İmalat Mühendisliği Bölümü Makale Koleksiyonu

Bu koleksiyon için kalıcı URI

https://hdl.handle.net/20.500.12418/300

Listeleniyor 1 - 20 / 49

Effect of long-term nanofluid usage on horizontal ground source heat pump performance
(Elsevier, Aralık 2024) Kapıcıoğlu, Abdullah; Esen, Hikmet
Nanofluids in thermal systems such as heat pumps are one of the innovative approaches due to their high thermal conductivity. However, nanofluids suffer from effects such as agglomeration and settling. Gravitational sedimentation occurs in the absence of circulation or mean flow conditions; this is a common problem in real-life engineering applications. The current experimental study focuses on how the system performance will be affected in this long standby situation. The study investigated the effect of nanofluid on the system performance in a Nanofluid-Assisted Ground Source Heat Pump (NAGSHP) system, which was examined experimentally long term. The findings show a loss of up to 3 % in the performance of the Ground Heat Exchanger (GHE) and a 2.5 % decrease in the coefficient of performance (COP) of the system. These values are even lower than the results obtained from experiments with ethylene glycol-water (without nanofluid) base fluid in the previous study. These results show that nanofluids cause performance degradation in long standby conditions. Further studies can investigate the interaction between surfactants and nanoparticles that reduce the sedimentation rate, considering different flow conditions, and show the implications of these results in engineering applications.
EXPLORING THE IMPACT OF GEOMETRIC PARAMETERS ON HEAT TRANSFER AND FLUID FLOW CHARACTERISTICS IN CROSS-TRIANGULAR GROOVED CHANNELS: A COMPUTATIONAL STUDY
(03.06.2024) Alnak,Yeliz
In this study, the impact of geometric parameters of rectangular baffles with varying location angles and heights is investigated on the heat transfer and fluid flow characteristics of cross-triangular grooved channels. Computational methods are employed to explore these effects, utilizing the Ansys-Fluent program to solve the Navier-Stokes and energy equations, incorporating the k-ε turbulence model for numerical simulations. The inlet temperature of the air, serving as the working fluid, is set at 293 K, while the wall surface temperature of the lower triangular grooved channel remains fixed at 373 K. Rectangular baffles are tested with angles of 30°, 60°, and 90°, and heights of 0.25H, 0.5H, and 0.75H, respectively. The numerical results show good agreement with a 3.53% deviation compared to existing empirical data in the literature. The obtained findings are presented in terms of mean Nusselt (Num) number, fluid temperature, and Performance Evaluation Criterion (PEC) number variations taking into consideration of pressure drop for each rectangular baffle angle and height. Additionally, contour distributions of temperature and velocity are evaluated for different Reynolds numbers (Re) and arrangements of rectangular baffles. It has been determined that the Nu number value increases by 197.56% at a 90° angle and 0.75H height, compared to the 0.25H baffle height at Re=6000. Furthermore, at Re=1000, the PEC number is 84.50% higher with a baffle height of 0.25H and a baffle angle of 30° compared to the condition with a 90° angle.
Numerical investigation of different combustion chamber on flow, combustion characteristics and exhaust emissions
(2023) ilker temizer; Ömer cihan; Öncel Öncüoğlu
This study includes numerical analysis of diesel engines with different bowl geometry. Numerical analyzes of the diesel engine with asymmetrical bowl geometry were performed in Ansys Forte software. In the study, four-stroke, air cooled, a single-cylinder and direct injection diesel engine were used. It has been tested where the maximum torque is obtained as the operating condition at 2000 rpm. According to the results obtained from the analyzes, the new combustion chamber system geometry provided a 40.3% reduction in soot emissions while NO emissions increased slightly with the 8-cavity bowl geometry created in the chamber compared to the standard combustion chamber system. Increasing air velocity, and turbulent kinetic energy values in the chamber affected the evaporation levels of the fuels. As a result, the improved mixture formation caused a decrease in incomplete combustion products (CO, HC and soot). The new combustion chamber system geometry according to standard combustion chamber system type, an increase of approximately 4.2% occurred in the calculated squish rates. It has been observed that the increase in the bowl surface area causes the combustion, and thus the temperature to spread over a larger area on the piston.
