Makine Mühendisliği Bölümü Koleksiyonu

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https://hdl.handle.net/20.500.13055/47

Listeleniyor 1 - 17 / 17

Effect of test parameters on the recovery of underground after a Thermal Response Test and optimum waiting time between tests
(Elsevier, 2025) Aydın, Murat; Gültekin, Ahmet
Thermal Response Test (TRT) is an important method to determine the thermal properties of underground. These tests can be interrupted by unexpected reasons and a new test must be started in the same borehole, or the test must be repeated because of various reasons. In this paper, optimum waiting duration for a second test after a completed TRT is investigated through analyzing thermal behavior of a borehole during and after the test. A computational model is built, and it is verified with an experimental test. After the verification, the numerical model is used further parametric investigations. Different cases are considered and the results are discussed. The effect of thermal conductivity and test duration on the minimum waiting times are also investigated. It is shown that optimum waiting duration depends highly on the test conditions, however it varies between 10 and 23 days.
Process parameter optimization of laser beam machining for AISI -P20 mold steel using ANFIS method
(Elsevier, 2025) Eaysin, Abdullah; Kabir, Sarower; Günister, Ebru; Jahan, Nur; Hamza, Amir; Zinnah, Muhammad Ali; Bin Rashid, Adib
AISI P20 mold steel is commonly used for injection molds to produce plastic materials, car accessories, and electronic equipment molds. This study employed a fiber laser beam for precise machining of AISI P20 mold steel. The experimental design, based on the Taguchi 27 model, was carried out using Minitab software to optimize machining parameters, including cutting speed, gas pressure, and laser power. Surface roughness (Ra) and kerf width were the response parameters investigated. The ANFIS model, developed and analyzed using MATLAB, successfully predicted response parameters and was experimentally validated, showing improved predictions over actual measurements. The Brute Force algorithm identified the minimum combination for an optimal parameter set. The Taguchi method determined the best process parameters, indicating that cutting speed had the most significant impact. The optimum Ra was achieved with 1 m/min cutting speed, 2 bar gas pressure, and 1.8 kW laser power, while the lowest kerf width was obtained with 2 bar gas pressure, 1 m/min cutting speed, and 1.9 kW laser power. Based on the Brute Force algorithm, the minimum combination resulted in a kerf width of 0.84 mm and a surface roughness of 4.48175 μm. Microstructural analysis was performed on samples with high and low surface roughness to assess the machining surface quality.
Energy, exergy, exergoenvironmental, and exergoenviroeconomic assessment of a two stroke UAV small engine using JP5 aviation fuel and hydroxy (HHO) gas
(Elsevier, 2024) Özer, Salih; Tunçer, Erdal; Demir, Üsame; Gülcan, Halil Erdi; Çelebi, Samet
Hydroxy gas (HHO) is a gas produced by the electrolysis of water, which involves breaking down water molecules (H2O) into hydrogen (H2) and oxygen (O2) gases. When the electricity used for electrolysis comes from renewable energy sources, the resulting hydrogen can be classified as 'green hydrogen.' Therefore, by using renewable green energy sources to produce HHO gas, its application in internal combustion engines can promote clean combustion and enhance sustainability. This study explores the enhancement of performance and emission characteristics in a two-stroke Unmanned Aerial Vehicle (UAV) engine using Hydroxy gas (HHO), a green energy source produced via water electrolysis. The primary objective is to improve engine efficiency and reduce environmental impacts by employing HHO in dual-fuel mode with JP5 aviation fuel. Addressing a clear research gap in the literature, this study is the first to evaluate the energy, exergy, exergoenvironmental, and exergoeconomic aspects of a two-stroke, air-cooled UAV engine using the JP5+HHO fuel blend. Experiments were conducted at five shaft speeds (3250, 3750, 4500, 5250, 6250 rpm) and four HHO flow rates (1.0, 1.5, 2.0, 4.0 lpm). The results demonstrate that incorporating HHO gas leads to a significant improvement in engine performance, with a 10% average reduction in Brake Specific Fuel Consumption (BSFC) and a 10% increase in exergy efficiency. Additionally, the JP5+HHO 4 lpm mixture reduces exergy destruction by approximately 10% and increases heat transfer exergy by 3–10%. On the environmental front, while HHO slightly increases CO2 emissions, the exergoenvironmental impact rises by a manageable 4%. Importantly, the high HHO flow rate (4 lpm) achieves a 2% average reduction in both exergoenvironmental and exergoeconomic impacts. These findings underscore the potential of HHO as a sustainable fuel source, offering both performance gains and reduced environmental and economic costs.
