRISES LTD, 2017) Sürmen, Ali; Arslan, Ridvan; Kopmaz, Osman; Avci, Atakan; Karagoz, Irfan; Karamangil, M. Ihsan
    In this study, it is aimed to develop a new concept camshaft for continuously variable valve timing (CVVT). The concept is based on obtaining a curvilinear cam surface by integrating a number of conventional cam contours. Thirteen unworked camshafts, with arbitrary different contours, i. e., valve opening and closing times, were machined and tested on a fourstroke single-cylinder diesel engine to determine their volumetric efficiency at varied engine speeds. Then with suitable axial arrangement of these individual contours on a camshaft and integration of them, a single curvilinear cam surface was obtained. It is expected to get the same volumetric efficiency, with a ball contact follower when it follows a specific contour, as obtained when the specific cam of the same contour individually yielded. By giving an axial motion to the camshaft, allowing the follower to follow different contours, continuous variation of valve timing will be achieved.
  • Öğe
    Optimal design of automobile structures using moth-flame optimization algorithm and response surface methodology
    (WALTER DE GRUYTER GMBH, 2020) Yıldız, Betül Sultan
    In order to present an integrated approach to optimal automobile component design, this research is focused on a shape optimization problem of a bracket using moth-flame optimization algorithm (MFO) and response surface methodology. First, the multiple disc clutch brake problem is optimized using the MFO. Finally, the design problem is posed for shape optimization of the bracket with a mass objective function and a stress constraint. Actual function evaluations are based on finite element analysis while the response surface method is used to obtain the equations for objective and constraint functions. Weight reduction of the bracket is 45.2 % using the MFO. The results show the ability of the MFO to optimize automobile components in the industry.
  • Öğe
    Numerical analysis of a reactivity controlled compression ignition engine
    (Elsevier Ltd, 2021) Görmez, Gonca; Ceper, Bilge Albayrak
    Nowadays, internal combustion engines have great importance due to the increasing need for vehicles. Since the engines in the vehicles cause air pollution, different combustion strategies are being tried more and more every day. Emissions are aimed to be reduced thanks to the reactivity controlled "compression ignition (RCCI) engine", which is one of the low temperature combustion strategies. In this study, Continental AVDS 1790-2A tank engine was numerically investigated for gasoline/diesel fuels at RCCI combustion mode. Ansys-Fluent and GT-Power programs were used for numerical analysis. Different lambda values (2.0, 2.5 and 3.0), different exhaust gas recirculation (EGR) values 0%, 30%, and 50% and different start of injection (SOI) timing (340 degrees, 345 degrees and 347 degrees CA) parameters were evaluated. In RCCI combustion mode values were obtained closest to the conventional diesel combustion pressure value at lambda = 2.5, EGR = 30% and SOI = 340 degrees CA.
  • Öğe
    Investigation of adhesive wear properties of glass fiber reinforced polyester composites having different chemical compositions
    (SAGE Publications Ltd, 2021) İlhan, Recep; Feyzullahoglu, Erol
    Glass fiber reinforced polyester composite materials are widely used in various areas due to their high specific strength, low weight, excellent elasticity, high corrosion resistance, and high thermal stability. This study aims to investigate the effects of resin materials and various fillers and wear parameters such as different loads and speeds on the tribological properties of glass fiber reinforced polyester composite materials. In this experimental study, various resins (tensile additive orthophthalic polyester and plain orthophthalic polyester), fillers (alumina and glass beads), and reinforcing materials were used during the sample preparation. The samples were subjected to an adhesive wear test at two different speeds (n = 100 r/min and n = 200 r/min) and different loads (F = 10 N and F = 20 N) at 150 m sliding distance. The friction coefficient and friction force were measured by the tribometer. The thickness of the wear trace was later measured and the wear rate was calculated. Wear surfaces of samples were visualized with a three-dimensional laser profilometer in order to obtain surface topographies and surface roughness values. The sample surfaces were examined by scanning electron microscopy in order to understand the wear mechanisms and to characterize the morphology of worn surfaces. Experimental results have shown that alumina or glass beads fillers can reduce the average friction coefficient when used in the correct amounts. The use of glass bead filler in orthophthalic polyester resin with tensile additive is more effective than reducing the wear rate compared to alumina filler. The load on the wear behavior of glass fiber reinforced polyester composite materials is more effective than the speed.
