Research Project: Ultra Enerji Verimli Değişken Kapasiteli Kompresör Geliştirlmesi İçin Araştırmacı Yetiştirilmesi
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Contributors
Funders
ID
TB.00427
Authors
Lazoğlu, İsmail
Faculty Member
Publications
Negative additive manufacturing of Al2O3-Al cermet material by fused deposition and Direct Ink Writing
(Elsevier, 2022) Balcı, Özge; Khan, Shaheryar Atta; Lazoğlu, İsmail; Paksoy, Aybike; Shahzad, Aamir; Department of Chemistry; Graduate School of Sciences and Engineering; MARC (Manufacturing and Automation Research Center); KUBAM (Koç University Boron and Advanced Materials Application and Research Center); Yes; College of Sciences; GRADUATE SCHOOL OF SCIENCES AND ENGINEERING; Research Center
Although additive manufacturing is an attractive alternative for the manufacturing of complex ceramic geom-etries, the manufactured parts have low mechanical properties due to low solid loading, high porosity, and geometrical distortions. Introducing ductile metal particles into the brittle ceramic matrix is an effective tech-nique to enhance the geometrical accuracy and mechanical properties of the printed part. In the current research, the Direct Ink Writing technique is used to fabricate alumina-based matrix composite reinforced with Al particles by negative additive manufacturing. A homogenous cermet mixture in the form of Al2O3-Al with various Al compositions (5 vol%, 10 vol%, 15 vol%, and 20. vol%) was achieved by high-energy ball milling. A slurry was prepared by mixing the milled powder with the carboxymethyl cellulose binder and sodium silicate in the deionized water. Rheological measurements of all the slurries were carried out to investigate the shear-thinning behavior of the pastes. The slurry was cast into the polylactic acid mold as the mold was built up layer by layer simultaneously using a Mitsubishi robotic manipulator. The printed parts were dried, demolded by dissolving in Dichloromethane (DCM) solution, and sintered at 1400 degrees C for 6 h. X-ray diffraction results revealed two distinguished phases (ceramic and metal) in the finished part. It is possible to formulate printable alumina -aluminum cermet slurries with solid content as high as 50 vol% and 97 % density. It was found that by the inclusion of metallic Al phase, the micro-hardness reduces as compared to monolithic alumina ceramic.
Effect of starting position of crankshaft on transient body vibrations of reciprocating compressor
(Elsevier , 2023) Subaşı, Ömer; Lazoğlu, İsmail; Oral, Atacan; Sahin, Caglar; Ul Haque, Umar; Department of Mechanical Engineering; MARC (Manufacturing and Automation Research Center); Yes; College of Engineering; Research Center
The maximum reciprocating compressor vibrations occur during the startup and shutdown operations and un-derstanding the factors that influence the transient vibrations can help in developing solutions to reduce the excessive displacements. In this study, the effect of crankshaft starting position on the vibration phenomenon is investigated and the optimal starting position to deliver a smooth start is proposed. The structural forces are analytically modeled to estimate the body displacements by considering the system resonance frequencies and modal vectors. An experimental setup is also constructed to validate the prediction model results, with the integration of an encoder to track the crankshaft angular position and transducers to measure the discharge and suction pressures. The transient responses of three different crankshaft start positions are then compared using the experimental setup and the analytical model. The results indicate that if the crankshaft starts to rotate from positions close to the bottom dead center, a higher amount of startup vibrations is observed, revealing the optimal starting position zone. The magnetization effect can potentially be addressed by the sensorless starting strategy developed by Lee et al. (2008) that implements a phase current controller for a smoother startup. While out of scope for this study, shutdown strategies can also be devised to have the piston consistently land at the favorable SAP range. By separately investigating the instances when the 'stop' command is provided to the steady-state operating compressor, solutions that attempt to replicate the conditions that lead to the favorable stop position can be developed; a limiting factor in mass production will be implementing the encoder for continuous position tracking and an accompanying undesirable cost increase in manufacturing. Nevertheless, the investigation of passive and active strategies is ripe for research in literature.