Farklı Yükseklikli ve Kanatçıklı Birleşik Jet Akışlı Kanallarda Isı Transferi İyileştirilmesinin İncelenmesi
(2022) Alnak, Dogan Engin
Yüksek hıza sahip cihazlar elde edebilmek amacıyla yarı iletken levhalar üzerine çok sayıda yerleştirilen mikroçipler beraberinde çözülmesi gerekli önemli bir problem olan ısınma sorununu gündeme getirmektedir. Bununla birlikte, mikroçiplerin küçültülebilmeleri teknolojinin elverdiği ölçüde soğutulabilme kapasitelerindeki artışa bağlıdır. Bu nedenle, bu elemanların soğutulmasında çeşitli soğutma teknikleri uygulanmaktadır. Çapraz akış ile soğutma yöntemi, bu tekniklerden en yaygın olarak bilinenidir. Bu yöntem, soğuk akışkanın bir fanla tüm bileşenler üzerine gönderilmesi ve bu sayede elektronik bileşenlerinin bütününün soğutulması esasına dayanmaktadır.
Nanoakışkan Kullanılan Birleşik Jet Akışlı ve Kanatçıklı Kanallarda Isı Transferi ve Performans Değerlendirme Sayısının İncelenmesi
(2022) Alnak, Dogan Engin
Bu çalışmada, birleşik jet akışlı kanallarda bulunan sabit ısı akılı küp ve dairesel oyuklu desenlerden olan ısı transferi su ve %0,02 hacimsel konsantrasyonlu GO (Grafen Oksit)-Su nanoakışkanı kullanılarak sayısal olarak araştırılmıştır. Sayısal çalışma, sürekli ve üç boyutlu olarak k-ε türbülans modelli Ansys-Fluent programının kullanılmasıyla ger-çekleştirilmiştir. Nanoakışkanın termofiziksel özellikleri deneysel olarak elde edilmiş-tir. Literatürdeki çalışmalar da göz önüne alınarak kanallara üçer adet desenli yüzey yerleştirilmiştir. Kanallara ayrıca jet girişinden itibaren 1,5D jet giriş çapı ölçüsünde sabit bir uzaklıkta (N) 30° ve 90° açılı kanatçıklar eklenmiştir. Kanal yükseklikleri 3D iken akışkanların Re sayısı aralığı 7000-11000’dir. Çalışmadan elde edilen sonuçların doğruluğu ve kabul edilebilirliği deneysel araştırmalar sonucu elde edilen eşitlik kulla-nılarak kanıtlanmıştır. Çalışmanın sonuçları, kanallardaki her bir desen için ortalama Nu sayısının değişimleri olarak su ve nanoakışkan kullanılarak kanatçıksız ve kanatçıklı durumlarda karşılaştırmalı olarak incelenmiştir. Bununla birlikte, kanallardaki her üç desenli yüzeyin tümü için farklı Reynolds sayılarında performans değerlendirme sayıları (PEC) ve ortalama Nu sayısı (Num) ve yüzey sıcaklık değerleri (Tm) Re=11000 için değer-lendirilmiştir. Ayrıca, birleşik jet akışlı kanallarda nanoakışkanın hız ve sıcaklık konturu dağılımları sunulmuştur. 30° kanatçıklı nanoakışkanlı küp ve dairesel oyuklu desenli yüzeylerde ortalama Num değerlerinin kanatçıksız ve su akışkanı kullanılan kanallara göre %18,66 ve %15,93 daha fazla oldukları bulunmuştur.