  • Öğe
    Estimation of adhesive wear behavior of the glass fiber reinforced polyester composite materials using ANFIS model
    (SAGE Publications Ltd, 2021) Yilmaz, Serhat; İlhan, Recep; Feyzullahoglu, Erol
    Glass fiber reinforced polyester (GFRP) composite materials are widely used in various applications. The prediction of wear values for composite materials is very complex and nonlinear phenomena. Artificial intelligence methods (AI) and expert systems such as artificial neural networks (ANNs) and fuzzy inference systems (FIS) have a series of properties on modeling nonlinear systems. In some situations, ANNs are insufficient under abrupt changes in input variables. Adaptive Neuro Fuzzy Inference System (ANFIS) is capable of integrating the linguistic expressions of FIS with the adaptation and learning skills of the ANNs. The aim of this study is to determine the optimum material content and working conditions in terms of wear resistance. This study proposes an ANFIS sub-clustering based prediction model for estimation of wear behavior of GFRP composites within various concentrations of materials and under diverse loads and speeds. Proposed ANFIS model extracted optimum concentrations and operating parameters to obtain the minimum wear rate. Due to the wear rate estimation model, optimum wear rate value is reached to 25.0013 (mm(3)/Nm)*10(-6) at CaCO3, polystyrene, glass fiber, glass bead, alumina, load and speed values of 49%, 0%, 11%, 10%, 0.8%, 10 N and 100 rpm respectively. A high estimation capability (R-2 = 0.964) has been achieved using ANFIS Model.
  • Öğe
    Pd, Ag and Rh doped (8,0) single-walled carbon nanotubes (SWCNTs): A DFT study on furan adsorption and detection
    (Elsevier, 2021) Yüksel, Numan; Köse, Ahmet; Fellah, Mehmet Ferdi
    In this study, the use of single-walled carbon nanotubes (SWCNTs) with doping Pd, Ag and Rh as both a sensor and an adsorbent for furan molecule was investigated by Density Functional Theory (DFT) method. The WB97XD method with 6-31G(d,p)/LanL2DZ basis sets have been utilized in theoretical calculations. The charge distribution indicates that the charge transfer happened (as an electron accepting system) from the adsorbed furan molecule to the Pd, Ag and Rh atoms of SWCNT structures. The HOMO-LUMO gaps of the Pd, Ag and Rh doped carbon nanotubes decreased slightly with adsorption of furan molecule. The electrical conductivities of Pd, Ag and Rh doped (8,0) SWCNT clusters increased somewhat after a furan molecule adsorption. Furthermore, adsorption enthalpies (-49.6 kJ/mol, -62.9 kJ/mol and -64.3 kJ/mol, respectively) of furan molecule adsorption on Pd, Ag and Rh doped (8,0) SWCNTs show that these materials have the ability to adsorb furan molecule. Consequently, Pd, Ag and Rh-doped SWCNTs might be used as both sensors and adsorbents for furan molecule at room temperature.
  • Öğe
    Solar process heat for sustainable production of concentrated peach puree
    (Blackwell Publishing Inc., 2021) Colak Gunes, Neslihan; Güngör, Emrah; Gunes, Mustafa
    The food industry is one of the most suitable sectors for solar process heat applications. Concentrating solar power (CSP) systems generate steam using mirrors or lenses to concentrate a large area of sunlight onto a receiver. In this study, how a CSP system connected hybrid to the boiler system can be utilized to produce more sustainable peach puree concentrate (PPC) have been examined. The amount of steam required for PPC production was calculated using the measurements rendered in a real fruit juice concentrate plant and the data obtained from them. A parabolic trough-type CSP system of 1 MWth was designed, which is placed in the area of the plant, and it was determined that the steam quantity obtained during the production period is able to meet how much of the current consumption. Also, it has been shown how much CO2eq emission reduction will be achieved by using CSP. Practical Applications: Concentrated fruit juice production is one of the thermal energy intense food processes. Therefore, utilization of renewable energy sources for process heat is very important. We designed a CSP system in this study with using production data from a real fruit juice factory. This CSP system is naturally applicable to both fruit juice and all food industry using steam at similar temperatures and pressures. Fossil fuels are one of the main responsible for global warming. For this reason, the use of solar thermal systems is promising to ensure sustainability in food production and reduce the environmental impacts of the product.