Comparison of constant and variable discharge flow and force coefficients for reciprocating compressor
(Elsevier, 2023) Pashak, Pouya; Lazoğlu, İsmail; Malik, Anjum Naeem; Karabay, Ahmet Yasin; Sahin, Caglar; MARC (Manufacturing and Automation Research Center); Department of Mechanical Engineering; Yes; College of Engineering; Research Center
Enhancing the mathematical models always have been a critical issue in every field, and the reciprocating compressors are not exceptional. Flow and force coefficients are two empirical factors that help to calculate the mass flow rate through the valve and gas force, respectively. These coefficients can be considered constant values or valve lift dependent. However, in the discharge process, the piston is close to the top dead center, which may affect the discharge flow field and, subsequently, the coefficients.These coefficients should be determined by experiments or numerical simulations such as computational fluid dynamics (CFD). Experiments are expensive, and the exact geometry may not always be available to perform the CFD analysis. Also, CFD analysis for various valve lifts and piston positions is computationally expensive.This study studied the effect of constant, single variable (valve lift dependent) and double variable (valve lift and piston position dependent) coefficients on compressor performance and discharge valve movement in three operating conditions. A mathematical model was developed for this purpose, and a 3-D CFD simulation was used to compute the coefficients. To validate the results, a strain gauge and a calorimeter were used as measurement tools.The single and double variable models captured the valve behavior, and pressure picks better than the constant model. However, the constant model estimated the indicated power, cooling capacity, and COP with good accuracy. In predicting the discharge losses, the double variable model was the most reliable among the others.
A novel approach to tube design via von Mises probability distribution
(Taylor & Francis Ltd, 2024) Lazoğlu, İsmail; Oral, Atacan; Öztürk, Çağlar; Subaşı, Ömer; Subay, Şehmuz Ali; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; MARC (Manufacturing and Automation Research Center); Yes; College of Engineering; GRADUATE SCHOOL OF SCIENCES AND ENGINEERING; Research Center
Discharge tube is a critical component in a reciprocating compressor that carries the refrigerant. It also transmits vibrations from compressor body to housing, making the design of tube a complex engineering problem combining static, modal and flow behaviour. This study proposes a novel design algorithm for discharge tube, to decrease the dependency on the trial-and-error approach commonly used by manufacturers. The computational approach creates a tube that connects the inlet and outlet using von Mises probability distribution. The created geometries are checked for static and dynamic properties using FEA. The algorithm continues until a candidate design passes the imposed thresholds. The candidate designs perform similarly to benchmark in evaluated aspects, demonstrating promising results. The presented algorithm is successful in generating alternative tube designs from scratch and can accommodate varying requirements. The main novelty of this study is the development of a comprehensive decision algorithm that considers multiple engineering parameters simultaneously.
A novel unibody axial flow pump for the lubrication of inverter type hermetic reciprocating compressors
(Elsevier, 2022) Lazoğlu, İsmail; Pashak, Pouya; Shahzad, Aamir; MARC (Manufacturing and Automation Research Center); Yes; Research Center
Lubrication at low speeds is a general problem in the hermetic reciprocating compressors for household refrigerators. The aim of this article is to present a new method using a novel 3D printed unibody axial flow pump for the lubrication oil supply system of an inverter type hermetic reciprocating compressor during a low speed (< 2000 rpm) operation. The system is based on a 3D printed unibody bladeless impeller axial flow pump attached to the bottom end of the vertical rotating crankshaft partially immersed in the oil sump inside hermetic reciprocating compressor sealed casing. A Computational Fluid Dynamics (CFD) simulation besides the experiment is used to simulate the flow inside the pump to calculate the mass flow rate of the lubrication oil and to optimize the helix angle of the pump. Volume of Fluid (VoF) and Multi Reference Frame (MRF) methods are used for modeling the two-phase flow (air and lubrication oil) and rotary domain respectively. The mass flow rate and climbing time of the lubrication oil in the unibody axial pump are analyzed. The results show that the designed pump is capable to supply the lubrication oil at a low speed i.e., 1400 rpm. Moreover, results indicate that the mass flow rate of the lubrication oil increases as the viscosity decreases. The average climbing time is observed to be 1 s at 1400 rpm and 0.4 s at 2000 rpm.