Effect of heat treatment on corrosion behavior of S275 mild steel using accelerated DC voltage, LPR, and EIS
(2024) Jacob, Liyamol; Parapurath, Shahid; Vahdati, Nader; Günister, Ebru
This study used an external DC voltage of 1.5 V to accelerate corrosion in heat-treated S275 mild steel samples at different time intervals. LPR and EIS were used to study the corrosion behavior of original and quenched steel samples. There was only a negligible difference in the corrosion rate (CR) for the original and the quenched samples up to 30 min of voltage application in a 3.5% NaCl electrolyte media. When the exposure time increased to 60 min, the original sample showed seven times higher CR than the quenched samples. The pits on the surface of the original samples acted as cathodes, enhancing the reaction rate on the surface and increasing its CR dramatically. This led to bimodal corrosion, where the first part is led by concentration and diffusion; while, the second part is led by localized corrosion. The smaller pits on the original surface samples served as cathodic reaction centers, exacerbating corrosion. The corrosion rate of the original samples ranged from 0.8 to 7.8 mmpy; whereas, the corrosion rate of the quenched samples remained consistently around 0.8 mmpy. This trend can be observed in long-term corrosion in different metals. The uniformly oriented martensitic microstructure and the quenched samples’ small grain size prevented the enhanced ion penetration due to applied voltage. This study analyses the long-term stability of structural steel samples in marine environments by accelerating the corrosion rate by an applied external DC voltage.
Natural gas-fueled HCCI engine performance and emission analysis andcomparison with SI and spark-assisted operations
(Taylor & Francis, 2024) Tunçer, Erdal; Sandalcı, Tarkan; Balcı, Özgün; Karagöz, Yasin
The homogeneous charge compression ignition (HCCI) engine is a promising technology in terms of both soot and NOx emission. Natural gas (NG) is advantageous especially for HCCI engines with its single stage combustion, low C/H ratio, and high octane number. Since the main challenge of HCCI technology is stability and transient operations, using HCCI for constant speed operations may be advantageous. In this study, a CI diesel engine, which is used as a generator at constant speed, was modified and converted into an NG-fuelled, SI engine. Then, the engine was supplied with NG for SI, HCCI, and spark-assisted HCCI experiments. Spark-assisted operations were executed by using 3, 5, and 7 degree ignition advance values to assist HCCI combustion. In-cylinder pressure variations, exhaust temperature, specific fuel consumption, and emission values were investigated for comparison of different strategies. Experimental results showed that using the HCCI strategy and retardation of ignition advance of spark-assisted HCCI operations reduced maximum pressure. Therefore, these strategies improved NOx emissions, while HC emissions were slightly increased. The spark-assisted HCCI strategy improves the stability of operation while increasing CO emission. The specific fuel consumption value of HCCI was slightly higher than that of SI operation, while it was lower than spark-assisted strategies.
Assessing the usage of end-of-life tire pyrolysis oil as an alternativefuel in a diesel engine in the point of energy, exergy,exergoeconomic, exergoenviroeconomic, and sustainabilityparameters
(Taylor & Francis, 2024) Ertürk, Talha; Arslan, Ahmet; Tunçer, Erdal; Doğan, Battal; Yesilyurt, Murat Kadir
The present study examines the utilization of fuel blends comprising waste tire pyrolysis oil (WTPO) at varying ratios (10%, 20%, 30%, and 40%) in a compression-ignition (CI) engine at different loads (25%, 50%, 75%, and 100%). This is with a view to elucidating the performance and emission characteristics of the blends in detail. The performance and emission data were subjected to detailed analysis. Energy, exergy, exergoeconomic, exorgoenviroeconomic, and sustainability analyses were conducted with the objective of comparing the fuel blends. Based on these analyses, the energy dissipation of the engine, exergy losses, cost of power from the engine shaft, and sustainability index (SI) were calculated for each fuel at all operating conditions. As the fraction of WTPO in the fuel blends increased, fuel consumption increased and energetic efficiency declined owing to the lower energy content of the alternative fuel additive. As the percentage of WTPO in the fuel blends increased gradually, the exergy losses increased, resulting in a decline in exergy efficiency. At the highest load, the exergetic efficiency of TP20 was found to be 5.65% higher than that of TP40. Given that the cost of traditional diesel fuel (D100) was 73.3% higher than WTPO, the cost of power from the engine shaft decreased as the WTPO ratio ascended in the blends. Consequently, the aforementioned parameter for TP10 was calculated to be 144.55 $/GW at a load of 75% while 120.90 $/GW was found for TP40. The greatest quantity of CO2 released into the environment was 11,512.4 kg CO2/month in TP40 at the highest load. Under the same conditions, it was calculated as 5,958.2 kg CO2/month for D100. In the context of an SI based on load, a reduction of 5.89% was observed in the case of conventional D100 in comparison with TP40 in the CI engine operating at full load. The findings of the present examination indicate that WTPO may be a viable alternative fuel for CI engines running on D100.