Grafen Oksit (GO)-Su Nanoakışkanlı ve Kanatçıklı Birleşik Jet Akışlı Kanallarda Isı Transferinin Araştırılması
(2023) Alnak, Dogan Engin
Bu çalışmada, birleşik jet akışıyla kanatçıksız ve farklı kanatçık mesafeli (N = D ve 2D) ve 60o açılı kanal-larda su ve %0.02 hacimsel konsantrasyonlu GO (Grafen Oksit)-Su nanoakışkanı kullanılmasıyla yamuk ve taç desenli yüzeylerden olan ısı transferi ve performans analizi sayısal olarak incelenmiştir. Sayısal araştırma, zamandan bağımsız ve üç boyutlu, k-ε türbülans modelli Ansys-Fluent programıyla gerçekleşti-rilmiştir. Çalışmanın sonuçları, literatürdeki deneysel çalışmanın Nu sonuçlarıyla kıyaslanmış ve uyumlu oldukları görülmüştür. N = 2D ve Re = 15000’ de her üç yamuk ve taç desenli yüzeylerde nanoakışkanın ortalama Num sayılarının kanatçıksız ve su akışkanına göre sırasıyla %18.35 ve %24.09 daha fazla olduğu bulunmuştur.
Research of cooling performance in combined jet ?ow channels using different nano?uids
(15.01.2023) Alnak, Dogan Engin
In this work, heat transfer from the cube and circular hollow-shaped copper plate surfaces with a constant heat ﬂux of 1000 W/m2 was numerically investigated by using a combination of the cross-ﬂow-impinging jet. Numerical research was performed by solving the energy and Navier-Stokes equations as three-dimensional and steady, using the Ansys-Fluent computer program with the k-ϵ turbulence model. In order to direct the combined jet ﬂow in the channel to the heated surfaces, the ﬁns with 30o and 60o angles were placed in the channel horizontally with the impinging jet surface. While the channel height (H ) is 4D, the distance of the ﬁn from the jet inlet (N) is 2D. Fluids used in the channels are water, 0.02%GO-water and 2% diamond-water. The upper and lower surfaces of the channel and the ﬁn are adiabatic and the ﬂow Reynolds number range is 5000–15,000. The results of the work were compared with the experimental results of the studies in the literature and they were found to be consistent with each other. The results were presented as the mean Nu number and mean surface temperature variations for each model surface. Besides, the velocity and temperature contour distributions of the combined jet ﬂow along the channel for diamond-water nanoﬂuid were evaluated. Also, per-formance evaluation coefﬁcient and average Nu number (Num), and surface temperature values (Tm) were evaluated at different Reynolds numbers for all three patterned surfaces in the channels. At Re = 15,000, there are 18.42% and 17.08%increments in Num value for cube and circular hollow model surfaces in the channel with 60o ﬁn and GO-water nanoﬂuid compared to the channel with water ﬂow and without ﬁn.
THE EFFECT OF FIN ANGLE ON INCREASING THE HEAT TRANSFER FROM ELECTRONIC COMPONENTS BY APPLYING AN IMPINGING JET-CROSS FLOW
(12.11.2021) Alnak, Dogan Engin
With the advancement of technology, circuit elements in developing electronic devices heat up and their temperatures rise depending on the working load. Cross flow, which is one of the methods used to increase heat transfer from electronic circuits, may be insufficient for cooling circuit elements that have reached very high temperatures. The temperature is kept within safe limits by providing an efficient heat transfer from the circuit elements with the impinging jet-cross flow application. In this study, heat transfer from rectangular shaped surfaces with copper plate with constant heat flux of 1000 W/m2 in the channel was investigated numerically by using a combination of impinging jet and cross flow. Numerical research was carried out by solving the energy and Navier-Stokes equations as three dimensional and steady, using the Ansys-Fluent computer program with k-ε turbulence model. In order to direct the flow in the channel to the heated surfaces, the fins with 30o, 45o and 60o angles and the length of the D jet inlet diameter were placed in the channel horizontally with the impinging jet surface. The jet fluid used in the channel is water, and the upper and lower surfaces of the channel and the fin are adiabatic. The distance between the jet and the plate is 45 mm (3Dh), and the jet Reynolds number range is 5000-9000. The results of the study were compared with the experimental results of the study in the literature and they were found to be consistent with each other. The results were presented as the mean Nu number and surface temperature variation for each rectangular patterned surface. Besides, the velocity-streamline and temperature contour distributions of the impinging jet-cross flow along the channel for channels were evaluated comparatively. For Re = 9000, it was determined that the average Nu number value in the channel with 60o fin angle was 20.02% higher than the channel without fin.