  • Öğe
    Investigation of the usage potential of the evacuated tube and the flat plate collectors to assist an absorption chiller
    (Elsevier Ltd, 2021) Düzcan, Ahmed; Kara, Yusuf Ali
    In this study, the usage potential of the evacuated tube collectors (ETCs) and the flat plate collectors (FPCs) for assisting an absorption chiller (AC) are comparatively investigated by using TRNSYS software. ETC and FPC are examined under different load conditions and scenarios to see if the collectors satisfy the required source temperature for an absorption chiller system (ACS) with LiBr – H2O pair. Daily and seasonal analyses are carried out. Daily analyses consist of three scenarios: both the auxiliary heater and the load are turned off in the first scenario while only the load is turned on in the second; both the auxiliary heater and the load are turned on in the third scenario that is also performed for summer season as a fourth scenario. The working fluid in all scenarios is a heat transfer fluid (HTF). In the third scenario at 250 kg/h load, the maximum collector outlet temperature is 113 °C and 99 °C, the daily solar fraction (SF) is 83% and 57%, the temperature to load is 106 °C and 86 °C for ETC and FPC, respectively. In the seasonal analysis, the seasonal SF is 81% and 20.19% at 250 kg/h load for ETC and FPC, respectively. Higher temperature and SF are obtained when HTF is used instead of water. It has been observed that the required source temperature for ACS can be provided with ETC.
  • Öğe
    Assessment of wind energy potential: a case study
    (Bellwether Publishing, Ltd., 2021) Düzcan, Abdullah; Kara, Yusuf Ali
    Utilization and investments of wind energy have been speedily rising in the world due to harmful side of the fossil fuels. Assessment of wind energy potential analysis is a must before making investment decision of wind farm. Due to high capacity factor of Aegean Sea, Gökçeada location is chosen for wind energy potential analysis. One year hourly measured wind velocity and direction data supplied by Turkish State Meteorological Service (TSMS) is used to assess the wind potential in the terrain. Two different approaches are used for the assessment, the former employs power-law method for calculating wind velocity field while the latter employs Windsim software based on Computational Fluid Dynamics (CFD) method. After calculating wind velocity field, Weibull method is used for energy analysis in both approaches. Results from each approach are compared. The roughness is attained at only two points that are measurement site and turbine site in power-law method while it is taken into account for the whole domain in CFD method. Besides, unlike CFD method, wind direction is not considered in power-law method. The velocity profile is calculated at the height of 60 m and considered the same everywhere depend on the roughness in power-law method. On the other hand, Windsim calculates velocity profile over the terrain in consideration by solving Reynolds-averaged Navier-Stokes (RANS) equations. In this assessment, seven Vestas V90 2 MW wind turbines are employed. According to the results of power-law method and CFD method, the capacity factor is calculated as 31.67 and 49.5%, respectively. Windsim results indicate that annual energy production (AEP) is 60.2 GWh/y regarding wake loss, and the shape factor ranges from 1.57 to 1.64 whereas scale factor ranges from 9.49 to 10.77 m/s for the locations of turbines. It is strongly advised to build a wind farm in Gökçeada location according to the results from the analysis.
  • Öğe
    An acoustic structure design supported by shear thickening fluid for sound absorption
    (Elsevier Ltd, 2021) Aslan, Ramazan; Turan, Osman
    In this study, an acoustic structure consisting of cellular and perforated panel absorbers has been designed to noise control. Then, the sound absorption behaviour of designed acoustic structure has been investigated experimentally by reinforcing with STFs having different rheological properties. In addition, the sound absorption performance of the designed acoustic structure has been compared with the Gyroid which is a type of cellular sound absorber. The findings have indicated that the perforated panel activates significantly the sound absorption performance of the designed acoustic structure especially in the low (f[removed]3500Hz) frequency ranges. In addition, it has been also observed that this effect becomes stronger with STF reinforcement and significantly improves the sound absorption behaviour of the designed acoustic structure. Besides, it has been noticed that the sound absorption performance of the designed acoustic structure increases with increasing molecular weight of PEG for low frequencies (i.e. f[removed]3500Hz). Finally, it has been detected that the effectiveness of STF on the sound absorption performance of designed acoustics structure improves remarkably with increasing silica-nanoparticle ratio in the case of low and high frequencies (i.e. f[removed]3500Hz).