An integrated solar-driven chlor-alkali system for hydrogen and chlorine production
(Hamad Bin Khalifa University, 2023) Ayça, Sümeyya; Dinçer, İbrahim; Biçer, Yusuf; Al-Ansari, Tareq; Dinçer, İbrahim; Abedrabboh, Omer; Alherbawi, Mohammad; Yüzer, Burak
This paper deals with a review of the chlor-alkali process, an industrial application with significant promise for hydrogen production. In this process, the 2.6 MWh of power required for the operation of the system is met by an ingenious approach using a photovoltaic-based energy system. The research includes a comprehensive simulation of a chlor-alkali production system with the operating temperature set to 88°C using the Aspen Plus. The results demonstrate the remarkable potential of this system with a hydrogen production rate of 82.5 kg/h.
System design for green power generation with piezoelectric materials
(Haliç University, 2023) Ayça, Sümeyya; Yayla, Sedat; Dinçer, İbrahim; Utlu, Zafer; Karabuga, Arif
In this study; piezoelectric material is used to generate electrical energy within the scope of hydraulic energy, one of the renewable energy sources. In order to increase the electricity generation efficiency of the piezoelectric material used for energy conversion, turbulence intensity was tried to be increased in the existing closed system flow channel and vortex generating plates were designed. In order to establish the boundary conditions, experimental studies were carried out with the first vortex generator plates and then the data obtained with the numerical studies were compared. The number of blades and blade angle of the designed plate were modeled and numerical studies were carried out in ANSYS Fluent program to find the optimum values of the parameters considered. In addition, the optimum distances between the plates, nozzle plate and rotating plate were tried to be found experimentally. The final values obtained as a result of numerical and experimental studies were recorded as 0.019 TKE, 0.28 Volt. Considering the measured results, it was seen that approximately 1.6 times more efficiency TKE and 2.3 times more Volt were obtained than the previous studies.
The assessment of performance and emissions characteristics of a CI engine running on waste tyre pyrolysis oil as an alternative fuel and its blends with diesel fuel
(Türkiye Enerji Stratejileri ve Politikaları Araştırma Merkezi (TESPAM), 2023) Ertürk, Talha; Arslan, Ahmet; Tunçer, Erdal; Doğan, Battal; Yeşilyurt, Murat Kadir
The target of the present research is to examine the performance and emissions of waste tyre pyrolysis oil (WTPO) added into diesel fuel (DF) at different percentages in a compression-ignition (CI) engine. In the engine, tests were undertaken at four ranging loads (25%, 50%, 75%, and 100%) at 1500 rpm. The lower viscosity and energy content of WTPO compared to DF affected performance and emissions. Adding WTPO to DF increased fuel consumption, CO2, HC, and CO emissions, while reducing exhaust gas temperature (EGT). At the same load, HC emission increased by 13.3% as the fraction of WTPO in the blend ascended. While the EGT value of DF was 261oC at 25% load, this temperature dropped to 251oC for P40 fuel. When the load was 25%, the amount of CO2 emission ascended between DF and P40 fuel was 38.67%, while this increment reached 59.5% at the highest load. In the study, monthly CO2 emissions of fuel blends were calculated. In line with these calculations, it has been deemed environmentally appropriate to use end-of-life (EOL) tyres as fuel instead of scrapping them.