Effect of Ni on microstructure and wear behaviour of 13Cr-W-Mo-2C white cast iron
(CONSEJO SUPERIOR INVESTIGACIONES CIENTIFICAS-CSICEditorial CSIC, C/VITRUVIO 8, 28006 MADRID, SPAIN, 30 June 2023) Teker, Tanju; Serdar, Osman
The effect of Ni concentration on the microstructure and wear performance of 13Cr-(0.5-7.0) Ni-W-Mo-Mn-2C white cast iron subjected to homogenization heat treatment was examined. Concentration of Ni was altered in the range 0.5-7.0 wt.% to obtain a stable microstructure against for dry sliding wear resistance as long sliding distance. The effect of Ni on the microstructure was analysed by X-ray diffraction, scanning electron microscopy, energy dispersive x-ray spectroscopy, elemental mapping and hardness. The wear performances were tested under the loads of 40, 90 and 140 N. Differential thermal analysis of samples with dissimilar Ni values was performed. The increase of Ni concentration decreased the secondary arm spacing of dendrites, refined the dendritic structure and raised the eutectic carbide ratio. The greatest wear performance was obtained for the sample having Ni over 6 wt.%.
Weldability and mechanical behavior of CMT welded AISI 430 and HARDOX 500 steels
(WALTER DE GRUYTER GMBHGENTHINER STRASSE 13, D-10785 BERLIN, GERMANY, 31 August 2023) Kocadağistan, Mustafa Engin; Çinar, Oğuzhan; Teker, Tanju
In this study, AISI 430 and HARDOX 500 steels were joined by cold metal transfer (CMT) welding method. The properties and microstructural changes of the welding and HAZ regions were investigated by OM and SEM analyses. Microhardness, notch impact, and tensile tests were performed to determine the mechanical properties of the welded specimens. The ruptured surfaces of the test specimens after the impact test were examined using SEM. Coarse grains were formed in the HAZ regions but were limited to the low-temperature input of the cold metal transfer welding. The N3 specimen was broken from AISI 430 base metal and the elongation amount was 16.32 mm. Tensile strengths were from 380 to 493 MPa. The mechanical properties of AISI 430 and HARDOX 500 steels combined with CMT welding increased significantly and weldability was proven possible.
Structural analysis of Cu-based FeCr reinforced composites prepared by mechanical alloying
(WALTER DE GRUYTER GMBHGENTHINER STRASSE 13, D-10785 BERLIN, GERMANY, 01 July 2023) Yilmaz, S. Osman; Teker, Tanju; Aydin, Sinan
Production and structural investigations of Cu-based FeCr reinforced composite were performed by using mechanical alloying, optical microscope, scanning electron microscope, X-ray diffraction and hardness test. The increment in FeCr addition caused the increment in the cold deformation rate. This situation resulted in breakage of the powder particles throughout mechanical alloying. Thus, the grain dimension of the FeCr powders decreased and the Fe wt.% in the CuCr powders advanced. The collision force between the Cu-Cr powder and the grinding ball weakened with the increase of FeCr concentration and resulted as higher reinforcement size. After mechanical milling, FeCr grains decreased in size more than copper grains due to the ductility of copper grains. The smaller crystals occurred after grinding, and increased the grain boundary zone for further spread of Cr into the Cu. Despite the high sintering process, the high sintering temperature improved the compactness of the alloys, but caused coarsening of the nanoparticles. The mechanical alloying time, reinforcement wt.% and sinter temperature were effective on the microhardness of the microstructure.