  • Öğe
    Exergoeconomic and exergoenvironmental analysis of a coal-fired thermal power plant
    (Springer Science and Business Media Deutschland GmbH, 2021) Düzcan, Abdullah; Kara, Yusuf Ali
    When evaluating a thermal system, exergy analysis is performed in addition to energy analysis to determine the location and quantity of losses in the system. In this study, energy, exergy, exergoeconomic and exergoenvironmental analyses of Orhaneli thermal power plant located in Bursa are carried out. In exergy analysis, physical and chemical exergies are taken into consideration and potential and kinetic exergies are neglected. Exergoeconomic analysis is conducted by using specific exergy costing (SPECO) method and cost values corresponding to each exergy flows are calculated. According to exergoeconomic analysis, unit exergy cost and exergy cost of steam sent to high-pressure turbine are calculated as 17.94 $/GJ and 22,854 $/h, respectively. The highest exergoeconomic factor is measured in pump (P2) and followed by P3. For the life cycle assessment (LCA) analysis, eco-indicator 99 impact assessment method is selected. LCA results are transferred to exergy flows and then exergoenvironmental analysis is performed. Environmental impact per exergy unit and exergetic environmental impact rate of the steam sent to high-pressure turbine are calculated as 14,680 mPts/GJ and 18,700 Pts/h, respectively. The highest exergoenvironmental factor is measured in pump (P2) and followed by P3.
  • Öğe
    An Investigation of Thermal Comfort for Mold, Welding and Turning Technicians and the Effects on Performance in Naturally Ventilated Area
    (2019) Sökmen, Kemal Fürkan
    In this study, thermal comfort measurements were made for mold, welding, and turning technicians in naturally ventilated industrial establishments. Metabolic rates were determined as 100 W/m2 for welding and turning and 190 W/m2 for mold technicians. The clothing insulation factor was calculated as 0.68 clo. The measurements were done in three different companies on 17-19 July 2017 during working hours without stop working. In terms of PMV findings, it was determined that the thermal comfort conditions are not met according to the ASHRAE standard. As for the WBGT value, it was determined that there was heat pressure on 17.07.2017 and there was no heat pressure on 18.07.2018 on all the employees. On 19.07.2017, it was determined that there was a heat pressure after 13:00 for mold technicians and after 17:00 for welding and turning technicians. Calculated PMV values were compared with the survey results and ıt was determined that results were compatible with values. It was made firm that people who were overweight and obese felt their working environment warmer than normal weight worker. The performance loss ratios which are dependent on ambient temperature were calculated and compared with the literature and was determined that they are compatible.
  • Öğe
    (2018) Lekesiz, Hüseyin
    Yarı-hermetik soğutma kompresörleri, arıza durumunda kolay müdahale kolaylığı sağlarlar. Bu kompresörlerde kullanılan krank milleri hem hafif hem de dayanıklı olmalıdır. Bu sebeple, doğru tasarım ve doğru malzeme seçimi çok önemlidir. Bu kompresörler yüksek hızda çalıştığından, zamana bağlı dinamik analiz kaçınılmaz olmaktadır. Ancak bu yöntemle problem çözümü çok uzamaktadır ve yakınsama sağlamak zorlaşmaktadır. Özellikle yataklardaki yağ basıncı değişimi vs gibi yapıdaki tüm dinamik etkiler dikkate alındığında problem iyice karmaşıklaşmaktadır. Probleme hızlı ancak statik yaklaşımdan daha doğru bir çözüm elde etmek amacıyla bu çalışmada sanki-statik yaklaşım kullanılmıştır. Kinematik ve kinetik analiz sonucu elde edilen kuvvetler yapıya belli kabuller altında statik olarak uygulanmıştır. Ortaya çıkan maksimum gerilme krank milinin yağlama plakasına bağlanan ucundaki fatura dibinde olup, bu literatürdeki hasar örnekleriyle uyuşmaktadır. Analizler sonucunda atalet etkisi %1,7 civarında olup, ele alınan krank mili için sanki-statik yaklaşımın oldukça doğru bir yaklaşım olduğu gösterilmiştir.