Microstructure and mechanical performance of low-cost biomedical-grade titanium-316L alloy
(Elsevier, 2023) Shahed, Chowdhury Ahmed; Ahmad, Faiz; Günister, Ebru; Altaf, Khurram; Ali, Saad; Raza, Abbas; Malik, Khurshid; Haider, Waseem
A 316L stainless steel (SS) alloy was developed with 1, 3, and 5 vol% titanium (Ti) reinforcement using the powder injection molding route, representing a low-cost option for biomedical implants. The investigation encompassed 1300 °C, 1350 °C, and 1380 °C sintering temperatures to ascertain the optimal physical and mechanical properties. Both sintering temperature and Ti influenced sintered density, and Ti mitigated the deleterious effects of residual carbon. At higher sintering temperatures, carbon and silicon tended to migrate and accumulate at the brink of Ti, leading to the formation of intermetallic compounds and increased brittleness. Dispersed Ti particles within the 316L matrix acted as nucleation sites and enhanced solid solubility with improved density. An astounding 96.11 % sintered density was achieved at 3 vol% Ti sample sintered at 1380 °C. During the tensile test, 5 vol% Ti at 1380 °C exhibited a low modulus of 58.9 GPa, which is highly desirable for orthopedic implant application. The XRD, SEM, tensile test, and nano-indentation results collectively provide evidence of beta-titanium formation during the sintering process. Conversely, the sample incorporating 3 vol% titanium, sintered at 1380 °C, demonstrated a balanced performance, showcasing 432.94 ± 12.8 MPa ultimate tensile strength, 3.06 ± 0.17 % elongation, 74.2 GPa modulus, and 322 MPa and 423 MPa 0.2 % offset flexural and compressive yield strengths, respectively. Notably, an improvised wear resistance test underscored its aptitude for sliding wear resistance, solidifying its potential as a promising candidate for biomedical implants.
Mechanical investigation of kenaf/carbon hybrid composites for building and construction applications
(American Society of Civil Engineers, 2024) Malik, Khurshid; Ahmad, Faiz; Yunus, Nurul Azhani; Günister, Ebru; Shahed, Chowdhury Ahmed
Single-kenaf fiber-reinforced polymer composites are typically characterized by relatively low strength and stiffness properties that make them unsuitable for structural applications. However, they are lightweight, economical, and ecofriendly. This paper presents a study on the manufacturing and mechanical characterization of bidirectional kenaf (K) fiber-reinforced epoxy composites hybridized with carbon (C) fibers in various stacking sequences and the effects of hybridization on salient physical and mechanical properties. Single and hybrid fiber composites were fabricated utilizing the vacuum infusion molding technique. The density, tensile, flexural, and interlaminar shear properties in hybrid composites increased significantly when carbon fiber volume increased from 9% to 16%. Stacking sequences in a hybrid affected the mechanical properties of the composites. The highest tensile strength and modulus were shown by the seven-layer hybrid composite with an alternate K/C stacking sequence and C layers as skin layers, i.e., C/K/C/K/C/K/C, among all tested hybrid composites. Sandwich design in the hybrid (C2/K3/C2) had higher flexural strength (+300%), flexural modulus (+414%), interlaminar shear strength (+278%), lower water absorption (−46%), and thickness swelling (−30%) compared to single-fiber kenaf/epoxy composites. Density increased by 5% in hybrid composites. The highest fracture toughness (+134%) was achieved using the dual sandwich design structure hybrid (C/K2/C2/K2/C). The developed composite has applications in stairways, walkways, and bridges.