Austempering Ce-La inoculated solution strengthened ferritic ductile cast irons
(REDAKCIA KOVOVE MATERIALYUL RACIANSKA 75, PO BOX 95, 830 08 BRATISLAVA 38, SLOVAKIA, 01 February 2023) Yılmaz, Serdar Osman; Teker, Tanju; Demir, Demet
The influence of austempering conditions on the microstructure, hardness, tensile strength, and impact toughness of Ce-La inoculated solution-strengthened ferritic ductile irons was analyzed. The austempering was performed at temperatures 280, 320, 420, 520, and 620◦C for periods of 1.5 and 2.5 h. Metallurgical characterization of the samples was determined using scanning electron microscopy, optical microscopy, X-ray diffraction, microhardness, impact, and tensile test. The fracture surfaces of the tensile samples were examined by scanning electron microscopy. Austempering heat treatment significantly enhanced the mechanical characteristics of solution-strengthened ferritic ductile cast iron. This led to the birth of solutionstrengthened Ce-La inoculated ferritic cast iron, a new spheroidal graphite cast iron family member with a unique microstructure in an ausferritic matrix. Samples austempered for low temperature exhibited higher impact toughness and tensile strength due to the nano-sized ausferrite phase. Austempering for high temperatures displayed higher elongation.
Microstructure and wear analysis of CoWC alloy layers deposited by PTA process
(EDP SCIENCES S A17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE, 12 April 2023) Ozabaci, Murat; Teker, Tanju; Yılmaz, S. Osman
CoWC composite coatings were produced on AISI 430 steel by the plasma transfer arc cladding. Three different powder mixtures containing WC (90%, 85% and 80%) and Co (10%, 15% and 20%) were used. Phase composition, microstructural characterization and coating properties were investigated by using scanning electron microscope (SEM), energy dispersive spectrometry (EDS), X-ray diffraction (XRD), elemental mapping, hardness and wear test. The wear shape morphology of coatings was determined by SEM. The increased ratio of WC in CoWC powders reduced the degradation of CoWC. The substrate hardness of 180 HV gained a coating hardness value of approximately 462 HV. An increase in the hardness of the coating alloy compared to the substrate was achieved. W2C, WC, CoC and Co6W6C phases were determined on the coating surface. The high levels of WC concentration on the coating surface increased the wear resistance.
Effect of alloying elements on mechanical behaviour of Cu-Zn-Sn bronzes
(WALTER DE GRUYTER GMBHGENTHINER STRASSE 13, D-10785 BERLIN, GERMANY, 8 March 2023) Teker, Tanju; Yilmaz, S. Osman; Bulus, Ercan
The effect of Fe, P and Mn on microstructure and fatigue properties of CuZnSn bronzes investigated with optical microscopy and scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, hardness, tensile and fatigue tests. The addition of Fe, Mn and P to Cu-Zn-Sn bronzes formed Cu31Sn8, Cu6Sn5, ZnSn2, PbSnS2, ZnS, Cu2S, FeZn9 and FeZn21 phases. These phases were deposited between the dendrite arms and were dissolved in the matrix in small amounts. Especially, these precipitated phases were effective in fatigue properties. The formation of Cu-Sn, Cu-Zn and Zn-Sn intermetallic phases emitted due to the addition of Fe, Mn and P increased the fatigue strength. The spread of ferrous phases caused an increase in mechanical properties. The beneficial effect of P addition on the fatigue life far surpassed that ofMn and Fe additives.
Long term endurance analysis of the effects on ring wear and lubrication oil of biofuel used in a DI diesel engine
(2023) Temizer, İlker; Arı, Ayşegül
In this study, the long-term endurance tests were carried out in an engine that was used 100% diesel and 90% diesel 210% bioethanol blend. The lubricating oil and ring wear were investigated in the direct injection diesel engine using two different fuels under partial load and for 110 h. As a result of long-term endurance tests, ash content, density, viscosity, acid number determination, and flash point values of engine lubricating oil were detected. Moreover, the metal residues (Fe, Al, Cu, Pb, Zn, Mg, Mn, Ni) were signs of wear in the lubricating oil were observed. Samples were taken from the lubricating oil at 55 and 110 h and examined by the Inductively Coupled Plasma-Mass Spectrometer method. Also, tribological and morphological analyses of the replaced piston rings were made for each fuel mixture. The piston rings (first ring, second ring and third ring) had been examined by using the Energy Dispersive X-ray Spectroscopy and Scanning Electron Microscopy. As a result, it was observed that the metal residues in the oil changed over time. Metal residues were showed that after the 55th hour there were more metal residues in the lubricating oil with B10, compared to diesel. While the TAN value of lubricating oil was measured as 3.08mg KOH/g in the D100 operation, this value was 3.29mg KOH/g in the B10 operation.