  • Öğe
    (2018) Sökmen, Kemal Fürkan
    Bu çalışmada otomotiv sektöründeki firmanın termal konfor şartları ve çalışan kilosu, giysi yalıtım faktörü, metabolik oranın termal konfor üzerinde etkilerini incelenmiştir. Konfor ölçümleri 6 bölümde yapılmıştır. Ölçümlerin yapıldığı bölümler kalıphane, kaynak, pres, boya, montaj ve boyahane bölümleridir. Ölçümler DELTA OHM 52.1 marka ekipmanlar ve yazılımı ile yapılmıştır. Giysi faktörü ölçümlerde 0,8 clo olarak alınmıştır. Metabolik oran değerleri bölümlerine bağlı olarak düşük 100 W/m2 ve orta 135 W/m2 değerler olarak kabul edilmiştir. Giysi faktörü etkisinin incelenmesinde değerler 0,5, 0,6, 0,7, 0,8, 0,9, 1 clo olarak seçilmiştir. Çalışma sonucunda fabrika içinde termal konfor bakımından en iyi ve kötü bölümün sırasıyla lojistik ve kalıphane olduğu tespit edilmiştir. Çalışanların düşük giysi faktörü değerlerinde özellikle iş yoğunluğunun yüksek olmadığı sabah saatlerinde ortamı daha konforlu hissettikleri görülmüştür. Çalışmada dikkate değer bir sonuç olarak ağırlığı 80 kg’ın üzerindeki kişilerin ortamı daha sıcak hissettikleri yapılan anket sonucu belirlenmiştir. Yüksek metabolik oranda çalışan kişilerin düşük metabolik oran gerektiren işlerle değişimli çalışmasının konfor hissi bakımından önemli olduğu tespit edilmiştir.
  • Öğe
    Numerical investigation of laminar mixed convection in a square cross-sectioned cylindrical annular enclosure
    (2020) Turan, Osman
    Abstract:Steady-state laminar mixed convection of Newtonian fluids in a square cross-sectioned cylindrical annular enclosure with rotating inner wall and heated top cover has been numerically analysed based on axisymmetric incompressible flow simulations. ...
  • Öğe
    Taşıt Elemanlarının Yapısal Optimizasyon Teknikleri ile Optimum Tasarımı
    (2017) Yıldız, Ali Rıza
    Otomotiv endüstrisinde optimum ürünlerin geliştirmesi süreci ürün maliyeti üzerinde önemli etkiye sahiptir. Bu nedenle, ürün tasarım sürecinde, optimum tasarımın elde edilmesi gerekmektedir. Optimizasyon çalışmaları sırasında seçilecek yöntem optimum tasarıma ulaşmada en önemli unsurlardan birisidir. Bu bağlamda optimum noktaya hızlı ve doğru şekilde yakınsayan yöntemlerin seçimi çok önemlidir. Bu çalışmada otomobillerin ön süspansiyon sisteminde kullanılan salıncak kolunun, sırasıyla topoloji ve şekil optimizasyonu yapılarak optimum boyutları bulunmuştur. Bu çalışmada şekil optimizasyonu için yeni geliştirilen interior arama algoritması literatürde ilk defa optimum ürün tasarımı sürecinde kullanılmıştır.
  • Öğe
    (2019) Beytüt, Hüseyin; Karagöz, Selçuk; Özel, Serkan
    Thin-walled structures (TWTs) are widely used in automotive and aerospace industries due to their easy formability, high energy absorption capacity, low cost, and lightweight advantages. In this study, considering the forming history, the crashworthiness of spot-welded and double-hat shaped elliptical TWT was numerically investigated under dynamic axial load, by the finite element method (FEM). In addition, a bead-shaped trigger mechanism was added to the TWT to reduce the peak crushing force. Non-uniform thickness distribution (thickening or thinning of some elements), plastic strain and work hardening may occur during forming. To investigate the effect of the forming history on crashworthiness, the sheet metal was formed by single-acting deepdrawing process and forming data were mapped to the TWT. The results showed that forming history has an effect on the crashworthiness of the tube. With deep-drawing results mapped to the tube, energy absorption decreased by 5.218% and peak crushing force decreased by 3.614%. Numerical simulations were conducted by using the nonlinear finite element codes RADIOSS/explicit.