Mechanical Engineering / Makina Mühendisliği

Permanent URI for this collectionhttps://hdl.handle.net/11147/4129

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Access Right: Closed AccessInstitution Author: search.filters.institutionAuthor.Özkol, Ünver

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  • Article
    Citation - WoS: 9
    Citation - Scopus: 11
    Experimental Investigation of Spray Characteristics of Ethyl Esters in a Constant Volume Chamber
    (Springer, 2024) Ulu, A.; Yildiz, G.; Özkol, Ü.; Rodriguez, A.D.
    Abstract: Biodiesels are mainly produced via the utilization of methanol in transesterification, which is the widespread biodiesel production process. The majority of this methanol is currently obtained from fossil resources, i.e. coal and natural gas. However, in contrast with methanol, biomass-based ethanol can also be used to produce biodiesels; this could allow the production line to become fully renewable. This study aimed to investigate the spray characteristics of various ethyl ester type biodiesels derived from sunflower and corn oils in comparison to methyl esters based on the same feedstocks and reference petroleum-based diesel. Spray penetration length (SPL) and spray cone angle (SCA) were experimentally evaluated in a constant volume chamber allowing optical access, under chamber pressures of 0, 5, 10 and 15 bar and injection pressures of 600 and 800 bar. Sauter mean diameter (SMD) values were estimated by using an analytical correlation. Consequently, ethyl esters performed longer SPL (2.8–20%) and narrower SCA (5.1–19%) than diesel under ambient pressures of 5 and 10 bar. Although the SMD values of ethyl esters were 48% higher than diesel on average, their macroscopic spray characteristics were very similar to those of diesel under 15 bar chamber pressure. Moreover, ethyl esters were found to be very similar to methyl esters in terms of spray characteristics. The differences in SPL, SCA and SMD values for both types of biodiesels were lower than 4%. When considering the uncertainty (± 0.84%) and repeatability (±5%) ratios, the difference between the spray characteristics of methyl and ethyl esters was not major. Graphical abstract: [Figure not available: see fulltext.] © 2022, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.
  • Article
    Citation - WoS: 1
    Citation - Scopus: 2
    Off-Design Analysis of Transonic Bypass Fan Systems Using Streamline Curvature Through-Flow Method
    (Walter de Gruyter GmbH, 2019) Acarer, Sercan; Özkol, Ünver
    The two-dimensional streamline curvature through-flow modeling of turbomachinery is still a key element for turbomachinery preliminary analysis. Basically, axisymmetric swirling flow field is solved numerically. The effects of blades are imposed as sources of swirl, work input/output and entropy generation. Although the topic is studied vastly in the literature for compressors and turbines, combined modeling of the transonic fan and the downstream splitter of turbofan engine configuration, to the authors' best knowledge, is limited. In a prior study, the authors presented a new method for bypass fan modeling for inverse design calculations. Moreover, new set of practical empirical correlations are calibrated and validated. This paper is an extension of this study to rapid off-design analysis of transonic by-pass fan systems. The methodology is validated by two test cases: NASA 2-stage fan and GE-NASA bypass fan case. The proposed methodology is a simple extension for streamline curvature method and can be applied to existing compressor methodologies with minimum numerical effort.
  • Conference Object
    Computational Determination of Volume Averaged Transport Properties of Heat and Fluid Flow in Porous Media by Using Microtomography Images
    (Begell House, 2017) Çelik, Hasan; Mobedi, Moghtada; Nakayama, Akira; Özkol, Ünver
    In this study, the theory and techniques for obtaining VAM (Volume Average Theory) transport properties of a porous medium from micro-tomography images are described. The validation of the results with reported experimental or numerical values in literature may not be sufficient, hence a comprehensive attention is paid to the techniques that can be used for verification of the obtained numerical results at each step of this long computational process. The suggested verification techniques are categorized and explained in details. © 2017, Begell House Inc. All Rights Reserved.