Analysis of an innovative combustion chamber with the wall guided fuel injection in a small diesel engine
(2023) Temizer, İlker; Ömer, Cihan; Öncüoğlu, Öncel
This paper has included the effects of different bowl geometries which has the wall guided fuel injection. Bowl geometries, which affect in-cylinder air flows, have a great influence on the change of mixture formation. Also, the region where the fuel hits in the bowl affects all engine parameters. In this presented numeric study, the standard combustion chamber geometry of a single-cylinder, air-cooled, and direct-injection diesel engine is compared with the designed new combustion chamber. Four different rotation angles (0 , 7.5 , 10 , and 15 ) were determined for the new combustion chamber geometry and compared with the standard geometry. The three-dimensionally modeled bowl geometries in 3D Computational Fluid Dynamics simulation were examined in terms of in-cylinder pressure and temperature, instantaneous and cumulative heat release rate, exhaust emissions (NO, soot, CO, and CO2), temperature/spray, and equivalence ratio/spray at different CA’s. The effects of the different rotation angles of the designed new bowl geometry on both the air movement and the region where the fuel hits were investigated for the engine parameters. When the results obtained are examined, maximum in-cylinder pressures for standard combustion chamber, new combustion chamber 1, new combustion chamber 2, new combustion chamber 3, and new combustion chamber 4 geometries were obtained 79.5, 75.2, 78, 78.1, and 78 bar respectively, and the maximum in-cylinder temperatures were found 1766, 1742, 1805, 1817, and 1818K, respectively. According to the results obtained from the numerical analysis, CO, CO2, and soot emissions decreased while NO emissions increased in the new combustion chamber, compared to the standard combustion chamber. Examined the spray distributions in bowl, it was seen that the fuel sprays distributed more homogeneously and flame propagates which is spread throughout the chamber in the new combustion chamber type, which improved the mixture formation. The wall guided fuel flow in the novel designed chamber geometries beneficial to turbulence kinetic energy, spray distribution, emissions.
Effect of piston geometry on combustion characteristics of CI engine used Sal seed oil
(2023) Temizer, İlker; Cihan, Ömer
The effect of piston bowl geometry on reducing soot emissions, improving combustion, and in-cylinder flow movements in a direct injection diesel engine was investigated. Standard combustion chamber (SCC) and newly modified combustion chamber (MCC) geometries were compared at the same compression ratio (17.5:1). Experimental analysis of diesel engines is expensive and time consuming, and therefore the Computational Fluid Dynamics program was used to analyze the combustion, flow and emission process. AVL Fire ESE Diesel software was used in the numerical study. The numerical work was compared with the experimental results, and it was validated. In addition, 10% biodiesel mixture (10% Sal seed oil methyl ester + 90% diesel fuel) and diesel fuel were used in the analysis. These fuels and two different bowl geometries were investigated at 2000 rpm and full load conditions. Thus, the effect of the used biodiesel fuel and the developed bowl geometry were investigated. Sal seed oil methyl ester was used as biodiesel fuel. The results show that higher turbulence velocity distribution, better mixture fraction values and lower soot formation distribution are obtained by directing the MCC type fuel according to SCC type. When the pressure, temperature and heat release in the combustion chamber are examined, the highest values were obtained with B10 blended fuel used at the SCC type combustion chamber. The maximum heat release rates are 8.72, 9.38, 8.21, and 9.30 J/ for SCCD100, SCCB10, MCCD100 and MCCB10 fuels, respectively.