Antibacterial mechanism with consequent cytotoxicity of different reinforcements in biodegradable magnesium and zinc alloys: A review
(KeAi Communications Co., 2023) Shahed, Chowdhury Ahmed; Ahmad, Faiz; Günister, Ebru; Foudzi, Farhana Mohd; Ali, Saad; Malik, Khurshid; Harun, Wan Sharuzi Wan
Benefits achieved by the biodegradable magnesium (Mg) and zinc (Zn) implants could be suppressed due to the invasion of infectious microbial, common bacteria, and fungi. Postoperative medications and the antibacterial properties of pure Mg and Zn are insufficient against biofilm and antibiotic-resistant bacteria, bringing osteomyelitis, necrosis, and even death. This study evaluates the antibacterial performance of biodegradable Mg and Zn alloys of different reinforcements, including silver (Ag), copper (Cu), lithium (Li), and gallium (Ga). Copper ions (Cu2+) can eradicate biofilms and antibiotic-resistant bacteria by extracting electrons from the cellular structure. Silver ion (Ag+) kills bacteria by creating bonds with the thiol group. Gallium ion (Ga3+) inhibits ferric ion (Fe3+) absorption, leading to nutrient deficiency and bacterial death. Nanoparticles and reactive oxygen species (ROS) can penetrate bacteria cell walls directly, develop bonds with receptors, and damage nucleotides. Antibacterial action depends on the alkali nature of metal ions and their degradation rate, which often causes cytotoxicity in living cells. Therefore, this review emphasizes the insight into degradation rate, antibacterial mechanism, and their consequent cytotoxicity and observes the correlation between antibacterial performance and oxidation number of metal ions.
Influence of drilling parameters on the delamination and surface roughness of insulative-coated glass/carbonhybrid composite
(Hindawi, 2023) Kabir, Sarower; Ahmad, Faiz; Shahed, Chowdhury Ahmed; Günister, Ebru
Drilling in synthetic fiber-reinforced polymer composites is facing challenges due to their anisotropic, inhomogeneity, and abrasive machining behavior. The joining of composite parts using fasteners is commonly done by the drilling, and the generated heat is one of the main causes to damage the drilled hole in the composite. Moreover, the quality of drilled hole is crucial for joining parts effectively. The paper presents the design, fabrication, and drilling of a hybrid fiber-reinforced polymer (HFRP) based on insulative coating. These composites were fabricated using vacuum infusion molding (VIM) and coated with different thicknesses to investigate the influence of drilling parameters and associated damages. Cutting speed, feed rate, and coating thicknesses were varied, and a full factorial design of the experiment was formulated. High-speed steel (HSS) twist drill bit was used to drill the coated composite and test samples, and delamination factor and surface roughness were measured. ANOVA and full factorial response optimizer were used to evaluate the influence and optimum drilling parameters. The delamination factor (DF) at the entry and surface roughness were found to decrease with the increasing cutting speed. However, the DF at the exit showed the opposite. Coating thickness influenced the delamination at the entry whereas delamination at the exit has been found insignificant. For drilling HFRP composite with 1 mm coating thickness, 3000 RPM spindle speed and 0.08 mm/rev feed rate were found optimum parameters in minimizing surface roughness and delamination damage. However, 6000 RPM and 0.02 mm/rev were found optimum parameters for drilling HFRP composite with 1.5 mm coating thickness.
Damlacık sayısı ve damlacıklar arası yatay mesafenin maksimum yayılma alanı ve ısı transferi performansı üzerine etkilerinin sayısal incelenmesi
(Journal of Thermal Science and Technology, 2023) Gültekin, Ahmet; Erkan, Nejdet; Çolak, Üner; Suzuki, Shunichi
Özet: Damlacıkların katı bir yüzeye etki etmesi fenomeni çok sayıda endüstriyel uygulamalarda görülebilir. Damlacıkların sıcak bir yüzeyle ve/veya diğer damlacıklarla etkileşimleri durumunda bu fenomen daha karmaşık hale gelmektedir. Katı bir yüzeye çok sayıda damlacık çarptığında, damlacıkların çarpma koşulları ve aralarındaki mesafeye bağlı olarak bir etkileşim meydana gelir. Bu etkileşim nedeniyle bir katman yükselmesi oluşur ve yüzeyde damlacık başına daha az yayılma gerçekleşir. Dolayısıyla, ortaya çıkan hidrodinamik ve ısı transferi değişimleri tek damlacık etkileşimlerinden oldukça farklıdır. Sprey soğutma olgusunda meydana gelen fiziksel mekanizmaları anlama ve modelleme ile ilgili zorluklar, damlacıkların rastlantısallığından ve izlenemez davranışlarından kaynaklanmaktadır. Bu nedenle, karmaşık yapı basitleştirilerek çoklu damlacıkların etkileşimleri sıvıların hacmi (VOF) metodu kullanılarak sayısal olarak incelenmiştir. Bu çalışmanın amacı, damlacık sayısının ve damlacık çarpma koşullarının yüzeyden gerçekleşen ısı transferi performansına etkisini incelemektir.