An experimental investigation of new chamber geometry on the combustion characteristics, performance and emissions in a light-duty diesel engine
(ELSEVİER, 2023) Temizer, İlker; Cihan, Ömer
Piston bowl geometry directly affects many parameters such as combustion, flow, turbulence, and mixture formation in-cylinder. This causes a change in engine performance, combustion characteristics and exhaust emissions. In the present study, the effects of piston bowl geometry on mixture formation, combustion characteristics, and emission characteristics of a direct injection compression ignition engine have been experimentally tested. Novel bowl geometries namely New Combustion Chamber (NCC) were developed and made comparison Standard Combustion Chamber (SCC). Air-cooled, four-stroke, single-cylinder and direct injection compression ignition engine was used in the experiments. The diesel engine was operated under full load and different speed conditions (1800, 1900, 2000, 2100 and 2200 rpm). Within the scope of the study, brake specific fuel consumption, engine torque, exhaust emissions (CO2, CO, O2, HC, NO and soot) and combustion characteristics (Instantaneous heat release rate, in-cylinder pressure change, rate of pressure rise and mass fraction burned) were examined. The results showed that the eight pockets and sub-base radius in the NCC geometry significantly improved the specified parameters. The NCC geometry according to the SCC, the specific fuel consumption decreased by approximately 6.89% and engine torque increase 6.32% in the achieved maximum torque at 2000 rpm. Exhaust emissions are generally reduced thanks to the NCC bowl geometry. However, NO emissions increased due to increased temperatures, improved combustion and mixture formation at all speeds. When the combustion analyzes were examined, it was seen that the new type of bowl improved the combustion. The reason was that the increase of the bowl in the surface area, and the increased turbulence with it provided easier evaporation of the fuel droplets and better mixture formation with the air. The spread of combustio
Joint performance of medium carbon steelaustenitic stainless steel double-sided TIG welds
(WALTER DE GRUYTER GMBHGENTHINER STRASSE 13, D-10785 BERLIN, GERMANY, 3 February 2023) Teker, Tanju; Aydın, Sinan; Yılmaz, Serdar Osman
AISI 1040 and AISI 304 steel plates of 10 mm were joined without pretreatment by double-sided TIG arc welding (DSAW). Joints were manufactured by using welding currents of 420, 440, and 460 A. The microstructural variations in the interface of the weld samples were defined by optical microscopy, scanning electron microscopy, energy dispersive spectroscopy and microhardness analysis. V-notch impact and tensile tests were done to detect the weld strength of the weld samples. In DSAW welding of different steels, a full penetration joint was achieved without opening the weld edge. The current intensity had a major effect on the symmetrical and hourglass shape in welds. Welding at 460 (A) showed acceptable joint quality. Tensile and impact energy quantities of welded joints had significant ratios. Fractures in the weld metal of the samples were ductile mode.
Improvement of metallurgical properties of A356 aluminium alloy by AlCrFeSrTiBSi master alloy
(WALTER DE GRUYTER GMBHGENTHINER STRASSE 13, D-10785 BERLIN, GERMANY, 3 February 2023) Teker, Tanju; Yılmaz, Serdar Osman; Karakoca, Alper
A new AlCrFeSrTiBSi master alloy was manufactured by in situ synthesis in Al melt, and compared with AlBSr master alloy. Microstructures of A356 alloy modified with AlCrFeSrTiBSi master alloy were investigated, and the structural details of the new cast A356 alloy were evaluated by X-ray diffraction (XRD), optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), microhardness and differential thermal analysis (DTA). AlBSr master alloy typically formed α-Al and granular SrB6 phases in A356, and the samples inoculated with AlCrFeSrTiBSi master alloy consisted of additionally AlCrFeSi phase with irregular blocks. The addition of 0.1 wt%AlCrFeSrTiBSi alloy to the A356 alloy significantly refined and modified the grain structure together. The structure of eutectic Si converted from acicular form to fibrous. The size of α-Al dendrites declined from ∼1000 μm to ∼100 μm. The strength values of the A356 alloy were developed by ∼70% with the addition of 0.1 wt%AlCrFeSrTiBSi master alloy.

Güncel Gönderiler