Investigating the dynamics of droplet spreading on a solid surface using PIV for a wide range of Weber numbers
(Springer, 2023) Gültekin, Ahmet; Erkan, Nejdet; Çolak, Üner; Suzuki, Shunichi
The investigation of the underlying physical processes involved in the impact of droplets has various practical applications in engineering and science. In this research, the spreading velocities within droplet impingement on a sapphire glass were investigated for a wide range of Weber numbers using particle image velocimetry (PIV), which involves tracking the movement of polymeric fluorescent particles (6 µm) within the droplet. The experiments were carried out at room temperature, and the droplets had impact velocities ranging from 0.41 to 2.37 m/s, which corresponded to Weber numbers of 5–183. The results showed that the radial velocity was generally linear over a wide range of spreading radius but the velocity at the exterior radial positions became nonlinear over time due to the influence of capillary and viscous forces. This nonlinearity was more pronounced for lower Weber numbers because the viscosity effects in the droplet were more significant compared to the inertia forces. As the Weber number decreases, the spreading and receding of the droplets are completed faster, leading to different trends in the radial velocity profiles.
Physical and mechanical properties of kenaf/flax hybrid composites
(Wiley Online Library, 2023) Malik, Khurshid; Ahmad, Faiz; Yunus, Nurul Azhani; Günister, Ebru; Ali, Saad; Raza, Ali
This research investigates the physical and mechanical properties of hybrid composites made of epoxy reinforced by kenaf and flax natural fibers to investigate the hybridization influences of the composites. Pure and hybrid composites were fabricated using bi-directional kenaf and flax fabrics at different stacking sequences utilizing the vacuum-assisted resin infusion method. The pure and hybrid composites' physical properties, such as density, fiber volume fraction (FVF), water absorption capacity, and dimensional stability, were measured. The tests of tensile, flexural, interlaminar shear and fracture toughness (Mode II) were examined to determine the mechanical properties. The results revealed that density remained unchanged for the hybrid compared to pure kenaf/epoxy composites. The tensile, flexural, and interlaminar shear performance of flax/epoxy composite is improved by an increment of kenaf FVF in hybrid composites. The stacking sequence significantly affected the mechanical properties of hybrid composites. The highest tensile strength (59.8 MPa) was obtained for FK2 (alternative sequence of flax and kenaf fibers). However, FK3 (flax fiber located on the outer surfaces) had the highest interlaminar shear strength (12.5 MPa) and fracture toughness (3302.3 J/m(2)) among all tested hybrid composites. The highest water resistance was achieved for FK5 with the lowest thickness swelling.
Effect of microstructure on electrochemical properties of the EN S275 mild steel under chlorine-rich and chlorine-free media at different pHs
(MDPI, 2022) Parapurath, Shahid; Jacob, Liyamol; Günister, Ebru; Vahdati, Nader
This study examines microstructural modification as an effective strategy for reducing corrosion and its impact on the mechanical properties of mild steel. The effect of heat treatment on morphology, strength, toughness, and ductility was studied using optical microscopy, SEM, Scherrer equation, Vickers's hardness test, and tensile-strength measurement. The heat treatment changed the microstructures, grain sizes, and particle sizes of the samples. It also increased the material strength by 56% and 25% for the quenched and tempered samples, respectively. The hardness was increased to 95% by quenching. The effect of the microstructural changes on the corrosion rate in chlorine-rich and chlorine-free media at different pH was studied using linear-polarization-resistance and dynamic-polarization-resistance methods. In both media, the quenched samples showed a lower corrosion rate compared to the original and tempered samples. The heat treatment resulted in the formation of homogenous martensite with coarse grains and small particle sizes that seemed to reduce the corrosion rate significantly. It also had an impact on the corrosion mechanism of these materials. The original and tempered samples showed pitting-corrosion behavior with high corrosion rates, while the quenched samples were more susceptible to intergranular corrosion. The rate of corrosion was investigated further at different pH, and it was shown to decrease when the pH was raised. This study confirms the impact of microstructural changes on the corrosion behavior of S275 structural steel.

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